Dysfunctional response preparation and inhibition during a visual Go/Nogo task in children with two subtypes of attention-deficit
hyperactivity disorder
Stuart J.Johnstone ?,Adam R.Clarke
School of Psychology,University of Wollongong,Northfields Avenue,Wollongong,NSW 2522,Australia
Received 16April 2007;received in revised form 13December 2007;accepted 2March 2008
Abstract
While a response inhibition problem is well-established in children with attention-deficit/hyperactivity disorder of the combined subtype (AD/HDcom),the predominantly inattentive subtype (AD/HDin)has not been investigated previously.This study examined control versus subtype differences in visually evoked response inhibition using task performance and event-related potential (ERP)measures.Children with AD/HDcom (n =15)and AD/HDin (n =15)and age-matched controls (n =15)performed a cued visual Go/Nogo task requiring either activation or inhibition (30%)of a button-press response to the S2(Go or Nogo stimulus)following the S1(warning stimulus),presented 1380ms earlier.Task performance and ERP indices of Warning,Go and Nogo stimulus processing,as well as preparation during the S1–S2interval,were examined for group differences.Behavioural results indicated a response inhibition deficit in children with AD/HDcom and AD/HDin,with additional response activation problems in AD/HDcom.Topographic ERP differences between controls and both clinical groups suggested atypical (a)preparation for S2as indexed by the late CNV ,(b)early sensory/attentional processing of both S1and S2,and (c)response inhibition as indexed by N2and P3.In addition to replicating previous AD/HDcom findings,these results indicate that children with AD/HDin differ from controls in response preparation and inhibition during a cued visual Go/Nogo task.?2008Elsevier Ireland Ltd.All rights reserved.
Keywords:Event-related potentials;Contingent negative variation;Child psychiatry;Attention;Impulsivity
1.Introduction
The DSM-IV (American Psychiatric Association,1994)outlines three subtypes of attention-deficit/hyperactivity disorder (AD/HD);the combined type (AD/HDcom),the predominantly inattentive type (AD/
HDin),and the predominantly hyperactive/impulsive type (AD/HDhyp).These subtypes are based on dif-ferent clusters of symptoms from within the two core symptom domains of Inattention and Hyperactivity/Impulsivity.Specifically,the diagnostic criteria for AD/HDcom require evidence of significant impairment across both domains,while AD/HDin and AD/HDhyp require evidence of significant impairment in only one domain,i.e.Inattention or Hyperactivity/Impulsivity,respectively.Diagnoses of AD/HDhyp are rare,with a prevalence rate of only 0.2%in Australia (Gomez et al.,
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1999).This was confirmed in our setting,with no children fulfilling the diagnostic criteria for this subtype. Further,as questions have been raised about the validity of this subtype(Barkley,1997a;Power and DuPaul, 1996),it is not further addressed in this article.
The DSM-IV criteria indicate that hyperactive and impulsive symptoms differentiate AD/HDcom from AD/HDin.This distinction has apparent validity in the day-to-day life of the child,with a high prevalence of academic and behavioural problems in those with AD/ HDcom(73%and92%,respectively)and a high incidence of academic,but reduced behavioural,prob-lems associated with AD/HDin(75%and40%,respec-tively;Wolraich et al.,1996).Some of the hyperactive/ impulsive symptoms(e.g.fidgeting,excessive talking, interrupting others)can be viewed as related to response inhibition problems.While deficient inhibition has been put forward as being at the core of AD/HD(Barkley, 1997b;Quay,1988b,1997;Sergeant,2000),the rele-vance of these theoretical positions to subtypes is un-clear,as Sergeant and Quay do not make reference to subtypes of AD/HD,and Barkley specifically refers only to the AD/HDcom and AD/HDhyp types,with AD/ HDin considered a disorder of inattention.Diamond (2005)has proposed that AD/HDin is not a subtype of AD/HD,but rather a different disorder,with core prob-lems in motivation and working memory functioning but not response inhibition.Note also that the influence of intra-individual response variability,within the con-text of inhibition and other executive function tasks,is receiving increased research interest(e.g.Castellanos et al.,2006;Klein et al.,2006).
Previous behavioural research comparing the AD/ HD subtypes on inhibition tasks is limited and has produced mixed results.Some studies report problems of disinhibition in AD/HDcom but not AD/HDin(Nigg et al.,2002;Wang et al.,2003),while others show similar levels of poor inhibition performance in both subtypes(Lane,2004;Yonghui et al.,2005).This study will examine response inhibition during the Go/Nogo task in these subtypes,examining task performance and additionally using event-related potentials(ERPs)to investigate underlying neural activation related to res-ponse inhibition.
It has been consistently reported that children with AD/HDcom have problems with response inhibition, typically displaying higher levels of commission errors to Nogo/Stop stimuli(i.e.,those stimuli requiring the covert inhibition of a response)than control children (Iaboni et al.,1995;Nigg,1999;Rubia et al.,1999; Schachar et al.,1993).These behavioural findings are supported by brain imaging reports of atypical frontal activity during inhibitory processing in children with AD/HD(Rubia et al.,2000),and reports of atypical activation of inhibition-related ERP components such as the fronto-central N2(Broyd et al.,2005;Dimoska et al., 2003;Pliszka et al.,2000;Smith et al.,2004;Yong-Liang et al.,2000)and P3(Brandeis et al.,1998;Liotti et al.,2005;Overtoom et al.,2002).Group differences are not restricted to these endogenous components, however,with topographic differences and differential Nogo effects(i.e.,a larger component to Nogo than Go stimuli)reported in earlier exogenous(i.e.,obligatory/ sensory)components,such as the N1and P2(Broyd et al.,2005;Smith et al.,2004).
While their functional significance is currently con-troversial(Nieuwenhuis et al.,2003;Smith et al.,2006), the N2and P3ERP components have shown reasonably consistent relationships with inhibition-related beha-viours(Falkenstein et al.,1999;Jodo and Kayama, 1992),and are generally considered to be electrophysio-logical markers of aspects of the inhibition processing sequence.The N2is maximal over frontal scalp regions (Kiefer et al.,1998)and is typically larger to Nogo than Go stimuli(Eimer,1993),an augmentation resulting from the inhibitory process and described as a“red flag”that the response to the stimulus is to be inhibited(Kok, 1986).The latency of N2is reduced in good compared with poor inhibitors(Falkenstein et al.,1999),providing further support for N2as related to the inhibition me-chanism.Nogo effects have been reported for N2in children(Broyd et al.,2005;Dimoska et al.,2003; Smith et al.,2004)and adults(Kiefer et al.,1998).The P3component typically exhibits a centro-parietal maxi-mum to Go stimuli,but is more anterior to Nogo stimuli (Bruin and Wijers,2002).Nogo P3latency is typically prolonged relative to Go stimuli(Eimer,1993),and in older compared to younger adults(Falkenstein et al., 2002).
We have previously investigated these subtypes using a task that primarily engages attention control (i.e.,a two-tone oddball),a process from the symptom domain common to both AD/HD subtype groups (Johnstone et al.,2001).There we reported that children with AD/HDin did not differ significantly from controls or AD/HDcom in task performance,but did show ERP differences from controls,several that were common to both subtypes and represent shared processing problems (e.g.increased P2amplitude),as well as unique dif-ferences(e.g.target N1,P2and P3topography).Further, each subtype showed differing patterns of abnormal age-based development for several ERP components, indicating qualitative differences in information proces-sing stage deficits in each of these AD/HD subtypes.
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The task used in the present study was a cued visual Go/Nogo,with a constant interval between Stimulus1, or S1(i.e.the Warning stimulus)and Stimulus2,or S2 (i.e.the imperative stimulus),allowing examination of responses to S1and S2and also the contingent negative variation(CNV),an electrophysiological index of response preparation,during the S1–S2interval.We have previously reported that children with AD/HDcom process cue stimuli differently than controls during a cued auditory Go/Nogo task,with increased commis-sion errors and concurrent differences in P1,N1and P2 components to these stimuli(Smith et al.,2004).Cue processing problems in AD/HD have also been reported in the visuospatial attention context(Huang-Pollock and Nigg,2003).
