Models Of Hemispheric Specialization Research Articles

Comparison of two models of hemispheric specialization with unilaterally lesioned patients: Material-specific impairment vs response-bias distortion

Validity of two models of hemispheric specialization was compared. The “material-specific impairment” model was radicalized as postulating that left hemisphere (LH) lesions impair processing of verbal material and that right hemisphere (RH) lesions impair processing of visuospatial material, independently of response-bias distortions. The “response-bias distortion” model was radicalized as postulating that LH lesions distort response style toward omissiveness and that RH lesions distort response style toward commissiveness, regardless of material-specific impairments. Participants had comparable left (N=27) or right (N=24) hemisphere cortical lesions having occurred between birth and early adolescence. Four cognitive neuropsychological tests were adjusted to optimize applicability and comparability of the two theoretical models: Rey Complex Figure, Kimura's Recurring Figures, the Story Recall subtest of the Children's Memory Scale, and the California Verbal Learning Test. Both models significantly, independently, and equally distinguished the LH from the RH patients. Both these forms of hemispheric specialization seemed to be implemented very early in life and very rigidly. Intrahemispheric lesion sites, e.g., frontal vs nonfrontal, held no significant relation to the effects described above.

Models of hemispheric specialization in facial emotion perception—a reevaluation.

A considerable amount of research on functional cerebral asymmetries (FCAs) for facial emotion perception has shown conflicting support for three competing models: (i) the Right Hemisphere Hypothesis, (ii) the Valence-Specific Hypothesis, and (iii) the Approach/Withdrawal model. However, the majority of studies evaluating the Right Hemisphere or the Valence-Specific Hypotheses are rather limited by the small number of emotional expressions used. In addition, it is difficult to evaluate the Approach/Withdrawal Hypothesis due to insufficient data on anger and FCAs. The aim of the present study was (a) to review visual half field (VHF) studies of hemispheric specialization in facial emotion perception and (b) to reevaluate empirical evidence with respect to all three partly conflicting hypotheses. Results from the present study revealed a left visual field (LVF)/right hemisphere advantage for the perception of angry, fearful, and sad facial expressions and a right visual field (RVF)/left hemisphere advantage for the perception of happy expressions. Thus, FCAs for the perception of specific facial emotions do not fully support the Right Hemisphere Hypothesis, the Valence-Specific Hypothesis, or the Approach/Withdrawal model. A systematic literature review, together with the results of the present study, indicate a consistent LVF/right hemisphere advantage only for a subset of negative emotions including anger, fear and sadness, rather suggesting a "negative (only) valence model."

Test-Retest Reliability of fMRI Brain Activity during Memory Encoding

The mechanisms underlying hemispheric specialization of memory are not completely understood. Functional magnetic resonance imaging (fMRI) can be used to develop and test models of hemispheric specialization. In particular for memory tasks however, the interpretation of fMRI results is often hampered by the low reliability of the data. In the present study we therefore analyzed the test-retest reliability of fMRI brain activation related to an implicit memory encoding task, with a particular focus on brain activity of the medial temporal lobe (MTL). Fifteen healthy subjects were scanned with fMRI on two sessions (average retest interval 35 days) using a commonly applied novelty encoding paradigm contrasting known and unknown stimuli. To assess brain lateralization, we used three different stimuli classes that differed in their verbalizability (words, scenes, fractals). Test-retest reliability of fMRI brain activation was assessed by an intraclass-correlation coefficient (ICC), describing the stability of inter-individual differences in the brain activation magnitude over time. We found as expected a left-lateralized brain activation network for the words paradigm, a bilateral network for the scenes paradigm, and predominantly right-hemispheric brain activation for the fractals paradigm. Although these networks were consistently activated in both sessions on the group level, across-subject reliabilities were only poor to fair (ICCs ≤ 0.45). Overall, the highest ICC values were obtained for the scenes paradigm, but only in strongly activated brain regions. In particular the reliability of brain activity of the MTL was poor for all paradigms. In conclusion, for novelty encoding paradigms the interpretation of fMRI results on a single subject level is hampered by its low reliability. More studies are needed to optimize the retest reliability of fMRI activation for memory tasks.

