Regional blood flow changes in the left cerebral hemisphere during word pair learning and recall

Regional cerebral blood flow measurements were made in the left hemisphere of 11 young healthy volunteers during learning and during recalling of word pair associates. Compared to the resting baseline, both tasks caused significant increases of average hemispheric flow, indicating an elevated neuronal activity level. Regionally both tasks were accompanied by considerable activation of parietal and occipital regions. The main difference between learning and recalling was that only the former task activated the prefrontal regions.     

Focal changes in cerebral blood flow produced by monetary incentive during a mental mathematics task in normal and depressed subjects

The purpose of this experiment was to determine the effect of incentive-induced arousal on the diffuse and regional cerebral blood flow (rCBF) response during cognitive activation for normal and depressed groups. Two normal rest CBF measurements were followed by two mental mathematics activation CBF measurements. For the first activation measurement, half the subjects in each group were offered monetary incentive for correct performance and half the subjects received no monetary incentive. All subjects were offered monetary incentive on the final activation run. The effect of monetary incentive on the first activation run was to increase CBF activation at four detectors in the left hemisphere. Incentive did not affect the CBF activation response when introduced following practice on the activation task (on the final run). Depressed groups had lower resting blood flow than normals, but the distribution of flow and the CBF response to incentive were almost identical in the two groups.     

Right hemisphere participation in reading

This study examined whether the right hemisphere's contribution to lexical semantic processing is greatest when it is "disinhibited." Skilled reading may require the controlled modulation of interhemispheric interaction: the left hemisphere (or some other control mechanism) may regulate the subprocesses of reading by selectively "inhibiting" and "disinhibiting" right hemisphere function. Right-handed undergraduates concurrently performed two tasks: a lateralized semantic or rhyme task and a verbal memory task. It was hypothesized that right hemisphere reading processes would be disinhibited when the left hemisphere was "occupied" with the memory task. This hypothesis was supported for a subgroup of subjects who showed evidence of inhibition of right hemisphere function (i.e., left hemisphere dominance for lexical processing) when the lateralized semantic task was performed alone. Across subjects, there was a strong correlation between the degree of left hemisphere dominance in the single-task semantic conditions and the degree of disinhibition of right hemisphere function in the dual-task semantic condition.     

身体活动与心理活动动词加工的ERP比较

在19名右利手被试完成词汇判断任务的同时,通过119个头皮电极记录其事件相关电位（ERP）,以此来探讨表示身体活动的动词与表示心理活动的动词之间的加工差异。研究结果表明,在200~300ms时窗,在左半球枕区附近,身体活动动词所诱发的ERP比心理活动动词所诱发的ERP在正走向上更小。在300~400ms（即类似的N400）时窗,动词类型效应出现在中线和左半球的更大的区域上,特别是中央区附近,身体活动动词所诱发的ERP比心理活动动词所诱发的ERP在负走向上更大。语言表征的神经生物学理论可以解释本研究的部分结果。     

Defects of immediate memory related to the cerebral blood flow distribution

Different forms of memory defects were studied in 16 patients with organic dementia. The test performance was related to the regional cerebral blood flow (rCBF) in the left (dominant) hemisphere. Verbal memory (Paired Associates) correlated to the blood flow in temporal and parietal regions. Spatial recognition (Memory for Objects, Memory for Geometrical Design) correlated to the temporal and lower frontal regions. One spatial memory test (Visual Retention test) correlated to the temporal region only. Another spatial memory test (Memory for Design) did not show correlations to any regions of the dominant hemisphere. Finally it was found that the hemisphere mean flow values did not correlate to performance. This emphasizes the main finding—the regional correlations. It is concluded that memory performance involves various extratemporal regions depending upon the specific quality of the memory task to be performed.     

Patterns of regional cerebral blood flow during attempted reading aloud by stutterers both on and off haloperidol medication: Evidence for inadequate left frontal activation during stuttering

Two stutterers, both recent college graduates, were subjected to regional cerebral blood flow measurements while attempting to read aloud. Each one received two measurements, one of which was under the influence of haloperidol, 3 mg daily. Both subjects showed improvement on medication, allowing a stuttering versus essentially no stuttering comparisons for each subject. Both subjects showed higher Broca's area flow in the right compared to the left hemisphere, during stuttering. Both showed higher Wernicke's area flow in the left compared to the right hemisphere, however, during stuttering. During reading aloud without stuttering, however, the Brocas's area flows were reversed, now showing a left hemisphere advantage. The results were interpreted as consistent with H. M. Sussman and P. F. MacNeilage's (1975, Neuropsychologia, 13, 19–26) proposal that stutterers exhibit conventional left cerebral dominance for speech reception, but inadequate left cerebral dominance for speech production.     

