Hemispheric specialization in visual, tactile and crossmodal assembling tasks

There is ample evidence that the right or non-language related hemisphere of the brain is superior in processing of spatial information. This issue appears less clear when a task involves elaborate mental operations that require the integration of spatial information at a stage beyond mere perceptual discrimination. Examples are block design tasks, which are frequently used as estimates of general intelligence. Results of these tests have been contradictory as to whether there is a right hemispheric advantage for their execution. This study was aimed to look at a possible hemispheric preponderance in block design tasks comparing visual, tactile and crossmodal spatial performance. A two-dimensional template had to be reproduced by arranging cubes with surfaces different in both colour and texture. In the visual condition the template was given in the visual modality and the cube arrangement was under visual control. In the tactile condition the template was presented tactually and the cube assembly had to be done under entirely tactual control. In the crossmodal condition the template was presented visually and the assembly was restricted to tactual control. Task completion time (TCT) and number of correct responses (NCR) were compared between right hand and left hand responses. Only in the crossmodal condition a constant left hand superiority of performance was found. Non-crossmodal tasks did not show a constant hemispheric preponderance. In the tactile condition allowing for easy differentiation of input to one or the other hemisphere TCTs varied only according to the compatibility of side of afferent input and side of assembling action irrespective of the hemisphere engaged. It is concluded that mental operations requiring spatial assembling not necessarily engage the non-dominant hemisphere to a larger extent than the language dominant hemisphere. For crossmodal information processing, however, the non-dominant hemisphere appears to be superior.     

Hemispheric specialization during mental imagery of brisk walking

Objectives:

Brisk walking, a sensitive test to evaluate gait capacity in normal and pathological aging such as parkinsonism, is used as an alternative to classical fitness program for motor rehabilitation and may help to decrease the risk of cognitive deterioration observed with aging. In this study, we aimed to identify brain areas normally involved in its control.

Methods:

We conducted a block‐design blood oxygen level dependent function magnetic resonance imaging (BOLD fMRI) experiment in 18 young healthy individuals trained to imagine themselves in three main situations: brisk walking in a 25‐m‐long corridor, standing or lying. Imagined walking time (IWT) was measured as a control of behavioral performance during fMRI.

Results:

The group mean IWT was not significantly different from the actual walking time measured during a training session prior to the fMRI study. Compared with other experimental conditions, mental imagery (MI) of brisk walking was associated with stronger activity in frontal and parietal regions mainly on the right, and cerebellar hemispheres, mainly on the left. Presumed imagined walking speed (2.3 ± 0.4 m/s) was positively correlated with activity levels in the right dorsolateral prefrontal cortex and posterior parietal lobule along with the vermis and the left cerebellar hemisphere.

Interpretations:

A new finding in this study is that MI of brisk walking in young healthy individuals strongly involves processes lateralized in right fronto‐parietal regions along with left cerebellum. These results show that brisk walking might be a non automatic locomotor activity requiring a high‐level supraspinal control. Hum Brain Mapp, 2012. © 2011 Wiley Periodicals, Inc.

     

Hemispheric specialization and the perception of emotion: Evidence from right-handers and from inverted and non-inverted left-handers

Right-handers and inverted and non-inverted left-handers viewed emotional expressions in one hemifield and, simultaneously, a neutral expression of the same poser in the other hemifield. Subjects were required to identify the side containing the affective face. Happy faces with open (i.e. salient) and closed mouth smiles and sad faces were used as stimuli. For right-handers and inverters reaction time was faster to right hemifield presentations for happy faces and to left hemifield presentations for sad faces. Non-inverters showed the reverse pattern. The saliency of the happy expressions had no effect on the magnitude and direction of asymmetry for any group. The data support the hypothesis of differential hemispheric specialization for positive and negative emotion and demonstrate opposite patterns of asymmetry in affect perception for inverted and non-inverted left-handers.     

