Hemisphere Tasks Research Articles

Cognition is cool: Can hemispheric activation be assessed by tympanic membrane thermometry?

Hemispheric activation during cognitive tasks using functional magnetic resonance imaging (fMRI) can be difficult to interpret, uncomfortable, and is not widely available. This study investigated whether tympanic membrane thermometry could be used as a broad measure of hemispheric activation. Infrared probes measured ear temperature continuously while subjects performed left or right hemisphere tasks. Temperature decreased in the left ear as activation increased in the left hemisphere during a verbal task, and in the right ear during a visuo-spatial task. When compared to a baseline, ear temperature measurements appeared to reflect relative changes in activation of the left and right hemispheres. Tympanic membrane thermometry therefore may be used as a broad marker of hemispheric activation. Its ability to demonstrate relative involvement of the two hemispheres during cognitive processes makes it especially useful in studies of hemispheric interaction. Its low cost, rapid set-up, and non-invasive nature also make it particularly attractive.

Sex Differences in Right Hemisphere Tasks

We tested the hypothesis that sex differences in spatial ability and emotional perception are due to sex differences in intrahemispheric organization of the right hemisphere. If the right hemisphere is differently organized by sex—primarily specialized for spatial ability in men, but primarily specialized for emotional perception in women—then there should be a negative correlation between spatial ability and emotional perception within sex, and the greatest disparity between abilities should be found in people with characteristic arousal of the right hemisphere. Undergraduate men (N= 86) and women (N= 132) completed tests of Mental Rotation, Surface Development, Profile of Nonverbal Sensitivity, Progressive Matrices, and Chimeric Faces. Although the expected pattern of sex differences was observed, there was no evidence for the hypothesized negative correlation between spatial ability and emotional perception, even after statistical control of general intelligence.

Language Experience and Right Hemisphere Tasks: The Effects of Scanning Habits and Multilingualism

This study explores the effects of multilingualism and reading scanning habits on right hemisphere (RH) abilities. Native Hebrew speakers and Arabic–Hebrew bilinguals performed three tasks. Experiment 1 employed an odd/even decision paradigm on lateralized displays of bar graphs. Both groups of subjects displayed the expected LVFA within the range previously reported for readers of English. Experiment 2 consisted of a chair identification task designed to tap asymmetry of hemispheric arousal and a chimeric face task designed to tap RH specialization for facial emotion. Neither scanning habits nor language experience affected performance on the chair task. Scanning habits seem to have affected performance on the chimeric faces task: there was no preference for the left smile in these right-to-left readers, as opposed to previous results in the literature using left-to-right readers. Correlations between measures from the three tasks and all the subject's scores on an English proficiency test and on a Hebrew test for the bilinguals reveal tentative relationships between proficiency in a second language and RH abilities. The results do not support the hypothesis that multilingualism can affect the manner in which these nonlanguage tasks are subserved by the RH. They do support the hypothesis that scanning habits particular to specific languages can affect performance asymmetries on some nonlanguage tasks that have been posited to reflect RH specialization.

The effects of gender, menstrual phase and practice on the perceived location of the midsagittal plane

Women show menstrual phase-related cognitive changes that suggest altered hemispheric activation for a particular task, such that they demonstrate the greatest lateral performance differences on prototypical left hemisphere tasks during the luteal phase and on prototypical right hemisphere tasks during menstruation. Additionally, menstrual phase may alter total cerebral responsiveness, such that response times and performance accuracy for many tasks are best during the luteal phase and most impaired during the menstrual phase. We evaluated the effect of menstrual phase on spatial bisection (a perceptuospatial task) to help further understand hormonally-mediated changes in interhemispheric dynamics. Healthy young adult women and men blindly pointed to their midsagittal plane with either hand. Women were repeatedly tested according to menstrual phase, and men were tested at similar intervals. The mean pointing error in the luteal phase differed significantly from that of all other phases and did not differ significantly from those of men, who pointed significantly to the left across test sessions. These findings suggest that, in space bisection tasks, women are more likely to have asymmetric hemispheric activation during the luteal phase than during the menstrual phase. Thus, space bisection did not resemble other prototypical right hemisphere behaviors. The luteal phase may have nonspecifically activated both hemispheres on this task instead of suppressing right hemisphere function, and a slight functional asymmetry favoring the right hemisphere may have been promoted. In addition, intermanual pointing discrepancies in both subject groups decreased over repeated sessions. This suggests that, while practice alters an internal kinesthetic reference, it does not influence an imaginal extrapersonal spatial reference.

