Hisao Maekawa

Electrophysiological abnormalities of spatial attention in adults with autism during the gap overlap task

OBJECTIVE We evaluated event-related potentials (ERPs) elicited by attentional disengagement in individuals with autism. METHODS Sixteen adults with autism, 17 adults with mental retardation and 14 healthy adults participated in this study. We recorded the pre-saccade positive ERPs during the gap overlap task under which a peripheral stimulus was presented subsequent to a stimulus in the central visual field. Under the overlap condition, the central stimulus remained during the presentation of the peripheral stimulus and therefore participants need to disengage their attention intentionally in order to execute the saccade to the peripheral stimulus due to the preservation of the central stimulus. RESULTS The autism group elicited significantly higher pre-saccadic positivity during a period of 100-70 ms prior to the saccade onset than the other groups only under the overlap condition. The higher amplitude of pre-saccadic positivity in the overlap condition was significantly correlated with more severe clinical symptoms within the autism group. CONCLUSIONS These results demonstrate electrophysiological abnormalities of disengagement during visuospatial attention in adults with autism which cannot be attributed to their IQs. SIGNIFICANCE We suggest that adults with autism have deficits in attentional disengagement and the physiological substrates underlying deficits in autism and mental retardation are different.

Spatial attention in individuals with pervasive developmental disorders using the gap overlap task

The present study examined spatial attention in individuals with pervasive developmental disorders (PDD) using the gap overlap task and analyzed the express saccade, which is defined by its extremely short reaction time, as a measure of the state of attention. Participants were required to move their eyes to the target stimulus appearing on the left or right side of a fixation point. In this task, participants had to disengage their attention from the central fixation point and shift it to the peripheral target stimulus. In the gap condition, the fixation point disappeared 200 ms before the target stimulus was presented, and in the overlap condition, the fixation point remained while the target stimulus was presented. Saccade latencies were not different between the groups. However, the express saccade was more frequent in the PDD group than in the normal group in the overlap condition. We conclude that individuals with PDD have deficiencies in attentional engagement. Moreover, our study suggests that analysis of the express saccade will be useful in further examinations of attentional processes in PDD.

Speech Perception in Noise Deficits in Japanese Children with Reading Difficulties: Effects of Presentation Rate.

We examined the effects of presentation rate on speech perception in noise and its relation to reading in 117 typically developing (TD) children and 10 children with reading difficulties (RD) in Japan. Responses in a speech perception task were measured for speed, accuracy, and stability in two conditions that varied stimulus presentation rate: high rate and same rate conditions. TD children exhibited significantly more stable responses in the high rate condition than they did in the same rate condition. Multiple regression analyses indicated that response stability in the high rate condition accounted for a unique amount of variance in reading and mora deletion. As a group, children with RD performed less accurately than did TD children in the high rate condition, but not in the same rate condition. Findings suggest that the dependence of speech perception on stimulus context relates to reading proficiency or difficulty in Japanese children. The influences of phonology and orthography of language on the relationships between speech perception and reading are discussed.

EEG coherence pattern during simultaneous and successive processing tasks.

In order to investigate psychophysiological basis of two different types of information processing (simultaneous and successive), we investigated EEG coherence patterns during five tasks of the Das-Naglieri Cognitive Assessment System. The investigation was based on the perspective of the similarities among the tasks of the same processing type and discrepancies between the different processing types. EEG coherence of eighteen volunteers during two simultaneous and three successive tasks varying in task content (verbal-nonverbal) and modality (auditory-visual) was computed. First, we compared the coherence patterns between the tasks of the same processing type, then compared between the tasks of different processing types. Result revealed a specific theta coherence pattern associated with processing type regardless of task contents and modality. Theta coherence during the simultaneous processing showed increased short-range inter-hemispheric connections over central and parietal regions as compared to the successive tasks. Upper beta coherence indicated task-dependent effect regardless of processing types. In addition, our data indicated no hemispheric differences for both processing types. It suggested that confounding of verbal-nonverbal and processing type (simultaneous-successive) dimension could be avoided. Our result presented psychophysiological evidence for the existence of two types of information processing, which has been supported by psychological studies with factor analysis.

Topographic changes of ERP during a CPT-AX task at pre- and post-medication of methylphenidate in children with ADHD

Abstract To examine cerebral process of motor control in children with Attention-Deficit/Hyperactivity Disorder (ADHD; mean age, 11 years), event-related potentials (ERPs) during a cued continuous performance test (CPT-AX) were recorded from ADHD children an hour after psychostimulant (methylphenidate) dosage (Medicated ADHD), and without psychostimulants (Non-Medicated ADHD). These data were compared with ERPs in unmedicated age-matched normal controls (Non-ADHD). Hit rate in Non-medicated ADHD was significantly lower than that in Non-ADHD. However, their performance improved significantly due to psychostimulant medication, up to levels comparable to those of Non-ADHD subjects. In the ERP elicited by nontargets, P2 amplitudes in Non-Medicated ADHD were smaller than in Non-ADHD. Due to medication, P2 amplitudes increased and became comparable to that in Non-ADHD. Medication also improved a delayed onset of the P2 brain electric field in ADHD. Reduced amplitude of ERP in Non-Medicated ADHD suggests a lower activation at this relatively early stage of visual information processing in ADHD. In contrast, enhancement of ERP in Medicated ADHD implies that the medication contributes to allocate resources for orienting their attention to distinguish stimulus relevance, and to inhibit later processing of irrelevant stimuli properly. These results imply that methylphenidate improves response control in ADHD.

