The effects of covert attention and stimulus complexity on the P3 response during an auditory continuous performance task

Effects of a Manual Response Requirement on Early and Late Correlates of Auditory Awareness

In hearing, two neural correlates of awareness are the auditory awareness negativity (AAN) and the late positivity (LP). These correlates of auditory awareness are typically observed with tasks in which subjects are required to report their awareness with manual responses. Thus, the correlates may be confounded by this manual response requirement. We manipulated the response requirement in a tone detection task (N = 52). Tones were presented at each subject's individual awareness threshold while high-density electroencephalography (EEG) activity was recorded. In one response condition, subjects pushed a button if they were aware of the tone and withheld responding if they were unaware of the tone. In the other condition, subjects pushed a button if they were unaware of the tone and withheld responding if they were aware of the tone. To capture AAN and LP, difference waves were computed between aware and unaware trials, separately for trials in which responses were required and trials in which responses were not required. Results suggest that AAN and LP are unaffected by the response requirement. These findings imply that in hearing, early and late correlates of awareness are not confounded by a manual response requirement. Furthermore, the results suggest that AAN originates from bilateral auditory cortices, supporting the view that AAN is a neural correlate of localized recurrent processing in early sensory areas.

Stimulus complexity matters when you hear your own voice: Attention effects on self-generated voice processing

The ability to discriminate self- and non-self voice cues is a fundamental aspect of self-awareness and subserves self-monitoring during verbal communication. Nonetheless, the neurofunctional underpinnings of self-voice perception and recognition are still poorly understood. Moreover, how attention and stimulus complexity influence the processing and recognition of one's own voice remains to be clarified. Using an oddball task, the current study investigated how self-relevance and stimulus type interact during selective attention to voices, and how they affect the representation of regularity during voice perception. Event-related potentials (ERPs) were recorded from 18 right-handed males. Pre-recorded self-generated (SGV) and non-self (NSV) voices, consisting of a nonverbal vocalization (vocalization condition) or disyllabic word (word condition), were presented as either standard or target stimuli in different experimental blocks. The results showed increased N2 amplitude to SGV relative to NSV stimuli. Stimulus type modulated later processing stages only: P3 amplitude was increased for SGV relative to NSV words, whereas no differences between SGV and NSV were observed in the case of vocalizations. Moreover, SGV standards elicited reduced N1 and P2 amplitude relative to NSV standards. These findings revealed that the self-voice grabs more attention when listeners are exposed to words but not vocalizations. Further, they indicate that detection of regularity in an auditory stream is facilitated for one's own voice at early processing stages. Together, they demonstrate that self-relevance affects attention to voices differently as a function of stimulus type.

Electrophysiological correlates of cognition improve with nap during sleep deprivation

The efficacy of a 30-min nap as a countermeasure in the reduction of cognitive decline following 24 h of sleep deprivation (SD) on subjective sleepiness scales, event-related potential (ERP) P300, and contingent negative variation (CNV) was evaluated. The experiment was performed in three sessions on different days between 7 and 8 a.m. on nine normal, healthy males, of age 25-30 years: Session 1. Baseline recordings; Session 2, after one night's total sleep deprivation, and; Session 3, after 1 week of Session 1, following one night's sleep deprivation along with a 30-min nap opportunity between 1.00 and 3.00 a.m. Subjective sleepiness scores increased after SD as compared to baseline, but reduced significantly after nap (P < 0.05). There was an increase in P3 peak latency of ERP following SD (16%, P < 0.01), which was reduced with nap (10.7%, P < 0.05).There was an increase in CNV M1 peak latency after SD (18%) which decreased with the use of nap (12.5%) (P < 0.01). The CNV reaction time increased following SD (39.3%) and decreased with the use of nap (24%) (P < 0.01). No significant effects on ERP N1, P1, N2 latencies, P2 and P3 amplitudes and CNV N1, P3, M2 peak latencies and M1, and M2 amplitudes were observed. It was concluded that a 30-min nap, between 1.00 and 3.00 a.m. during night SD, reduces the cognitive decline following 24 h of SD in terms of its electro-physiological correlates. The study is of applied value in optimization of cognitive performance in professions demanding night work schedules.

What's behind an inference? An EEG study with conditional arguments

Conditional reasoning studies typically involve presenting a major conditional premise (If P then Q), a minor premise (P) and a conclusion (Q). We describe how most fMRI studies investigate reasoning and point out that these studies neglect to take into consideration the temporal sequence of cognitive steps generated by the interaction of the premises. The present study uses EEG to address this issue and compares the processing of the minor premise P when it is presented before vs. after the conditional statement (P; If P then Q vs. If P then Q; P). When the minor premise comes after the conditional statement and matches the antecedent its processing results in a P3b component, known to reflect the satisfaction of expectations, and in two later components, a PSW component and a CNV component. These two components are discussed in light of a conclusion generation phase and a maintenance phase. We also investigated the effect of violating expectations through the presentation of a minor premise that mismatches the antecedent of the conditional statement (If P then Q; R). The data indicate that the processing of such a premise yields an N2 component which is known to reflect perceptual conflict.

Behavioural and neurophysiological correlates of dyslexia in the continuous performance task

OBJECTIVE

To investigate whether attentional difficulties are a "core" feature of developmental Dyslexia.

METHODS

Behavioural indices and event related potentials (ERPs) were recorded from 10 dyslexic participants (ages 15.5-17.4) and 10 control participants (ages 14.4-18.3) in the Continuous Performance Task (CPT), an established test of attentional performance. Participants were screened to ensure that none was diagnosable as attention deficit (ADHD).

RESULTS

There were no significant differences in mean reaction time, error rate or sustained attention between the groups. By contrast, the P3 amplitude was significantly smaller and its latency significantly longer for the dyslexic group. This component was significantly lateralised in controls, whereas in dyslexics it was symmetrical.

CONCLUSIONS

Under the relatively light workload conditions of the CPT, "pure" dyslexic participants showed no behavioural signs of attentional difficulties. The attenuated, delayed and symmetrical ERPs in our dyslexic group may reflect abnormal information processing in the right parietal lobe and abnormal interhemispheric asymmetry in Dyslexia.

SIGNIFICANCE

The behavioural data suggest that abnormal attentional performance is not a "core" feature of developmental Dyslexia, and highlight the importance of distinguishing between dyslexic participants with and without ADHD symptoms. The presence of electrophysiological markers of Dyslexia in CPT revealed the atypical brain organisation that characterises "pure" Dyslexia.