While early research reported reduced CNV in child-ren with concentration problems(Grunewald-Zuberbier et al.,1978),more recent investigations have yielded variable results.The early CNV,which is a frontally maximal component linked to orienting/expectancy (Loveless,1979),has been reported to be attenuated in AD/HDcom(Hennighausen et al.,2000;van Leeuwen et al.,1998).The fronto-central late CNV,an index of preparation for the target(Walter et al.,1964),has been reported to be reduced(Aydin et al.,1987;Banaschewski et al.,2003;Dumais-Huber and Rothenberger,1992; Perchet et al.,2001;van Leeuwen et al.,1998),increased (Hennighausen et al.,2000)and not different(Strand-burg et al.,1996;Yordanova et al.,1996)in children with AD/HD compared to controls.Given these varied re-sults,further investigation in this area is warranted,with this study extending previous research to include the AD/HDin subtype.
This study aimed to investigate response prepara-tion and response inhibition in children with AD/ HDcom and AD/HDin using the visual Go/Nogo task with the inclusion of electrophysiological information to provide an insight into the neural bases for task performance,especially in relation to the inhibition process.The CNV as well as N2and P3components(to S2)will be examined as indices of response preparation and inhibition,respectively.Other earlier components will also be evaluated,given the potential cascading nature of early processing issues as related to later endogenous aspects of processing.
2.Methods
2.1.Subjects
Participants comprised45children between8and14 years of age(M=11.7years,S.D.=1.9years)participated in the years),with15in each of the control(4female), AD/HDin(3female)and AD/HDcom(2female)groups. For inclusion in the study,each child had to obtain an estimated IQ of80or greater(M=110.7,S.D.=14.4), based on the Raven's Progressive Matrices(Raven,1989) and report no hearing or vision problems.Subjects were excluded if they had been known to suffer an epileptic seizure,serious head-injuries,periods of unconscious-ness,or serious psychiatric https://www.doczj.com/doc/2210632653.html,rmed written consent was obtained from the parent(s)after provision of an outline of the procedure,and verbal assent was ob-tained from the child after the testing procedure had been explained.The experimental protocol was approved by the University of Wollongong and Illawarra Area Health Service Human Research Ethics Committee.
Clinical subjects were diagnosed by a psychologist/ psychiatrist according to DSM-IV criteria,with con-firmation by an independent experienced psychologist. Subjects with a clinically significant comorbid disorder, based on consideration of questions related to autism, Asperger's syndrome,depression and anxiety during diagnostic interview,as well as behavior rating scales, were excluded from the sample.Those AD/HD subjects taking stimulant medication(73%of the AD/HDin group;87%of the AD/HDcom group)were required to refrain from taking it in the24h(5half-lives)prior to testing.
Control subjects were recruited from the local com-munity via newspaper advertising,and had no known health,mental or developmental problems,as reported by each child's parent(s).Control children were required to score in the non-clinical range on all scales of the Conners'Parent Rating Scale-Revised(CPRS-R;T b60) and Child Behaviour Checklist(CBCL;T b65).
2.2.Procedures
Parents completed the CPRS-R and CBCL to char-acterise their child’s typical behaviour,and an in-formation sheet used to screen for stimulant use, handedness and a brief history of health and physical concerns.Each child completed the South Australian Spelling Test(SAST)and Raven's Standard Progres-sive Matrices(Raven,1989),a test of general cognitive ability.
After familiarisation with the testing equipment and procedure and subsequent equipment fitting,the child was taken to a sound-attenuated air-conditioned testing room where he/she completed three experimental tasks. After electrophysiological testing was completed,sub-jects were given a short break before moving to another quiet room where they completed the SAST and Raven's
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tasks.The entire session lasted for approximately2h. Independent of task performance,children received a certificate and a chocolate bar for their participation in the study,while their parent(s)received A$10to compensate for traveling expenses incurred,and a report on their child’s spelling and general cognitive ability test performance.
2.3.Tasks
All subjects completed a visual cued Go/Nogo task,as well as auditory and visual stop-signal tasks, with task presentation order rotated between subjects. Data from the stop-signal tasks are not presented here.
Stimuli in the visual Go/Nogo task consisted of the letters“W”(Warning),“G”(Go)and“S”(Stop,i.e., Nogo)presented centrally on a15-inch computer monitor1meter from the child at eye-level.The stimuli measured3×3cm on the screen.The sequence for each trial consisted of the presentation of the warning letter (S1)followed by a second letter(S2)which required either a button press response(Go)or the inhibition of a response(Nogo),depending on the letter presented.S2 required response execution on70%of trials,and the inhibition of a response on the remaining30%.The S1–S2interval was fixed at1380ms,while the S2–S1 interval varied randomly between1500and2500ms (mean2000ms).A central fixation cross was on screen at all times,except during discrete stimulus presenta-tions.A10-trial practice block was followed by two recording blocks,each consisting of100trials.If re-quired,children were given a2–3min break between blocks.Subjects responded with the index finger of their dominant hand(all but one subject in the con-trol group were right-handed)with a keyboard button press.Only presses to the Go tone with reaction time RT b1000ms were regarded as correct,although all button presses were recorded to allow omission and commission errors to be monitored.
It was explained to the children that the letter“W”represented a warning,instructing them to“get ready to press the button”,and that this would be followed by either the letter“G”which meant“Go,that is,press the button”,or the letter“S”which meant“Stop,that is,do not press the button”.Both speed and accuracy were encouraged.Subjects were asked to remain as still as possible,to watch the central fixation cross on the computer monitor,to respond as quickly and as ac-curately as possible to the presentation of Go stimuli, and to attempt to withhold that response if a Nogo stimulus occurred.2.4.Electrophysiological recording
The continuous scalp electroencephalogram(EEG) was recorded using an electrode cap with electrodes placed at19sites(Fp1,Fp2,F3,F4,F7,F8,Fz,C3,C4, Cz,P3,P4,Pz,T3,T4,T5,T6,O1,O2)of the Inter-national10–20system.The electro-oculogram(EOG) was measured vertically with two tin cup electrodes, 1cm above and below the left eye.All electrodes were referenced to linked ears.Impedance was kept below 5kΩfor EOG and reference electrodes,and3kΩfor cap electrodes.The subject was grounded by a cap electrode located between Fpz and Fz.EEG and EOG signals were amplified5000times,with a bandpass down3dB at0.01and100Hz(the high and low band-pass settings,respectively),via24channels of Grass amplifiers(Grass-Telefactor,USA),and sampled through a12-bit A/D card at512Hz.Prior to processing,the EEG data were digitally filtered using a low-pass filter3dB down at30Hz.
2.5.Data quantification
The ERP epoch was defined as100ms pre-stimulus to(a)1380ms post-stimulus for Warning trials,and (b)900ms post-stimulus for Go and Nogo trials. Epochs were excluded from analysis if they contained amplitudes outside the range of±100μV at any non-frontal site.EOG activity was subtracted from EEG epochs using a regression method in the time domain (Semlitsch et al.,1986).ERPs were calculated using correct responses only.To ensure comparability within subjects,the number of epochs available for averaging was determined for Nogo stimuli initially,with Go and Warning epochs restricted to the same number,being selected randomly from the total available.The mean number of epochs in each ERP for the control,AD/ HDin and AD/HDcom groups was50.4(S.D.2.8),47.9 (S.D.2.9)and47.6(S.D.9.1),respectively,with no dif-ferences between groups.
Grand average ERP waveforms for each trial type and task were displayed for the purpose of defining each component's latency range.Peak picking was carried out by an automatic peak-picking program,measured relative to the pre-stimulus baseline,with manual con-firmation by an experienced ERP researcher who was blind to any subject information.Peak latency at all sites was locked to the peak latency of the site of maximum amplitude.The peak search parameters for both Warn-ing and Go/Nogo stimuli were:N1(100–190ms;locked to Fz),P2(190–260ms;Cz),N2(260–360ms;Fz),P3 (360–750ms;Pz).CNV-E and CNV-L were quantified
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by determining the mean amplitude in the ranges 500–950ms and 950–1380ms after the Warning stimulus,respectively.
2.6.Statistical analyses
One-way Analyses of Variance (ANOVAs)were used to compare the groups on age,as well as psychometric,task performance and ERP latency variables.