The right hemisphere's contribution to emotional word processing in currently depressed, remitted depressed, and never-depressed individuals

To examine how unipolar depression influences hemispheric processing of emotional stimuli, words with clear affective content were assessed by depressed, remitted depressed, and never depressed participants. Semantic stimuli were selected for both their valence (positive vs. negative) and for their ability to engender affective arousal (high vs. low). After completing a structured clinical interview to determine depression experience, participants were asked to make valence judgements for laterally presented emotional words. Study results suggest that the right hemisphere (RH) is particularly sensitive to the affective semantic content of emotional stimuli, furthermore, two interesting higher order interactions were observed in the RH. First, in a replication of recent findings by Atchley et al. [2003. Hemispheric asymmetry in the processing of emotional content in word meanings: The effect of current and past depression. Brain and Language, 84, 105–119], individuals who have experienced depression (both currently depressed and remitted depressed groups) show an advantage when processing negatively valent words, while the never depressed individuals show an advantage for positive words. Also in the RH, affective arousal interacted with stimulus valence (but not diagnostic group), such that all participants exhibited an advantage when categorizing highly arousing negative information, while for positive words the low arousing stimuli were identified more accurately. These results are discussed in the context of models of depressive cognition and in regards to general models of hemispheric specialization for emotion processing.

A left hemisphere, but not right hemispace, advantage for tactual simultaneity judgments.

Hemispheric asymmetries for tactile simultaneity judgments were investigated in 34 dextral adults. Pairs of vibrotactile stimuli with simultaneous or successive onsets were delivered unilaterally to the left or right hand. Participants made a forced-choice, bipedal response, indicating whether a stimulus was simultaneous or successive. The effect of hemispatial attentional biases was investigated, using ipsilateral (arms uncrossed) and contralateral (arms crossed) hand placements. Trials presented to the right hand were associated with fewer errors and a trend for faster response times than were those presented to the left hand. There was no asymmetry in response bias. Manipulations of hemispace did not affect the right hand advantage. These results confirm the existence of a left hemisphere temporal-processing advantage but fail to demonstrate that the asymmetry is the result of a rightward attentional bias. The implications of these results for absolute and relative models of hemispheric specialization are discussed.

Behavioral and Electrophysiological Indices of Voicing-Cue Discrimination: Laterality Patterns and Development

Voicing is an important phonetic dimension that distinguishes voiced (i.e., /b/) from voiceless–aspirated stop consonants (i.e., /ph/) in English. Perception of discrete voicing categories is affected by a number of acoustic cues. The present paper reviews evidence from brain-damaged populations indicating that the perception of certain voicing cues is less dependent upon left hemisphere mechanisms than the ability to perceive place of articulation contrasts (e.g., /b/ vs. /d/). In addition, electrophysiological and dichotic listening studies with neurologically normal individuals support the view that the right hemisphere may play a special role in the categorical processing of voicing. These findings are discussed in relation to current models of hemispheric specialization and laterality for language.

Disruption of prosody after frontal lobe seizures in the non-dominant hemisphere

Abstract The perception and production of linguistic and affective prosody at the word, phrase, and sentence levels were examined to delineate the nature of a prosodic deficit evident in a 20-year-old female with a history of seizures in the non-dominant frontal lobe. Acoustic–perceptual analysis of conversational and elicited speech revealed that both perception and production of affective and linguistic prosody were impaired. Acoustic analysis further indicated that timing and intensity were impaired, whereas fundamental frequency (F 0) was relatively spared. Her prosodic profile indicated that disruption of F 0 in longer and more complex prosodic units was secondary to an underlying timing deficit. Findings are interpreted to support the view that prosody is a multifaceted process that is not adequately described by current models of hemispheric specialization for prosody. In addition, findings are brought to bear on issues concerning language and epilepsy, as well as psycholinguistic models of languag...

