Speech dominance and handedness in the normal human

Spectral analysis was used to measure the coherence or similarity of form between occipital and temporal evoked potentials. In both right- and left-handers, coherence was greater in the left hemisphere for click stimuli and in the right hemisphere for flash stimuli. Similar asymmetries occurred in left but not right speech dominant patients whose speech lateralization has been determined by the intracarotid amytal test. Right-handers and males, however, showed significantly larger amplitudes of auditory responses in the right hemisphere. Left-handers and females reversed this pattern. It was concluded that within a basically left speech dominant organization, males and right-handers would emphasize the verbal, temporal structure of auditory information and the nonverbal, spatial structure of visual information. Females and left-handers would tend to reverse this emphasis.     

Right-hemisphere responses from preschool children to temporal cues to speech and nonspeech materials: electrophysiological correlates

Auditory-evoked responses (AERs) were recorded from scalp electrodes placed over the left and right temporal hemisphere regions of 12 preschool children while they listened to a series of velar stop consonants which varied in voice onset time (VOT) and to two-formant tone stimuli with temporal lags comparable to the speech materials. A late occurring negative peak (N400) in the right hemisphere AERs discriminated between both the speech and nonspeech materials in a categorical-like manner. Sex-related hemisphere differences were also noted in response to the two different stimulus types. These results replicate earlier work with speech materials and suggest that temporal delays for both speech and nonspeech auditory materials are processed in the right hemisphere.     

Hemispheric asymmetries in human infants: Spectral analysis of flash and click evoked potentials

Evoked potentials of 16 human infants (mean age = 5.0 weeks, SD = 1.8 weeks) were recorded from the left and right, occipital and temporal areas. Spectral analysis showed a high amplitude, localized, coherent center of activity within the left temporal area for click stimuli, and a high amplitude, localized center of activity in the right occipital area for flash stimuli. It was proposed that the structured auditory information of the click and the unstructured visual information of the flash represented different degrees of familiarity to the subjects. With this hypothesis, left hemisphere involvement in stimulus processing would increase as the stimulus became more referrable to previous long- or short-term experience. Conversely, right hemisphere involvement would increase with unfamiliar stimuli which could not be readily associated with earlier data.     

Lateralization of auditory rhythm length in temporal lobe lesions

In the visual modality, short rhythmic stimuli have been proven to be better processed (sequentially) by the left hemisphere, while longer rhythms appear to be better (holistically) processed by the right hemisphere. This study was set up to see if the same holds in the auditory modality. The rhythm task as originally designed by Seashore was computerized and is part of the Fepsy Neuropsychological battery. This task was performed by 85 patients with intractable temporal lobe epilepsy (left TLE = 32; right TLE = 53) enrolled in the Dutch Collaborative Epilepsy Surgery Program. They performed the task before and 6 months after surgery. The task consists of 30 pairs of rhythmic patterns in 3 series of 10 items. The series contains patterns of 5, 6, or 7 notes. The purpose is to indicate whether the two patterns are the same or different. Reaction times are also measured. If the hypothesis is true, the short-item sequence will be better processed by patients with right temporal lobe epilepsy (nonimpaired left temporal lobe), the longer sequence will be better processed by the left temporal epilepsy group (nonimpaired right temporal lobe). No overall laterality effect on rhythm perception could be found and no difference was found between both test moments. IQ did not correlate with rhythm performance. However, there was an interaction effect of laterality and rhythm length on performance and reaction time. This effect can be explained by the increase after the operation of the score of the left focus group and a decrease in the right focus group on the longer rhythms. This effect was somewhat less strong in the reaction times: a clear tendency for faster reaction times after surgery in the left and longer reaction times in the right focus group. The effect could not be explained for by the difference in extent of resection in either temporal lobe. This study showed that memory for and discrimination of auditory rhythm is dependent on which hemisphere is used in processing. The effect could be demonstrated for the right hemisphere, which uses a holistic processing of stimuli, which outperforms the left in rhythms consisting of a long sequence. In left temporal resections an improvement occurs on the longer rhythms and in right temporal resections the performance on the longest rhythms decreases.     

Effect of temporal constraints on hemispheric asymmetries during spatial frequency processing

Studies on functional hemispheric asymmetries have suggested that the right vs. left hemisphere should be predominantly involved in low vs. high spatial frequency (SF) analysis, respectively. By manipulating exposure duration of filtered natural scene images, we examined whether the temporal characteristics of SF analysis (i.e., the temporal precedence of low on high spatial frequencies) may interfere with hemispheric specialization. Results showed the classical hemispheric specialization pattern for brief exposure duration and a trend to a right hemisphere advantage irrespective of the SF content for longer exposure duration. The present study suggests that the hemispheric specialization pattern for visual information processing should be considered as a dynamic system, wherein the superiority of one hemisphere over the other could change according to the level of temporal constraints: the higher the temporal constraints of the task, the more the hemispheres are specialized in SF processing.     