Intermanual differences on motor and psychomotor tests in alcoholics: no evidence for selective right-hemisphere dysfunction.

Some previous studies have suggested that alcoholics exhibit selective right-hemisphere dysfunction, based on alcoholics' poor performance on tests believed to subserve the right hemisphere. However, some of these experiments did not account adequately for differences in difficulty or novelty in putative right hemisphere tasks. This experiment was designed to evaluate and compare intermanual differences in grip strength, motor speed, fine-motor dexterity, and nonverbal problem-solving ability in 93 recently detoxified alcoholics, 54 long-term abstinent alcoholics, and 73 nonalcoholic controls. All subjects were right-handed men, matched for age and education, and both alcoholic groups had similar drinking histories. Using percent difference scores to assess intermanual differences, adjusted for demographics where appropriate, we found that, although recently detoxified alcoholics demonstrate some motor and psychomotor impairments, there is no evidence using these tests to suggest the right hemisphere is selectively more vulnerable to the effects of chronic alcohol abuse.

Changes in Cognitive Asymmetries from Waking to REM and Nrem Sleep

In previous studies, a right hemisphere superiority was shown during REM sleep with respect to Wake and NREM states for right hemisphere tasks. The question can be raised whether the increasing right hemisphere performance during REM is related to right hemisphere tasks only, or whether it is of more general nature. This hypothesis was tested by giving the lateralized Consonant Recognition Task to 16 subjects during waking and upon awakenings from REM and NREM sleep. Results support the hypothesis that right hemisphere superiority in REM sleep is not restricted to right hemisphere tasks.

EEG coherence during hemispheric activation in schizophrenics

We studied the change of EEG alpha-band coherence between resting and motor performance ("reactivity of EEG coherence") in 18 chronic schizophrenics and 30 normal controls, examining differences between left and right hemisphere tasks. Three coherences were examined for each hemisphere. The central-parietal coherence in normals increased on the left for left hemisphere tasks, and decreased on the right for right hemisphere tasks, whereas the patients showed a decrease of both measures, more on the left side. Thus, the interhemispheric difference of central-parietal coherence reactivity was reversed for the schizophrenics (P less than 0.06) and suggested a left-sided deviation. The lateral-percentral and precentral-central coherences showed no left-right deviations of reactivity in the patients. Since coherence increase is considered to be a sign of the coupled function between the studied regions, our findings suggest a defective coordination of left central-parietal regions during a task in schizophrenics.

Effects of feedback control on EEG alpha asymmetry during covert mental tasks

EEG alpha (8–12 Hz) was recorded bilaterally from O1-P3 and O2-P4 during two eyes-closed sessions in 40 women. During one session subjects performed two covert right-hemisphere activation tasks and two covert left-hemisphere activation tasks (no-biofeedback condition). During the other session subjects performed the same tasks while trying to control their EEG asymmetries, being provided with EEG asymmetry auditory feedback (biofeedback condition). The ratios of integrated EEG alpha amplitudes were calculated as measure of hemispheric asymmetry, and the number of times that the right and left alpha had the same phase angle was determined as index of hemispheric synchrony (alpha phase index). In both conditions, subjects rated orally after each task their degree of subjective fullfilment of the task. There were significant differences between the EEG asymmetry during right- and left-hemisphere tasks. Significant differences of integrated alpha amplitudes and ratios between the no-biofeedback and biofeedback condition were also found. There was more hemispheric asymmetry in the biofeedback than in the no-biofeedback condition, and a significantly higher alpha phase index. There was no correlation between fullfilment ratings and alpha ratios in the no-biofeedback condition, but there was such correlation during right and left hemisphere tasks in the biofeedback condition. The study demonstrated that biofeedback regulation and covert mental activity can have effects on EEG alpha asymmetry which are cumulative.

