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)     

Congruency, attentional set, and laterality effects with emotional words.

The present study investigated the influence of attention and word-emotion congruency on auditory asymmetries with stimuli that include verbal and emotional components. Words were presented dichotically to 80 participants and were pronounced in either congruent or incongruent emotional tones. Participants were asked to identify the presence of a target word or emotion under 1 of 2 conditions. The blocked condition required detection of a word or emotional target in separate blocks. In the randomized condition, the target was changed across trials by means of a postcue. A right-ear advantage (REA) and a left-ear advantage (LEA) were found for word and emotion targets, respectively. However, the finding of a Condition × Stimulus Type × Ear × Congruency interaction indicated that in the randomized condition, a REA was obtained for words when the stimuli were congruent and a LEA was observed for emotions when the stimuli were incongruent. The findings suggest that randomizing the target reduced the influence of the attentional set established by blocking the target. It is likely that this promoted the detection of hemispheric interference in the randomized condition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure of dominant left-hemispheric activation to right-ear stimulation in schizophrenia

Schizophrenia is associated with an absence of the lateralizations that typify the human brain. Previous evidence emphasized structural changes, particularly reduced asymmetry in extension and surface of the planum temporale, although gross structural deviations occur only in a minority of patients. The present study describes an absence of lateralization on a robust functional measure that characterized schizophrenia patients: healthy subjects but not schizophrenics displayed a contralateral left-hemispheric dominance of the auditory evoked magnetic field to right-ear auditory stimulation. Absence of contralateral dominance in response to auditory stimuli among schizophrenia patients may indicate a failure to establish unequivocal left-hemispheric dominance of the phonological loop as hypothesized by Crow.     

Hemispheric laterality and memory bias for threat in anxiety disorder.

Examined auditory perceptual asymmetries and explicit memory biases for threat in patients with panic disorder and generalized anxiety disorder relative to healthy control Ss. They did not find a greater explicit memory bias for threat in the anxiety patients. However, explicit memory biases for threat were associated with perceptual asymmetry scores; patients with a greater right-ear (left hemisphere) advantage exhibited an explicit memory bias for threat material, whereas patients with a lower right-ear advantage displayed apparent cognitive avoidance of threat material. Memory for threat words was unrelated to perceptual asymmetry in healthy control Ss. These findings suggest that neuropsychological variables may partly determine the degree to which anxiety patients process threatening stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of intrathecal morphine on blood glucose, glucagon and tissue glycogen in rat: comparison with the effect of xanthan gum on blood glucose

Eleven patients suffering from chronic disabling tinnitus underwent an FDG-PET study (positron emission tomography with [18F]deoxyglucose). Nine tinnitus patients revealed a significantly increased metabolic activity in the left, 1 in the right primary auditory cortex (PAC, Brodmann area 41). These results were statistically significant when compared to 14 healthy control individuals without tinnitus. A negative result was obtained from a chronic tinnitus patient but who had no subjective complaints during the period of PET investigation. One patient was first investigated during a disabling tinnitus period, later during a period with tinnitus relief and again when suffering from severe tinnitus. The metabolic activity of his left PAC was in good accordance with the subjective degree of tinnitus complaints present during each PET investigation. Although for the first time these results give objective evidence of tinnitus sensation and localization, they are difficult to interpret because of the limited research data available that combine functional brain imaging and acoustic stimuli.     

Temporal distinctiveness and modality.

It has been proposed that auditory stimuli are more temporally discriminable in memory than visual stimuli. Studies using the continual-distractor paradigm have provided both supporting and contradictory evidence for this hypothesis. The conflicting reports differed, however, in the modality of the interleaved distractor tasks. The present experiments manipulated both word and distractor-task modality. Results showed that aurally presented word lists were more sensitive to temporal schedules of presentation when the distractor task was auditory than when it was visual. The same effect was not consistently found for visually presented word lists. Such an interaction may help explain the previously reported disparate findings and suggests that the auditory modality, in the presence of silent distraction, can reduce participants' use of temporal-distinctiveness information at retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Asymmetries of selective listening and attention switching in children.

Administered a selective listening task to 155 normal right-handed 3–12 yr old children. The stimuli consisted of dichotic digits, ranging from single pairs to strings of 4 pairs/trial. Each S attempted to focus attention on 1 ear for 8 practice trials and 28 test trials before switching attention to the opposite ear. Separate analyses of correct responses and intrusion errors yielded almost identical results: There was a significant right-ear advantage (REA) and a developmental increase in overall performance, but there was no developmental change in degree of asymmetry. The REA increased with increasing list length, but independent analyses for each list length failed to reveal any developmental changes in REA. Listening asymmetry was influenced markedly by the order in which the ears were monitored; Ss of all ages had difficulty in switching attention from right ear to left. Results support the developmental invariance hypothesis of cerebral lateralization and demonstrate that auditory asymmetry is not merely a direct reflection of some fixed structural asymmetry in the brain. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral lateralization and cognitive functioning in patients with congenital adrenal hyperplasia.

