Selective lateralization of cognitive style related to occupation as determined by EEG alpha asymmetry

Associations between cortisol awakening response and resting electroencephalograph asymmetry

The cortisol awakening response (CAR), a rapid cortisol rise in the morning after awakening, has been proposed to provide energy to cope with daily demands and suggested to be associated with brain functions. Electroencephalogram (EEG) asymmetry studies have implicated asymmetric cortical activation, especially in frontal cortex, in approach-withdrawal motivation. In this study, we examined the relationship between the CAR and lateralized cortical activity under rest in 55 university male students. Saliva samples were collected at 0, 15, 30 and 60 min after awakening on the two consecutive workdays. The lateralized cortical activity at frontocentral sites was examined by alpha asymmetry score. The results showed that a higher CAR was positively associated with alpha asymmetry score, which indicated that the higher CAR is linked with more left-sided cortical activity at frontocentral sites under resting state. This association still existed even after controlling psychological and sleep quality variables. These results suggested that appropriately mobilizing energy resource storage after awakening revealed as CAR might be associated with goal-directed approach tendencies before any eventual stressful situation, characteristic of more left than right resting-state frontocentral cortical activity.

EEG stability in infants/children of depressed mothers

The stability of EEG was examined in infants of depressed (BDI > 16) and non-depressed mothers (BDI < 9) from 3 months to 3 years. Of the 32 infants seen at 3 months, 15 were seen again at 3 years of age. Seven of the eight children who had exhibited right frontal EEG asymmetry as infants still showed that EEG asymmetry pattern at the 3 year visit. Children with right frontal EEG asymmetry at 3 years were observed to be more inhibited during an exploratory play task, and children of depressed versus non-depressed mothers were less empathetic during simulated maternal distress.

Asymmetrical brain electrical activity discriminates between psychometrically-matched verbal and spatial cognitive tasks

This study compared the asymmetry of different features of brain electrical activity during the performance of a verbal task (word finding) and a spatial task (dot localization) that had been carefully matched on psychometric properties and accompanying motor activity. Nineteen right-handed subjects were tested. EEG was recorded from F3, F4, C3, C4, P3, and P4, referred to both CZ and computer-derived averaged-ears references, and Fourier transformed. Power in the delta, theta, alpha, and beta bands was computed. There were significant Task X Hemisphere effects in all bands for CZ-referenced data and for the alpha and beta bands for ears-referenced data. The effects were always either greater power suppression in the hemisphere putatively most engaged in task processing or greater power in the opposite hemisphere. Correlations between EEG and task performance indicated that CZ-referenced parietal alpha asymmetry accounted for the most variance in verbal task performance. Power within individual hemispheres or across hemispheres was unrelated to task performance. The findings indicate robust differences in asymmetrical brain physiology that are produced by well-matched verbal and spatial cognitive tasks.

Relationship between conjugate lateral eye movements, brain organization, and cognitive style

The relationship between individual differences in conjugate lateral eye movements (CLEMs) and inferential reasoning was investigated in two experiments. Subjects were given inference tasks in sentence and pictorial form and were later tested for recognition of correct inferences as well as literal recognition of the acquisition items. In Experiment 2, for example, subjects were given logical syllogisms during acquisition. Theoretically, right-eye movement/left-hemispheric (REM/LH) subjects should have excelled at this highly logical task but no significant differences between eye-movement groups were found. However, support for previous research showing the moderating effects of gender on hemispheric activation (measured by CLEMs) and hemispheric competence came from the memory data of Experiment 2. These data indicated that male REM/LH subjects recognized more acquisition sentences than the other eye movement/gender groups. It was suggested CLEMs and other measures of hemispheric activation and competence, coupled with data collected using complex cognitive tasks, can eventually lead to explanatory brain models of cognitive processing.

Cognitive style and dichotic asymmetries of disabled readers

On a test of cognitive stylistic preference backward readers exhibited a less verbal style than did age-matched controls. The groups did not differ significantly in asymmetry on a verbal dichotic test. Relative spatial rather than verbal preference could contribute to difficulty in learning to read. It seems unnecessary to implicate lateralization differences in explanations of reading disability.

The effect of sex and task difficulty of EEG alpha activity in association with arithmetic

The effects of arithmetic task difficulty and sex of subject on parietal alpha activity (8-13 Hz) and alpha asymmetry (RH-LH/LH + RH) were investigated using a series of eyes closed self-generated tasks. Sixteen right-handed subjects (8 males, 8 females) were asked to carry out sets of successive addition and multiplication tasks divided into three levels of difficulty. In comparison to a simple counting task, more difficult tasks showed lower alpha power. All tasks except the counting condition and the successive addition of 3's task (right hemisphere only) were associated with below-baseline levels of alpha activity. When laterality ratios were considered, all addition tasks and the easy multiplication task were found to be relatively left lateralized in relation to baseline and spatial task values. A sex by task interaction, however, was detected. Males exhibited relative left hemisphere activation for the more difficult addition task and the multiplication task of medium difficulty. Females, on the other hand, showed relative left lateralization for the easy tasks and one of the more difficult addition tasks. When the harder arithmetic tasks were repeated, females showed an increase in relative left hemisphere activation for one of the more difficult multiplication tasks. Males computed the problem sets significantly faster than females. These data suggest that the effects of difficulty may interact with ability such that ability may determine the maximum level of relative hemisphere activation achieved within a given difficulty range. While no absolute differences in asymmetry were found between the sexes, females tended to show greater asymmetry differences between spatial and arithmetic tasks. Finally, no significant relationship was found between the degree of alpha asymmetry and performance measures.