Bilateral capacity for speech sound processing in auditory comprehension: evidence from Wada procedures

Data from lesion studies suggest that the ability to perceive speech sounds, as measured by auditory comprehension tasks, is supported by temporal lobe systems in both the left and right hemisphere. For example, patients with left temporal lobe damage and auditory comprehension deficits (i.e., Wernicke's aphasics), nonetheless comprehend isolated words better than one would expect if their speech perception system had been largely destroyed (70-80% accuracy). Further, when comprehension fails in such patients their errors are more often semantically-based, than-phonemically based. The question addressed by the present study is whether this ability of the right hemisphere to process speech sounds is a result of plastic reorganization following chronic left hemisphere damage, or whether the ability exists in undamaged language systems. We sought to test these possibilities by studying auditory comprehension in acute left versus right hemisphere deactivation during Wada procedures. A series of 20 patients undergoing clinically indicated Wada procedures were asked to listen to an auditorily presented stimulus word, and then point to its matching picture on a card that contained the target picture, a semantic foil, a phonemic foil, and an unrelated foil. This task was performed under three conditions, baseline, during left carotid injection of sodium amytal, and during right carotid injection of sodium amytal. Overall, left hemisphere injection led to a significantly higher error rate than right hemisphere injection. However, consistent with lesion work, the majority (75%) of these errors were semantic in nature. These findings suggest that auditory comprehension deficits are predominantly semantic in nature, even following acute left hemisphere disruption. This, in turn, supports the hypothesis that the right hemisphere is capable of speech sound processing in the intact brain.     

Deficits in temporal sequencing of verbal material: The effect of laterality of lesion

Temporal sequencing of verbal materials (digits, words, and geometric forms) presented in two sensory modalities (auditory and visual) to three groups of subjects (Broca's with left anterior lesions, patients with right hemisphere lesions, and normals) was examined. Each subject was asked to point to a set of stimuli in the same sequence as presented by the examiner. Results indicated that patients with left hemisphere lesions were more impaired on all tasks than the right hemisphere lesioned patients who, in turn, were impaired compared to normal controls. Response to auditory presentation was superior to response to visual presentation. Also, digits were the easiest for all groups, and words were easier than geometric forms. Of special interest was the finding which suggested that right hemisphere lesions are associated with impairment of verbal temporal sequencing under either auditory or visual presentation.     

Syntactic, prosodic, and semantic processes in the brain: evidence from event-related neuroimaging

The neural network supporting aspects of syntactic, prosodic, and semantic information processing is specified on the basis of two experiments using functional magnetic resonance imaging (fMRI). In these two studies, the presence/absence of lexical-semantic and syntactic information is systematically varied in spoken language stimuli. Inferior frontal and temporal brain areas in the left and the right hemisphere are identified to support different aspects of auditory language processing. Two additional experiments using event-related brain potentials investigate the possible interaction of syntactic and prosodic information, on the one hand, and syntactic and semantic information, on the other. While the first two information types were shown to interact early during processing, the latter two information types do not. Implications for models of auditory language comprehension are discussed.     

Pure word deafness and the bilateral processing of the speech code

The analysis of pure word deafness (PWD) suggests that speech perception, construed as the integration of acoustic information to yield representations that enter into the linguistic computational system, (i) is separable in a modular sense from other aspects of auditory cognition and (ii) is mediated by the posterior superior temporal cortex in both hemispheres. PWD data are consistent with neuropsychological and neuroimaging evidence in a manner that suggests that the speech code is analyzed bilaterally. The typical lateralization associated with language processing is a property of the computational system that acts beyond the analysis of the input signal. The hypothesis of the bilateral mediation of the speech code does not imply that both sides execute the same computation. It is proposed that the speech signal is asymmetrically analyzed in the time domain, with left‐hemisphere mechanisms preferentially extracting information over shorter (25–50 ms) temporal integration windows and right mechanisms over longer (150–250 ms) windows.     

Coding strategies and cerebral laterality effects

In a short-term recognition memory task, Ss were given relational imagery and rehearsal coding strategies in different sessions, with probes presented to the left or right cerebral hemisphere. Consistent with a model of separate processing systems for verbally and visually coded information, Ss yielded significantly faster response latencies for probes to the left hemisphere than the right when employing the rehearsal strategy, and significantly faster latencies for probes to the right hemisphere than the left when using the imagery code. This suggests that cerebral laterality effects are functionally related to coding strategies, and argues for the inclusion of imagery, or generated visual information, as part of the visual processing system. As such, generated visual information may be viewed as a coding alternative to verbal mediation.     

Electrographic correlates of lateral asymmetry in the processing of verbal and nonverbal auditory stimuli

A veraged evoked potentials (AEP) to verbal (digits) and nonverbal (clicks) auditory stimuli were recorded from left and right temporal leads in ten right-handed Ss. With dichotic presentation, there was no significant difference in accuracy of report of the clicks heard in each ear, but significantly more digits were identified correctly from the right ear than from the left. Dichotic verbal stimuli elicited AEP whose early components were of greater amplitude, and whose later components were of shorter latency, from the left hemisphere than from the right. No consistent latency or amplitude differences were observed between AEP from the left and right hemispheres when clicks were presented dichotically.     