A battery of tests was administered to 17 patients with congenital adrenal hyperplasia (CAH) and 17 normal controls to investigate the effect of prenatal androgen exposure on cerebral lateralization and cognitive performance. Individuals were compared on measures of hand preference, verbal and performance IQ, and temporal processing asymmetry. A higher incidence of left-handedness was found among CAH participants. CAH individuals exhibited higher performance IQs as opposed to verbal IQs. Temporal processing asymmetries were investigated using an auditory gap detection task. Measures of reaction time and response error revealed a right-ear, therefore left-hemisphere, advantage for gap detection. This right-ear advantage did not differ between CAH individuals and controls. Results partially support the hypothesis that prenatal androgen exposure causes a shift in cerebral lateralization toward right-hemisphere dominance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploring cerebral asymmetries for the verb generation task.

This study investigated potential right hemisphere involvement in the verb generation task. Six divided visual field experiments explored cerebral asymmetries for word retrieval in the verb generation task as well as in rhyme generation and immediate and delayed word pronunciation. The typical right visual field/left hemisphere (RVF/LH) advantage was observed for pronunciation and rhyme generation. For verb generation, the RVF/LH advantage was obtained only when stimulus items had a single prepotent response and not when there were multiple response alternatives. A semantic priming experiment suggested that activation for less common, related verbs was maintained for a longer time course within the right than within the left hemisphere. The authors suggest that the right hemisphere may play a role in continued activation of semantically related response alternatives in word generation and discuss methodological implications of their findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory and visual word processing studied with fMRI

Brain activations associated with semantic processing of visual and auditory words were investigated using functional magnetic resonance imaging (fMRI). For each form of word presentation, subjects performed two tasks: one semantic, and one nonsemantic. The semantic task was identical for both auditory and visual presentation: single words were presented and subjects determined whether the word was concrete or abstract. In the nonsemantic task for auditory words, subjects determined whether the word had one syllable or multiple syllables. In the nonsemantic task for visual words, subjects determined whether the word was presented in lower case or upper case. There was considerable overlap in where auditory and visual word semantic processing occurred. Visual and auditory semantic tasks both activated the left inferior frontal (BA 45), bilateral anterior prefrontal (BA 10, 46), and left premotor regions (BA 6) and anterior SMA (BA 6, 8). Left posterior temporal (middle temporal and fusiform gyrus) and predominantly right-sided cerebellar activations were observed during the auditory semantic task but were not above threshold during visual word presentation. The data, when averaged across subjects, did not show obligatory activation of left inferior frontal and temporal language areas during nonsemantic word tasks. Individual subjects showed differences in the activation of the inferior frontal region while performing the same task, even though they showed similar response latency and accuracy.     

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.     

Re-evaluating split-fovea processing in word recognition: Effects of retinal eccentricity on hemispheric dominance.

Several studies have claimed that hemispheric asymmetries affect word recognition right up to the point of fixation because each fovea is split precisely at its vertical midline and information presented either side of this midline projects unilaterally to different, contralateral hemispheres. To investigate this claim, four-letter words were presented to the left or right of fixation, either close to fixation entirely in foveal vision (0.15, 0.25, and 0.35 degrees from fixation) or further from fixation entirely in extrafoveal vision (2.00, 2.10, and 2.20 degrees from fixation). Fixation location and stimulus presentation were controlled using an eye-tracker linked to a fixation-contingent display and performance was assessed using a forced-choice task to suppress confounding effects of guesswork. A left hemisphere advantage was observed for words presented in extrafoveal locations but no hemisphere advantage (left or right) was observed for words presented in any foveal location. These findings support the well-established view that words encountered outside foveal vision project to different, contralateral hemispheres but indicate that this division for word recognition occurs only outside the fovea and provide no support for the claim that a functional split in hemispheric processing exists at the point of fixation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal processing deficits in schizophrenia.

The authors reported that a subgroup of schizophrenic patients performed well on a tone serial position task but was impaired on an auditory word serial position task (Wexler, Stevens, Bowers, Cerniak, & Goldman-Rakic, 1998). This study assessed 30 schizophrenic and 32 controls (matched for comparable tone discrimination) on 4 versions of the verbal serial position tasks and 2 tone serial position tasks. Patients performed poorly on all verbal tasks but performed comparably to controls when tones served as stimuli. Proactive interference and visual presentation further compounded the verbal deficits. Deficits persisted with pronounceable nonword stimuli. These findings provide evidence of specific deficits in language-related processing, although the authors could not rule out the possibility that the differential effects that were observed between the tone and word tasks, and particularly among the verbal tasks, may result from differing discriminating power of the different tests. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification of emotion in a dichotic listening task: event-related brain potential and behavioral findings

