Right Hemisphere Superiority Research Articles

Brief Report: Perception and Lateralization of Spoken Emotion by Youths with High-Functioning Forms of Autism

The perception and the cerebral lateralization of spoken emotions were investigated in children and adolescents with high-functioning forms of autism (HFFA), and age-matched typically developing controls (TDC). A dichotic listening task using nonsense passages was used to investigate the recognition of four emotions: happiness, sadness, anger, and neutrality. The participants with HFFA did not differ significantly in overall performance from the TDC, suggesting that the pervasive difficulty in processing emotions is not uniformly present in emotions expressed verbally. Both groups demonstrated a left-ear effect for the perception of emotion in nonsense passages, consistent with overall right-hemisphere superiority for this function.

Reading from Left to Right

PSYCHOLOGY Categorical perception is a robust phenomenon and can be illustrated by the more rapid discrimination of two colors separated by a fixed chromatic distance when the colors fall on opposite sides of a category boundary, such as blue/green, than when they both lie within a single category. Both adults and infants exhibit this capacity, and Franklin et al. have investigated the influence of hemispheric lateralization and of language in a pair of studies. First, by presenting the colors in the left or right visual field (LVF or RVF), they show that adults react more quickly to RVF stimuli and hence that categorical perception of color is lateralized (in a relative, though not absolute, sense) to the left hemisphere, to which the RVF projects. Consistent with a left-hemispheric predominance of language skills, a verbal interference task blocked categorical perception in adults, whereas a visual interference task did not. Prelinguistic infants, on the other hand, displayed a right-hemispheric (LVF) superiority in the categorical perception of colors. Second, they recruited a group of toddlers 2 to 5 years of age and assessed their comprehension of the words blue and green. When tested on the same paired colors, the reaction times of these toddlers did not vary as a function of semantic knowledge, but those that had mastered the words demonstrated a hemispheric lateralization that was adult-like; that is, categorical perception for RVF stimuli. Toddlers who were still learning about blue and green retained the LVF pattern of categorical perception. — GJC Proc. Natl. Acad. Sci. U.S.A. 105 , 3221; 18221 (2008).

The symmetry of visual fields in chromatic discrimination

Both classical and recent reports suggest a right-hemisphere superiority for color discrimination. Testing highly-trained normal subjects and taking care to eliminate asymmetries from the testing situation, we found no significant differences between left and right hemifields or between upper and lower hemifields. This was the case for both of the cardinal axes of color space. In addition, there was no difference according to whether the discriminanda were delivered to the same or to different hemispheres, and we note that the same number of synapses may lie between the retina and the site of comparison whether or not the stimuli are delivered to the same hemisphere.

Night-time right hemisphere superiority and daytime left hemisphere superiority: A repatterning of laterality across wake–sleep–wake states

During the sleep onset period (SOP), there is a state-specific relative advantage of the right hemisphere (RH). This superiority could either be due to the ability of the RH when operating at levels of reduced arousal, as suggested by its superiority in sustaining vigilance, or it could depend on a more pronounced homeostatic deactivation of the left hemisphere (LH). To evaluate whether variations of lateralization from wake to sleep are consistent with one of these two hypotheses, we considered a finger tapping task (FTT) bimanually performed during two wakeful conditions, during the SOP, upon experimental awakenings from stage 2 and REM sleep in the first and in the second part of the night, and upon morning awakening. The RH advantage in sustaining vigilance would be supported if the relative RH advantage was present throughout the sleep period. Finding that the repatterning of hemispheric asymmetry is present and/or prominent in the first part of the night would support the homeostatic hypothesis, i.e. when the homeostatic process is more pronounced. Results from 16 subjects revealed a significant superiority of the LH during the two wakeful conditions. At sleep onset, a clear reversal of dominance was observed and it was followed by a steady RH superiority upon both REM and NREM sleep awakenings, and upon the morning sleep–wake transition. Therefore, performance in a FTT reveals a repatterning of laterality across wake–sleep–wake states. These results are interpreted as consistent with the hypothesis concerning an advantage of the RH in sustaining vigilance.

