Hemisphere Interference Research Articles

Creativity-Related Hemispheric Selective Processing: Correlations on Global and Local Levels of Attentional Set

Creativity-related characteristics of hemispheric attentional processes operating on local and global level were examined using a hierarchical letter paradigm comparison task. The figural originality of college students (N = 116) was predicted by reaction times (RT) during information selection on the global level, with local-global interference effects. High originality was related to faster right-hemispheric RT and slower cooperative hemispheric processing RT. Other predictors of originality included an increase in right hemispheric local-global interference effects and decreases in interhemispheric interference. The results suggest that figurative creativity is associated with global selective processing in the right hemisphere and weak global-to-local interference effects in interhemispheric interaction.

Congruency, attentional set, and laterality effects with emotional words.

The present study investigated the influence of attention and word-emotion congruency on auditory asymmetries with stimuli that include verbal and emotional components. Words were presented dichotically to 80 participants and were pronounced in either congruent or incongruent emotional tones. Participants were asked to identify the presence of a target word or emotion under 1 of 2 conditions. The blocked condition required detection of a word or emotional target in separate blocks. In the randomized condition, the target was changed across trials by means of a postcue. A right-ear advantage (REA) and a left-ear advantage (LEA) were found for word and emotion targets, respectively. However, the finding of a Condition x Stimulus Type x Ear x Congruency interaction indicated that in the randomized condition, a REA was obtained for words when the stimuli were congruent and a LEA was observed for emotions when the stimuli were incongruent. The findings suggest that randomizing the target reduced the influence of the attentional set established by blocking the target. It is likely that this promoted the detection of hemispheric interference in the randomized condition.

Atypical brain laterality in adults with ADHD during dichotic listening for emotional intonation and words

Few studies directly examined the nature of hemispheric specialization and interaction in ADHD. The present experiment investigated left/right brain dynamics in unmedicated right handed adults with ADHD ( n = 19) and in controls ( n = 19), using a dichotic listening task to assess hemispheric differences in word and emotion recognition. We also assessed how focusing attention on a single ear modulated lateralized performance and affected cross-callosal interference effects. Analysis of variance indicated that ADHD subjects showed reduced left hemisphere specialization, were better at processing emotions, and worse at processing words compared to controls. These differences were eliminated during focused attention. Finally, during presumed right hemisphere processing of linguistic stimuli, subjects with ADHD showed reduced left hemisphere interference. We concluded that ADHD subjects demonstrated greater right hemisphere and reduced left hemisphere contribution during this task relative to controls. We posit that these hemispheric differences were due to management or use of available cognitive resources rather than inherent capacity.

The lateralized Stroop: A meta-analysis and its implications for models of semantic processing

The prevailing theory in the literature concerning the lateralization of Stroop effects involves a speed of processing account (see MacLeod, 1991). Because the left hemisphere (LH) demonstrates an overall advantage relative to the right hemisphere (RH) on most verbal tasks, interference effects are hypothesized to be greater in the LH than in the RH. Inspection of the data, however, reveals that many studies find no difference in magnitude of Stroop interference between the hemispheres. Given findings within the lateralized semantic priming literature, this is not surprising. A meta-analysis on a subset of lateralized Stroop experiments was conducted to determine whether or not the LH produces significantly more interference than the RH in this paradigm. Based on a number of exclusionary criteria, a total of 19 different studies were included, representing a potential 26 effect size estimates of differential interference. The effect size representing interference using congruent conditions as the baseline ( d+=.06) reveals that there is no significant difference between the hemispheres in magnitude of the Stroop interference effect. The LH interference effect was d+=.73, which is significant. Likewise, the RH interference effect, d+=.67, was significant. In summary, while there was no significant difference between the hemispheres, each hemisphere, when examined independently, did exhibit significant within hemisphere interference effects. These findings are presented in light of the lateralized semantic priming literature.