The lateralization of emotion perception has been examined using stimuli in both auditory and visual modalities. Studies using dichotic stimuli have generally supported the hypothesis of right-hemisphere dominance for emotion perception, whereas studies of facial and verbal emotion perception have provided evidence for the right-hemisphere and valence hypotheses. A dichotic target detection task was developed to enable acquisition of event-related potentials (ERP) from subjects engaged in emotion detection. Nonsense syllables (e.g., ba, pa) stated in seven different emotional intonations were dichotically presented to 24 young adults, in a target detection task during four separate blocks (target emotions: happiness, interest, anger, or sadness). Accuracy and reaction time and ERP measures were also collected. ERPs were recorded from 14 scalp electrodes with a nose reference and quantified for N100, sustained negativity, late positivity, and slow wave. Significantly greater left- than right-ear accuracy was obtained for the identification of target prosodic emotion. Hemispheric asymmetries of N100 and sustained negativity were found, with left-hemisphere amplitudes greater than right-hemisphere amplitudes. These ERP asymmetries were not significantly correlated with the left-ear dichotic advantage and may be related more to early phonetic processing than to emotion perception. Since the behavioral evidence supports the right-hemisphere hypothesis for emotion perception, behavioral and ERP asymmetries evident in this task reflect separable patterns of brain lateralization.     

Hemispheric asymmetry in Down's Syndrome children.

Examined auditory processing of linguistic stimulation presented dichotically to groups of 30 Down's Syndrome (DS) children, 20 non-DS retarded children who were MA and CA matched, and 20 MA matched nonretarded children, all of whom were right-handed. Ss completed a knowledge-of-numbers test and the Slosson Intelligence Test. They then listened to 20 trials of a dichotic message at approximately 70–75 db and repeated digits they heard. DS Ss showed a significant left ear advantage in processing the auditory linguistic material, while the other Ss showed the normal right ear advantage. Findings corroborate that having DS has a specific effect on the functional organization of the CNS auditory system. The right hemisphere may not be as efficient as the left hemisphere at language processing. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reaction time during cocaine versus alcohol withdrawal: longitudinal measures of visual and auditory suppression

Visual and auditory stimulus discrimination tasks, analogous to those used in the Reitan-Klove Sensory Perceptual Examination, were performed by 12 cocaine-dependent and 5 alcohol-dependent patients after 1 week, 3 weeks, and 3 months of verified abstinence. Sixteen control subjects, who were not substance-dependent, performed the same tasks after comparable intervals. During each task, either visual or auditory stimuli were presented in the left, in the right, or in both sensory fields. A simple key press was made to discriminate these conditions. Cocaine-dependent patients responded more slowly than control subjects during both tasks. The reaction-time slowing persisted across all three sessions, spanning a 3-month period of abstinence. There were no significant differences between the cocaine-dependent and control groups in response accuracy. In the context of other findings, these findings are interpreted as reflecting an enduring effect of prior cocaine dependence on motor as opposed to sensory functioning.     

Hemispheric specialization and ear advantages in processing speech.

Reviews research on the hemispheric asymmetry model of relative ear advantages in the processing of auditory stimuli. Physiological studies of activation of the hemispheres in humans support left-hemisphere speech-processing specialization and contralateral sound field dominance. Electrophysiological studies in animals, effects of commissurotomy, hemispherectomy, and unilateral temporal lobe lesions on dichotic performance in humans, as well as stimulus dominance effects in intact Ss indicate that the assumption of ipsilateral sensory pathway suppression during competitive stimulation is unwarranted. Dichotic presentation is not necessary to produce a right-ear advantage (REA), and selective attention to one or the other ear frequently tends to alter the magnitude of the REA. A modified structural model that incorporates the effects of directed attention is proposed. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prenatal exposure to diethylstilbestrol (DES) and the development of sexually dimorphic cognitive abilities and cerebral lateralization.

Investigated the possibility that the perinatal hormonal environment is related to the development of cognitive sex differences in humans by comparing 25 women who had been exposed prenatally to DES, a synthetic estrogen, to their unexposed sisters. All Ss completed word fluency and spatial relations tests, the Wonderlic Personnel Test, and a dichotic listening task. The DES-exposed Ss showed a more masculine pattern of lateralization (i.e., a stronger right-ear advantage) than did their sisters on a verbal dichotic task. However, no differences were observed between exposed and unexposed Ss in verbal or visuospatial ability. Although interpretation of these data must be cautious, they provide some support for a relationship between high prenatal estrogen levels and the development of masculine-typical function in humans. Implications for previous studies of biological contributions to cognitive sex differences and possible mechanisms for estrogenic effects on the development of lateralization are discussed. (114 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The up–right/down–left advantage for vertically oriented stimuli and horizontally oriented responses: A dual-strategy hypothesis.

C. Umiltà's (1991) proposal that the up–right/down–left advantage for up and down stimuli mapped to left and right responses is due to verbal coding was evaluated. Two approaches were used in separating spatial from verbal codes. The 1st approach used a reaction time distribution bin analysis to examine the effect of response speed on the up–right/down–left advantage. The 2nd approach attempted to create task conditions that would promote either a verbal or visual strategy. Results show that the up–right/down–left advantage increased as response speed slowed down. This finding was interpreted in terms of the dual-strategy hypothesis, which asserts that participants may use the visual or the verbal stimulus code and that, depending on the task constraints, a visual or verbal strategy may prevail. With a visual strategy, no compatibility effect arises. With a verbal strategy, the up–right/down–left advantage emerges. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)