Foot-preference behavior: a developmental perspective.

The developmental course of foot-preference behavior was examined in participants spanning early childhood to young adulthood. Results indicated significant age-group differences, with no effect for gender. Evidence suggests that footedness adheres to some variant developmental features characterized primarily by a significant shift toward greater right-footedness between 8 and 11 years, after which preferences remain relatively stable. Complementing this shift is a substantial decrease in mixed-footedness across the same time line. Of the existing models of hemispheric specialization, Annett's (1978, 1985) right-shift hypothesis, which considers cultural and environmental effects, provides a partial explanation for the findings. Hand-preference data were also collected and are contrasted with foot-preference data.

On the Interdependency between Attentional Biases and Visual Field Effects with Bilateral Presentations of Stimuli

Previous research indicates that bilateral presentations of visual stimuli yield greater visual field differences than unilateral ones. Although this fact has generally been interpreted by reference to functional models of hemispheric specialization, an alternative explanation has been offered, which suggests that it is artifactually caused by an attentional bias (AB). Indeed, consistent positive correlations between the direction of ABs and that of visual field effects have been reported. However, this relationship remains uncertain since different tasks, presented at different moments, have been used in order to document it. We report on a bilateral presentation task which controlled this potential discrepancy by mixing trials measuring ABs with those assessing visual field effects. We showed that, in a group of dextrals, the direction of the visual field effect is intimately correlated with that of the AB; subjects with a right AB showed a right visual field advantage, whereas subjects with a left AB showed a left visual field advantage; moreover, subjects with no overall AB did not show any visual field advantage. The results of this experiment confirm the fact that the formally reported correlations between the direction of ABs and visual field effects are determined by individual differences in ABs rather than by the task being used to assess them. This observation points to the necessity for further research on variables affecting the between-subjects variability in ABs with the use of bilateral presentations of visual stimuli.

Handedness in great apes: A review of findings

We present data on hand preference in great apes and discuss them in the context of theoretical models of hand preference in nonhuman primates presented by MacNeilageet al. (1987) and by Fagot and Vauclair (1991). We also discuss several methodological and statistical issues as they pertain to the assessment of hand preference in great apes and other primate species. Finally, we present a comparative framework for the study of hand preference, emphasizing the importance of studies with great apes in developing evolutionary models of hemispheric specialization.

Hemispheric specialization for familiar voice recognition: Dichotic listening evidence

Previous dichotic listening studies of voice recognition have produced ambiguous results, perhaps due to the use of unfamiliar voices as stimuli: Evidence from brain‐damaged subjects [e.g., D. Van Lancker and J. Kreiman, UCLA Working Papers in Phonetics 62, 50–60 (1985)] suggested that both hemispheres are required to discriminate among unfamiliar voices. In contrast, recognition of familiar voices was observed to require an intact right hemisphere in the unilaterally brain‐damaged population. To obtain data on ear advantages for dichotically presented voice stimuli, therefore, we used voices of politicians and entertainers familiar to many listeners. Subjects monitored one ear at a time and identified both the speaker and the word spoken on each trial. Although not significant, the ear advantage observed for voice recognition did differ significantly from the significant right ear advantage found for word identification. In light of current models of hemispheric specialization, we interpret this relative left ear advantage for voice recognition as a reflection of a right hemisphere superiority for familiar speaker recognition in normal subjects.

The asymmetry of facial actions is inconsistent with models of hemispheric specialization.