Effects of a concurrent memory task on hemispheric asymmetries in categorization

Recent research on the division of processing between the two cerebral hemispheres has often employed two concurrent tasks to investigate the dynamic nature of hemispheric asymmetries. The experiment reported here explored the effects of two concurrent high-level cognitive tasks (memory retention and semantic categorization) on the direction and magnitude of hemispheric differences in the processing of words and pictures. Subjects were required to categorize words and pictures presented to either the left visual field-right hemisphere (LVF-RH) or the right visual field-left hemisphere (RVF-LH). The categorization could be performed while holding either verbal material in memory (digit span), pictorial material in memory (serial nonsense figure recognition), or with no concurrent memory task. The effects produced hemisphere-specific, material-nonspecific interference. The verbal task removed a RVF-LH advantage at word categorization and enhanced a LVF-RH advantage on picture categorization; the pictorial task interfered with picture categorization in the LVF-RH, while enhancing a RVF-LH advantage at word categorization. The results are discussed in terms of multiple resource models of hemisphere function, capacity limitations, and the functional locus of processing required to produce various dynamic hemispheric effects.     

Residual differences in language processing in compensated dyslexics revealed in simple word reading tasks

Using regional cerebral blood flow as an index of cerebral activity we studied dyslexic and control subjects during simple word reading tasks. The groups were pre-tested for reading skill and the dyslexic group had a lower reading performance but could read and comprehend standard texts. The aim was to elucidate differences in the cerebral activation pattern during reading. The tasks were simple enough that performance differences between the groups could be excluded. We found specific differences between the two groups that were dependent on the language task. When the visual route for language information was used, minor qualitative differences were found between the groups pertaining to the dominant hemisphere. Increasing the complexity of the task by using pseudowords activated the left frontal region more in the dyslexic group than in the control group. A similar effect was seen in a minor region in extrastriate lateral occipital cortex (BA 19). This finding indicates that the dyslexics used areas in these regions that the controls did not. On the other hand, the dyslexics activated less in the right angular gyrus, right dorsolateral prefrontal cortex, and in the right pallidum. Reading skill correlated with the level of activity in the right frontal cortex. We conclude, that cerebral activation pattern elicited by reading is different in dyslexics compared to controls in spite of an almost complete functional compensation.     

Focal changes in cerebral blood flow produced by a test of right-left discrimination

A sensorimotor control activation task was used to isolate the focal cerebral blood flow changes resulting from the visual and cognitive processing of a right-left discrimination task. Eleven normal right-handed males participated. The sensorimotor control task produced significant bilateral increases in flow in most cortical channels. Significant bilateral parieto-occipital activation was found for the right-left discrimination task over and above the flow changes produced by the sensorimotor control task. The left occipital flow increase resulting from the right-left discrimination task was found to be negatively related to task performance. An inverse relationship was also found between WAIS Performance IQ and the blood flow change in the left parietal channel. These results suggest areas for further testing concerning potential individual differences in cognitive processing during the performance of a right-left discrimination task.     

Hemispheric asymmetry,early visual processes,and serial memory comparison

Observers indicated whether a single probe letter presented to the left visual field/right hemisphere (LVF-RH) or to the right visual field/left hemisphere (RVF-LH) matched one of two, three, four, or five set letters in both name and case. For positive trials during the initial experimental session, the slope of the linear memory set size reaction time function was increased by perceptually degrading the probe letter on LVF-RH trials, but not on RVF-LH trials. In addition, perceptual degradation of the probe letter increased the intercept of the memory set size function more on RVF-LH trials than on LVF-RH trials. During subsequent experimental sessions, the same pattern of intercept results was obtained but perceptual degradation of the probe no longer changed the slope for either LVF-RH or RVF-LH trials. However, the slopes were uniformly lower on RVF-LH trials than on LVF-RH trials. The major results are consistent with hypothesized right-hemisphere efficiency for early processing stages and left-hemisphere efficiency for serial processing of alphanumeric information. The results further illustrate the importance of separating stages of processing in studies of cerebral laterality and indicate that the relative difficulty of the various stages can be a determinant of laterality results.     

Regional cerebral blood flow response in a patient with remitted global amnesia

A case of remitted global amnesia, believed to have residual left medial temporal lobe damage, is tested by the same recognition memory paradigm used by Wood, Taylor, et al. in the previous paper. On two different testing occasions, once using an intentional and once an incidental memory procedure, the patient's right occipital flows were inversely correlated with memory accuracy and the values were very close to the regression line for 10 normals relating occipital flow to memory accuracy. The left occipital flows did not fit the regression line, however. The results were interpreted as consistent with the notion that occipital flow is inversely related to medial temporal lobe activation. Another surprising feature of this case is the unexpected persistence of amnesia for a period from about 5 to 10 years before her episode to about 2 weeks after the episode, with recovery of memory functioning for the period since that time.     