Hemispheric specialization using SPECT and stimulation tasks in children with dysphasia and dystrophia

Developmental dysphasia, a severe childhood learning disorder, is thought to result from problems in hemispheric specialization involving both left and right cerebral hemispheres. Regional cerebral blood flow (rCBF) was measured at rest and during stimulation of both hemispheres independently: dichotic listening for the left, dichaptic palpation for the right. Eight right-handed boys with expressive dysphasia, aged 8 to 12 years, were investigated using SPECT and compared with eight right-handed age-matched boys with Duchenne muscular dystrophy with reading disorders but normal speech. rCBF values at rest were also compared with those of five right-handed age-matched normal boys. In the dichotic task, children with dysphasia differed from children with dystrophia by failure to increase rCBF in the left hemisphere, in Broca's area, but rCBF increased in the right hemisphere, in the region homologous to Broca's area. In the dichaptic task, rCBF increased bilaterally for children with dysphasia whereas in children with dystrophia rCBF increased only in the right hemisphere. At rest the physiological asymmetry was reversed in favor of the right hemisphere in all areas except Broca's area. Surprisingly, the same applied at rest and for all areas in children with dystrophia. These results confirm that functional specialization of both hemispheres is impaired in developmental dysphasia. Moreover, they suggest that learning disabilities associated with Duchenne muscular dystrophy could also be related to abnormal hemispheric specialization.     

Hemispheric specialization in the detection of subjective objects

Three experiments were conducted to examine hemispheric specialization for the detection of subjective objects. In the first two experiments, observers searched for the presence of a square defined by subjective contours. The first experiment demonstrated that the left hemisphere made more errors for detecting these objects. The second experiment showed that the increased errors were due to the left hemisphere responding to the individual features of the objects and not the objects as a whole. In the second experiment, the right hemisphere was also faster for detecting the absence of a subjective object. A third experiment was conducted to determine if performance for the right hemisphere was due to object level processing. It was shown that the right hemisphere only makes illusory conjunctions for features within perceptual groups while the left hemisphere makes illusory conjunctions both within and across perceptual groups, providing converging evidence for object level processing in the right hemisphere. The results suggest that the right hemisphere conjoins feature information for the perception of objects.     

Superior digit memory of abacus experts: an event-related functional MRI study

Abacus experts exhibit superior short-term memory for digits, but the underlying neurophysiological mechanism remains unknown. Using event-related fMRI, we examined the brain activity of abacus experts and non-experts during the memory retention period of a delayed match-to-sample task using digits as stimuli. In controls, activity was greater in cortical areas related to verbal working memory, including Broca's area. In contrast, in experts, activity was greater in cortical areas related to visuo-spatial working memory, including the bilateral superior frontal sulcus and superior parietal lobule. This provides neurophysiological evidence that abacus experts utilize a visuo-spatial representation for digit memory.     

Hemispheric specialization in the assessment of female physical attractiveness

Female physical attractiveness has been widely related to waist-to-hip ratio (WHR) and body weight (BW). The present study was conducted to examine the role of hemispheric specialization in the perception of physical attractiveness. Drawings of female figures that differed in BW (underweight, normal and overweight) and WHR (0.7 and 1.0) were presented to both male and female subjects using the visual half-field technique. The stimuli were presented for an unusually short duration (180 msec). Under these conditions, male but not female subjects rated the various female figures as differing in attractiveness. Thus, male judgements of female attractiveness depended on weight and WHR. Reaction time and accuracy scores obtained from male subjects suggested that the left hemisphere (LH) was slower but more accurate than the right hemisphere in detecting differences in the attractiveness of the figures. Additionally, the most attractive figure was detected significantly more accurately than the least attractive figure when the figures were presented to the LH. The findings were discussed in terms of evolutionary views of sex differences in mate selection.     

Interhemispheric cooperation of left- and right-handers in mental calculation tasks

Relations between handedness and interhemispheric processing in cognitive tasks were examined. Thirty six right-handers and thirty left-handers (familial and nonfamilial left-handers) were asked to add two numbers which were presented tachistoscopically. Two numbers were displayed either to one visual field, or one to the left and one to the right visual field simultaneously. In Experiment 1, the numbers were displayed in Arabic numerals, and in Experiment 2 one of the numbers was displayed in Kanji and one in Arabic numerals. The results of Experiment 1 showed a bilateral advantage, however no subject group difference was shown in the performance of the three (left unilateral, right unilateral, and bilateral) presentation conditions. Though familial left-handers showed a weaker tendency to different patterns than right and non-familial left-handers, the results of Experiment 2 were largely similar to those of Experiment 1. These findings suggest that interhemispheric processing may not differ between left- and right-handers.     

