Functional lateralization for auditory temporal processing in male and female rats.

In 3 studies, adult male rats showed significantly better discrimination of tone sequences with the right ear than with the left ear. This result parallels similar findings of left-hemisphere specialization for auditory temporal processing in humans and nonhuman primates. Furthermore, because clinical evidence supports a link between specialization of the left hemisphere for auditory temporal processing and for speech processing, these results may reflect evolutionary precursors to left-hemisphere language specialization. Because male rats showed a stronger ear advantage than female rats, the findings may relate to evidence of a stronger right ear advantage in men than in women. Finally, results suggest that neonatal handling enhances lateralization for auditory temporal processing in both sexes. Combined results implicate neuroendocrine mechanisms as important factors in the development of lateralization for auditory temporal processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of concurrent auditory input on tactual processing in very young children: Developmental changes.

Investigated right-hemispheric specialization for tactual processing in 96 2–5 yr old right-handed children. Cross-modal transfer from touch to vision was assessed under conditions where Ss palpated shapes with either their left or right hand while music was simultaneously played to the left ear, right ear, or neither ear. This task pitted music against palpation such that both tasks involved the same or different cerebral hemispheres (if music and haptic perception are both lateralized in the right hemisphere as is thought). Results show that in the absence of music, Ss at each age showed a left-hand (right-hemisphere) advantage. The adultlike patterns of ipsilateral interference from music were evident among 4- and 5-yr-olds, in that music to the left ear selectively disrupted left-hand performance. The adultlike pattern was absent at ages 2 and 3 yrs, and music to the right ear disrupted left-hand performance at these ages. Music had an overall, nonselective interference on right-hand performance at all ages. The early appearing left-hand advantage and the lateralized nature of the interference observed among older Ss support the idea of a right-hemispheric specialization for tactual processing of form in young children. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of aphasic and non-brain-injured adults on a dichotic CV-syllable listening task

A dichotic CV-syllable listening task was administered to a group of eleven non-brain-injured adults and to a group of eleven adult aphasics. The results of this study may be summarized as follows: 1)The group of non-brain-injured adults showed a slight right ear advantage for dichotically presented CV-syllables. 2)In comparison with the control group the asphasic group showed a bilateral deficit in response to the dichotic CV-syllables, superimposed on a non-significant right ear advantage. 3) The asphasic group demonstrated a great deal of intersubject variability on the dichotic task with six aphasics showing a right ear preference for the stimuli. The non-brain-injured subjects performed more homogeneously on the task. 4) The two subgroups of aphasics, a right ear advantage group and a left ear advantage group, performed significantly different on the dichotic listening task. 5) Single correct data analysis proved valuable by deleting accuracy of report for an examination of trials in which there was true competition for the single left hemispheric speech processor. These results were analyzed in terms of a functional model of auditory processing. In view of this model, the bilateral deficit in dichotic performance of the asphasic group was accounted for by the presence of a lesion within the dominant left hemisphere, where the speech signals from both ears converge for final processing. The right ear advantage shown by one asphasic subgroup was explained by a lesion interfering with the corpus callosal pathways from the left hemisphere; the left ear advantage observed within the other subgroup was explained by a lesion in the area of the auditory processor of the left hemisphere.     

Left-ear superiority in children for processing auditory emotional material.

Investigated hemispheric asymmetries in children for processing auditory material varying in emotional intonation or verbal content. 31 kindergartners, 32 4th graders, and 32 8th graders reported on the emotional content and on the verbal content of dichotically presented sentences. Ss listened to tapes of 4 phrases spoken in tones that were happy, sad, angry, or neutral and to sentences that varied in verbal content only. Ss also completed a handedness questionnaire and a hearing test. All age groups showed a left-ear advantage for reporting on the emotional material and a right-ear advantage for reporting on the verbal material. For the emotional task, the degree of ear asymmetry did not vary significantly as a function of emotional category. Findings indicate the the right hemisphere is specialized for mediating auditory emotional stimuli as early as 5 yrs of age. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple modes of right-hemisphere information processing: Age and sex differences in facial recognition.