Cerebral lateralization of language in deaf and hearing people

In Experiment 1 neither hearing nor prelingually deaf signing adolescents showed marked lateralization for lexical decision but, unlike the hearing, the deaf were not impaired by the introduction of pseudohomophones. In Experiment 2 semantic categorization produced a left hemisphere advantage in the hearing for words but not pictures whereas in the deaf words and signs but not pictures showed a right hemisphere advantage. In Experiment 3 the lexical decision and semantic categorization findings were confirmed and both groups showed a right hemisphere advantage for a face/nonface decision task. The possible effect of initial language acquisition on the development of hemispheric lateralization for language is discussed.     

Aging affects both perceptual and lexical/semantic components of word stem priming: An event-related fMRI study

In this event-related fMRI study, brain activity patterns were compared in extensive groups of young (N=25) and older (N=38) adults, while they were performing a word stem completion priming task. Based on behavioral findings, we tested the hypothesis that aging affects only the lexical/semantic, but not the perceptual component of word stem priming. To this end, we distinguished between priming-related activity reductions in posterior regions involved in visual processing, and regions associated with lexical/semantic retrieval processes, i.e., left lateral temporal and left prefrontal regions. Both groups revealed significant priming-related response time reductions. However, in accordance with earlier findings, a larger priming effect was found in the group of young participants. In line with previous imaging studies, the groups showed common priming-related activity reductions in the anterior cingulate, and the left inferior prefrontal cortex extending into the anterior portion of the left superior temporal gyrus, and at lower thresholds also in the right occipital lobe. However, when directly comparing the groups, greater priming-related reductions were found for the young group in the left anterior superior temporal gyrus and the right posterior occipital lobe. These findings suggest that, converse to current psychological views, aging affects both perceptual and lexical/semantic components of repetition priming.     

Psychopathy and cerebral asymmetry in semantic processing

A divided visual field (DVF) procedure was used to investigate the cerebral organization of language processes in psychopaths. The subjects consisted of four groups of 13 right-handed males: noncriminals (NC), and criminals with high (H), medium (M), and low (L) scores on the Psychopathy Checklist (Hare, 1980). The subject had to decide if a concrete noun, tachistoscopically presented in either the left (LVF) or the right visual hemifield (RVF), matched a pretrial work (SR task), or was an exemplar of a specific category (SC task) or an abstract category (AC task). There were no group differences in reaction time. As predicted, group differences in errors were confined to the AC task; Groups L and NC made fewer RVF than LVF errors (thus showing the sort of RVF advantage expected with semantic categorization), whereas the opposite was true of Group H. The results, along with those obtained in a recent dichotic listening study, lead us to speculate that psychopathy may be associated with weak or unusual lateralization of language function, and that psychopaths may have fewer left hemisphere resources for processing language than do normal individuals.     

Relationships among measures of visual imagery

As a step toward the development of an objective measure of visualization ability, five tasks which yielded seven separate measures were administered to 74 Ss and intercorrelated. The tasks were: paired associate recall improvement (RI), recognition memory (RM), the Bett's Questionnaire on Mental Imagery (QMI) as revised by Sheehan (1967a, b), a task calling for the production of visual images (PVI) where rated vividness and latency of image attainment were measured, and a task requiring the imagining of emotional scenes (ES) where rated vividness and rated anxiety were measured. The results indicated that although paired associate learning scores per se were related to RM, neither of the memory measures of visualization (RI and RM) were related to any of the other visualization measures. A cluster of intercorrelations was obtained among self-ratings of image vividness on the QMI, PVI and ES tasks. This cluster also included a measure of latency of report of “best image” attainable derived from the PVI task. None of the measures correlated with anxiety ratings on the ES task. These findings were discussed in relation to previous studies and the potential value of the latency measure as an adjunct measure of visualization ability was noted.     

Musicians processing music: Measurement of brain potentials with EEG

Abstract

In the present study, the EEG was recorded from the scalp of musicians while mentally active in their field. Analytic, creative and memory processes of the brain were observable using a special electrophysiological method called DC-potential recording. Music students listened to a sequence of four notes and subsequently were either to reverse the sequence (task 1 = analytic) or to compose a new continuation (task 2 = creative). In task 3, the initial segment of a well-known melody was presented and had to be continued (memory task). All tasks had to be solved mentally (imagery). In tasks 1 and 2, either tonal or atonal sequences were presented.