For Go and Nogo stimuli,four-way repeated mea-sures ANOVAs were used to analyse ERP compo-nent amplitudes at 9sites with Lateral (Left [F3,C3,P3],Midline [Fz,Cz,Pz],Right [F4,C4,P4]),Sa-gittal (Frontal [F3,Fz,F4],Central [C3,Cz,C4],Parietal [P3,Pz,P4])and Stimulus (Go vs.Nogo)as within-subject factors,and Group (control,AD/HDin,AD/HDcom)as a between-subjects factor.Additional three-way repeated measures ANOV As examined com-ponents to Warning stimuli,including the CNV (Lateral ×Sagittal ×Group ).
Planned contrasts,which allow confirmation of ex-pected and characteristic variation in ERP components dependent on scalp location,were performed on the within-subjects factors Lateral (Left vs.Right electro-des,and Midline vs.the mean of the Left and Right electrodes)and Sagittal (Frontal vs.Parietal electrodes,and Central vs.the mean of the Frontal and Parietal electrodes).Within Group,two planned non-orthogonal contrasts compared each clinical group with the control group separately.As these contrasts were planned and there were no more of them than the degrees of freedom for effect,no Bonferroni-type adjustment to alpha was necessary (Tabachnick and Fidell,1989).Also,single
degree of freedom contrasts are not affected by violations of symmetry assumptions common in repeated measures analyses,and thus do not require Greenhouse –Geisser type corrections (Howell,1997).
Data showing a Stimulus or Group main effect and an interaction with topography (https://www.doczj.com/doc/2210632653.html,teral or Sagittal factors)were normalised using the vector scaling procedure (McCarthy and Wood,1985).1This method removes the main effect amplitude difference between Stimuli/Groups —if the interaction remains significant after the procedure has been applied,it allows conclu-sions to be made about differing component generators between Stimuli/Groups.Accordingly,only interactions with topography that remained significant after this procedure are reported.3.Results
3.1.Demographic and psychometric
As can be seen in Table 1,the groups did not differ in mean age or IQ,but the AD/HDin group showed significantly reduced spelling performance,compared to controls.The AD/HDcom group showed average scores in the clinical range (i.e.,65+)for all CPRS subscales and the Attention Problem and Aggressive Behaviour subscales of the CBCL (clinical range =70+),with
Table 1
Mean scores of psychometric testing,Conners Parent Rating Scale (CPRS)and the Child Behaviour Checklist (CBCL)for each group.
Control
AD/HDin AD/HDcom Age 11.5(1.4)11.8(2.2)11.9(2.1)IQ
108.8(15.3)113.4(13.6)110.0(14.8)Spelling Age 13.4(2.1)10.8*(2.7)11.8(3.0)CPRS
ADHD Index
47.1(8.0)65.5***(6.2)77.5***(9.4)Cognitive Prob./Inattent.48.7(9.5)64.5***(6.9)74.7***(9.8)Hyperactivity 50.8(10.2)61.5*(13.2)81.6***(10.2)Oppositional
48.6(7.9)56.7(13.5)74.5***(17.3)CBCL
Anxious/Depressed 53.8(5.3)59.7*(9.4)60.6*(6.1)Withdrawn
55.4(6.6)59.0(8.4)59.3(6.5)Somatic Complaints 52.2(4.5)56.9*(5.3)58.9**(6.5)Social Problems 54.6(6.1)57.9(6.3)65.7***(8.7)Thought Problems 54.7(6.4)64.9**(8.8)69.3***(8.0)Attention Problems 53.0(5.8)64.9***(9.1)74.5***(10.1)Rule-breaking
51.6(3.7)59.5**(7.7)68.3***(9.8)Aggressive Behaviour
53.9
(6.0)
57.4
(9.0)
74.7***
(12.7)
Significant differences from controls for each AD/HD subtype are indicated by the asterisk (*P b 0.05,**P b 0.01,***P b 0.001).
1
Recent critical appraisals of the vector scaling method have resulted in an alternative method,which shows advantages especially when a linked-ear reference is used (Jing et al.,2006).When applied to the data from the current study,outcomes of the new method did not differ from those of the vector scaling method.
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Thought Problems and Rule-breaking subscales of the CBCL in the borderline range (i.e.,67–70).The AD/HDin group averaged a clinical level ADHD Index,as well as borderline clinical scores (i.e.,60–64)for the Cognitive Problems/Inattention and Hyperactivity sub-scales of the CPRS,with no borderline or clinical level scores for the CBCL.
In regard to group comparisons,the AD/HDcom group had higher scores than controls on all but one (i.e.,Withdrawn)subscale of the CPRS and CBCL.The AD/HDin group had higher scores than controls on all but the Oppositional subscale of the CPRS,and on the Thought Problems,Attention Problems and Rule Break-ing subscales of the CBCL.These results are consistent with previously reported subtype-specific symptom pro-files for children with AD/HD in Australia (Graetz et al.,2001).
3.2.Task performance
In relation to response activation,as shown in Table 2,both subtype groups had more errors of commission to warning stimuli than controls,with the AD/HDcom group showing reduced Go response accuracy compared with controls.This latter effect was not present in children
Table 2
Means (S.D.)for task performance measures for each group.
Control
AD/HDin
AD/HDcom
Warning Error %0.5(0.8) 1.2*(0.9) 1.5***(1.2)
Go Accuracy %96.2(4.6)94.8(4.0)92.6*(5.3)Go RT (ms)492.5(106.2)496.1(75.6)520.5(79.4)Inhibition probability %
95.2(3.9)89.3**(5.5)90.1**
(4.4)
Significant differences from controls for each AD/HD subtype are indicated by the asterisk (*P b .05,**P b .01,***P b
.001).
Fig.1.Grand mean ERP to Warning stimuli across the S1–S2interval at Cz (bottom panel)for the Control (solid line),AD/HDin (dotted line)and AD/HDcom (dashed line)groups.Note:Ticks on the x -axis=100ms;Stimulus onset is indicated by the y -axis (scale in μV).The top panels show topographic maps for each component labeled on the ERP plot,for each group.Darker shades equal larger positive amplitudes for each component.
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with AD/HDin.The RT to Go stimuli did not differ from
controls for either subtype.In relation to response inhi-
bition,the percentage of successfully inhibited responses
to Nogo stimuli was reduced in the AD/HDin and AD/
HDcom groups compared with controls.
3.3.ERPs
3.3.1.Warning stimuli
Fig.1shows the grand mean ERP to Warning stimuli
for each group at Cz and topographic maps of the quan-
tified components.N1peaked at141.9ms(with no Group
differences in latency)and was fronto-centrally maximal
in the sagittal dimension(Linear contrast F(1,42)=18.9,
P b0.001;Quadratic contrast F(1,42)=4.3,P b0.05)and
midline maximal in the lateral dimension(Quadratic
contrast F(1,42)=4.1,P b0.05).A near-significant
Group main effect and planned contrasts revealed that
N1tended to be larger in the AD/HDcom than control
group(?2.9vs.?1.3μV;P=0.07).A Frontal N Parietal
effect was larger in AD/HDin than the control group(F
(1,42)=6.3,P b0.05),highlighting a reduced parietal N1
in the AD/HDin group(see Figs.1and2A).
P2peaked at195.4ms(with no Group differences in
latency)and was maximal in the parietal region(Linear
F(1,42)=52.7,P b0.001),with no variation across the
Lateral regions.There was a group difference in the
Lateral distribution of P2,as the control group had
a Left N Right effect(4.3vs.3.5μV)while the AD/
HDin group showed an opposite effect(3.0vs.4.5μV;
F(1,42)=5.8,P b0.05).
N2peaked at328.9ms and was fronto-centrally
maximal(Linear F(1,42)=39.0,P N0.001;Quadratic
F(1,42)=25.0,P b0.001),with no lateral variation.
As shown in Figs.1and2B,although a Left N Right effect
(?1.3vs.0.4μV)was observed for the AD/HDin group,
the opposite effect occurred for the controls(?0.4vs.?0.9μV;F(1,42)=4.3P b0.05).P3peaked at527.7ms and was midline(Quadratic F(1,42)=6.0,P b0.05)and
parietally(Linear F(1,42)=41.9,P b0.001)maximal.
There were no differences between the groups in either
amplitude or latency.
CNV-E(600–950ms)was smaller in the midline
than hemispheres(Quadratic F(1,42)=29.7,P b0.001).
There were no group differences for this component.