Examined hemispheric differences in processing tachistoscopically presented faces in 8-, 11-, and 13-yr-old children of above-average intelligence. Ss viewed 4 female faces and were then asked to point to the face presented on each trial. The finding of a bimodal distribution of error scores among those Ss who showed a left visual-field (LVF) advantage supports the view that there are 2 types of information processing associated with the right hemisphere. The error scores of the younger Ss with an LVF advantage were unimodal and those of the 13-yr-olds bimodal. This bimodality characterized only the older girls. Since the unimodal error scores for the younger Ss were at a relatively high level, the data were interpreted as indicating that younger children and males at all ages use a diffuse right-hemisphere processing strategy in recognizing faces, whereas some older females use a more integrated right-hemisphere strategy. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric changes in information processing during development.

Hemispheric processing of visually presented words and pictures was examined in 3 groups of Ss with mean ages of 8 yrs 8 mo, 12 yrs 3 mo, and 27 yrs 9 mo (154 Ss). Pictorial or symbolic stimuli were presented singly to either the right or left visual hemifield. Ss had to decide whether the 1st stimulus in a pair matched the 2nd stimulus. The major results were that (a) age groups differed in the strength of lateral differences, and (b) for all age groups, the right hemisphere was significantly faster in processing unmatched stimuli. Results suggest that lateral specialization of the left hemisphere is not complete until adolescence and that over the age range tested, the left hemisphere becomes progressively more specialized for the processing of matched data. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A cardiac measure of cerebral asymmetries in infant auditory perception.

Examined the utility of cardiac habituation response recovery as a method for assessing infant cerebral asymmetries in auditory perception in a dichotic listening test. In a within-Ss design 12 3-mo-old infants were given a series of 4 10-trial tests during which their cardiac responses were habituated to a pair of dichotic speech syllables or music notes. The 10th trial in each test was a test trial on which one ear received its habituation stimulus while the other ear received a novel stimulus of the same type as the habituation pair (speech or music). Both stimulus type and ear receiving the novel stimulus were counterbalanced across tests. Overall, Ss' cardiac responses habituated during the tests and showed differential recovery to the novel stimuli. Specifically, greater response recovery occurred when a novel speech syllable was presented to the right, than to the left ear. Conversely, greater response recovery was found when a novel music note was presented to the left than to the right ear. Results indicate that young infants show a pattern of auditory perceptual asymmetries much like that found in older children and adults. Findings are consistent with the theory that in man the left hemisphere is superior at processing speech and the right hemisphere superior with nonspeech. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure to control prepotent pathways in early stage dementia of the Alzheimer's type: Evidence from dichotic listening.

The authors examined the right ear advantage in a dichotic listening task in healthy aging and very mild and mild stages of Alzheimer's disease. Subjects were simultaneously presented 3 pairs of digits to the left and right ears (e.g., left ear: 4, 3, 1; right ear: 9, 2, 5) for immediate ordered recall. Four lists of triads were presented, varying in presentation rate between digit pairs within a triad (0.5, 1.0, 1.5, 2.0 s). Results indicated that the very mild and mild Alzheimer's groups showed a larger right ear advantage in free recall compared with the healthy controls, indicating a tendency to respond to the prepotent left hemisphere pathway for language processing. Also, the right ear advantage and proportion of switches made during recall were correlated with psychometric measures of frontal lobe function in the mild Alzheimer's group but not in the very mild or healthy control groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual and semantic processing in reading Kanji.

A. Nakagawa (see record 1992-15549-001) showed hemispheric asymmetries during semantic processing of single English words. The right hemisphere passively maintained both strong and weak associations, whereas the left hemisphere maintained only strong associations when Ss were left free to attend. The present study extends the methodology to the study of Kanji characters. Contrary to the study of English characters, there was a general right-hemisphere advantage in single-character Kanji words. A study using a visual cue to direct attention suggested that the right-hemisphere advantage of Kanji was due to better representation of visual features by the posterior right hemisphere. However, the pattern of semantic priming found in English was replicated. Semantic analysis, mediated by more anterior systems, appears similar in the 2 languages. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of directed attention on cerebral asymmetries in normal and learning-disabled children.

