Are variations among right-handed individuals in perceptual asymmetries caused by characteristic arousal differences between hemispheres?

We propose that much of the variance among right-handed subjects in perceptual asymmetries on standard behavioral measures of laterality arises from individual differences in characteristic patterns of asymmetric hemispheric arousal. Dextrals with large right-visual-field (RVF) advantages on a tachistoscopic syllable-identification task (assumed to reflect characteristically higher left-hemisphere than right-hemisphere arousal) outperformed those having weak or no visual-field asymmetries (assumed to reflect characteristically higher right-hemisphere than left-hemisphere arousal). The two groups were equal, however, in asymmetries of error patterns that are thought to indicate linguistic or nonlinguistic encoding strategies. For both groups, relations between visual fields in the ability to discriminate the accuracy of performance followed the pattern of syllable identification itself, suggesting that linguistic and metalinguistic processes are based on the same laterally specialized functions. Subjects with strong RVF advantages had a pessimistic bias for rating performance, and those with weak or no asymmetries had an optimistic bias, particularly for the left visual field (LVF). This is concordant with evidence that the arousal level of the right hemisphere is closely related to affective mood. Finally, consistent with the arousal model, leftward asymmetries on a free-vision face-processing task became larger as RVF advantages on the syllable task diminished and as optimistic biases for the LVF, relative to the RVF, increased.     

Effects of initial success or failure in a stressful or relaxed environment on subsequent task performance

Forty male and 40 female undergraduate subjects worked on anagram problems in either a stressful or a relaxed environment after having experienced either success or failure on a similar task. Internal arousal, which was expected to be minimal following success in a relaxed setting and maximal following failure in the stressful environment, was assumed to bear an inverted U-shaped relation to performance. Consistent with the implications of these assumptions, achievement in a stressful setting was lower following initial failure than following initial success, while initial failure in a relaxed environment facilitated subsequent performance. The interpretation of these results was supported by the effects of the experimental variables on indirect measures of arousal as well as by the relationship between direct measures of arousal and task performance. In addition, the achievement of female subjects tended to be facilitated by failure while the performance of males was consistently debilitated by it.     

Effect of short lateralized signals on arousal versus activation on tasks requiring visuospatial or elementary semantic stimulus processing, a replication with a modified experimental design

In this experiment, which is basically a replication of an earlier experiment done in 1988, we tested the hypothesis that the brain self-regulates its own arousal and activation. When subjects perform a putative right-hemisphere task (visuospatial), the effect of a supplementary information-processing load is supposed to lead to a delayed reaction. The opposite is supposed to be true in a putative left-hemisphere task (semantic). The former effect is supposed to be the result of increased arousal, the latter is that of increased activation. In the present experiment the reactions subject to experimental treatment are compared with control reactions of the same subject. This was not the case in the earlier experiment. Still other improvements of the experimental design were made. The results clearly confirm the earlier findings. Additional evidence is offered to strengthen the plausibility of the basic hypothesis.     

Lateral asymmetry in phonological processing: relating behavioral measures to neuroimaged structures

Recent neuroimaging studies have revealed neuroanatomical centers of activation that appear to be linked specifically to phonological processes. Furthermore, there is evidence that these centers of activation are more likely to be bilaterally represented in women than in men. However, behavioral evidence of such hemispheric asymmetries or of related sex differences is somewhat inconsistent. Two experiments were carried out to determine whether behavioral correlates of the neuroimaging findings could be demonstrated. The first experiment employed a rhyme-matching task used in a recent neuroimaging study, in which two nonsense words were projected successively to the left or right sides of the visual field. The results indicated that the left hemisphere was superior for this task. An analysis of gender effects, however, revealed that the asymmetry was restricted to men. The second experiment employed a lateralized pseudohomophone detection task that was designed to determine whether the results of the first experiment could be confirmed in the context of a phonological task with a simpler structure. This experiment broadly supported the findings of the first experiment. The results support the specialization of the left hemisphere for phonological processing, and the existence of gender differences with respect to these processes.     

Right hemisphere sensitivity to arousal and depression.