Hemispheric specialization for motor sequencing: abnormalities in levels of programming

Left and right hemisphere stroke patients and control subjects performed sequences of hand postures which varied in complexity (repetitive and heterogeneous) and length (one to five). Performance in the hand ipsilateral to the stroke was compared to a control group using the same hand. Neither stroke group had problems preprogramming sequences prior to movement. The only deficit seen for the right hemisphere group was a greater difference in movement time (MT) between heterogeneous and repetitive sequences relative to controls, regardless of sequence length. This suggested right hemisphere damage results in subtle timing but not error deficits on more complex movements, perhaps due to increased external spatial demands. The left hemisphere group was slower to execute single postures, and had difficulty scheduling motor programs for repetitive and heterogeneous movements such that inter-response times (IRTs) were more affected by sequence length than for controls. Left hemisphere patients also made more errors on heterogeneous sequences as they increased in length, and the difference in MTs between repetitive and heterogeneous sequences increased more with increasing length relative to their control group. These results suggested the left hemisphere plays a role in controlling single postures, in scheduling motor programs during repetitive and heterogeneous movements, and in processes related to sequential ordering.     

Dual-task interference in left-handed subjects: Hemispheric specialization vs manual dominance

Thirty-six left-handed subjects performed a dichotic listening task and two concurrent (verbal plus finger-tapping) tasks. Baseline tapping scores revealed both left- and right-hand dominance within left-handed subjects. Moreover when subjects were categorized as consistent or inconsistent for ‘sidedness advantage’ (e.g. CONSISTENT=same side for dominant hand and ear advantage), it was shown that the dual-task interference effects found on the concurrent tapping tasks were due to both hemispheric specialization and manual dominance.     

Hemispheric dysfunction in schizophrenia: Assessment by visual perception tasks

Before and after a double-blind trial of haloperidol vs. mesoridazine, 24 hospitalized schizophrenics performed visual perception tasks designed to assess function of the cerebral hemispheres. Tasks involved identifying as "same" or "different" two images (either letters, digits, or unfamiliar shapes) projected tachistoscopically to the right or left visual field or to both together. Multivariate analysis of variance related response latency and accuracy to task type, hemisphere stimulated, and pre- vs. posttreatment testing. Both before and after treatment, subjects responded most slowly and least accurately to letter-matching. Bilateral presentation of stimuli resulted in faster and more accurate responses, except on shape-matching. Neuroleptic treatment improved speed and accuracy overall, though not under certain task conditions. Results accorded more with an impairment in verbal processing and interhemispheric coordination than with a specific left-hemispheric deficit in schizophrenia.     

Hemispheric specialization for language in the congenitally blind: The influence of the Braille system

The functional cerebral organization of two groups of congenitally blind persons of different age and schooling was studied by testing their dichotic listening to pairs of digits. The younger congenitally blind group showed a comparable level of performance to their control counterparts; however, older subjects shifted their initial right ear advantage to an increased left ear performance as they progressed in the mastery of the Braille system. As this system is founded on spatial strategies, we can concluded that this shift is related to the activation of some right hemispheric linguistic mechanisms.     

Hemispheric specialization of impaired disengagement of attention in depression: a tachistoscopic method

Difficulty shifting attention away from negative stimuli once engaged is a well-established cognitive bias observed in depression. This study attempted to determine whether this impaired disengagement of attention is lateralized in the brain. Thirty depressed and 30 control participants performed an attention disengagement task wherein the valence of the stimulus and the visual field was presented. The depressed group had longer reaction times than the control group, indicative of the typical cognitive and psychomotor slowing seen in depression. The effect of visual field presentation on the ability to disengage attention however was different for controls as compared to the patients. In controls, a distinct right hemisphere advantage was seen for disengaging attention which is in line with research that has identified right hemisphere structures as the seat of behavioural inhibition. In the depressed group, however, this right hemisphere advantage was not observed.     