Right hemisphere specialization for color detection

Three experiments were carried out to investigate hemispheric asymmetry in color processing among normal participants. In Experiment 1, it was shown that the reaction times (RTs) of the dominant and non-dominant hands assessed using a visual target presented at the central visual field, were not significantly different. In Experiment 2, RTs of ipsilateral hands to lateralized chromatic stimuli revealed that the processing time was 17 ms shorter in the right hemisphere (RH) than that in the left hemisphere among the right-handed participants, whereas no significant difference was found among the left-handed participants. On the other hand, RTs to lateralized achromatic stimuli showed no such asymmetry among both the right- and left-handed participants (Experiment 3). These findings strongly suggest RH superiority for detection of color among right-handed individuals.

Lateralized lexical decision in schizophrenia: hemispheric specialization and interhemispheric lexicality priming.

Reports of left-hemisphere dysfunction and abnormal interhemispheric transfer in schizophrenia are mixed. The authors used a unified paradigm, the lateralized lexical decision task, to assess hemispheric specialization in word recognition, hemispheric error monitoring, and interhemispheric transfer in male, right-handed participants with schizophrenia (n=34) compared with controls (n=20). Overall, performance and error monitoring were worse in patients. However, patients like controls showed left-hemisphere superiority for lexical processing and right-hemisphere superiority for error monitoring. Only patients showed selective-interhemispheric lexicality priming for accuracy, in which performance improved when the lexical status of target and distractor stimuli presented to each hemifield was congruent. Results suggest that schizophrenia is associated with impaired monitoring and with increased interhemispheric automatic information transfer rather than with changed hemispheric specialization for language or error monitoring.

Right-hemispheric superiority in split-brain monkeys for learning and remembering facial discriminations.

Right-hemispheric superiority in split-brain monkeys for learning and remembering facial discriminations.

Right-hemispheric superiority in split-brain monkeys for learning and remembering facial discriminations.

Twenty-six split-brain rhesus monkeys learned and remembered 8 go/no-go discriminations of monkey faces significantly better with the right hemisphere than with the left. Four discriminations required differentiating individual identity with expression held constant, and 4 required discriminating facial expression with identity held constant. There was no significant difference in the degree of laterality shown for these 2 types of problems. Female monkeys were more lateralized for learning to discriminate faces than were males. This sex difference in laterality was significant for learning but not for memory. Laterality for the facial discriminations was not significantly related to handedness of the monkeys. Overall, rhesus monkeys, like humans, show a right-hemispheric superiority for facial processing.

Contributions of stimulus encoding and memory search to right hemisphere superiority in face recognition: Behavioural and electrophysiological evidence

The relative contributions of stimulus encoding and memory search to right hemisphere (RH) superiority in face recognition were investigated in a memory search task with lateralized probe stimulus presentation. RH superiority in reaction time and latency of a positive ERP component was independent of stimulus degradations, but increased as a function of memory set size. These results suggest equal efficiency of the hemisphere in stimulus encoding, but RH superiority in memory search. In addition, a long-lasting ERP negativity contralateral to the stimulated hemifield is discussed with reference to models of hemisphere processing in hemifield studies.

Verbal Involvement of the Left Hemisphere in Processing Facial Expressions of Emotion

Verbal involvement of the left hemisphere in processing facial expressions of emotion was investigated with normal subjects by examining the effects for hemispheres (right or left hemisphere), stimulus processing codes (imagery or verbal code), and the degree of cognitive demands of the task (unilateral or bilateral tachistoscopic projection) on accuracy for recognizing emotional expressions. When a “target” cartoon-like face was unilaterally projected, right-hemisphere superiority in face recognition accuracy was observed whether the “test” emotional stimuli were imagery faces or verbal labels. But when two different target faces were bilaterally presented simultaneously (i. e., one face to the right hemisphere and the other to the left hemisphere), right-hemisphere superiority was obtained only when the test stimuli were emotional labels. These results were predicted and interpreted in terms of the inter ruption effect of verbal processing on visual processing in the left hemisphere and of the interference and collaboration effects between two hemispheres on processing of differentiated emotional codes of facial expressions.