ABSTRACTSeveral models of hemispheric specialization have been used to explain asymmetries in facial actions. This study measured the asymmetry of several different muscular actions individually, alone and in combination, and under different eliciting conditions. The findings did not fit any of the theoretical models. In the deliberate actions, some of the asymmetries were lateralized with greater intensity on the left side; others, on the right side. Spontaneous actions were more symmetrical than the deliberate, requested actions. We rejected specialization for emotion as a cause of the facial asymmetry observed, and discussed the weaknesses of other models.

Spécialisation hémisphérique et fréquences spatiales

Summary : Hemispheric specialization and spatial frequencies. The main models of hemispheric specialization, that is to say the verbal/visuospatial, analytic/holistic and serial/parallel (dichotomies), do not permit to explain the totality of the differences observed between the hemispheres. Though they are confirmed in many cases, they are fre-quently criticized, either for being too rigid, or for their unicity. Moreover, the work in tactile and auditory perception has provided some arguments against these dichotomies. At present, some authors think that what is important is neither the verbal or visuospatial nature of a stimulus, nor the processing that the hemispheres perform preferentially, but rather the different components of the stimulus. So, it seems that the cerebral hemispheres differ in their sensitivity to the different elements of a stimulus. This sensitivity seems to depend heavily on the frequencies (visual or auditory) characterizing these different components. The right hemisphere seems to be more sensitive to low frequencies, and the left hemisphere seems to use preferentially high frecuencies. An explanation of this phenomenon could lie in the neural organization characterizing each hemisphere (focal/diffuse). Key-words : Hemispheric specialization, frequency (spatial and audi-tors), neural organization, recognition (perceptual and mnesic).

Models of hemispheric specialization

Models of hemispheric specialization

Name and face matching in one or two visual fields: A test of models of hemispheric specialization

In two experiments a name and a face (each male or female) were simultaneously flashed to either the same or opposite visual fields (left or right), for matching congruent (same sex) or incongruent (opposite sex), to test the predictions of various models of hemispheric specialization. While overall best performance occurred with a face in the left visual field (LVF) and a name in the right visual field (RVF), and worst with the opposite configuration, the general pattern of results was incompatible with either a direct access model or an activational/ attentional account. The results were, however, most compatible with the predictions of a semispecialized hemispheres account, whereby cerebral asymmetries are seen as relative rather than absolute, either hemisphere being capable of processing either kind of material (verbal or visuospatial), but to different levels of efficiency. However, despite the fact that the stimulus materials had previously been shown to produce stable and consistent lateral asymmetries in the predicted directions when presented in isolation, in the composite, integrative matching task the position of the name seemed to be the major determinant of the resultant asymmetries. It would seem therefore that when such stimuli are to be cross matched, either left hemisphere (language) processes somehow dominate right hemisphere (visuospatial) processing (though not in the way that would be predicted by a simple activational/attentional account) or the left hemisphere's greater capacity predominates.

Do laterality measures relate to speed of response in central vision?

This study was aimed at determining whether an efficiency index (speed of response in central vision) related to a laterality index (difference in speed of response between right and left field presentations). In Experiment 1 female subjects were required to discriminate facial emotional expressions shown in either central vision or the periphery. In Experiment 2 male and female subjects had to classify as same or different pairs of letters printed in different typefaces. It was found that the efficiency index related (negatively) to the laterality index only in Experiment 1 so that slower responses indicate larger visual field differences. The results are discussed in terms of current models of hemispheric specialization.

Models of hemispheric specialization.

Models of hemispheric specialization.

Models of hemispheric specialization.

Models of hemispheric specialization.

Can alphabet recall be part of a visuo-spatial task?

Fifty male and 50 female undergraduates were subjects in an experiment where they were required to recall the alphabet and to count either the number of letters containing the sound 'ee' or the number of letters with curves in the upper-case form. The results fail to replicate those of Coltheart et al. (1975), but are consistent with current models of hemispheric specialization. Males were found to complete the visuo-spatial task slower than the females and it is argued that this is due to their greater degree of hemispheric specialization which necessitates transfer of information between hemispheres.