Left Hemisphere Advantage Research Articles

Do the right and left hemispheres attend to the same visuospatial information within a face in infancy?

Four‐ to 10‐month‐old infants process different information within geometrical patterns with each of the 2 hemispheres (Deruelle & de Schonen 1991,1995). This study was designed to test whether this early difference between the hemispheres’ modes of processing also holds in the case of face processing. Four‐ to 10‐month‐old participants had to discriminate and recognize with each hemi‐visual field the 2 members of a pair of faces. There were 3 pairs of faces that differed by either eye shape, eye size, or eye orientation. The results confirmed the predictions made on the basis of adult studies and infants’ hemispheric differences in geometrical pattern processing: A left hemisphere advantage was observed in the case of the 1st pair of faces and a right hemisphere advantage with the 2nd and 3rd pairs. It is suggested that the early right hemisphere advantage over the left observed by de Schonen and Mathivet (1990) in face recognition by 4‐ to 9‐month‐old infants may be mainly based on the difference in the kind of visuospatial information processed by each hemisphere.

Laterality in visual speech perception.

The lateralization of visual speech perception was examined in 3 experiments. Participants were presented with a realistic computer-animated face articulating 1 of 4 consonant-vowel syllables without sound. The face appeared at 1 of 5 locations in the visual field. The participants' task was to identify each test syllable. To prevent eye movement during the presentation of the face, participants had to carry out a fixation task simultaneously with the speechreading task. In one study, an eccentricity effect was found along with a small but significant difference in favor of the right visual field (left hemisphere). The same results were found with the face articulating nonlinguistic mouth movements (e.g., kiss). These results suggest that the left-hemisphere advantage is based on the processing of dynamic visual information rather than on the extraction of linguistic significance from facial movements.

Abnormal cerebral laterality in posttraumatic stress disorder.

Different studies’V2 have shown evidence of an augmented startle probe reflex in persons with posttraumatic stress disorder (PTSD). In normal subjects a potentiation of the startle probe reflex amplitude has been observed under conditions of negative emotional or during shock anti~ipation.~ Under conditions without shock anticipation (lack of anticipatory anxiety), the startle response was greater and of shorter latency when the acoustic startle probe stimulus was delivered to the left ear (i.e., right cerebral hemisphere) as opposed to the right ear? whereas under conditions of shock anticipation the right-left difference was in the opposite direction (significant interaction “condition x ear”). These findings suggest that the normally observed right hemispheric dominance of the startle response gets lost under stress; instead, a left hemispheric dominance develops. Other results are in line with this interpretation of a stress-induced abnormal cerebral laterality: under stress the normally observed left hemispheric advantage in processing verbal stimuli gives way to a right hemispheric ad~antage.~.’ Concerning these data it can be hypothesized that subjects with PTSD may show an abnormal cerebral laterality. The hypothesis is supported by data on auditory functions in PTSD subjects8 showing a more pronounced asymmetry in performance scores for right versus left ear stimulation in PTSD subjects than in controls. Data on auditory probe-evoked potential attenuation as an index of hemispheric activity reported by Schiffer et aL9 also hint at an abnormal or altered cerebral laterality in PTSD: subjects with a history of childhood trauma were reported to show a significant left dominant asymmetry during neutral memory, which markedly shifted to the right during unpleasant memory, whereas control subjects without childhood trauma did not display a significant asymmetry during either task or a significant shift between tasks. The present investigation was designed as a pilot study to test the hypothesis of abnormal or altered cerebral laterality in PTSD. Two functions that are dominated

Hemispheric Processing of Categorical and Coordinate Spatial Relations in Vision and Visual Imagery

Right-handed subjects participated in a visual half-field experiment using “clock” stimuli. For the Categorical task, subjects indicated whether the long and short hands of a clock were above or below the horizontal midline of the dial. For the Coordinate task, they indicated whether the long and short hands of a clock formed an angle that is more or less than 60°. For both tasks, clock stimuli were either analog clocks (Visual version) or digital clocks from which subjects generated images of analog clocks (Imagery version). The results indicated that for both the Visual and Imagery versions, there was a nonsignificant trend toward a left hemisphere advantage in the Categorical task, whereas there was a significant right hemisphere advantage in the Coordinate task. Implications of the results were discussed from the viewpoints of task factors in hemispheric processing of visual imagery, Kosslyn's (1987, 1994) computational model of vision and visual imagery, and vision/imagery isomorphism.

Hemispheric asymmetries for the temporal resolution of brief auditory stimuli.