Topographic change of ERP due to discrimination of CV syllables with various vowel durations

Abstract This study aims to investigate the cerebral process of discrimination of consonant–vowel (CV) syllables differing in vowel length. The subjects were normal adults. A single human CV syllable (/ma/) and five variants with reduced vowel duration were used as stimuli. EEGs were recorded from 16 scalp locations under the following two conditions: (1) ignore condition: subjects heard stimulus sounds while relaxing and (2) discriminate condition: subjects were asked to discriminate unreduced CV syllable (/ma/) as a target and press the button when they detected it. Regardless of the vowel lengths of the CV syllable, P2 and P3 components were observed in both conditions. With the reduction of the vowel duration, the scalp distributions of P2 shifted from anterior to vertex in the ignore condition and from posterior to vertex in the discriminate condition. Therefore, not only vowel duration but also the task condition affected the generators of the P2 component. Vowel duration also affected the generator of the P3 component. In the ignore condition, the unreduced CV syllable evoked an anterior positive, and CV syllables with reduced vowels evoked posterior positive P3s. However, in the discriminate condition, the P3 component was anterior-negative/posterior-positive distributed as long as the CV syllable was perceived as /ma/. Therefore, the brain electrical fields of the P3 component might reflect cortical discrimination in the categorical hearing of human CV syllables.

The attentional disengagement processing reflected by ERPs and saccade reaction times during a gap task

Abstract In this study, we examined cerebral process of attentional disengagement using ERPs and saccade reaction time (SRT) during a saccadic eye movement task to produce the gap effect. Ten healthy adults participated in this study. Subjects were required to execute saccadic eye movement when the target appeared. In the gap condition, a fixation point disappeared 200 ms prior to the target stimulus presentation. In the overlap condition, a fixation point remained after the target stimulus presentation. ERPs were analyzed separately for target stimulus and saccadic eye movement. SRT in the gap condition was significantly shorter than that in the overlap condition. For the target-locked ERPs in the gap condition, central positivity appeared around 60 ms before the onset of the target stimulus. This would reflect an automatic processing of attentional disengagement elicited by the offset of a fixation point. For the saccade-locked ERPs, pre-saccadic positivities were observed in both conditions. In the overlap condition, it appeared earlier and higher than that in the gap condition. It reflects a processing of attentional disengagement to the fixation point. These results indicated that the cerebral processing of attentional disengagement would be differentiated by the existence of gap.

P15-8 Neural connectivity during simultaneous and successive information processing assessed by sLORETA

the ambiguous stimulus (e.g., human face/house) through red and green filter glasses, thus they perceived one of the two pictures at a time while the other was suppressed. Subjects were instructed to report when their dominant percept changed clearly by pressing the buttons. The numbers of button press for each category were analyzed. EEGs were recorded by a 128-ch high density EEG machine and analyzed by time-frequency analysis. “Human faces” were perceived more frequently than “monkey face” or “house”. However, the number of button press for “monkey face” and “house” were comparable. There was also no significant difference between “green” and “red” stimuli. High density EEGs revealed that gamma-band amplitudes were increased over the left fronto-temporal region when one recognized “human face” than the other categories before the button press. Our psychophysical data revealed that human face recognition could dominate over the other categories during the perception of binocular rivalry. An increase in the amplitude of the gamma-band also suggested that the presence of the neural network specific for human face perception, while the rivalrous stimulus remained to be constant by presented.

P27-21 Event-related potential correlates of conflict detection processing of a rock-paper-scissors task in adults, normal children and children with ADHD

Mu rhythm, one of the alpha components, is recorded at the central region on the scalp corresponding to the sensorymotor area, and is reduced by activation of the brain motor system. It has been reported that high-functioning individuals with autism spectrum disorders (ASD) show mu power suppression related to self-performed hand movements but not when observing those performed by others. To clarify whether these phenomena were specific to high-functioning ASD individuals, we measured mu power for observing and executing movements in 11 ASD and 14 non-ASD children (the age ranged from 6 to 18 years old) with mental retardation (MR). EEG rhythms were recorded on the scalp while subjects were resting with eyes open; watching animated clips of ball throw, ball catch, paper rock (i.e., opening and closing of fist) and bouncing ball; moving their own hand to catch a ball and do paper rock. We focused on the alpha component at the central region contralateral to the dominant hand. In the non-ASD group, alpha power was distinctly suppressed when subjects observed other’s paper rock and performed their own, compared with rest and other conditions. We consider that this alpha component was mu rhythm and the power suppression indicated activation of the brain system for simple motor tasks than for complex tasks such as ball handling. Mu suppression for simple actual and observed tasks such as paper rock were less in ASD children than in non-ASD ones. We may suggest that this weak activation of observation and execution system for movement is characteristic among ASD individuals but not among non-ASD ones with MR.

A Study of Gender and Individual Differences in Skin Conductance Responses during a Gambling Task

The gambling task used here requires subjects to choose cards from four decks that varied in gains and losses in order to maximize their profit. Gender and individual differences have been reported in choice behaviors as measured with the gambling task. However, how individual differences influence gender differences in the gambling task remains unclear. The aim of this study was to investigate these influences; therefore, we divided the male participants into two groups based on choice behaviors in the gambling task and measured skin conductance responses (SCRs) in two male groups and a one female group. On comparing the three groups, males who chose riskless cards showed higher punishment and anticipatory SCRs than the second male and female groups. Moreover, males other than the participants who chose riskless cards had the same reward, punishment, and anticipatory SCRs as the females. These findings suggest that inclusion of participants who chose riskless cards in the male group causes gender differences in performance and SCRs during the gambling task. (Japanese Journal of Physiological Psychology and Psychophysiology, 25(3) : 245-254, 2007.)