CNV-L(950–1380ms)was maximal in the central
region(Quadratic F(1,42)=8.8,P b0.01).This non-
fronto-central distribution is typical of children of this
age(Klein and Feige,2005).A tendency towards a group difference in the midline b hemispheres effect, which was very small in controls(0.1μV)and large in AD/HDin(0.9),highlighted the reduced midline CNV-L in the AD/HDin group(F(1,42)=3.6,P=0.07).Figs.1 and2C display the central N frontal/parietal effect,which was reduced in the AD/HDcom group compared with controls(central vs.frontal/parietal difference:
AD/HDcom Fig.2.Group differences in ERPs to Warning stimuli for(A)N1, (B)N2and(C)CNV-L component amplitude.
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0.1μV ,control 1.2μV;F (1,42)=4.4,P b 0.05),high-lighting reduced central CNV-L in AD/HDcom.3.3.2.Go/Nogo stimuli
Fig.3shows the grand mean ERP to Go and Nogo stimuli for each group at Cz and topographic maps of the quantified components.N1peaked at 149.0ms (with no differences in latency between Groups or Stimulus type)and was maximal in the midline (Linear F (1,42)=23.9,P b 0.001)and fronto-central (Linear F (1,42)=30.5,P b 0.001;Quadratic F (1,42)=16.3,P b 0.001)regions.As can be seen in Figs.3and 4,the N1of the control group showed a fronto-central distribution for the Go stimulus but was frontally maximal with a linear reduction to the parietal region for Nogo stimuli (Central vs.Frontal/Parietal difference:Go 1.4μV ,Nogo 0.1μV)—each clinical group differed significantly from this,with both stimuli found to be fronto-centrally maximal for the AD/HDin group (Go 1.6μV ,Nogo 2.4μV;F (1,42)=7.7,P b 0.01),while the ADHDcom group showed frontal and fronto-central distributions for the Go and Nogo stimuli,respectively (Go 1.1μV ,Nogo 0.6μV;F (1,42)=5.7,P b 0.05).
P2(mean latency 230.9ms)occurred later to Go than Nogo stimuli (242.6vs.219.2ms,F (1,42)=18.29,P b 0.001),with P2amplitude maximal in the midline (Quadratic F (1,42)=8.4,P b 0.01)and parietal (Linear F (1,42)=58.2,P b 0.001)regions.There were no Stimulus by topography interactions.Relative to controls (3.2μV),both the AD/HDin (5.3μV ,F (1,42)=5.0,P b 0.05)and AD/HDcom (5.4μV ,F (1,42)=4.4,P b 0.05)groups had globally increased P2amplitude.P2was larger in the right than left hemisphere for the AD/HDin group (5.7vs.4.3μV),differing significantly from controls (2.8vs.3.0μV;F (1,42)=6.1,P b 0.05)who had an opposite pat-tern (i.e.Left N Right)of reduced size (see Fig.5).The control group showed parieto-central and parietal dis-tributions for P2for Go and Nogo stimuli,respectively (Central vs.Frontal/Parietal difference:Go 1.7μV ,Nogo 0.1μV),with a significantly different distribution for the AD/HDin group where both stimuli were parietally dis-tributed (Go 0.7μV ,Nogo 0.7μV;F (1,42)=5.0,P b 0.05).N2(mean latency 310.7ms)occurred later in the AD/HDcom than control group (322.5vs.299.1ms;F (1,42)=5.0,P b 0.05).As shown in Figs.3and 5,N2latency was slightly longer to Go than Nogo stimuli for controls (300.8vs.297.4ms),but was substan-
tially shorter to Go than Nogo in the AD/HDin group (289.6vs.331.6ms;F (1,42)=8.4,P b 0.01).N2was maximal in the left hemisphere (Linear F (1,42)=7.2,P b 0.05)and fronto-central region (Linear F (1,42)=40.8,P b 0.001;Quadratic F (1,42)=3.9,P =0.056),and was larger to Nogo than Go stimuli (1.1vs.3.4μV ,F (1,42)=10.0,P b 0.01),a difference that was largest in the central-posterior region (Linear F (1,42)=3.7,P =0.06;Quadratic F (1,42)=5.4,P b 0.05).Across the scalp,N2was larger in controls (0.5μV)than both the AD/HDcom (2.9μV ,F (1,42)=4.1,P =0.05)and AD/HDin (3.3μV ,F (1,42)=5.6,P b 0.05)groups.
P3latency averaged 534.1ms overall,being increased for Nogo compared to Go stimuli (562.3vs.505.9ms;F (1,42)=8.23,P b 0.01)and tended to be increased in AD/HDcom compared with controls (578.5vs.511.1ms;F (1,42)=3.79,P =0.058).P3was maximal in the midline-right (Linear F (1,42)=5.5,P b 0.05;Quadratic F (1,42)=53.1,P b 0.001)and central-parietal (Linear F (1,42)=109.1,P b 0.001;Quadratic F (1,42)=9.2,P b 0.01)regions,with no significant difference between Go and Nogo stimuli.A parietal N frontal effect was reduced in Nogo compared with Go stimuli (parietal vs.frontal difference:Nogo 6.8μV ,Go 11.8μV;F (1,42)=10.2,P b 0.01),reflecting the anteriorisation of P3to Nogo relative to Go stimuli.As shown in Figs.3and 4,this effect differed between groups,with a parietal maximum (linear reduction to frontal sites)for both stimuli for controls,along with a reduction in the parietal area for Nogo stimuli (central vs.fronto-parietal difference:Nogo 0.9μV ,Go 0.3μV),with a significantly different distribution for the clinical groups where both the AD/HDin (Nogo 1.3μV ,Go 3.5μV;F (1,42)=3.9,P =0.05)and AD/HDcom (Nogo 0.3,Go 2.9μV;F (1,42)=4.9,P b 0.05)groups showed increased central activity to Go stimuli.4.Discussion
The three groups did not differ in mean age or IQ.As expected,the clinical groups showed a reduced spelling age relative to controls,although it should be noted that while the AD/HDcom group lagged 1.6years behind controls,this difference was not significant.The CPRS-R and CBCL results indicate that unique groups with subtype-specific behavioural profiles were defined,confirming the initial diagnoses at the group level.Those diagnoses were based strictly on DSM-IV criteria,with
Fig.3.The middle panel shows the grand mean ERPs to Go (solid line)and Nogo (dashed line)stimuli at Cz for the Control (left side),AD/HDin (middle)and AD/HDcom (right side)groups.Note:Ticks on the x -axis=100ms;Stimulus onset is indicated by the y -axis on the middle plot;y -axis scale in μV .The top and bottom panels show topographic maps for each component labeled on the ERP plot,for Go (top panel)and Nogo (bottom panel)stimuli separately.Darker shades equal larger positive amplitudes for each component.
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independent confirmation by an experienced psychologist.The subtypes both showed higher levels of Inattention than controls,in the clinically significant range.In relation to Hyperactivity,the AD/HDin group scored higher than controls,but were not in the clinically significant range,while the AD/HDcom group showed a clinically sig-nificant group difference from controls.
In regard to task performance,the AD/HDcom group showed evidence of dysfunctional response inhibition,with increased commission errors to Nogo stimuli,in line with previous research (Iaboni et al.,1995;Nigg,1999;Nigg et al.,2002;Rubia et al.,1999;Schachar
et al.,1993;Wang et al.,2003).The AD/HDcom group also showed problems with performance related to Go stimuli,with reduced Go accuracy compared to controls,and although non-significant,the slowest Go RT (with the AD/HDin and control groups showing very similar RTs).
The AD/HDin group also showed dysfunctional res-ponse inhibition,in line with some previous behavioural research (Lane,2004;Yonghui et al.,2005),with in-creased commission errors to Nogo stimuli relative to controls,while their response activation variables did not differ from controls.Based on performance during the visual Go/Nogo task,it seems that both AD/HD subtypes showed evidence of dysfunctional response inhibition,with the addition of response activation problems in AD/HDcom.