Several lines of evidence show impaired right hemisphere function in depression. Lateralized simple reaction time tasks show impaired left visual field responses both in normals experiencing a depressed mood and in patients with mild unipolar depression. One interpretation for these findings is that depression impairs right hemisphere function by interfering with right hemisphere arousal and vigilance mechanisms. In order to test this hypothesis, subjects receiving either depression or relaxation mood suggestions performed an uncued reaction time task that has been shown to be sensitive to right posterior brain damage. Level of alertness was varied by contrasting uncued blocks with blocks in which targets were preceded by a warning tone. The results showed the predicted slowing of left visual field responses in the depressed mood, but only in women. The effect was significant only for the uncued blocks. The left visual field impairment was significantly larger during depression than in the relaxation state, but a smaller left visual field slowing was present in women in the relaxed state as well. These results may be consistent with the notion that depression interferes with right hemisphere function in part by influencing right hemisphere arousal mechanisms.     

Feeding-based arousal effects on visual recognition memory in early infancy.

Arousal effects on a 1-trial visual recognition paired-comparison task were studied at newborn, 1-month, and 4-month test ages. Infants were tested before and after feeding, with arousal assumed to be lower after feeding. Newborns and 1-month-olds shifted from a familiarity preference before feeding to a novelty preference after feeding. A control group tested only after feeding confirmed that this shift was not due to increased stimulus exposure from the prefeeding test. By 4 months, infants showed novelty preferences independent of feeding. This age by arousal interaction for recognition memory extends previous knowledge by including endogenous arousal with age, stimulus, and length of exposure as contributors to familiarity-novelty preferences. It also extends and provides converging evidence for arousal effects on visual attention in early infancy found previously with preferential looking. A shift from subcortical to cortical dominance is supported.     

Cognitive consequences of individual differences in arousal asymmetry

Prior research has demonstrated that semantic organization in the right hemisphere (RH) is more diffuse and specialized for distant semantic associates than is semantic organization in the left hemisphere (LH). The present research explored individual differences in this regard. If the RH is more specialized for distant semantic associates, then individuals with a more active RH should display greater activation of distant semantic associations. Two experiments were conducted to examine this issue. In both studies a line bisection task was used to assess arousal asymmetry. In Experiment 1, greater RH activation was associated with the ability to generate remote associates to three word stimuli. In Experiment 2, relatively greater RH activation was associated with enhanced priming of distant semantic associates. Taken together, these experiments demonstrate that arousal asymmetry is an individual difference variable that is related to variability in semantic organization and retrieval.     

Information processing and aspects of visual attention in children with the DSM-III-R diagnosis “pervasive developmental disorder not otherwise specified” (PDDNOS): II. sustained attention

A group of 15 nonhyperactive children of normal intelligence with the DSM-III-R diagnosis “pervasive developmental disorder not otherwise specified” (PDDNOS) performed a sustained attention task. Adopting a cognitive-energetical linear stage model of human information processing, we investigated whether task performances deteriorated due to a diminishing level of arousal, activation, or by the active ‘effortful’ mode of information processing. In comparison to an age-matched group of normal children, the patients showed no sharper decrease in perceptual sensitivity (d'). D' is assumed to be a measure of arousal. However, the children with PDDNOS exhibited large fluctuations in their response bias beta (β), which is assumed to be a measure of activation. During the first part of the task, they shifted between under- and overestimating negative responses. In the latter part of the task this pattern altered to significantly overestimating the number of negative responses. This indicates that the patients were not able to appropriately tune to the task-inherent response probability. Moreover, as compared to the control children, the patients showed a significantly sharper decrease in hit rate with time on task, despite the fact that feedback was given on the errors. The findings are interpreted as an increasing loss of the ability to control the response bias due to difficulties in maintaining the voluntary effortful mode of processing information with prolonged time on task.     

创造性的生理研究新进展

创造性的生理基础很复杂。关于创造性生理基础的研究集中在大脑皮质激活与脑半球不对称两个方面。研究发现,大脑皮质激活状态对创造性有影响,低水平的皮质激活,特别是低水平的前额叶激活,较有利于创造性．研究还发现,创造性和左右半球不对称活动有关,处于创造状态时,右半球相对要比左半球激活程度更高。     

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.     