A general theory concerning the prenatal origins of cerebral lateralization in humans.

The origins of cerebral lateralization in humans are traced to the asymmetric prenatal development of the ear and labyrinth. Aural lateralization is hypothesized to result from an asymmetry in craniofacial development, whereas vestibular dominance is traced to the position of the fetus during the final trimester. A right-ear sensitivity advantage may contribute to a left-hemispheric advantage in speech perception and language functions, whereas left-otolithic dominance may independently promote right-sided motoric dominance and a right-hemispheric superiority in most visuospatial functions. The emergence of handedness is linked to the assumption of an upright posture in the early hominids, whereas the failure to develop clear vestibular asymmetry may underlie the poor motoric lateralization found in several neurodevelopmental disorders.

How Knowledge of the Song Influences the Matching of “Melodies” to Rhythm Sequences Tapped in the Right and Left Palms

Previous work by O'Boyle and Sanford (1988) has demonstrated that the right hemisphere (RH) is superior to the left hemisphere (LH) in the matching of tape-recorded melodies to rhythm sequences tapped in the palms of the hands. This asymmetrical advantage was attributed to a RH superiority in the perceptual processing of intonation as compared to the rhythm component of these musical stimuli. In the present study, subjects were taught that the monotone sound of two wooden drumsticks struck together in a specified rhythm actually represented non-melodic translations of songs with identifiable melodies. After such mental associations had been formed, these non-melodic stimuli (which produced no asymmetric performance in Exp. 2 of the O'Boyle and Sanford study), now produced a RH advantage that was comparable to that induced by the original melodies. This finding suggests that the physical presence of intonation and its subsequent perceptual analysis, are not necessarily critical to the RH advantage reported by O'Boyle and Sanford (1988). Rather, the asymmetry may be related to a superior ability of the RH to generate and/or manipulate echoic images in memory.

Effects of stimulus degradation on letter-matching performance of left and right hemispheric stroke patients

Performance on a letter-matching task involving conditions of perceptual degradation was tested on 18 Right CVA patients, 18 Left CVA patients and 18 control subjects. Letter stimuli were presented in three conditions: Clear, Line-Masked, and Blurred. Subjects judged whether two letters of a pair were the same in name or different in name. Right CVA patients performed significantly less accurately than did Left CVA patients and control subjects when letters were perceptually degraded with a line mask overlay or by blurring. No significant differences were found between the two patients groups when the letters were presented without perceptual degradation (the Clear condition), but both patient groups were significantly less accurate than control subjects. The results are similar to findings reported in visual half-field studies with neurologically normal subjects and indicate right-hemisphere superiority for the processing of perceptually degraded visual information.

RELATIVE VS ABSOLUTE RIGHT HEMISPHERE SUPERIORITY FROM LATERAL DIFFERENCES IN VISUAL PROCESSING BY NORMALS: AN EXAMPLE OF UNCERTAINTY IN EXPERIMENTAL NEUROPSYCHOLOGY

Statistical tools (correlations and analyses of variance) have been proposed to decide whether a hemispheric functional asymmetry reflects absolute or relative cerebral superiority. A set of 16 normal subjects were given two tasks involving right hemisphere competences in the visual modality: the recognition of a small set of easily discriminated faces and meaningless geometrical figures, displayed in the lateral visual fields. The statistical tools did not perfectly agree with one another as had already been noted in a previous study. The results also showed a left hemisphere advantage, contrary to expectations; this last observation is linked with a possible asymmetrical effect of familiarization with the material

Relationship between Performance and Preference Measures of Cognitive Laterality

This study examined the relationship between two methods of assessing cognitive laterality, one by responses on a preference inventory and the other by assessing asymmetry of hemispheric performance on tests associated with processing in the left or right cerebral hemispheres. 87 graduate students were administered both instruments. Analysis showed negative or no relations between the preference and performance measures. The performance tests associated with left- and right-hemisphere functions were taken directly or adapted from tests showing left- or right-hemisphere superiority in unilateral lesioned patients, brain-divided patients, and normal subjects. The preference inventories were constructed on the basis of the same research but have not been validly related to brain functions. The results of this study suggest that the two types of instruments do not measure the same thing.

