Asymmetrical brain activity induced by voluntary spatial attention depends on the visual hemifield: a functional near-infrared spectroscopy study

The effect of the visual hemifield to which spatial attention was oriented on the activities of the posterior parietal and occipital visual cortices was examined using functional near-infrared spectroscopy in order to investigate the neural substrates of voluntary visuospatial attention. Our brain imaging data support the theory put forth in a previous psychophysical study, namely, the attentional resources for the left and right visual hemifields are distinct. Increasing the attentional load asymmetrically increased the brain activity. Increase in attentional load produced a greater increase in brain activity in the case of the left visual hemifield than in the case of the right visual hemifield. This asymmetry was observed in all the examined brain areas, including the right and left occipital and parietal cortices. These results suggest the existence of asymmetrical inhibitory interactions between the hemispheres and the presence of an extensive inhibitory network.     

Effects of attention state on electrodermal activity during auditory stimulation of children.

During passive and active listening tasks electrodermal activity of 49 healthy school children was studied. The procedure included baseline recording, a passive listening task, instructions, and simple and discriminative active-listening tasks. On the passive task from Trials 1 to 10, habituation of the amplitude of the skin conductance response (SCR) occurred. Habituation of SCR amplitude did not occur during the active tasks. The children seemed to pay more attention during the active tasks than during the passive task, since the need to press the key is apt to require and may even increase general attention. As for temporal variables of SCR, the frequency of spontaneous SCRs showed a significant negative correlation with SCR latency and rise time. Reaction time exhibited a significant negative correlation with age. An increase in reaction time was found during the discriminative active-listening task over that for the simple active-listening task during the course of 10 trials. The younger children (6-8 yr.) seemed to require longer to pay attention than the older ones (10-12 yr.). Children seemed to pay more attention during the discriminative than during the simple active-listening task, since the need to press the key for discrimination should require and is likely to increase general attention.     

Developmental transition of EEG spectra to alpha band in a sample of children with developmental disabilities

Developmental transition of EEG spectra to alpha band of 14 children with developmental disabilities (from 7 yr. and 3 mo. to 16 yr. and 1 mo. of age at the first EEG recording: M= 13.2, SD=2.6; 6 girls and 8 boys) was studied by auto-power spectrum analysis longitudinally. The results showed the mean age (14.1 yr. to 14.8 yr. in the four regions of the frontal, central, parietal, and occipital regions) for subjects and their mean frequency (4.2 Hz to 4.7 Hz in the 4 regions) at which EEG shift started from theta band, and those means (15.1 yr. to 15.7 yr. and 9.5 Hz to 9.6 Hz in the 4 regions) at which EEG shift reached the alpha band. Prior EEG research on healthy children has shown that approximately 10 years of age is critical for developmental transition of EEG spectra to alpha frequencies. It is suggested that the present data showed a delay of this critical age for this sample of children with developmental disabilities relative to 10 years for healthy children reported by Katada, et al. and Benninger, et al.     

Heart-rate variability during nocturnal sleep in mentally retarded children.

Heart-rate variability in four normal and 30 mentally retarded children was investigated during nocturnal sleep. In four normal and 25 mentally retarded subjects, a high frequency component defined as spectral activity between 0.15 and 0.5 Hz was found in the compressed spectral array of the power spectra. A periodic change was seen in the high frequency component which corresponded precisely to the sleep cycle. However, four children with mental retardation did not show normally expected changes in the high frequency components specific to the sleep stages: a quantity of the high frequency component in only one sleep cycle (n=2; 6 mo. and 3 yr., 8 mo.), a decreased quantity and discontinuity of the high frequency component in only the second sleep cycle (n=1; 1 yr., 2 mo.), and no high frequency component in any sleep cycle (n=1; 3 mo.) These findings suggest that some mentally retarded children have an abnormal parasympathetic nervous activity.     

Attention of preschool children: electrodermal activity during auditory stimulation

Electrodermal activity during passive and active listening tasks of 43 healthy preschool children (aged 4 yr., 8 mo. to 6 yr., 5 mo.) was studied. The procedure included the following phases: baseline recording (3 min.), a passive listening task, instructions, and an active listening task. An increase in mean amplitude of skin conductance response (SCR) was found during the active listening task over the level for the passive listening task over 10 trials. On the passive listening task from Trial 1 to Trial 10, habituation of mean SCR amplitude occurred. The younger children, moreover, exhibited significantly greater habituation than the older children. Habituation of mean SCR amplitude did not occur during the active listening task. No significant difference was found in mean SCR amplitude during the active listening task for the two age groups. The children seemed to pay more attention during the active listening task than during the passive listening task. The younger children, moreover, are believed to have shorter attention spans.     

Relation between polysomnographic measures during nocturnal sleep and a quotient of behavioral development in infants with developmental disabilities

Polysomnographic features during nocturnal sleep were investigated in 27 infants with developmental disabilities. With the use of a multiple regression analysis, 78% of the variance of a Development Quotient (DQ) measured by a questionnaire on behavioral development for infants was explained by sleep measures. Of 14 sleep measures employed in the study, (1) cumulative awakening time during a nocturnal sleep time, (2) duration of REM stage, and (3) percentage of REM to total sleep time were important in association with the DQ. The findings are consistent with the sleep-cognition hypothesis proposed by Espie, et al.     

Delta and spindle components in the integrated EEG during nocturnal sleep for infants with developmental disabilities

The delta and spindle components in the integrated EEG for 121 infants with developmental disabilities (from 4 mo. to 6 yr. of age: M=1.79, SD=0.14; 57 girls and 64 boys) were studied throughout nocturnal sleep. In 80 (66.1%, Group A) of 121 subjects, periodic changes of delta and spindle rhythm powers were noted in measurements of EEG made during sleep. In 28 (23.1%, Group B), delta but not spindle rhythm powers were found, and in the remaining 13 subjects (10.7%, Group C) neither delta nor spindle rhythm powers were found throughout measurements of EEG made during sleep. The Tsumori-Inage Questionnaire for Infants was administered to the parents to estimate subjects' behavioral developmental level as Developmental Quotients. Significantly lower mean Developmental Quotients were found for Groups B and C than Group A. These findings suggested that the presence or absence of delta and spindle rhythm powers in EEG measurements made during nocturnal sleep could be taken as an index of the severity of developmental disorders in infants with developmental disabilities.