Effects of smoking and nicotine on EEG lateralization as a function of personality

The effects of nicotine/smoking on lateralization of the EEG were evaluated in 40 smokers while they responded to a low-stress, visual vigilance task. Smoking a high-nicotine cigarette was associated with a relatively larger increase in right hemisphere EEG arousal in extraverts and Type-A individuals, but with a relatively larger increase in left hemisphere EEG arousal in introverts and Type Bs. These findings suggest that nicotine/smoking may differentially influence the left and right hemispheres and that this interaction may be a function of personality.     

Cross-linguistic parallels in processing derivational morphology: Evidence from Polish

Neuroimaging evidence in English suggests that the neurocognitive processing of derivationally complex words primarily reflects their properties as whole forms. The current experiment provides a cross-linguistic examination of these proposals by investigating the processing of derivationally complex words in the rich morphological system of Polish. Within the framework of a dual language system approach, we asked whether there is evidence for decompositional processing of derivationally complex Polish stems – reflected in the activation of a linguistically specific decompositional system in the left hemisphere – or for increased competition between the derived stem and its embedded base stem in the bilateral system. The results showed activation in the bilateral system and no evidence for selective engagement of the left hemisphere decompositional system. This provides a cross-linguistic validation for the hypothesis that the neurocognitive processing of derived stems primarily reflects their properties as stored forms.     

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.     

An investigation of bilateral asymmetries in electrodermal activity

Research in cerebral laterality supports the idea that functional differences between the left and right hemispheres exist with respect to cognitive style and perceptual ability. Related research, which has examined autonomic nervous system (ANS) correlates of cerebral laterality, suggests that a component of the ANS, electrodermal activity (EDA), is also lateralized. Some findings in the literature report the occurrence of bilateral asymmetries in phasic and tonic EDA as a function of a left or right hemisphere preference for information processing. This experiment used normal male subjects who were either left or right movers in a test of Conjugate Lateral Eye Movement (CLEM). This selection procedure served to maximize a subject’s preference for either a right or left hemisphere mode of information processing. Bilateral EDA was recorded continuously while subjects performed a visual recognition task using word (left hemisphere) and shape (right hemisphere) stimuli. The data do not support the contention that performance on a procedure chosen to selectively activate a given hemisphere elicits asymmetric tonic and/or phasic EDA. The results show no significant difference in the frequency of elicited skin conductance responses under either of the experimental conditions. Bilateral tonic EDA rose continuously over time and did not vary in either hand as a function of task. The present results fail to offer support for either of the hypotheses which argue for I) increased contralateralexcitation with selective hemispheric activation, or 2) increased contralateralinhibition of the EDR with hemispheric arousal.     

Categorization and affect: evidence for intra-hemispheric interactions

Both emotional reactivity and categorization have long been studied within the framework of hemispheric asymmetry. However, little attempt has been made to integrate both research areas using any form of neuropsychological research, despite behavioral data suggesting a consistent relationship between affective and categorization processes. The primary goal of the current study was to examine the possibility of a laterally mediated interaction between emotional reactivity and the cognitive process of categorization. Using a split visual fields categorization task combined with affect inducing procedures, we hypothesized that the relationship between state affect and categorization would be dependent on the nature of state affect and on the hemisphere targeted. Results offered support for this hypothesis, showing that state affect related changes in categorization appeared only in the hemisphere commonly associated with both a specific affective state and categorization strategy employed. Findings are discussed in terms of possible evidence for a hemispheric arousal effect underlying the relationship between affect and categorization.     

Improvement Strategies in Free-Throw Shooting and Grip-Strength Tasks

Participants performed a free-throw shooting task and a grip-strength task before and after imagery, nonspecific arousal, or no instructions. Imagery improved performance in the free-throw shooting task, which is assumed to have more cognitive components than the grip-strength task. Imagery did not improve performance in the grip-strength task, which is assumed to have fewer cognitive components than the free-throw task. Nonspecific arousal, on the other hand, improved performance in the grip-strength task but not in the free-throw shooting task. Athletic experience, confidence levels, and gender were correlated with actual performance levels in both tasks, but not with improvement. Results are discussed within the transfer-appropriate processing framework.     