Using a dichotic listening task employing both undirected and directed attention conditions, cerebral asymmetries were examined in matched populations of 32 normal and 32 learning-disabled (LD) children (ages 7 yrs 6 mo–13 yrs 2 mo). The analysis of recall performance indicated that development was not a significant factor in either group; both the normal and LD Ss showed a right-ear effect, although the LD Ss performed at a degraded level and were unable to demonstrate a right-ear advantage (REA) when attention was directed to the left ear, unlike normal Ss, who produced the REA despite the directed attention conditions. Results suggest that LD children probably do not suffer from developmental delays but rather from a defect in callosal functioning that interferes with their ability to process verbal information simultaneously. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deviant auditory stimuli activate human left and right auditory cortex differently

Infrequent "deviant' auditory stimuli embedded in a homogeneous sequence of "standard' sounds evoke a neuromagnetic mismatch field (MMF), which is assumed to reflect automatic change detection in the brain. We investigated whether MMFs would reveal hemispheric differences in cortical auditory processing. Seven healthy adults were studied with a whole-scalp neuromagnetometer. The sound sequence, delivered to one ear at time, contained three infrequent deviants (differing from standards in duration, frequency, or interstimulus interval) intermixed with standard tones. MMFs peaked 9-34 msec earlier in the right than in the left hemisphere, irrespective of the stimulated ear. Whereas deviants activated only one MMF source in the left hemisphere, two temporally overlapping but spatially separate sources, one in the temporal lobe and another in the inferior parietal cortex, were necessary to explain the right-hemisphere MMFs. We suggest that the bilateral MMF components originating in the supratemporal cortex are feature specific whereas the right-hemisphere parietal component reflects more global auditory change detection. The results imply hemispheric differences in sound processing and suggest stronger involvement of the right than the left hemisphere in change detection.     

Differential hemispheric processing of faces: Methodological considerations and reinterpretation.

Examines the procedures and stimuli (physiognomies) used in lateralized face recognition experiments with normal Ss, as well as in related perceptual and identification experiments. Results reveal that in general a left visual field (right hemisphere) advantage is obtained when: (a) stimulus information is degraded; (b) faces to be compared are highly discriminable; (c) set of unfamiliar faces is used; and (d) task requirements allow a lax criterion of recognition. These conditions seem to make holistic processing adequate for the task; if the conditions require analytic judgments, then a right visual field (left hemisphere) advantage may be obtained. Thus, no hemifield has an inherent or absolute advantage and these procedural conditions may critically determine what hemifield advantage is observed in any given experiment with faces (or other types of stimuli). Apparently, both hemispheres may contribute to the processing of faces but their contributions vary as a function of task demands. A right hemisphere advantage may reflect an enhanced role of the processes of configuration, completion, categorization, or set. A left hemisphere advantage need not involve the language function but it may reflect a genuine visuospatial contribution. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anxiety and perceptual structure: Individual differences in neuropsychological function.

Studied the cognitive performance of 24 high and 36 low trait anxious undergraduates under conditions of high and low situational stress, using tasks requiring greater contribution of the right or left hemisphere. In addition, a perceptual task was adapted from visual information processing research to assess Ss' global or analytic approaches to perception; if anxiety increased the left hemisphere's contribution to perception, anxious Ss might be expected to be more analytic and detail oriented. Results show no significant differences on left hemisphere tasks but a significant interaction of trait by state anxiety for right hemisphere tasks: Low trait Ss performed better and high trait Ss performed more poorly under situational stress. Trait anxiety showed a significant main effect on visual information processing strategy, low Ss tending to be more global and high Ss tending to process the stimulus analytically. Results support the utility of a neuropsychological model in describing the effects of emotion on perception. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What do babies listen to most? A developmental study of auditory preferences in nonhandicapped infants and infants with Down's syndrome.

Studied the auditory preferences of 10 Down's syndrome (DS; mean CA 12.4 mo; mean MA 9.3 mo) and 10 nonhandicapped (NH; mean CA 9.3 mo; mean MA 9.6 mo) infants at the developmental ages of around 9 and 18 mo. An apparatus that allows infants to choose to listen to 1 of a pair of auditory stimuli and that records their responses was used. At both ages, Ss had the choice of listening first to either a children's rhyme or a repetitive tone and then to either the mother talking to her own child (baby talk) or the mother talking to an adult. At both ages, both groups of Ss significantly preferred to listen to the children's rhyme and to the baby talk. At 9 mo, both groups listened significantly more to nursery rhymes than to spoken stimuli; by 18 mo, NH Ss showed a significant increase in listening to baby talk, which they then listened to longer than to rhymes. DS Ss showed a significant decrease in listening to baby talk at this age and still listened longer to rhymes. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developmental changes in hemispheric specialization for tactual processing in very young children: Evidence from cross-modal transfer.