Hemispheric specialization in children as reflected in the longitudinal development of ear asymmetry

The longitudinal development of ear asymmetry has been investigated in two samples of kindergarten and primary school children over an age range of six years. Ear preference in a dichotic digit test, administered four times, did not appear to be affected by age and sex: right ear advantage was predominant at all times. Individual comparison showed the development of ear advantage to depend on initial preference. Initially left eared subjects when changing ear advantage do so from left to right at early and from right to left at later school ages. The left-right shift may be due to the school teaching of linguistic skills which could selectively activate the left cerebral hemisphere. This explanation is supported by the finding that initially right eared subjects tended to conserve that preference at early school ages. Acknowledgements. We would like to thank Mr. P. Borgman and his staff of the Johannesschool in Amsterdam as well as their pupils who did not protest despite being examined year after year. The cooperation of the Free University Audio-Visual Center (Mr. Fred Van Hilst) is kindly acknowledged. Finally we would like to thank Dr. Paul Harris who was willing to read the English text critically and all others who assisted in the completion of this research.     

Hemispheric specialization for speech perception in four-year-old children from low and middle socio-economic classes.

Four-year-old male and female children from low and middle socio-economic class (SEC) were presented a dichotic syllable task. Both low and middle SEC males evidenced significant right-ear advantages. Neither low nor middle SEC females evidenced a significant right-ear advantage. The similar ear advantage in the low and middle SEC populations replicates a previous study with six-year-olds and suggests that the variations in rearing conditions which occur in low and middle SEC classes does not affect hemispheric lateralization for speech perception.     

Hemispheric specialization of language: an EEG study of bilingual Hopi indian children

Electroencephalographic (EEG) recordings were obtained from electrode placements over the left and right frontal and parietal lobes of the brain in sixteen Hopi Indian children listening to tape recorded children's stories in the Hopi and English languages. Spectral analysis of the EEG data revealed that, for the parietal leads, alpha desynchronization was relatively greater over the right hemisphere for listening to Hopi than for listening to English, which indicates a greater right hemisphere participation in the processing of the Hopi speech. The results of the experiment are directionally consistent with our hypothesis, and imply that linguistic relativity may exist on a neurolinguistic level, such that languages can differ in the relative degree to which they serve as instruments of thought in a propositional, left hemisphere mode, or in an appositional, right hemisphere mode.     

Hemispheric asymmetries in motor function: II. Ordering does not contribute to left-hemisphere specialization

Patients with unilateral brain lesions of vascular origin were administered tests designed to determine if the left hemisphere is specialized for the ordering of motor acts. Patients with left- and right-sided lesions responded similarly to manipulations of ordering demands in two motor tasks, one a test of manual sequence learning and the other a test of speeded performance. A detailed analysis of performance on an Ideational Apraxia task indicated that the deficit of patients with left-sided lesions was best characterized as a deficit in generating appropriate acts rather than ordering them. It was concluded that there is no evidence for left-hemisphere specialization for the ordering of motor acts. It was hypothesized that there are two broad stages of motor function: generation of motor "target" acts (which is lateralized to the left hemisphere) and the ordering and execution of these acts (which are not lateralized).     

Hemispheric asymmetries in motor function: I. Left-hemisphere specialization for memory but not performance

Patients with unilateral brain lesions of vascular origin were administered tests designed to determine if left-hemisphere specialization in manual-sequence tasks involves memory for these sequences, or performance of them, or both. Patients with left-sided lesions were worse than patients with right-sided lesions on two tasks requiring the recall of hand positions. Whereas patients with left-sided lesions showed a trend towards being worse on speeded performance of an already learned manual sequence, in both groups on this task there were a large number of failures to remember the sequence. When memory demands were better controlled by providing a model during the speeded performance task, there were no group differences. It is proposed that there is left-hemisphere specialization for memory but not performance of such motor tasks.     

Hemispheric asymmetry and the mental number line: comparison of double-digit numbers

To investigate the spatial representation of numbers and its possible hemispheric organisation, 46 participants were presented with a series of double-digit numbers in a fixed standard number comparison task using 65 (in Experiment 1) and 55 (in Experiment 2) as the standard. Visual field of presentation, distance from the target number and magnitude were manipulated. Reaction times decreased with increasing distance from the target number, in line with the well-established distance effect. There was no main effect of visual field, however the interaction between visual field, distance and magnitude was significant. For large distances, numbers of small magnitude were responded to faster in the left over the right visual field, while there was a right visual field advantage for large magnitude numbers. These results suggest that the representation of numbers has spatial qualities (i.e., smaller numbers are represented to the left of a comparison point, larger numbers to the right).