Benoit Brisson

Failure of temporal selectivity: Electrophysiological evidence for (mis)selection of distractors during the attentional blink

The attentional blink (AB) refers to the impairment in accurate report of a second target (T2) when presented shortly after a first target (T1) in a rapid serial visual presentation of distractors. The goal of the present study was to determine whether the AB is caused by a failure in early selection processes, which leads to the selection and consolidation of the wrong item in working memory, by measuring the frequency-related P3 to T2 and to T2 + 1. During the AB, an attenuation of the P3 to T2 was observed, as well as an increase in the amplitude of the P3 to T2 + 1. Whereas the P3 to T2 was observed only when T2 was correctly reported, the P3 to T2 + 1 was observed only in trials where T2 was incorrectly reported, and its amplitude was correlated to individual differences in misselection rate. These results support the claim that failure of temporal selection underlies the AB.

The tree to the left, the forest to the right: Political attitude and perceptual bias

A prominent model suggests that individuals to the right of the political spectrum are more cognitively rigid and less tolerant of ambiguity than individuals to the left. On the basis of this model, we predicted that a psychological mechanism linked to the resolution of visual ambiguity--perceptual bias--would be linked to political attitude. Perceptual bias causes western individuals to favour a global interpretation when scrutinizing ambiguous hierarchical displays (e.g., alignment of trees) that can be perceived either in terms of their local elements (e.g., several trees) or in terms of their global structure (e.g., a forest). Using three tasks (based on Navon-like hierarchical figures or on the Ebbinghaus illusion), we demonstrate (1) that right-oriented Westerners present a stronger bias towards global perception than left-oriented Westerners and (2) that this stronger bias is linked to higher cognitive rigidity. This study establishes for the first time that political ideology, a high-level construct, is directly reflected in low-level perception. Right- and left-oriented individuals actually see the world differently.

Task switching mediates direct interference of intertarget distractors in the attentional blink: An event-related potential study

The attentional blink (AB) refers to the difficulty in reporting a second target (T2) presented shortly after a first target (T1) in a stream of distractors. The goal of the present study was to investigate distractor-based interference in the AB by recording the P3 component of the event-related potential to both targets. An intertarget distractor was presented at lag 1 (T1+1), at lag 2 (T1+2), or at neither of these two lags (no distractor). T2 was always presented at lag 3, as the last item in the stream. In two experiments, the P3 from T1 was attenuated in the T1+1 condition compared to the two other distractor conditions. In absence of a task switch (Experiment 1), the P3 from T2 was delayed in both the T1+1 and T1+2 conditions. In the presence of a task switch (Experiment 2), the P3 from T2 was delayed only in the T1+1 condition. Results demonstrate that intertarget distractors can modulate the AB directly but only in absence of a task switch.

Electrophysiological correlates of motor sequence learning

BackgroundThe Error-related negativity (ERN) is a component of the event-related brain potentials elicited by error commission. The ERN is thought to reflect cognitive control processes aiming to improve performance. As previous studies showed a modulation of the ERN amplitude throughout the execution of a learning task, this study aims to follow the ERN amplitude changes from early to late learning blocks in relation with concomitant motor sequence learning using a serial reaction time (SRT) task. Twenty-two healthy participants completed a SRT task during which continuous EEG activity was recorded. The SRT task consists of series of stimulus-response pairs and involves motor learning of a repeating sequence. Learning was computed as the difference in mean response time between the last sequence block and the last random blocks that immediately follows it (sequence-specific learning). Event-related potentials were analysed to measure ERN amplitude elicited by error commission.ResultsMean ERN amplitude difference between the first four learning blocks and the last four learning blocks of the SRT task correlated significantly with motor sequence learning as well as with overall response time improvement, such that those participants whose ERN amplitude most increased through learning blocks were also those who exhibited most SRT task improvements. In contrast, neither sequence-specific learning nor overall response time improvement across learning blocks were found to be related to averaged ERN amplitude from all learning blocks.ConclusionFindings from the present study suggest that the ERN amplitude changes from early to late learning blocks occurring over the course of the SRT task, as opposed to the averaged ERN amplitude from all learning blocks, is more closely associated with learning of a motor sequence. These findings propose an improved electrophysiological marker to index change in cognitive control efficiency during motor sequence learning.

Long-Term Effects of Concussions on Psychomotor Speed and Cognitive Control Processes During Motor Sequence Learning

In asymptomatic multiple-concussion athletes, studies evidenced long-term impairments in psychomotor speed, motor sequence learning, and cognitive control processes, as indexed by the Error Negativity (Ne), also commonly referred to as the Error-related Negativity (ERN). In healthy controls, motor sequence learning during a Serial Reaction Time (SRT) task is associated with an increase in Ne/ERN amplitude. The objective of this paper is to investigate whether concussion effects on cognitive control are associated with sequence learning changes in asymptomatic multi-concussion athletes. Thirty-seven athletes (18 nonconcussed; 19 concussed) completed a SRT task during which continuous electroencephalographic (EEG) activity was recorded. Ne/ERN amplitude modulation from early to late learning blocks of the task was measured. Median reaction times (RTs) were computed to assess psychomotor speed and motor sequence learning. Psychomotor speed was significantly reduced in concussed athletes. Accentuated Ne/ERN amplitude from early to late learning blocks significantly correlated with motor sequence learning in nonconcussed athletes. In contrast, Ne/ERN amplitude was found to decrease significantly with task progression in concussed athletes who nonetheless achieved normal motor sequence learning. Multiple concussions detrimentally affect psychomotor speed. Unlike nonconcussed athletes, motor sequence learning in multi-concussion athletes was not associated with Ne/ERN amplitude modulation, indicating that cognitive control processes do not centrally contribute to learning of a motor sequence after repeated concussions.

Sexual Abuse Exposure Alters Early Processing of Emotional Words: Evidence from Event-Related Potentials

This study aimed to compare the time course of emotional information processing between trauma-exposed and control participants, using electrophysiological measures. We conceived an emotional Stroop task with two types of words: trauma-related emotional words and neutral words. We assessed the evoked cerebral responses of sexual abuse victims without post-traumatic stress disorder (PTSD) and no abuse participants. We focused particularly on an early wave (C1/P1), the N2pc, and the P3b. Our main result indicated an early effect (55–165 ms) of emotionality, which varied between non-exposed participants and sexual abuse victims. This suggests that potentially traumatic experiences modulate early processing of emotional information. Our findings showing neurobiological alterations in sexual abuse victims (without PTSD) suggest that exposure to highly emotional events has an important impact on neurocognitive function even in the absence of psychopathology.

Intertarget Distractors and Input Filter Compatibility in the Attentional Blink

The Attentional Blink (AB) refers to the impairment in report accuracy of a second target when presented shortly after a first target in a stream of distractors. The main goal of the present study was to understand the nature of intertarget distractor interference in the AB by manipulating the compatibility of the distractor immediately trailing the first target and the attentional filter set to select targets preferentially for conscious report. Results show that distractor/filter compatibil - ity had no impact on the AB, except when the distractor was of the same response category as the targets. In these conditions, the AB was larger in compatible than incompatible conditions, an effect that could be explained by an increase in misselection errors. Results are discussed in relation to extant theories of the AB.