Improvement strategies in free-throw shooting and grip-strength tasks

Participants performed a free-throw shooting task and a grip-strength task before and after imagery, nonspecific arousal, or no instructions. Imagery improved performance in the free-throw shooting task, which is assumed to have more cognitive components than the grip-strength task. Imagery did not improve performance in the grip-strength task, which is assumed to have fewer cognitive components than the free-throw task. Nonspecific arousal, on the other hand, improved performance in the grip-strength task but not in the free-throw shooting task. Athletic experience, confidence levels, and gender were correlated with actual performance levels in both tasks, but not with improvement. Results are discussed within the transfer-appropriate processing framework.     

Semantic and associative priming in the cerebral hemispheres: some words do, some words don't ... sometimes, some places

This study investigated spreading activation for words presented to the left and right hemispheres using an automatic semantic priming paradigm. Three types of semantic relations were used: similar-only (Deer-Pony), associated-only (Bee-Honey), and similar + associated (Doctor-Nurse). Priming of lexical decisions was symmetrical over visual fields for all semantic relations when prime words were centrally presented. However, when primes and targets were lateralized to the same visual field, similar-only priming was greater in the LVF than in the RVF, no priming was obtained for associated-only words, and priming was equivalent over visual fields for similar + associated words. Similar results were found using a naming task. These findings suggest that it is important to lateralize both prime and target information to assess hemisphere-specific spreading activation processes. Further, while spreading activation occurs in either hemisphere for the most highly related words (those related by category membership and association), our findings suggest that automatic access to semantic category relatedness occurs primarily in the right cerebral hemisphere. These results imply a unique role for the right hemisphere in the processing of word meanings. We relate our results to our previous proposal (Burgess & Simpson, 1988a; Chiarello, 1988c) that there is rapid selection of one meaning and suppression of other candidates in the left hemisphere, while activation spreads more diffusely in the right hemisphere. We also outline a new proposal that activation spreads in a different manner for associated words than for words related by semantic similarity.     

Right hemisphere participation in reading

This study examined whether the right hemisphere's contribution to lexical semantic processing is greatest when it is "disinhibited." Skilled reading may require the controlled modulation of interhemispheric interaction: the left hemisphere (or some other control mechanism) may regulate the subprocesses of reading by selectively "inhibiting" and "disinhibiting" right hemisphere function. Right-handed undergraduates concurrently performed two tasks: a lateralized semantic or rhyme task and a verbal memory task. It was hypothesized that right hemisphere reading processes would be disinhibited when the left hemisphere was "occupied" with the memory task. This hypothesis was supported for a subgroup of subjects who showed evidence of inhibition of right hemisphere function (i.e., left hemisphere dominance for lexical processing) when the lateralized semantic task was performed alone. Across subjects, there was a strong correlation between the degree of left hemisphere dominance in the single-task semantic conditions and the degree of disinhibition of right hemisphere function in the dual-task semantic condition.     

Stereotyping, self-affirmation, and the cerebral hemispheres

The authors used the processing characteristics of the left and right cerebral hemispheres to gain some insight into the relation between self-affirmation and stereotyping. In Study 1, self-affirmation led to greater stereotyping (of a librarian) and to greater left hemisphere activation, which in turn mediated the self-affirmation/stereotyping relationship. Study 2 replicated these results but also found that self-affirmation decreased stereotyping for a stigmatized target. However, relative hemisphere activation did not mediate this self-affirmation/stereotyping relationship. These studies showed that self-affirmation can either increase or decrease stereotyping depending on the status of the target and that relative hemisphere activation may provide clues as to underlying processes of stereotyping. In both studies, relative hemisphere activation was assessed using a line bisection task. Discussion focuses on possible mechanisms of different kinds of stereotyping and on the ways in which a consideration of relative hemisphere activation could help researchers gain insights into those mechanisms.