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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Reaction times and event-related potentials in correct and incorrect trials were studied in a bimanual choice reaction task. In a focused attention (FA) condition, the stimulus modality was constant (visual or auditory); in a divided attention (DA) condition, the modality was varied at random from trial to trial. Stimulus- and response-triggered averages were computed from the midline EEG leads. In error trials, the ERP amplitude was reduced in the P300 range (300-500 msec) and enhanced in the slow wave range (500-700 msec) compared to correct reaction trials. Difference plots between the ERPs (incorrect minus correct reaction trials) revealed a large fronto-central negativity ("NE") and a parieto-occipital "slow wave." These components appeared larger in the response-triggered averages. We believe that they reflect two different stages of error processing. After auditory stimuli the NE peaked much later for DA than for FA, which supports the idea of an asymmetrical allocation of processing resources to the disadvantage of the auditory modality in our DA condition.
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PMID:Effects of crossmodal divided attention on late ERP components. II. Error processing in choice reaction tasks. 171 80

The present study investigated brain mechanisms underlying the perception of illusory contours, using recordings of event-related potentials of the brain (ERPs) in right-handed individuals. Forty different stimuli were presented randomly 1600 times in foveal vision; twenty of them produced the perception of illusory contours of a Kanizsa square, the remaining were obtained rotating outwards the inducers and they did not produce any illusory percept. Half of them had white inducers on a black background and vice versa; half of them were symmetrical and the other half asymmetrical. In lateral occipital areas illusory percepts produced larger evoked responses starting as early as 145 ms post-stimulus with the N1 peak. ERP data did not provide evidence of right-sided lateralisation of the processes underlying illusory contours formation at sensory level, as suggested by some neuroimaging and neuropsychological studies. The two cerebral hemispheres were differently activated while the subjective patterns formation progressed through neural processing stages. Indeed, brain response to illusory contours was more pronounced in the left occipital area at N2 component level (about 250 ms post-stimulus) and at right parietal sites at the latency of P300 component. Both background luminance and stimulus symmetry interacted with illusory boundaries formation. Present results confirm the hypothesis that the integration of contours arises at early stages of visual processing and highlight the primary role of edges continuity and boundary alignment in illusory contours perception.
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PMID:Electrophysiological indexes of illusory contours perception in humans. 1174 78

Previous work found a significant reduction of the amplitude of the N2pc ERP component during the attentional blink in response to lateral visual targets, suggesting that the allocation of attention to visual targets is impaired during the attentional blink. Recent theorizing on the processes reflected by the N2pc suggests the possibility of distinct sets of neural mechanisms underlying its generation, one responsible for target activation, and one for distractor inhibition. To disentangle whether either or both of these mechanisms are impaired during the attentional blink, an RSVP sequence of circles, equidistant from fixation was used. The first target frame (T1) contained the same repeated target colour circle and target whereas the second target frame (T2) contained a distractor colour singleton as well as a target colour singleton. Only the target or only the distractor was presented at a lateral position; the other singleton was presented on the vertical midline so as not to elicit any event-related lateralization. Impaired T2 report accuracy at a short stimulus-onset asynchrony (SOA) was accompanied by a significant delay of the N2pc to lateral T2 targets when compared to a long SOA condition. No such delay was found when the lateralized stimulus was a distractor, suggesting that the attentional blink impacts attention allocation to targets, not distractors. We also observed a lateralized component earlier than the N2pc, a posterior contralateral positivity (Ppc) that did not depend on T1-T2 SOA and that was elicited by both lateral targets and distractors. We conclude that, contrary to N2pc, the Ppc likely reflects activity of bottom-up mechanisms responding unselectively to asymmetrical visual displays.
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PMID:The attentional blink freezes spatial attention allocation to targets, not distractors: evidence from human electrophysiology. 2460 98

The present study assessed brain activity changes related to perception of consonant and dissonant chords by musicians and non-musicians. Perception of dissonant chords in non-musicians was accompanied by increase of lower theta activity over right anterior regions, while consonant chords induced greater theta activity over left anterior regions; this pattern of asymmetrical activation was not observed in musicians. ERP analysis revealed that musicians had greater amplitude of early components (P100, N200) than non-musicians irrespective of chord type. The obtained results reflect more efficient musical harmony processing and, possibly, less emotional perception of chords in musicians.
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PMID:[Event-related brain activity changes to consonant and dissonant chords in musicans and non-musicans]. 2543 83

Traumatic brain injury (TBI) is a major public health concern that affects 69 million individuals each year worldwide. Neuropsychologists report that up to 40% of individuals undergoing evaluations for TBI may be malingering neurocognitive deficits for a compensatory reward. The memory recognition test of malingering detection is effective but can be coached behaviorally. There is great need to develop a novel neural based method for discriminating fake from true brain injury. Here we test the hypothesis that decision making of faking memory deficits prolongs frontal neural responses. We applied an advanced method measuring decision latency in milliseconds for discriminating true TBI from malingerers who fake brain injury. To test this hypothesis, latencies of memory-related brain potentials were compared among true patients with moderate or severe TBI, and healthy age-matched individuals who were assigned either to be honest or faking memory deficit. Scalp signals of electroencephalography (EEG) were recorded with a 32-channel cap during an Old/New memory recognition task in three age- and education-matched groups: honest (n = 12), malingering (n = 15), and brain injured (n = 14) individuals. Bilateral fractional latencies of late positive ERP at frontal sites were compared among the three groups under both studied (Old) and non-studied (New) memory recognition conditions. Results show a significant difference between the fractional latencies of the late positive component during recognition of studied items in malingerers (averaged latencies = 396 ms) and the true brain injured subjects (mean = 312 ms) in the frontal sites. Only malingers showed asymmetrical frontal activity compared to the two other groups. These new findings support the hypothesis that that additional frontal processing of malingering individuals is measurably different from those of actual patients with brain injury. In contrast to our previous reported method using difference waves of amplitudes at frontal to posterior midline sites during new items recognition (Vagnini et al., 2008), there was no significant latency difference among groups during recognition of New items. The current method using delayed left frontal neural responses during studied items reached sensitivity of 80% and specificity of 79% in detecting malingers from true brain injury.
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PMID:Discriminating Fake From True Brain Injury Using Latency of Left Frontal Neural Responses During Old/New Memory Recognition. 3161 60