4.1.ERPs to warning stimuli
The ERPs to Warning stimuli revealed group differ-ences in neural activation corresponding to processing this stimulus itself,and also in the subsequent prepara-tion for S2,as revealed by the CNV-L.The AD/HDcom group showed some evidence of atypical early proces-sing of the Warning stimuli,with a globally reduced N1indicating atypical activation of early sensory processing of,or attention to (Naatanen and Picton,1987)these stimuli.2The latter result is similar to our auditory mo-dality Go/Nogo findings (Smith et al.,2004)and reduc-tions reported during auditory attention tasks (Johnstone et al.,2001;Satterfield et al.,1994).This ERP effect is reported in the context of increased commission errors to Warning stimuli by this group.
Similarly,in conjunction with poorer task perfor-mance,the AD/HDin group showed several ERP dif-ferences,including reduced parietal N1,suggesting an early sensory/attentional deficiency,as well as differences in hemispheric maxima for P2and N2.These findings indicate that children with AD/HDin process these stimuli,which were essentially task-irrelevant and pro-vide only a cue to the upcoming S2,very differently from controls.
CNV-L was atypical in both AD/HD groups,being reduced across the midline (i.e.,Fz,Cz,Pz)for AD/HDin,and across the central region (i.e.,C3,Cz,C4)for
2
These N1effects should be considered with a degree of caution.Examination of the P100-N140complex present in occipital recordings during visual task would allow stronger conclusions to be drawn about the sensory/attention effects reported here as indexed here by N1.However,low quality occipital recordings for several subjects did not allow accurate quantification of these components at occipital locations in these
data.
Fig.5.Significant interactions for P2amplitude (Group×Lateral;top panel,y -axis scale in μV)and N2latency (Group×Stimulus;bottom panel,y -axis scale in ms)for ERPs to Go/Nogo stimuli.
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AD/HDcom.Although the CNV-L of each clinical group differed from controls in different ways,both showed indications of inadequate expectation of,or preparation for(Rohrbaugh and Gaillard,1983),the imperative Go or Nogo stimulus during the fixed S1–S2 interval.The present AD/HDcom finding supports previous research(Aydin et al.,1987;Banaschewski et al.,2003;Dumais-Huber and Rothenberger,1992; Perchet et al.,2001),with this study revealing the first evidence of this deficit in children with AD/HDin. 4.2.Go/Nogo ERPs
Across Groups,several characteristic Go vs.Nogo effects,such as larger N2to Nogo than Go stimuli and P3latency being longer in Nogo than Go stimuli,were found,supporting previous research in children(Broyd et al.,2005;Jonkman et al.,2003;Smith et al.,2004) and adults(Bokura et al.,2001;Falkenstein et al.,1999). N1topography differed between stimulus types(reduced frontally and increased parietally in Nogo compared to Go),suggesting differential activation of early sensory or attentional processes dependent on stimulus type,an effect reported previously in children(Johnstone et al., 2005).Other effects replicating previous research in children include increased P2latency to Go vs.Nogo stimuli(Broyd et al.,2005),and similar P3amplitude to Go and Nogo stimuli(Johnstone et al.,2005),both during auditory Go/Nogo tasks.
Our AD/HDcom group showed further ERP evi-dence for both exogenous and endogenous inhibitory processing deficiencies,with corresponding poorer inhibitory task performance.The regional maximum of N1to Go and Nogo stimuli differed from controls (who showed a frontal maximum for Nogo,and fronto-central maximum for Go,stimuli)—similar to our recent auditory modality finding(Broyd et al.,2005). Parietal P2was globally increased in AD/HDcom com-pared to controls,replicating an auditory finding(Broyd et al.,2005),and in line with reports of localized group differences(Smith et al.,2004),as well as data from auditory attention tasks(Johnstone et al.,2001;Oades et al.,1996).The anteriorisation of P3to Nogo,relative to Go,stimuli differed between the control and both AD/ HD subtype groups.A larger Go N Nogo P3effect has been reported previously in AD/HDcom compared to controls(Yong-Liang et al.,2000).The frontal N2was globally reduced in amplitude in children with AD/ HDcom,an effect reported in the context of poorer inhibitory performance,replicating previous findings from visual(Yong-Liang et al.,2000)and auditory Go/ Nogo tasks(Broyd et al.,2005),as well as findings from the stop-signal task(Dimoska et al.,2003;Pliszka et al., 2000).Note that we have previously reported a larger N2 Nogo effect in children with AD/HDcom than controls, during a cued auditory Go/Nogo task with a random S1–S2interval,in the context of similar inhibitory perfor-mance for each group(Smith et al.,2004).N2peaked later in the AD/HDcom group compared to controls, similar to an effect that occurred when a visual Go/Nogo task was performed first,but not second,in a two para-digm protocol(Yong-Liang et al.,2000).This pattern of N2results across these studies gives some support to the proposal that AD/HDcom suffer from an inhibition re-gulation problem(Yong-Liang et al.,2000).
The AD/HDin group also differed from controls in the processing of Go/Nogo stimuli,in conjunction with poorer task performance.Some of these differences from controls were similar to those found in the AD/HDcom group,including globally decreased N2,globally in-creased P2,and the Nogo anteriorisation effect for P3. Further,similar to AD/HDcom,the distribution of N1to Go and Nogo stimuli(fronto-central for Go and Nogo stimuli)differed from controls.Unique group differences were also found,including P2distribution effects(L vs.R distribution,distributions of Go vs.Nogo),and N2latency being longer to Nogo than Go(opposite to controls)—these effects differentiate the neural responses of AD/ HDcom and AD/HDin groups to Go/Nogo stimuli.
https://www.doczj.com/doc/2210632653.html,mon differences
A number of important effects were present for both groups,warranting further consideration.Increased P2 amplitude has been reported previously in these AD/HD subtypes during the oddball task(to both target and standard stimuli),an effect that was present across an age-range of8to18years,suggesting that this com-ponent might serve as an age-and subtype-independent marker of AD/HD(Johnstone et al.,2001).Further,P2 features importantly amongst ERP variables that pro-vide maximum discrimination of children with AD/HD from controls,as well as AD/HDcom and AD/HDin groups from each other(Smith et al.,2003).The present data add weight to that position,with similar differences in the inhibitory context.Including P2measurements from the Go/Nogo task,along with oddball data,might enhance the utility of ERPs in differentiating children with AD/HD from controls.
There were no differences between any of the groups in the N2Nogo effect(confirmed by quantification and analysis of Nogo–Go difference waveforms)—instead, N2was globally reduced for both subtypes regardless of stimulus type.Thus,in regard to amplitude(seen as
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an indicator of the extent to which the process it represents was activated),a deficiency/atypicality in this stage of the processing sequence is evident for both AD/ HD subtypes relative to control children,and this differ-ence is not specific to Nogo stimuli.The timing of this inhibition-related component differed between groups, with the N2peaking later than controls regardless of stimulus type in AD/HDcom,suggesting a non-specific slowing of this process,while N2was slightly earlier to Go and much later to Nogo stimuli in AD/HDin com-pared to controls,suggesting a specific slowing of this process to Nogo stimuli.
The P3was larger to Go than Nogo stimuli for each group,consistent with previous findings in children (Johnstone et al.,2005;Jonkman et al.,2003),and interpreted as reflecting a relatively immature frontal inhibition system.Interestingly,each subtype had a dif-ferent P3anteriorisation effect than controls,with the subtypes showing evidence of a stronger effect(see Fig.4).While the effect is indeed larger in the subtypes, we consider that the results still indicate atypical processing in both AD/HD subtypes,given that healthy adults who perform the inhibition task with few errors typically show both the P3anteriorisation effect and a larger P3to Nogo than Go stimuli(Falkenstein et al., 2002;Johnstone et al.,2005;Kopp et al.,1996).
4.4.Conclusions
This study has provided further evidence of response inhibition problems in children with AD/HDcom,with several key ERP differences from controls replicated here in the context of poorer inhibition performance. Importantly,these Go/Nogo processing differences were subsequent to early sensory/attentional differences to Warning stimuli,as well as inefficient expectation of the imperative stimulus.
This was the first investigation of response inhibition in children with AD/HDin using concurrent ERP mea-sures.We report evidence of both behavioural and ERP indices of response disinhibition in children with AD/ HDin.More specifically,the results indicate(a)consi-derable differences in the processing of Warning stimuli compared to controls,including an early sensory/atten-tional deficiency,(b)inadequate expectation of the S2 as indicated by the CNV to S2,and(c)for Go/Nogo processing,similar problems to AD/HDcom,such as those with early visual detection(P2),and aspects of the inhibition process(N2and P3).Unique differences from controls were also found with aspects of the sensory/ exogenous responses(P2distribution)as well as with the timing of aspects of the inhibition process(N2latency).These findings are contrary to the notion that AD/HDin is primarily a disorder of Inattention,and that Hyper-activity/Impulsivity are the key differentiating features of AD/HDcom and AD/HDin.
