Cortical activation patterns of affective speech processing depend on concurrent demands on the subvocal rehearsal system. A DC-potential study.
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In order to delineate brain regions specifically involved in the processing of affective components of spoken language (affective or emotive prosody), we conducted two event-related potential experiments. Cortical activation patterns were assessed by recordings of direct current components of the EEG signal from the scalp. Right-handed subjects discriminated pairs of declarative sentences with either happy, sad or neutral intonation. Each stimulus pair was derived from two identical original utterances that, due to digital signal manipulations, slightly differed in fundamental frequency (F0) range or in duration of stressed syllables. In the first experiment, subjects were asked: (i) to denote the original emotional category of each sentence pair and (ii) to decide which of the two items displayed stronger emotional expressiveness. Participants in the second experiment were asked to repeat the utterances using inner speech during stimulus presentation in addition to the discrimination task. In the absence of inner speech, a predominant activation of right frontal regions was observed, irrespective of emotional category. In the second experiment, a bilateral activation with left frontal preponderance emerged from discrimination during additional performance of inner speech. Compared with the first experiment, a new pattern of acoustic signal processing arose. A relative decrease of brain activity during processing of F0 stimulus variants was observed together with increased activation during discrimination of duration-manipulated sentence pairs. Analysis of behavioural data revealed no significant differences in evaluation of expressiveness between the two experiments. We conclude that the topographical shift of cortical activity originates from left hemisphere (LH) mechanisms of speech processing that centre around the subvocal rehearsal system as an articulatory control component of the phonological loop. A strong coupling of acoustic input and (planned) verbal output channel in the LH is initiated by subvocal articulatory activity like inner speech. These neural networks may provide interpretations of verbal acoustic signals in terms of motor programs and facilitate continuous control of speech output by comparing the signal produced with that intended. Most likely, information on motor aspects of suprasegmental signal characteristics contributes to the evaluation of affective components of spoken language. In consequence, the right hemisphere (RH) holds a merely relative dominance, both for processing of F0 and for evaluation of emotional significance of sensory input. Psychophysically, an important determinant on expression of lateralization patterns seems to be given by the degree of communicative demands such as solely perceptive (RH) or perceptive and verbal-expressive (RH and LH). (+info)
A comparison of verbal and tangible stimulus preference assessments.
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Tangible preference assessments were compared with verbal preference assessments for 6 individuals with mental retardation, behavior disorders, or both. In the tangible assessment, items were placed in front of the participant. In the verbal assessment, participants were asked, "Do you want X or Y?" and the items were not present. The two assessments yielded similar high-preference items for 4 of the 6 participants. The verbal assessment was typically completed in less time than the tangible assessment. (+info)
Psychiatric symptoms in adults with learning disability and challenging behaviour.
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BACKGROUND: In people with learning disability one of the most frequent reasons for psychiatric referral is challenging behaviour. AIMS: To determine what proportion of people with challenging behaviour actually have psychiatric symptoms. METHOD: Using an instrument specifically designed for use by informants, a sample of 320 people with administratively defined learning disability, with and without challenging behaviour, was surveyed for the presence of psychiatric symptoms. RESULTS: Increasing severity of challenging behaviour was associated with increased prevalence of psychiatric symptoms, depression showing the most marked association. Anxiety symptoms were associated with the presence of self-injurious behaviour. CONCLUSIONS: There is clearly the potential for reducing challenging behaviour by improved identification and treatment of coexisting psychiatric disorders. The possibility of modifying diagnostic criteria for depression in people with learning disability, by including aspects of challenging behaviour, merits attention. (+info)
Handedness and hemispheric language dominance in healthy humans.
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In most people the left hemisphere of the brain is dominant for language. Because of the increased incidence of atypical right-hemispheric language in left-handed neurological patients, a systematic association between handedness and dominance has long been suspected. To clarify the relationship between handedness and language dominance in healthy subjects, we measured lateralization directly by functional transcranial Doppler sonography in 326 healthy individuals using a word-generation task. The incidence of right-hemisphere language dominance was found to increase linearly with the degree of left-handedness, from 4% in strong right-handers (handedness = 100) to 15% in ambidextrous individuals and 27% in strong left-handers (handedness = -100). The relationship could be approximated by the formula: f1.gif" BORDER="0">. These results clearly demonstrate that the relationship between handedness and language dominance is not an artefact of cerebral pathology but a natural phenomenon. (+info)
Validation and application of verbal autopsies in a rural area of South Africa.