Examined whether young children show any evidence of right hemispheric specialization for tactual processing. 72 1-, 2-, and 3-yr-old right-handed children were each administered 6 cross-modal tasks in which they palpated a shape with either their left or right hand for 25 sec and then viewed the familiar and a novel shape in a 10-sec test of visual recognition. Although Ss of all 3 ages showed significantly more visual fixation to novel shapes, regardless of which hand had been used for palpation, scores were enhanced among 2- and 3-yr-olds following palpation with the left as compared with the right hand. This left-hand (right hemisphere) superiority was not evident in 1-yr-olds. These results are the first to demonstrate a left-hand superiority for information processing in children as young as 2 yrs and to suggest that this adultlike pattern is developed by at least the 2nd year of life. Left-hand superiority may be due to asymmetries in tactual sensitivity, motor control, and/or information processing. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple resources in divided attention: A cross-modal test of the independence of hemispheric resources.

Used a dual-task methodology to assess a multiple-resources account of information processing in which each cerebral hemisphere is assumed to have access to its own finite amount of attentional resources. A visually presented verbal memory task was paired with an auditory tone memory task, and Ss, 19 right-handed male undergraduates, were paid to emphasize one task more than the other. When Ss were trying to remember tones presented to the right ear, they could trade performance between tasks as a function of the emphasis condition, whereas on left-ear trials they could not. A control session indicated that stimuli presented to the unattended ear demanded processing resources, even when it was to the detriment of performance. Data support the 2nd author and M. C. Polson's (see record 1982-07236-001) model of independence between the hemispheres' resource supplies. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of classroom noise on performance and activity of second-grade hyperactive and control children.

Two experiments assessed the effects of task-overlapping linguistic noise (ambient noise including conversations) on activity and performance of 24 hyperactive and 24 control children. High and low levels of linguistic classroom noise were each presented while Ss were performing tasks requiring auditory processing of information in a repeated-measures crossover design. Hyperactive Ss were most active and performed math and alphabet tasks worse in high than in low linguistic noise. Control Ss showed the opposite performance and activity pattern. The differential effects of linguistic noise were less pronounced in Exp II when the task was new and more challenging for the control Ss, suggesting that task difficulty may play a role in the effects of overlapping stimulation on both groups. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recall strategies in three-channel immediate memory.

Digits were spoken through earphones via 3 simultaneous auditory "channels," created by having 1 digit spoken to the left ear only, another to the right ear only, and a third (middle channel) to both ears at once. Also, each channel was spoken by a different voice, a woman's in the middle, and different men's voices to left and right. 18 right-handed and 18 left-handed Ss heard a series of 2 such triplets, with onsets of 1 sec. apart. Ss instructed to report the digits channel by channel recalled as many digits as those instructed to report them triplet by triplet, but Ss who were permitted free recall chose the triplet-by-triplet strategy more often than the channel-by-channel one. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetries in the preparation and control of manual aiming movements.

Conducted 2 experiments with 20 undergraduates to determine if typical right hand target aiming advantages could be reduced or eliminated by increasing the spatial demands of the aiming task. In Exp 1, right hand advantages were found for both movement time and error regardless of spatial characteristics of the task. When a greater degree of spatial uncertainty was introduced in Exp 2, Ss exhibited a left hand reaction time advantage. Taken together, results suggest that the right cerebral hemisphere may have a special role to play in preparing the spatial aspects of an aiming movement, while the left hemisphere is more important for movement execution. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Left hemisphere dysfunction and left hemisphere overactivation in schizophrenia.

Reports 2 experiments relating schizophrenia to functional brain asymmetry. In Exp I, 24 schizophrenics (mean age, 30.8 yrs) were compared to 24 matched controls (mean age, 37.3 yrs) on 2 tachistoscopic tasks (Syllable Test and Dot Location Test) designed to measure verbal and spatial information processing in the 2 hemispheres. Unlike the controls, the schizophrenics showed a right hemisphere superiority both on the verbal and on the spatial tests, indicating left hemisphere dysfunction in the initial processing of verbal information. In Exp II, lateral eye movements, as an index of contralateral hemispheric activation, were measured in a group of 24 paranoid schizophrenics (mean age, 28.9 yrs), 24 nonparanoid schizophrenics (mean age, 32.7 yrs), and 24 matched controls (mean age, 31.2 yrs). The eye movements were elicited by presenting the Ss with verbal neutral, verbal emotional, spatial neutral, and spatial emotional questions. The schizophrenics had significantly more rightward eye movement, compared to controls, regardless of question type, indicating left hemisphere overactivation. Results suggest that schizophrenia is associated with a pattern consisting of both left hemisphere dysfunction and overactivation. (63 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)