Despite the multifaceted nature of the processing problems in these subtypes of AD/HD,both would benefit from operant training of response preparation and inhibition abilities.In relation to AD/HDin specifically, our results indicate that management and treatment approaches should additionally consider the response inhibition problem,not previously thought to be a pro-minent feature for this subtype.
While strict criteria were used to accurately identify the subtype of AD/HD participants,there is undoubtedly a margin for error when relying of subjective informa-tion provided mostly by parents–thus it must be con-sidered possible that the AD/HDin group were not a pure subtype group,but rather a subthreshold AD/ HDcom group–a group which would also suffer from inhibition problems,albeit at a reduced level.Accord-ingly,replication of these results is required.Future investigations in this area would benefit from reliable objective measures of subtype group membership(such as cognitive or neuropsychological tests)so that diag-nostic accuracy is increased,as well as a sample large enough to allow the consideration of age.Additionally, examining other types of inhibition,including response inhibition tasks such as the stop-signal,and those accessing interference control,such as the flanker task, would allow further clarification of the nature of the inhibition problem in AD/HD subtypes. Acknowledgements
We thank the children who participated and their parents, as well as Aneta Dimoska,Janette Smith and Rodney Croft for helpful comments on earlier drafts of this article.This study was supported by the Australian Research Council Discovery funding scheme(DP0559048).
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新闻评论的格式写法 新闻评论的格式写法新闻评论的文体结构与其他新闻文体相比基本是一致的，它包括标题、导语、主体、结尾四个部分，而在具体写作新闻评论时，各个构成部分又有其独特的写法。1．引人注意的标题新闻评论的标题既可以标明论题的对象和范围，也可以直接提出评论的观点和主旨；总的要求是生动活泼、言简意赅，使标题成为引人耳目的招牌。首先，要巧用动词，强化动词在评论标题中的动态感和鲜活感。2005年11月4日《经济日报》的评论《扬起企业品牌之帆》，这篇评论的标题用动词“扬起”，既揭示出我国目前实施自主品牌的必要性，也展现了我国企业界创新品牌的信
心与决心，给人以昂扬向上的感2005年8月23日《人民日报》的评论标题是《匹夫不可夺志国难见气节》，运用了引用的否定式陈述句的标题能够直接给受众一个非常坦率的态度；疑问句式的标题使受众始终带着一种特定的悬念去思考。《文化产业呼唤”中国创造”》，其标题运用肯定式陈述句，非常鲜明地揭示了媒体所要表达的一种态度和观点；《不该误读”平民医院，’))，虽用表面否定的句式却表达了非常干脆的态度；《洋教材冲击了我们什么？》，这一个带着问号的标题首先就会给受众留下悬念：谁在用洋教材？到底怎么回事？带着种种谜团就会循文找答案了。依据评论的思想内容，善于调动不同的句式，能够造成一种特有的情感效果。评论的标题写作方法不止这些。只要能吸引受众、揭示评论的思想内容，就是好的评论标题。新闻评论标题的写作原则追求有个性、有创新，这样的评论标题才更具魅力。2．富有悬念的导语新闻评论的导语，即开头部分、
引论部分。导语的设计应始终以受众为着眼点，总的要求是：要把最能吸引受众兴趣、最能引起受众关注的事实、观点或问题放在前面。的主体由两个层次构成，一是老百姓对”平民医院” 的错误理解，二是一些地方政府主管部门对”平民医院”的误读。哪个程度更为严重呢？该评论指出：”百姓们对’平民医院’是对眼下’公立医院’就医门槛过高的无奈”，而一些地方政府主管部门也会误读”平民医院只能说明”政府服务功能的缺位”，而后者也是评论者在文中所要着重阐明的重点内容。前后两个层次之间形成一种必然的逐层递进的关系。③对比式。就是主体部分的事实材料及其所要表达的思想内容是相互对照的，通过对比的手法论述论题和观点，有力地证实某一论点的正确或谬误。2005年12月26日《人民日报》”人民论坛”发表的《在磨砺中成长》，主体部分在重点叙述洪战辉自强不息、顽强奋斗的先进事迹，评价其崇高的道德品质的同时，也对目前
注意：每道题的难度等级不同，*越多，难度等级越高。可以根据自己的能力，选做恰当难度的题。 8.1改写第五章编程练习5.4题的程序，使该程序在程序结束之前，先判断字典内容是否发 生了变化（单词的添加、修改、删除）。如果字典内容已经被修改，则提示是否保存修改后的新字典；若选择保存，则将字典的全部内容写入一个纯文本文件，该文件可以命名为dictionary.txt。每次程序重新运行时，先尝试打开dictionary.txt。如果该文件存在，则打开文件，并从该文本文件中输入产生一个字典。 难度等级：** 8.2编写一个用于统计英文纯文本文件的各项信息：文件内容的总字符数（包括标点符号）， 单词个数，文本行数。 要求： 1.提示用户输入一个扩展名为.txt的纯文本文件名，如果指定文件存在，则打开该文 件，否则显示错误提示信息。 2.统计文件内容的上述信息，并显示所统计的信息。信息的显示格式自行确定，例如 可以按如下格式显示： 文件名：Information.txt 字符数：4854 单词数：853 文本行数：56 3.每个文件的信息显示后，提示用户是否继续统计其他文本文件，如果继续，则重复 1和2中的操作。 提示： 1.判断文本行的依据可以是每行的结尾应为‘\n’。 难度等级：*
8.3编写一个程序用于某大学的某信息专业学生的基础课成绩的录入、显示和相应数据文件 的读写。 要求： 1.成绩的按如下顺序录入： ⑴在学生成绩录入之前，先通过输入确定基础课程的门数和课程名称。例如： 基础课程1：高等数学 基础课程2：大学物理 基础课程3：大学英语 基础课程4：C语言程序设计 基础课程5：数据结构 … ⑵每个学生的成绩录入的内容包括学生的姓名、学号、性别和各门课程的成绩。成 绩按照A,B,C,D四个等级划分。录入格式可以参照如下： 姓名：李建国 学号：200410001 性别：男 高等数学：C 大学物理：B 大学英语：C C语言程序设计：B 数据结构：A … 2.保存学生成绩数据的文件的种类和结构、内容如下 ⑴课程信息索引文件courses.inx用于保存所有课程的索引信息，每门课程的索 引信息由课程索引序号和课程名组成。例如： 课程序号课程名 1高等数学 2大学物理 3大学英语 4C语言程序设计 5数据结构 … 注意，课程门数不得少于5门。 ⑵学生信息文件student.inx用于保存所有学生的索引信息，每个学生的索引信息 由学号和学生基本信息（姓名、性别）组成。例如： 学生学号学生基本信息 200410001李建国，男 … ⑶分课程成绩数据索引文件XXX.inx用于保存一门课程的所有学生成绩的索引信 息，每个学生的成绩索引信息由学号和成绩等级组成。每门课程有一个成绩数据 索引文件，文件名XXX由课程名确定。例如： 文件名：“高等数学.inx” 学生学号成绩等级 200410001C
CoverLetter英文简历书写模板 Writing the Cover Letter Writing the Cover Letter What is A Cover Letter? What is A Cover Letter Writing: Invitation to find out Persuasive Writing: Invitation to find out more about you and land Targeted Response to A Job Description and/or a Particular organization and/or a Particular organization—— THESE QUESTIONS: Can you do the job? Can you do the job? Will you do the job? Will you do the job? Will you fit in? Will you fit Cover Letter Four Steps for Cover Letter Writing From https://www.doczj.com/doc/2210632653.html, Writing From https://www.doczj.com/doc/2210632653.html, 1. 1. Conduct Research on The Conduct Research on The Organization Organization 2. 2. Deconstruct the job or internship Deconstruct the job or internship description description 3. 3. Consolidate and prioritize the key Consolidate and prioritize the key requirements you have extracted requirements you have extracted 4. 4. Plug yourself into the organizational Plug yourself into the organizational and job requirements and job requirements The Job Description The Job Description Climate and Energy Program (CEP) Climate and Energy Program (CEP) Internship, WRI Internship, WRI Position Summary WRI's Climate and Energy Program (CEP) seeks a WRI's Climate and Energy Program (CEP) seeks a motivated, well motivated, well--organized, and detail organized, and detail--oriented oriented intern to support our climate change and energy intern to support our climate change and energy policy work. The successful candidate will support policy work. The successful candidate will support CEP staff in a wide variety of activities including CEP staff in a wide variety of activities including publications management, event coordination, publications management, event coordination, database management, financial management, database management, financial management, and other tasks related to general program and other tasks related to general program administration. administration. 1. Research: 1. Transport Climate, Energy and Transport Division Projects: Division Projects: ––COP COP--15: Countdown to Copenhagen 15: Countdown to Copenhagen ––U.S. Federal Climate Policy U.S. Federal Climate Policy ––International & U.S. Action International & U.S. Action ––Business & Markets Business & Markets ––Technology & Green Power Technology & Green Power ––Energy Security & Climate Change Energy Security & Climate Change ––Information & Analysis Tools Information & Analysis Tools 1. Research: 1. Research: World Resources Institute --18, 2009, the world will 18, 2009, the world will convene in Copenhagen, Denmark to create convene in Copenhagen, Denmark to create a new global climate agreement to reduce a new global climate agreement to reduce greenhouse gas emissions at the greenhouse gas emissions at the United United Nations Climate Change Conference Nations Climate Change Conference (COP (COP-- experts have been actively involved in WRI’s experts have been actively involved in the negotiations leading up to the negotiations leading up to COP COP--15 15 and and are analyzing various dimensions of a new are analyzing various dimensions of a new agreement, among them: Vulnerability and agreement, among them: Vulnerability and Adaptation; Adaptation; Forestry and Reduced Emissions Forestry and Reduced Emissions for Degradation and Deforestation (REDD); for Degradation and Deforestation (REDD); Technology and Technology Transfer; Technology