This study investigates a left-hemisphere (LH) advantage for the discrimination of fine temporal events within the auditory modality in 24 normal adults. Brief noise bursts were delivered monaurally to the left or right ears, half of which contained a gap lasting between 2 and 8 msec. Subjects were required to indicate whether or not the noise burst contained a gap. Research within this area has yielded conflicting results. It is possible that variations in gap position or the properties of the noise burst may have contributed to this conflict. The effect of gap position was investigated by systematically varying the position of the gap during half of the trials. White noise bursts were used to avoid the use of spectral cues. Reaction time, response bias, and response error measures revealed a right-ear (and hence LH) advantage for gap detection. Stable gap positions were recognized more accurately than variable gap positions. Gap position had no effect on the observed LH advantage. These results suggest that the auditory properties of noise burst, rather than gap position, play an important role in the discrepancies observed in this area.

Time course of semantic activation in the cerebral hemispheres

Recent visual half-field studies using relatively long stimulus onset asynchronies (SOAs) and non-associated category members (e.g. deer–pony) as word pair stimuli have indicated that with a low proportion of related stimuli, automatic priming of non-associated category information is larger in the right than in the left hemisphere [Chiarello and co-workers]. The present study examined semantic priming of non-associated category members, with a low proportion of related stimuli in the visual fields/hemispheres across SOAs of 165, 250, 500, and 750 msec. Eighty normal, right-handed subjects were tested (20 subjects/SOA). The results revealed a left hemisphere advantage in priming at the 165 msec SOA, whereas the right hemisphere advantage reported in earlier studies was observed at the longest 750 msec SOA only. The results challenge the view that a larger range of related meanings is activated in the right than in the left hemisphere. Rather, the time course of semantic activation may be different in the hemispheres. Copyright©1997 Elsevier Science Ltd.

The Effect of Auditory Experience on Hemispheric Asymmetry in a Post-Lingually Deaf Child: A Case Study

We have previously shown that cerebral asymmetry in congenitally deaf children differs from that observed in normal hearing children. The effect of early auditory experiences on this process was investigated in a 14 year-old boy who had completely lost his hearing at the age of 5 due to meningitis. His recognition of laterally projected words and faces was compared with that of 18 congenitally deaf and 18 normal hearing children.In the word recognition test, a right hemisphere advantage was found in the patient and in congenitally deaf subjects and a left hemisphere advantage in normal hearing subjects. In the face recognition test, the left hemisphere was more proficient in the patient and the right hemisphere in normal hearing subjects. There was no hemispheric difference in the congenitally deaf. While hemispheric asymmetry has an ontogenetic base, these findings suggest that the degree and nature of such asymmetries can be influenced by environmental factors during development.

A failure to produce a left hemisphere advantage through verbal priming

The proposition that visual field asymmetries can be produced through priming the left hemisphere with verbal material was investigated. In the first experiment a two-choice neutral detection task was established to measure biases of attention between the visual fields. In the second experiment, a priming effect was achieved by superimposing each trial with a verbal recognition task. Reaction time and error measures showed no sign of a right visual field advantage. In the third experiment, the neutral detection trials were intermixed with trials associated with a word recognition task. A significant right visual field advantage was found for the word recognition task. However, this pattern of asymmetry was not found for the neutral detection task. In the fourth experiment the level of difficulty associated with neutral detection task was increased. The effect of expectancy was investigated by manipulating the proportion of neutral and verbal stimuli. Despite these manipulations, the pattern of results was essentially the same as those observed in the previous experiment. These experiments demonstrate that verbal priming does not affect the distribution of spatial attention.

Dichaptic scanning of Braille letters by skilled blind readers: lateralization effects.

Dichaptic scanning of Braille letters was studied in 14 skilled blind readers, using Posner's paradigm. A right-hand (left-hemisphere) advantage was found when letters could be matched on the basis of their names (Name Identity Condition), a genuinely linguistic task, while no effects of lateralization appeared when matching could be performed on the basis of perceptual identity (Perceptual Identity Condition) or on "Different" responses. This result provides information about the cerebral lateralization of Braille reading and casts doubts about the current claim that linguistic material, when presented in the tactile modality, is initially analysed in a spatial code by the right hemisphere.

Temporal Processing Asymmetries Between the Cerebral Hemispheres: Evidence and Implications

This paper reviews a large body of research which has investigated the capacities of the cerebral hemispheres to process temporal information. This research includes clinical, non-clinical, and electrophysiological experimentation. On the whole, the research supports the notion of a left hemisphere advantage for temporal resolution. The existence of such an asymmetry demonstrates that cerebral lateralisation is not limited to the higher-order functions such as language. The capacity for the resolution of fine temporal events appears to play an important role in other left hemisphere functions which require a rapid sequential processor. The functions that are facilitated by such a processor include verbal, textual, and fine movement skills. The co-development of these functions with an efficient temporal processor can be accounted for with reference to a number of evolutionary scenarios. Physiological evidence favours a temporal processing mechanism located within the left temporal cortex. The function of this mechanism may be described in terms of intermittency or travelling moment models of temporal processing. The travelling moment model provides the most plausible account of the asymmetry.