Temporal lobe epilepsy and the selective reminding test: the conventional 30-minute delay suffices

Conventional memory assessment may fail to identify memory dysfunction characterized by intact recall for a relatively brief period but rapid forgetting thereafter. This study assessed learning and retention after 30-min and 24-hr delays on auditory and visual selective reminding tests (SRTs) in right (n=20) and left (n=22) temporal lobe epilepsy (TLE) patients and controls (n=49). The left TLE group performed significantly worse than controls on all 3 trials of both tests. The right TLE group differed from the controls on all 3 visual SRT trials and on learning for the auditory SRT. There were no between-groups differences in rate of information lost at the 30-min versus the 24-hr delay. At the individual level, there was no difference in the percentage of patients versus controls who demonstrated isolated memory impairment at the 24-hr delay. Accelerated forgetting over 24 hr is uncommon in TLE patients.     

人类工作记忆的某些神经影像研究

采用神经影像技术研究人类工作记忆的脑机理是目前一个十分活跃的研究领域。研究表明存在负责不同信息加工的工作记忆系统 ,如词语工作记忆、空间工作记忆等 ,其中词语工作记忆主要由大脑左半球参与 ,空间工作记忆主要由大脑右半球参与。前额叶在工作记忆中的作用相当复杂 ,包括对记忆信息的注意和抑制、管理、整合等功能。合理巧妙的实验设计、多种研究手段的综合应用必将使人类工作记忆的脑机理得到充分阐明。     

Hemispheric asymmetries in the visual evoked potentials to temporal frequency: preliminary evidence

Steady-state evoked potentials were recorded in eight adult subjects from occipital and temporal leads of both hemispheres to investigate the effect of temporal frequency on the hemispheric specialization for basic visual information. A 3 cycles deg-1 grating was phase-reversed at different temporal frequencies (from 4 to 18 Hz), and the frequency spectrum of evoked potentials was computed by means of a fast Fourier transform program. Significant results were obtained for the component at twice the temporal frequency of stimulation. Occipital evoked potentials did not show hemispheric asymmetry, whereas temporal evoked potentials showed an interaction between hemisphere and temporal frequency: right and left hemispheres were respectively prominent for low (4 and 6 Hz) and for high (8-18 Hz) temporal frequencies. The results are discussed in the context of current research on hemispheric specialization for basic spatiotemporal parameters of visual information processing.     

记忆状态下儿童青少年脑波超慢涨落特点的研究

用ET技术对24名7—18岁的儿童青少年进行了静息状态和记忆状态下脑电超慢涨落特点的比较研究,结果表明,在记忆状态下：(1)被试S1、S2频率明显下降,记忆成绩好的被试这一特点更为明显;(2)男生左脑功率明显下降,女生右脑功率明显上升;(3)左脑优势被试左前脑功率下降,右脑优势被试右前脑功率上升。     

The right hemisphere and temporal processing of consonant transition durations: electrophysiological correlates

Auditory evoked responses (AER) were recorded from frontal, temporal, and parietal scalp regions to a series of consonant-vowel syllables which varied in the duration of the consonant transition. Multivariate analyses of the AER waveforms identified one component of the AERs occurring only over right hemisphere regions which discriminated between differences in transition durations. A second component detected over only left hemisphere areas discriminated differences in place of articulation. These data are consistent with previous behavioral and electrophysiological reports that the right hemisphere is sensitive to temporal discriminations.     

Plasticity for recovery, plasticity for development: cognitive outcome in twins discordant for mid-childhood ischemic stroke.

Cognitive and language profiles in a set of likely monozygotic 13-year-old twins raised together and discordant for an extensive left hemisphere stroke are described 6 years post-stroke. Recovery differed across four skill profiles, created based on a model of plasticity. Full recovery of lost skills and full or partial development of new skills typically involved either semantic memory or right hemisphere lateralized functions such as visual perception skills. Limited development of new skills and full or partial recovery of lost skills took place in either active verbal memory or oral language skills that are left hemisphere lateralized. Language skills concerned with real-time lexical retrieval, or the use and understanding of morphology and grammar, phonological processing skills, and auditory working memory were least likely to recover and continue to develop.     

Hemispheric asymmetries in auditory distraction

Serial-verbal short-term memory is impaired by irrelevant sound, particularly when the sound changes acoustically (the changing-state effect). In contrast, short-term recall of semantic information is impaired only by the semanticity of irrelevant speech, particularly when it is semantically related to the target memory items (the between-sequence semantic similarity effect). Previous research indicates that the changing-state effect is larger when the sound is presented to the left ear in comparison to the right ear, the left ear disadvantage. In this paper, we report a novel finding whereby the between-sequence semantic similarity effect is larger when the irrelevant speech is presented to the right ear in comparison to the left ear, but this right ear disadvantage is found only when meaning is the basis of recall (Experiments 1 and 3), not when order is the basis of recall (Experiment 2). Our results complement previous research on hemispheric asymmetry effects in cross-modal auditory distraction by demonstrating a role for the left hemisphere in semantic auditory distraction.