While processing, the results show that the analytic task elicited the highest brain activity. The analytic task involved mainly parieto-temporal areas of both hemispheres, the left hemisphere showing a tendency for domination. The memory task produced predominant activity over the right hemisphere. The creative task caused the lowest brain activation and elicited an unexpected lateralisation to the left, though we expected creativity to be a right hemispheric holistic-synthetic phenomenon.

Comparing listening with processing of the perceived music, we found a significant shift from an insignificant right hemispheric to an insignificant left hemispheric predominance (except with the memory task). This indicates that musicians do not lateralise to the left hemisphere per se when listening to music. Whether one finds a left hemispheric lateralisation in listening tasks or a right hemispheric one probably depends on the amount of simultaneous analytic-sequential processing the musician undertakes.     

Bilingualism and brain functional asymmetry

The task of the neural organization of the native language, acquired by a direct method and of another language, studied at school, performed correspondingly by the left and the right hemispheres, was studied in the bilingual patient after unilateral electroconvulsive therapy used in psychiatry. It was established that in such a bilingual type the right hemisphere is concerned with the formation of deep semantic structures of the native language while the left hemisphere is responsible for the formation of second language deep structures and of surface structures of both languages. The effect of language learning method on cerebral organization of bilingualism is postulated.     

Adult age differences in visual word identification: functional neuroanatomy by positron emission tomography

Adult age differences in the neural systems mediating semantic (context-independent) memory were investigated using positron emission tomography (PET). Younger (20-29 years) and older (62-70 years) participants performed lexical decision (word/nonword discrimination) and nonsemantic (simple visual search) baseline tasks during PET scanning. Within the lexical decision task, display duration and presentation rate were varied across scans. The behavioral data suggested that although an age-related slowing was evident in visual feature and response processing, the retrieval of semantic/lexical information was similar for younger and older adults. For both age groups, lexical-related activation occurred in inferior prefrontal and occipitotemporal regions of the left hemisphere. Differential activation, as a function of age group, was observed in the left occipitotemporal pathway as a result of older adults' maintaining higher levels of neural activity in striate cortex (during visual search) and in inferior temporal cortex (during lexical decision). The prefrontal activation was similar for the two age groups. Thus, although this form of semantic memory retrieval does not undergo significant age-related decline, an age-related change in the associated pattern of neural activation is evident. These findings differ from previous neuroimaging studies of episodic (context-dependent) memory retrieval, which have suggested that age-related compensatory mechanisms are expressed primarily by greater activation of prefrontal regions for older adults than for younger adults.     

Automatic and conscious processing in retarded and nonretarded adolescents

Educable mentally retarded and nonretarded adolescents participated in incidental learning tasks that emphasized the utilization of processes that were consciously controlled but not deliberately aimed at memory (Experiment 1). Retarded individuals' performance on a standard recognition test was equivalent to that of nonretarded subjects following phonetic encoding and nonstrategic encoding, but was deficient following semantic encoding. Retarded subjects also demonstrated a lower level of performance on a rhyme recognition task. In Experiment 2, retarded subjects provided a pattern of responding identical to that of nonretarded subjects on a picture-word interference task designed to assess automatic processing. The two groups produced equivalent levels of semantic activation. It was argued that the results of the two experiments indicate deficient semantic processing on the part of retarded individuals relative to that of nonretarded individuals that cannot be accommodated by a structural-deficiency model, a developmental-lag model, or a hypothesis that predicts intelligence-related differences only when the task involves the use of deliberate mnemonic strategies.     

Language processing in bilinguals

The present study investigated the language processing strategies of three subgroups of adult bilinguals with different histories of language acquisition: infant bilinguals whose bilinguality dated from infancy; childhood bilinguals who became bilingual around 5 years of age; and adolescent bilinguals who had become bilingual at secondary school age only. All were completely balanced bilinguals in French and English at the time of testing. The experimental procedure, a language recognition task, required the subjects to indicate, by pressing a response button, whether each of a series of words, presented monaurally through earphones, was French or English. Concomitantly, left and right hemisphere EEG activity was monitored, with measures taken of latency to N₁, latency to P₂, and N₁-P₂ peak-to-peak amplitudes. Results indicated shorter latencies to N₁ in the left than in the right hemisphere for the infant and childhood bilinguals but shorter latencies in the right hemisphere for the adolescent bilinguals. Overall, the N₁ latency was shorter for the adolescent subgroup than for the two other subgroups. There were no RT differences. The findings appear to reflect strategy differences: The adolescent group seemed to rely more on a right hemisphere-based, possibly more gestalt-like or melodic strategy, while the early bilinguals relied more on a left hemisphere-based, possibly semantic or analytic type of strategy. The results are discussed in terms of previous research on bilingual subtypes and general forms of language processing among bilinguals.