雅思口语素材汇总之端午节 雅思口语素材:Dragon Boat Festival(端午节) Qu Yuan The Dragon Boat Festival, also called the Duanwu Festival, is celebrated on the fifth day of the fifth month according to the Chinese calendar. For thousands of years, the festival has been marked by eating zong zi (glutinous rice(糯米)wrapped to form a pyramid using bamboo or reed leaves) and racing dragon boats. The festival is best known for its dragon-boat races, especially in the southern provinces where there are many rivers and lakes. This regatta(赛舟会)commemorates the death of Qu Yuan , an honest minister who is said to have committed suicide by drowning himself in a river. Qu was a minister of the State of Chu situated in present-day Hunan and Hubei provinces, during the Warring States Period (475-221BC)(战国时期). He was upright, loyal and highly esteemed for his wise counsel that brought peace and prosperity to the state. However, when a dishonest and corrupt prince vilified Qu, he was disgraced and dismissed from office. Realizing that the country was now in the hands of evil and corrupt officials, Qu grabbed a large stone and leapt into the Miluo River on the fifth day of the fifth month. Nearby fishermen rushed over to try and save him but were unable to even recover his body. Thereafter, the state declined and was eventually conquered by the State of Qin. The people of Chu who mourned the death of Qu threw rice into the river to feed his ghost every year on the fifth day of the fifth month. But one year, the spirit of Qu appeared and told the mourners that a huge reptile(爬行动物)in the river had stolen the rice. The spirit then advised them to wrap the rice in silk and bind it with five different-colored threads before tossing it into the river. During the Duanwu Festival, a glutinous rice pudding called zong zi is eaten to symbolize the rice offerings to Qu. Ingredients such as beans, lotus seeds(莲子), chestnuts(栗子), pork fat and the golden yolk of a salted duck egg are often
小学生新闻消息写法技巧 导读：消息的特点 1、短小精练：消息要短小精练，这是新闻写作的基本要求。就小记者采写新闻来说，写好短消息，便于迅速及时的报道新闻事实，同时也锻炼小记者的采写能力;就读者阅读新闻来说，它便于阅读。 2、语言生动简洁：消息的语言只有生动、简洁，才能吸引读者 3、“倒金字塔”结构：消息的写作是将最重要、最新鲜的事实写在新闻的最前面，按事实重要性程度和读者关注的程度先主后次的安排，内容越是重要的，读者越是感兴趣的'，越要往前安排，然后依次递减。这在新闻写作中称为“倒金字塔”结构。 二、消息导语的几种写作方法 1、叙述式导语的写作：就是直截了当地用客观事实说话，通过摘要或概括的方法，简明扼要地反映出新闻中最重要、最新鲜的事实，给人一个总的印象，以促其阅读全文。 2、描写式导语的写作：记者根据目击的情况，对新闻中所报道的主要事实，或者事实的某个有意义的侧面，作简练而有特色的描写，向读者提供一个形象，给人以生动具体的印象，这就是描写式导语的一般特点。一般用在开头部分，以吸引读者，增强新闻的感染力。 3、议论式导语的写作：往往采用夹叙夹议的方式，通过极有节制、极有分寸的评论，引出新闻事实。一般分为三种形式：评论式、引语式、设问句。
三、学会恰当运用新闻背景材料 背景材料在不少新闻中占据一定的位置，是新闻稿件中不可缺少的内容。交代背景应根据需要因稿而异，更要紧扣主题，还有交代背景时不宜太多，材料要写的生动活泼。 【小学生新闻消息写法技巧】 1.小学生新闻消息的写法技巧 2.新闻消息的写作方法 3.新闻通讯的写法 4.盘点新闻消息写作方法大全 5.2015年新闻时事评论的写法 6.有关将新闻稿改写为消息 7.2015新闻的写作基础知识：消息的写作 8.新闻宣传报道的格式与写法 上文是关于小学生新闻消息写法技巧，感谢您的阅读，希望对您有帮助，谢谢
分享两篇SCI发表的经历 三年前对于我来说SCI就是天书一样，在我踏进博士的门槛后我以为自己进入了地狱，也纠结也彷徨，整天刷虫友们对于博士、SCI的帖子，我选择了虫友们鼓励的那一部分来激励自己继续前行。我告诉自己坚持就是胜利，当然那是积极的坚持。在好几月之前就有这个想法，今天早上收到第二篇的接收通知后，我便想今天一定要在小木虫上谢谢那些给予我帮助的虫友们。 话不多说，我把自己这两篇投稿的经历与大家共享，希望能给大家带来一点点用处。 第一篇发表在Fitoterapia Cover letter Dear Editor Verotta: We would like to submit the manuscript entitled "××××××题目" by ××××××所有作者姓名which we wish to be considered for publication in Journal of Fitoterapia. All authors have read and approved this version of the article, and due care has been taken to ensure the integrity of the work. Neither the entire paper nor any part of its content has been published or has been accepted elsewhere. It is not being submitted to any other journal. We believe the paper may be of particular interest to the readers of your journal as it is the first time of ××××××研究的精华所在 Thank you very much for your reconsidering our revised manuscript for potential publication in Fitoterapia. We are looking forward to hearing from you soon. Correspondence should be addressed to Jinhui Yu at the following address, phone and fax number, and email address. 地址、学院、学校名称 Phone: + 86×××××× Fax number: + 86571××××××
口语常用背诵素材 一，喜好和厌恶： 1.（释放压力）I guess most young people enjoy listening to music. It’s a perfect way to reduce stress/relieve stress. (*It’s a perfect stress-buster.) 2.（休闲）I think the best way to relax and kill time (kick back and relax) is to be with friends. Chatting with them helps me unwind/wind down (* Chatting with them is very therapeutic). 3.（放松）I found it pretty relaxing to flick through a magazine before going to bed (*before hitting the sack/hitting the hay). 4.（运动）Jogging on sunny days and simply basking in the sun(bathing in the sun) is super enjoyable(pleasurable). /Jogging is my favorite workout. It can always cheer me up after I’ve been down and depressed. And it can help me shed some unwanted weight. 5.（喜欢，提升心情）I’m quite into watching sitcom (I’m fascinated by, I’m crazy about, I adore, I’m very fond of...). Spending 20 minutes in front of the screen and having a good laugh after dinner really puts me in a better mood/ switch my mood/ lift my spirits. 6.（天气）I fancy spring most compared to the other three. Summer is simply too hot and stuffy (*muggy), and you can’t stay out for two minutes without getting sweaty and smelly. Autumn is too dry and winter too freezing cold. 7.（电影）I’m a movie buff (Movies are my biggest pastime), and I would either catch one on my couch or go to the movie theatre when they have the one I like on the big screen./ It's a great form of relaxation for me to while away the hours of a long flight, to keep my family together on the sofa, and to give me a bit of a thrill. 8.（无聊困难）I’m terrible at what I study now./(History is never my forte/ my strong suit). The classes are kind of a drag (It’s super dull/ *It’s mind-numbing), and there’s always loads of (tons of) homework to do. Memorizing those facts and years is a lot of effort (is tricky; is no picnic; is challenging for me). 9.（不能忍）I can’t stand (I hate, I totally dislike) the busy traffic in my city. I’m sick and tired of always getting stuck in traffic for a long time during rush hours. It really bothers me (It drives me crazy, *It drives me up the wall). 10. （受欢迎）Hip-hop is really trendy (is catching on, is all the rage) among young people these days. 二，时间和地点 11. （优点）What’s great about my home town is that there are plenty of shopping malls, coz I’m a shopaholic and I can shop for hours. 12. （远）The stadium is quite far away from where I live, and every time I want to do there, it takes me roughly 40 minutes by bus to arrive. (It’s one-hour drive from the city center.) 13. （方便）My apartment is in the center/heart of the city, a handy location where I can find supermarkets and clubs right on my doorstep. It’s a bit noisy though. 14. （近）I’m a movie-goer and and there’s a movie theater pretty close to my home, so I go there quite often (frequently). (close to my home= *within walking distance of my home , *in close proximity to my home) 15. （经常）I have a heavy workload at school, so I have to go to the library to study pretty much