Cerebral asymmetries in inspection time?

Recent studies have suggested that there are low-level processing asymmetries across the cerebral hemispheres, with a right visual field-left hemisphere advantage in tasks involving temporal resolution. In the present report, one such task, inspection time, was measured separately for each cerebral hemisphere in 10 right-handed male subjects over 5 days. A number of methodological improvements were made on previous studies in which a general right visual field-left hemisphere advantage had been found relative to the left visual field-right hemisphere in inspection time performance. The present results suggest that there is no general left hemisphere advantage in inspection time, although there might be asymmetries in practice effects across the hemispheres. The findings also suggest the existence of individual differences in the extent and direction of hemispheric specialisation for this task (ranging from left hemisphere dominance to marked right hemisphere dominance for some subjects) even in right-handed subjects.

Laterality and Types of Dyslexia

ANNETT, M. Laterality and types of dyslexia. NEUROSCI BIOBEHAV REV 20(4) 631–636, 1996.—The right shift theory of handedness and cerebral specialization suggests that there is an underlying substrate of random lateral asymmetries in all higher animals and a specific factor in humans which increases the probability of left hemisphere advantage. The specific factor displaces the random distribution along a continuum of asymmetry in favour of the left hemisphere and the right hand. The distribution of handedness in families can be explained if the shift to dextrality depends on a single gene, rs +, when the frequency of the gene is estimated from the proportion of dysphasics with unilateral lesions of the left versus the right hemisphere. The genotype proportions suggested a genetic balanced polymorphism with heterozygote advantage for laterality and ability. Application of the model to developmental dyslexia led to the hypothesis that both homozygotes (rs −− and rs ++ genotypes) are at risk for reading. The critical question was whether the type of cognitive problem differs as expected, speech based processing for the rs −− and non-speech based for the rs ++. The former should include more left and mixed handers, while the latter should be more strongly dextral than controls. Evidence for this double dissociation between type of cognitive disability and type of handedness has been found in poor readers and in other samples. Copyright © 1996 Elsevier Science Ltd.

Effect of Practice on Laterality in a Mental Rotation Task

The purpose of the present study was to investigate the effect of practice on the lateralization of mental rotation skills. Forty-six females and 46 males completed four blocks of 64 trials in a lateralized mental rotation task. Results revealed a reduction in reaction time and error rate across blocks, thus demonstrating a practice effect. A shift from a right hemisphere advantage to a left hemisphere advantage across blocks of trials was also found. The results are discussed in terms of their implication for hypotheses linking laterality and training. Practical implications for laterality research are also discussed.

Asymmetries in ear movements and eyebrow raising in men and women and right- and left-handers.

The abilities to move ears and eyebrows were examined in 442 subjects (204 men, 238 women) categorized as right-handed (n = 382) and left-handed (n = 60, including mixed and ambidextrous-handed subjects). Approximately 22% could move one or the other ear and about 18% could move both ears simultaneously, but significantly more men could move both ears simultaneously. Significantly more men than women were able to move both the left and right eyebrow and the left ear. No differences were observed between right- and left-handers. Significant contingency correlations were observed between raising eyebrows and moving ears. Results are discussed with reference to a possible left ear-right hemisphere advantage for localising environmental sounds, primitive ear-moving abilities no longer functional in modern humans, and epiphenomenal by-products of other adaptive sex differences.

Smaller right ear (left hemisphere) advantage for dichotic fused words in patients with schizophrenia

The purposes of this study were to compare right ear (left hemisphere) advantage for dichotic words in schizophrenia and depression and to assess its association with antipsychotic medication, symptom ratings, and gender. Thirty-two schizophrenic patients and 65 patients with major depression were given the Fused Rhymed Words Test, a dichotic listening measure of hemispheric dominance for language. An earlier finding of smaller left hemisphere advantage in schizophrenic patients was replicated. There was no significant change in ear advantage in a subgroup of the schizophrenic patients tested when they were taking neuroleptics and when they were not. The smaller left hemisphere advantage in the schizophrenic patients was not dependent on gender but was related to symptom ratings on the Positive and Negative Syndrome Scale. The findings are consistent with a left hemisphere dysfunction in schizophrenia, which is associated with positive symptoms.