Hemispheric asymmetries for complex visual patterns.

Three tachistoscopic studies examined the laterality of spatial-form perception in normal adults using randomly generated eight-point and 12-point patterns (Vanderplas & Garvin, 1959) as the lateralized stimuli. In the first study of recognition accuracy, 36 subjects were tested in a partial replication of Fontenot. No laterality effects were found, and over-all recognition was better for the more complex 12-point patterns. In a second similar study with 20 subjects, the lateralized stimulus was followed by a central masking pattern. A left-hemisphere superiority for recognition and better over-all recognition for more complex patterns was obtained. These data do not support Fontenot's report of right-hemisphere superiority in complex visuospatial processing. Given these diverse findings, a reaction time study using mental rotation was conducted using the same patterns to determine whether latency would reflect accuracy of recognition. Twenty-six subjects judged whether a rotated lateralized test pattern was the same or different from a central target pattern. Measures of both latency and accuracy were separately assessed. No main effect of visual field was obtained on either measure. These studies suggest that the nature of hemispheric involvement in spatial form perception is far from resolved.

Witelson's dichaptic stimulation test and children with different levels of musical talent

In a three-stage longitudinal study with children at the beginning of puberty, we found differences between male musicians and male non-musicians in Witelson's Dichaptic Stimulation Test. Data indicated a shift from right-hemisphere superiority for spatial processing in the first stage to left-hemisphere superiority in the third stage. The shift was due to musicians' results only. In girls, musical talent did not influence the relative participation of left- and right-hemisphere functions for spatial processing.

Familiarity decisions for faces presented to the left and right cerebral hemispheres

Right-handed subjects were asked to decide whether or not faces presented briefly in the RVF or in the LVF were familiar (familiar faces were those of famous people). This task avoids the need for extensive semantic processing or temporary storage involved in conventional naming or identification tasks, and thus eliminates the contribution of such factors to any observed asymmetry. The resulting finding of faster reaction times to LVF faces, with no overall visual hemifield difference in error rates, is taken to indicate a right-hemisphere superiority either in the processes used to construct facial representations or in the accessing of face recognition units, or both.

Processing of faces by patients with unilateral hemisphere lesions: I. Dissociation between judgments of facial affect and facial identity

In this study, right-hemisphere-damaged (RHD) subjects performed significantly worse than LHD and NHD controls across a series of seven facial identity and facial affect tasks. Even when the patient groups were statistically equated on a measure of visuoperceptual ability, the RHD group remained impaired on three emotional tasks—naming, picking, and discriminating emotional faces. These findings suggest that the defects shown by RHD patients on facial affect tasks cannot be solely attributed to defects in visuoperceptual processing and that the right-hemisphere superiority for processing facial affect exists above and beyond its superiority for processing facial identity.

Right-hemisphere superiority in the discrimination of spatial phase.

Visual field differences have been investigated in various detection and discrimination tasks for simple sinusoidal gratings or for complex gratings composed of two sinusoids of spatial frequencies f and 3f. Sinusoidal gratings were employed to evaluate contrast sensitivity, subthreshold summation effects, aftereffects of adaptation to a high-contrast grating, and spatial-frequency discrimination. The tasks with complex gratings were detection of the 3f component in the presence of a high-contrast f component and spatial-phase discrimination. The stimuli were presented either in the left or in the right visual hemifield. The results indicate a lack of lateralization for detection and spatial-frequency discrimination of sinusoidal gratings, and for the bandwidth of subthreshold summation effects and adaptation aftereffects, whereas the detection of the 3f component in the presence of a high-contrast f component, as well as spatial-phase discrimination of f +3f gratings, show a left-field advantage. This suggests a right-hemisphere superiority in the processing of spatial phase.