Hemisphere asymmetry and the processing of emotional words in anxiety

High- and low-trait anxious subjects participated in a divided visual field emotional Stroop task. Subjects identified the colour of unilaterally presented threat-related, positive and neutral words. The high- and low-trait groups differed in terms of their accuracy scores but not in their reaction times. Analysis of the accuracy data revealed that the high-trait group exhibited right hemisphere interference for emotional relative to neutral trials whereas the low-trait showed right hemisphere interference for threat-related trials only. The idea that the right hemisphere is differentially specialised for the processing of emotional information was supported.

Cerebral Lateralization of Familiar and Unfamiliar Music Perception in Nonmusicians: A Dual Task Approach

In a dual task procedure that controls for attentional trade-off effects, asymmetrical in terference effects were observed in dual task conditions of finger tapping and concurren processing of familiar and unfamiliar music. Laterality effects suggested that perception of orchestral presentations is largely lateralized to the left hemisphere in both males and females. In a second dual task condition of vocalization and music processing, both males and females displayed interference in speech production during concurrent music processing. Males showed greater left hemispheric interference effects during simultaneous vocalization and music processing.

Left hemispheric interference with nonverbal performance in aphasics: Comparison with data from split-brain studies

Two nonverbal tasks (Nebes' Figural Unification Test and Arc-Circle Matching Task) were given to 10 aphasic patients and 10 normal controls. Observations in split-brain patients have shown that the right hemisphere performs almost normally on these tasks while the left hemisphere fails completely. Left and right hand performances of aphasics and controls were compared with those of split-brain patients as reported in the literature. In the Figural Unification Test the aphasics' left hand performance was significantly poorer than that of split-brain patients. This is interpreted as an effect of left hemispheric interference with right hemispheric nonverbal performance. The lack of a similar impairment of left hand performance in the Arc-Circle Matching Task suggests that this interference is only provoked by tasks which, due to the possible verbalization of stimulus material, tend to stimulate left hemispheric activity.

Hemisphere specific effects in reasoning performance.

Subjects frequently produce matching responses to Wason's selection problem. Some authors have proposed that such responses are a result of information processing functions which are lateralised to the right hemisphere and that compete with left hemisphere verbal/logical processes for the control of overt responding. Support for this position has come mainly from studies of patient populations. The present paper reports a series of experiments in which attempts were made to obtain similar confirmation from normal subjects using the technique of selective hemispheric interference. Subjects worked on the selection problem while concurrently performing a unimanual balancing task. Weak but persistent effects of hemispheric interference on the pattern of responses th the selection porblem were observed. In general, the data are consistent with the hypothesis that matching responses reflect right hemisphere processing.

Hemispheric interference: A dual-task investigation of youngsters who stutter

Hemispheric interference was studied in this investigation by requiring 24 right-handed grade-school children who stutter to tap a button, as rapidly as possible, in five randomized conditions. Hand order was counterbalanced in the single-task silent control condition and in the four increasingly demanding dual-task conditions. In three of the experimental conditions tapping and speech occured concurrently. In the fourth dual-task condition the subjects were to vocalize the sound of a siren (in an irregularly patterned way) as they tapped the button. Analysis of the tapping rates in this two-by-five factorial study revealed statistically significant differences among hands and conditions. The tapping rate was faster with the right than with the left hand and the rate decreased as the demands of the dual-task conditions increased. Interaction was not evidenced; the interference pattern was similar in both hands across the conditions. Since interference was significantly present in both the speech and vocalic conditions, the data are not consistent with a laterality model. This finding and the increase in interference with increased attentional demand, however, are consistent with a capacity framework.

Right hemisphere interference during negative affect: a reaction time study

Two experiments are described in which simple reaction times (RTs) to lateralized visual stimuli were measured in normal subjects during negative affect and during recollection of everyday life scenes. In both experiments the mental activity produced a remarkable increase of RTs with respect to a control situation without interfering activity. During production of the negative affect there was a selective lengthening of RTs mediated by the right hemisphere. The role of the right hemisphere in producing emotions is discussed.

