Neural correlates of audiovisual integration of semantic category information

Previous studies have found a late frontal-central audiovisual interaction during the time period about 150-220 ms post-stimulus. However, it is unclear to which process is this audiovisual interaction related: to processing of acoustical features or to classification of stimuli? To investigate this question, event-related potentials were recorded during a words-categorization task with stimuli presented in the auditory-visual modality. In the experiment, congruency of the visual and auditory stimuli was manipulated. Results showed that within the window of about 180-210 ms post-stimulus more positive values were elicited by category-congruent audiovisual stimuli than category-incongruent audiovisual stimuli. This indicates that the late frontal-central audiovisual interaction is related to audiovisual integration of semantic category information.     

Anterior cingulate cortex activation is related to learning potential on the WCST in schizophrenia patients

The remediation of executive function in patients with schizophrenia is important in rehabilitation because these skills affect the patient's capacity to function in the community. There is evidence that instructional techniques can improve deficits in the Wisconsin Card Sorting Test (WCST) in some schizophrenia patients. We used a standard test/training phase/standard test format of the WCST to classify 36 schizophrenia patients as high-achievers, learners or non-retainers. All healthy controls performed as high-achievers. An event-related fMRI design assessed neural activation patterns during post-training WCST performance. Patients showed a linear trend between set-shifting related activation in the anterior cingulate cortex and learning potential, i.e. increased activation in high-achievers, a trend for increased activation in learners, and no activation in non-retainers compared to controls. In addition, activation in the temporoparietal cortex was highest in patients classified as learners, whereas in non-retainers activation was increased in the inferior frontal gyrus compared to controls and high-achieving patients. These results emphasize the relevance of the ACC's neural integrity in learning set-shifting strategies for patients with schizophrenia. Also, our results support the hypothesis that compensatory neural activation in patients with schizophrenia helps them to catch up with healthy controls on cognitive tasks.     

Evidence for mental ability related individual differences in the attentional blink obtained by an analysis of the P300 component

Attentional blink (AB) refers to impaired identification of a target (T2) when this target follows a preceding target (T1) after about 150-450 ms within a stream of rapidly presented stimuli. Previous research on a possible relation between AB and mental ability (MA) turned out to be highly ambiguous. The present study investigated MA-related individual differences in consolidation of T2 in working memory during the AB as indicated by the P300 component of the event-related potential. Thirty high (HA) and 30 low MA (LA) female participants performed an AB task while their brain activity was recorded. The AB did not differ between the two groups. HA individuals exhibited a larger P300 amplitude and longer P300 latencies during the AB suggesting higher mental effort. This higher mental effort, however, did not result in better performance presumably because of more competition between target and distractor stimuli in HA than LA individuals.     

Age-related differences in working memory: ERPs reveal age-related delays in selection- and inhibition-related processes

Faulty inhibition is implicated in age-related working memory decline. ERP signs of selection and inhibition of items in working memory (WM) are, respectively, a cue-locked parietal positivity (～350 ms) and a probe-locked frontal negativity (～520 ms). To determine when in the older age range differences in selective and inhibitory processes might occur, ERPs were recorded in a WM task from 20 young (20–28), 20 young–old (60–70), and 20 old–old (71–82) adults. A 4-digit display was followed by a cue indicating which 2 of 4 digits were relevant. Proactive interference (PI), the reaction time difference between a matching and non-matching to-be-ignored digit was larger, relative to the young, in both older groups. Compared to the young, both the cue- and probe-locked activities were prolonged in the older groups. Although there were no topographic differences among the age groups, the prolonged PI and associated ERPs suggest a relative age-related deficit in inhibition.     

Investigating letter recognition in the brain by varying typeface: An event-related potential study

We aimed to investigate the contributions of visual letter form and abstract letter identity to the time course of letter recognition, by manipulating the typeface (i.e. font) in which letters were presented. Twenty-six adult participants completed a modified one-back task, where letters where presented in easy-to-read typefaces (“fluent” letter stimuli) or difficult-to-read typefaces (“disfluent” letter stimuli). Task instructions necessitated that participant’s focus on letter identity not visual letter form. Electroencephalography was collected and event-related potentials (ERPs) were calculated relative to letter stimuli. It was found that typeface affected both early-mid (N1 amplitude and P2–N2 amplitude and latency) and late processing (450–600 ms), thereby including time points whereby it is theorised that abstract identity is extracted from visual letter form (that is, 300 ms post-stimulus). Visual features of the letter therefore affect its processing well beyond the currently theorised point at which abstract information is extracted; which could be explained by a feedback loop between abstract letter representations and lower-level visual form processing units, which is not included in current cognitive reading models.     