1、新闻要素：不可忽略5W1H。（Who、What、When、Where、Why、How） 2、新闻构成：题、文、图、表。 3、题：简要、突出、吸引人。 4、文：导语100至200字：开宗明义，人事时地物。 5、主体300至500字：深入浅出，阐扬主旨。 6、结语100字：简洁有力，强调该新闻的意 义与影响，或预告下阶段活动。7、图：视需要加入有助于读者理解的图片。 8、表：视需要加入有助于读者理解的表格。9、写作要律：具有新闻价值、正确的格式、动人的标题。简洁切要的内容、平易友善的叙述、高度可读性、篇 幅以1至2页为宜（一页尤佳）。写作技巧：清晰简洁、段落分明、使用短句、排版清爽。切忌偏离事实、交代不清、内容空洞。一篇好的新闻稿除了必须具有 新闻价值、把握主诉求与正确的格式外，行文应力求简洁切要，叙述应有事实基础，文稿标题则以简要、突出、吸引人为原则，用字要避免冷僻艰深，以提高文 稿的可读性。此外，篇幅也不宜长篇大论，一般以1至2页为原则，必要时可以加入图表，增加文稿的专业性，切忌内容空洞、语意不清、夸大不实。 倒金字塔结构是绝大多数客观报道的写作规则，被广泛运用到严肃刊物的写作 中，同时也是最为常见和最为短小的新闻写作叙事结构。内容上表现在在一篇新闻中，先是把最重要、最新鲜、最吸引人的事实放在导语中，导语中又往往是将 最精彩的内容放在最前端；而在新闻主体部分，各段内容也是依照重要性递减的 顺序来安排。犹如倒置的金字塔，上面大而重，下面小而轻。此种写作方式是目 前媒体常用的写作方式，亦即将新闻中最重要的消息写在第一段，或是以「新闻提要」的方式呈现在新闻的最前端，此种方式有助于媒体编辑下标题，亦有助于阅听人快速清楚新闻重点。基本格式（除了标题）是：先在导语中写一个 新闻事件中最有新闻价值的部分（新闻价值通俗来讲就是新闻中那些最突出，最
Dear Editors and Reviewers, Thank you for your letter and comments on our manuscript titled “Temporal variability in soil moisture after thinning in semi-arid Picea crassifolia plantations in northwestern China” (FORECO_2017_459). These comments helped us improve our manuscript, and provided important guidance for future research. We have addressed the editor’s and the reviewers’comments to the best of our abilities, and revised text to meet the Forest Ecology and Management style requirements. We hope this meets your requirements for a publication. We marked the revised portions in red and highlighted them yellow in the manuscript. The main comments and our specific responses are detailed below: Editor: Please explain how the results in this paper are significantly different from those in Zhu, X., He, Z.B., Du, J., Yang, J.J., Chen, L.F., 2015. Effects of thinning on the soil moisture of the Picea crassifolia plantation in Qilian Mountains. Forest Research. 28, 55–60.)
雅思口语素材 Document serial number【LGGKGB-LGG98YT-LGGT8CB-LGUT-
Useful Expressions: Words and phrases Friends and communication: solidify/ strengthen/ enhance/ promote communication / connection with mutual understanding relationship network/circle of f r i e n d s cultivate/develop friendship with s b . keep steady relationship with sb. establish interpersonal networksac build up the social circle spur message transmission Knowledge and experience widen one’s outlook broaden one’s vision/horizon acquire knowledge and skills comprehensive/overall quality
expand/enlarge one’s scope of knowledge knowledge reserve/base/storage theoretical knowledge practical skills social experience broaden one’s knowledge base promote one’s overall/ comprehensive competence accumulate experiences learn lessons from past experiences Work and experience the scarcity of employment o p p o r t u n i t i lay the foundations for career p r o s p e r i t y
Case 1 Dear Editor, We would like to submit the enclosed manuscript entitled "GDNF Acutely Modulates Neuronal Excitability and A-type Potassium Channels in Midbrain Dopaminergic Neurons", which we wish to be considered for publication in Nature Neuroscience. GDNF has long been thought to be a potent neurotrophic factor for the survival of midbrain dopaminergic neurons, which are degenerated in Parkinson’s disease. In this paper, we report an unexpected, acute effect of GDNF on A-type potassium channels, leading to a potentiation of neuronal excitability, in the dopaminergic neurons in culture as well as in adult brain slices. Further, we show that GDNF regulates the K+ channels through a mechanism that involves activation of MAP kinase. Thus, this study has revealed, for the first time, an acute modulation of ion channels by GDNF. Our findings challenge the classic view of GDNF as a long-term survival factor for midbrain dopaminergic neurons, and suggest that the normal function of GDNF is to regulate neuronal excitability, and consequently dopamine release. These results may also have implications in the treatment of Parkinson’s disease. Due to a direct competition and conflict of interest, we request that Drs. XXX of Harvard Univ., and YY of Yale Univ. not be considered as reviewers. With thanks for your consideration, I am Sincerely yours, case2 Dear Editor, We would like to submit the enclosed manuscript entitled "Ca2+-binding protein frequenin mediates GDNF-induced potentiation of Ca2+ channels and transmitter release", which we wish to be considered for publication in Neuron. We believe that two aspects of this manuscript will make it interesting to general readers of Neuron. First, we report that GDNF has a long-term regulatory effect on neurotransmitter release at the neuromuscular synapses. This provides the first physiological evidence for a role of this new family of neurotrophic factors in functional synaptic transmission. Second, we show that the GDNF effect is mediated by enhancing the expression of the Ca2+-binding protein frequenin. Further, GDNF and frequenin facilitate synaptic transmission by enhancing Ca2+ channel activity, leading to an enhancement of Ca2+ influx. Thus, this study has identified, for the first time, a molecular target that mediates the long-term, synaptic action of a neurotrophic factor. Our findings may also have general implications in the cell biology of neurotransmitter release. 某杂志给出的标准Sample Cover Letter Case 3 Sample Cover Letter Dear Editor of the : Enclosed is a paper, entitled "Mobile Agents for Network Management." Please accept it as a candidate for publication in the . Below are our responses to your submission requirements. 1. Title and the central theme of the article. Paper title: "Mobile Agents for Network Management." This study reviews the concepts of mobile agents and distributed network management system. It proposes a mobile agent-based implementation framework and creates a prototype system to demonstrate the superior performance of a mobile agent-based network over the conventional client-server architecture in a large network environment.