EEG activity during cognitive processing: Influence of attentional factors

The research draws upon two separate areas of inquiry: (1) that of lateralized electrocorical processing of cognitive material; and (2) that of psychophysiological information processing studies related to foci of attentional demands. Eighteen subjects on each of three separate days were presented with tasks considered to be ‘right hemispheric’ or ‘left hemispheric’. These tasks were paired in a 2 x 2 design with an attentional factor requiring attention to the environment or to internal processing. All subjects received all types of tasks. Bilateral EEG measures were taken from the frontal and parietal areas referenced to linked ears. Major frequency bands were determined by a Fast Fourier Transform (FFT) and appropriate ANOVAs performed. The results suggest that task factors (left vs right hemisphere tasks) and attentional demands (internal vs external) are differentially represented in terms of EEG functioning. In general the higher beta frequencies were more sensitive to the hemispheric tasks demands and the middle frequencies (alpha and low beta) more sensitive to the attentional demands especially in the parietal areas.

Hemispheric lateralization in 47,XXY Klinefelter's syndrome boys

Thirty-two boys with a 47,XXY karyotype were compared with chromosomally normal male controls in their performance on six tasks of hemispheric specialization. The results revealed that the 47,XXY subjects had smaller asymmetries on left hemisphere tasks and larger asymmetries on right hemisphere tasks than controls. Analyses of individual right and left side scores revealed that the atypical lateral asymmetries of the 47,XXYs were due to a shift toward greater right hemisphere involvement on four of the six measures. It was postulated that the slower fetal growth rates of the extra X chromosome group might contribute to their atypical hemispheric specialization and the failure of their left hemisphere to gain dominance over their right in language processing.

Hemisphere-specific deficits on cognitive/perceptual tasks following REM sleep deprivation.

Current research and theory support the position that there are diurnal changes in the relative functional dominance of the hemispheres in the "normal" population. In one example of this position, Bakan (1978) has stated that REM sleep allows for right hemisphere dominance with a relative absence of left hemisphere interference. The present study involved pre- and postREM deprivation visual presentation of cognitive/perceptual performance tasks that had previously been demonstrated to have lateralizing value. Ten right-handed adult males each spent three nights in a sleep laboratory completing these tasks and a variety of questionnaires. After REM deprivation, performance decreased on right hemisphere tasks presented to the right hemisphere first. However, left-hemisphere-first presentation of one of the right hemisphere tasks (facial recognition) actually resulted in performance improvement after REM deprivation. This improvement was attributed to a suppression or diminution of capacity of the primary processing style of the left hemisphere. Results are further discussed in terms of Bakan's theory, the different processing "styles" of the two hemispheres, possible functions of REM and relationships of the biological cycles to possible shifts in cerebral laterality.

Interference of concomitant tasks on simple reaction time: Attentional and motor factors

Simple reaction times to lateralized unstructured visual stimuli were measured in normal subjects while they were carrying out concomitant left hemisphere tasks. Three tasks were used. In the first task the subjects had to pay attention to strings of digits, acoustically presented, and detect letters randomly interspersed among the digits; in the second task the subjects had to memorize strings of acoustically presented digits; inthe third task they had to repeat each digit of a string as soon as they heard it. In spite of the greater difficulty of the first two tasks with respect to the third one, only this last task, the only one requiring a verbo-motor response, produced a significant disadvantage for the left hemisphere responses to light. It is argued that in RT experiments a specific left hemisphere interference takes place when the secondary task requires the organization of a motor response.

Bilateral Electrodermal Activity, Lateralized Cerebral Processing and Sex

ABSTRACTThe present study involved the assessment of systematic differences between skin conductance measures recorded bilaterally and concomitantly from 59 right‐handed subjects while they were exposed to three types of stimuli. The stimuli were 5 min each of: a quiet period, a period of music, and a period of listening to a series of paragraphs. The music and paragraph conditions served, respectively, as operational definitions of right and left hemisphere tasks. Sex and genetic handedness were also assessed. Results showed that subjects with a family history of sinistrality gave more frequent SCRs on the left hand than on the right hand under the verbal condition, while those with entirely dextral families showed no left‐right differentiation. In addition, musical stimulation produced more frequent responses in males than females, while the reverse was true for verbal stimuli. Finally, tonic SCL was higher on the right hand in males and on the left in females. Stimulation intended for a specific hemisphere did not produce significantly greater electrodermal activity on the contralateral hand.