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.

Contrastive patterns of intrahemispheric interference to verbal and spatial concurrent tasks in right-handed, left-handed and stuttering populations

A time-sharing paradigm was used to assess hemispheric lateralization for both language and visuo-spatial processing in right-handed, left-handed and stuttering populations. A right hand only tapping disruption, indicative of left hemisphere interference, accompanied concurrent verbal tasks only in the dextral group. Left-handers and stutterers revealed symmetrical patterns of hemispheric language interference. Significantly different absolute levels of language interference were found for the three groups, with dextrals having the least, followed by sinistrals, and being greatest for stutterers. These magnitude differences were explained in relation to a hypothesis of strength of language representation within a given hemisphere. Visuo-spatial right hemisphere interference was shown for left-handers with a concurrent object chimera task.

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.

Unimanual tactile anomia consequent to corpus callosotomy: Reduction of anomic deficit under hypnosis

Unimanual tactile anomia for objects palpated with the left-hand was studied in a 28-year-old callosotomy patient. Previous assessment of this patient Larrabee et al., [9]) and two currently reported assessments without inducing hypnosis showed marked anomic deficit. A series of assessments conducted under hypnosis showed substantially improved naming ability, especially in hypnotic sessions suggesting that the patient did not feel like speaking and that speaking was difficult. Among the possible mediators of this reduction of anomic impairment one can suggest factors such as motivational and attentional enhancements, suppression of left hemisphere interference, and even right hemisphere speech facilitation under hypnosis. These and other results also suggest that an hypothesized right hemisphere dominance during hypnosis may be accurate and possibly more obvious in callosotomy patients than in normal persons.

Sex and Handedness in Simple and Integrated Task Performance

Spatial and sequential tasks which were performed both independently and jointly were compared for 40 college undergraduates grouped by sex and dominant hand. The two tasks were selected based on prior research suggesting that each is controlled in a different brain hemisphere. When the two tasks were performed independently there was no handedness effect nor was there any sex-hand interaction. There was an expected slight spatial superiority of males. However, when both tasks were performed simultaneously, there was a significant advantage for right-handers and again a slight advantage for males. Results were attributed to the hemispheric interference left-handers experienced on the joint task due to their less distinct hemispheric specialization.

Cerebral lateralization of haptic perception: interaction of responses to Braille and music reveals a functional basis.

Normally, haptic perception of the left hand surpasses that of the right. But simultaneously playing music into the left (but not the right) ear reverses this superiority. This suggests that the left cerebral hemisphere has full haptic perceptual capability, which is subject to right hemisphere interference unless the latter's attentional mechanisms are engaged by contralateral peripheral stimulation.

Effects of concurrent verbal memory on recognition of stimuli from the left and right visual fields.

Two experiments examined the effect of concurrently holding 0, 2, 4, or 6 nouns in memory on the recognition of visual stimuli briefly presented to the left or right visual fields. When stimuli to be visually recognized were complex visuospatial forms it was found that a relatively easy memroy load of 2 or 4 nouns improved visual recognition accuracy on right visual field (left-hemisphere) trials relative to the no-memory condition; however, a more difficult memory load of 6 nouns decreased visual recognition accuracy to a level slightly below the no-memory condition. There were no effects of concurrent verbal memroy on visual form recognition on left visual field (right-hemisphere) trials. When the stimuli to be visually recognized were words it was found that a relatively easy memroy load of 2 or 4 nouns improved visual recognition accuracy and a more difficult load of 6 nouns decreased visual recognition accuracy on both left and right visual field trials. The complete pattern of results indicates that several factors including cerebral hemisphere specialization, stimulus codability, selective perceptual orientation, and selective cerebral hemisphere interference interact in systematic ways to produce overall visual laterality effects.