内隐多效性选择的ERP证据

采用事件相关电位技术,考察内隐多效性选择及其神经机制。被试的任务是认真观看配对的纯色图片刺激,并进行分类按键反应。实验结果发现,在P2上,积极启动刺激比对照刺激激发了更大的P2波幅; 对比对照刺激,积极启动刺激在左脑、大脑中部和后脑诱发了更大的P2波幅,其中右脑的效应最大。在N2上,积极启动刺激比对照刺激激发了更小的N2波幅; 对比对照刺激,积极启动刺激在左脑、大脑中部和后脑诱发了更小的N2波幅,其中右脑的效应最大。在P3上,积极启动刺激比对照刺激激发了更大的P3波幅; 对比对照刺激,积极启动刺激在左脑、大脑中部和后脑诱发了更大的P3波幅,其中右脑的效应最大。研究结果表明当外显目标与内隐目标同时被呈现时,被试趋向于做多效性选择,这可能表明无意识信息加工具有相当大的权重。且右后部脑区可能是加工多效性刺激的核心和关键区域,P3成分可能反应了内隐多效性选择的精细加工过程,能够作为内隐多效性选择的有效的ERPs指标。     

Force versus fury: Sex differences in the relationships among physical and psychological threat potential,the facial width‐to‐height ratio,and judgements of aggressiveness

Individuals with larger facial width‐to‐height ratios (FWHRs) are judged as more threatening, and engage in more threat‐related behavior, than do individuals with smaller FWHRs. Here we identified components of threat potential that are related to the FWHR. In Study 1, the FWHR was correlated positively with physical threat potential (bicep size) in women and with both physical and psychological (anger proneness) threat potential in men. Behavioral aggression was measured in a subset of these participants using the Point Subtraction Aggression Paradigm (costly aggression) and a Money Allocation Task (non‐costly aggression). Psychological (but not physical) threat potential predicted non‐costly aggression and physical (but not psychological) threat potential predicted costly aggression. In Study 2, a separate set of participants judged the anger proneness, strength, or aggressiveness of male participants photographed in Study 1. Participants’ judgements of all three characteristics were associated with the FWHR, and there were sex differences in how aggressiveness was conceptualized (for women, aggressiveness was associated with anger proneness, for men, aggressiveness was associated with strength). These results are consistent with the hypothesis that the FWHR may be an adaptation to cue the threat potential of men.

     

Hypnotizing Libet: Readiness potentials with non-conscious volition

The readiness potential (RP) is one of the most controversial topics in neuroscience and philosophy due to its perceived relevance to the role of conscious willing in action. Libet and colleagues reported that RP onset precedes both volitional movement and conscious awareness of willing that movement, suggesting that the experience of conscious will may not cause volitional movement (Libet, Gleason, Wright, & Pearl, 1983). Rather, they suggested that the RP indexes unconscious processes that may actually cause both volitional movement and the accompanying conscious feeling of will (Libet et al., 1983; pg. 640). Here, we demonstrate that volitional movement can occur without an accompanying feeling of will. We additionally show that the neural processes indexed by RPs are insufficient to cause the experience of conscious willing. Specifically, RPs still occur when subjects make self-timed, endogenously-initiated movements due to a post-hypnotic suggestion, without a conscious feeling of having willed those movements.     

An investigation of DIF mechanisms in the context of differential testlet effects

This study investigated differential item functioning (DIF) mechanisms in the context of differential testlet effects across subgroups. Specifically, we investigated DIF manifestations when the stochastic ordering assumption on the nuisance dimension in a testlet does not hold. DIF hypotheses were formulated analytically using a parametric marginal item response function approach and compared with empirical DIF results from a unidimensional item response theory approach. The comparisons were made in terms of type of DIF (uniform or non‐uniform) and direction (whether the focal or reference group was advantaged). In general, the DIF hypotheses were supported by the empirical results, showing the usefulness of the parametric approach in explaining DIF mechanisms. Both analytical predictions of DIF and the empirical results provide insights into conditions where a particular type of DIF becomes dominant in a specific DIF direction, which is useful for the study of DIF causes.