An ERP study on the specificity of facial expression processing

Facial expression processing specificity was investigated by means of event-related potentials (ERPs). Stimuli consisted on happiness facial expressions (H) along with three other visual stimuli with different physical and affective characteristics: neutral facial expressions, landscapes and grey slides. The 32 subjects had to rate the stimuli with respect to two affective dimensions: ‘valence’ and ‘arousal’. EEG was recorded at T7, T8, Fz and Cz, and the epoch was of 1000 ms (100 ms prior to stimulus onset). Analyses revealed that the variability of N200 and P200 components, which were not able to detect a differential activity in response to H stimuli, could be explained in terms of physical complexity and relevance of the stimuli. N300 did detect a differentiation between H and the rest of stimuli, sharing some characteristics of previous and later components. With respect to late components, P 300 seemed to reflect the trends of ‘arousal’ ratings and SW results suggest that its amplitude was influenced by the stimulus recognition effort. Not a clear right or left hemisphere advantage in facial expression processing was found. These ERP results suggest that the specificity of facial expression processing is not strictly circumscribed to a particular latency or to a specific neural area, but it resides in a particular combination of discrete processes.

Neurophysiological and MRI assessment in demyelinating optic neuritis

Two experiments utilizing a spatial-temporal movement sequence were designed to determine if the memory of the sequence is lateralized in the left or right hemisphere. In Experiment 1, dominant right-handers were randomly assigned to one of two acquisition groups: a left-hand starter and a right-hand starter group. After an acquisition phase, reaction time (RT) was measured in a recognition test by providing the learned sequential pattern in the left or right visual half-field for 150 ms. In a retention test and two transfer tests the dominant coordinate system for sequence production was evaluated. In Experiment 2 dominant left-handers and dominant right-handers had to acquire the sequence with their dominant limb. The results of Experiment 1 indicated that RT was significantly shorter when the acquired sequence was provided in the right visual field during the recognition test. The same results occurred in Experiment 2 for dominant right-handers and left-handers. These results indicated a right visual field left hemisphere advantage in the recognition test for the practiced stimulus for dominant left and right-handers, when the task was practiced with the dominant limb.

Hemispheric Asymmetries for Temporal Resolution: A Signal Detection Analysis of Threshold and Bias

Divided visual field techniques were used to investigate hemispheric asymmetries for (a) the threshold of fusion of two flashes of light and (b) the detection of simultaneous versus successive events for a group of normal, right-handed adults. A signal detection analysis revealed a higher level of accuracy for the right visual field-left hemisphere (RVF-LH) relative to the left visual field-right hemisphere (LVF-RH) for both tasks. These results were interpreted in terms of a general left-hemisphere advantage for the discrimination of fine temporal events. The implications of these results for models of temporary asymmetry that describe the left hemisphere's advantage in terms of an exclusive specialization or relative superiority are then discussed.

Effect of Skill on Visual Laterality: Now You See It - Now You Dont (Comments on Clancy and Hoyer, 1993)

Clancy and Hoyer (1993) have recently investigated the effects of domain-specific expertise and hemispheric asymmetry on detecting featural differences in visual patterns. Based on the pattern of reaction time results, they concluded that there is a left-hemisphere advantage for making difficult, domain-relevant visual discriminations in skilled experts but not in unskilled control subjects. However, response accuracy data from the same experiment contradict their conclusions about the relationship of skill to the pattern of hemispheric asymmetry and favor an alternative interpretation in terms of the specific aspects of visual information needed to make different types of discrimination.

幼児の言語情報認知の右耳優位性に注意配分教示が及ぼす影響

Using a dichotic listening test, the effects of attention on the right-ear-advantage (REA) for word recognition in 4-6 year children was analyzed. In Experiment 1, ear differences for word recognition was measured under free recall condition. The results showed REA in all year groups and suggested that the degree of left hemisphere advantage for word recognition did not change over 4-6 year group. In Experiment 2, ear differences during attentional condition was measured with the same children as Exp. 1. Attention was manipulated by requiring children to report from left or right ear first. In 4-5 year group, REA was obtained in both left- and right-ear-first conditions, but REA was not obtained in left-ear-first condition in 5-6 year group. These suggested the difference of attentional effects on REA between two year groups. In Experiment 3, ear differences during both left- and right-ear-first conditions was re-examined, six months later, with 4-5 year group. The results showed that REA was obtained in right-ear-first condition, but ear difference was not observed in left-ear -first condition. These findings suggested the possible effects of attention on the dichotic REA for word recognition even in preschool children.