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OBJECTIVE: To validate the causes of death determined with a single verbal autopsy instrument covering all age groups in the Agincourt subdistrict of rural South Africa. METHODS: Verbal autopsies (VAs) were conducted on all deaths recorded during annual demographic and health surveillance over a 3-year period (1992-95) in a population of about 63 000 people. Trained fieldworkers elicited signs and symptoms of the terminal illness from a close caregiver, using a comprehensive questionnaire written in the local language. Questionnaires were assessed blind by three clinicians who assigned a probable cause of death using a stepwise consensus process. Validation involved comparison of VA diagnoses with hospital reference diagnoses obtained for those who died in a district hospital; and calculation of sensitivity, specificity and positive predictive value (PPV) for children under 5 years, and adults 15 years and older. RESULTS: A total of 127 hospital diagnoses satisfied the criteria for inclusion as reference diagnoses. For communicable diseases, sensitivity of VA diagnoses among children was 69%, specificity 96%, and PPV 90%; among adults the values were 89, 93 and 76%. Lower values were found for non-communicable diseases: 75, 91 and 86% among children; and 64, 50 and 80% among adults. Most misclassification occurred within the category itself. For deaths due to accidents or violence, sensitivity was 100%, specificity 97%, and PPV 80% among children; and 75, 98 and 60% among adults. Since causes of death were largely age-specific, few differences in sensitivity, specificity and PPV were found for adults and children. The frequency distribution of causes of death based on VAs closely approximated that of the hospital records used for validation. CONCLUSION: VA findings need to be validated before they can be applied to district health planning. In Agincourt, a single verbal autopsy instrument provided a reasonable estimate of the frequency of causes of death among adults and children. Findings can be reliably used to inform local health planning and evaluation. (+info)
Characterizing the neural mechanisms of skill learning and repetition priming: evidence from mirror reading.
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The changes in brain activity related to skill learning and repetition priming in a mirror-reading task were examined using functional MRI. Subjects exhibited significant learning across five training sessions and this learning generalized significantly to different spatial transformations (inverted-mirror reversed text and normal letters spelled backwards). Mirror reading, compared with reading normal text, was associated with extensive activation in occipital, temporal, parietal and frontal regions. Learning to read mirror-reversed (MR) text was associated with increased activation in left inferior temporal, striatal, left inferior prefrontal and right cerebellar regions and with decreased activity in the left hippocampus and left cerebellum. Short-term repetition priming was associated with reduced activity in many of the regions active during mirror reading and extensive item-specific practice (long-term repetition priming) resulted in a virtual elimination of activity in those regions. Short- and long-term repetition priming thus appeared to rely upon common neural mechanisms. Nearly all of the regions exhibiting significant learning-related changes also exhibited increased repetition priming effects, suggesting common neural substrates for priming and skill learning in this task. Comparison of MR items with other spatially transformed typographies showed that the learning-related changes were general to all of the spatial transformations. The results confirm the importance of striatofrontal neural networks for the acquisition of skills, and suggest that skill learning and repetition priming may have common substrates within a particular task. (+info)
Separate neural subsystems within 'Wernicke's area'.
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Over time, both the functional and anatomical boundaries of 'Wernicke's area' have become so broad as to be meaningless. We have re-analysed four functional neuroimaging (PET) studies, three previously published and one unpublished, to identify anatomically separable, functional subsystems in the left superior temporal cortex posterior to primary auditory cortex. From the results we identified a posterior stream of auditory processing. One part, directed along the supratemporal cortical plane, responded to both non-speech and speech sounds, including the sound of the speaker's own voice. Activity in its most posterior and medial part, at the junction with the inferior parietal lobe, was linked to speech production rather than perception. The second, more lateral and ventral part lay in the posterior left superior temporal sulcus, a region that responded to an external source of speech. In addition, this region was activated by the recall of lists of words during verbal fluency tasks. The results are compatible with an hypothesis that the posterior superior temporal cortex is specialized for processes involved in the mimicry of sounds, including repetition, the specific role of the posterior left superior temporal sulcus being to transiently represent phonetic sequences, whether heard or internally generated and rehearsed. These processes are central to the acquisition of long- term lexical memories of novel words. (+info)
Stability of the preclinical episodic memory deficit in Alzheimer's disease.
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We sought to determine the course of the preclinical episodic memory deficit in Alzheimer's disease. Using data from a population-based study, we compared persons who developed Alzheimer's disease n = 15) with persons who were non-demented n = 105) 6 and 3 years prior to the diagnosis of dementia. Participants were tested on tasks assessing episodic memory free recall and recognition of words) and short-term memory digit span). The incident Alzheimer's disease cases performed more poorly than their non-demented counterparts both 3 and 6 years before diagnosis on recall and recognition. There were no group differences in either forward or backward digit span. The selective impairment of episodic memory before the diagnosis of Alzheimer's disease is consistent with the view that early changes in the hippocampal complex play an important role in the memory deficit in preclinical Alzheimer's disease. On both preclinical measurement occasions, recall and recognition made independent contributions to group classification in logistic regression analyses. However, there was no evidence for accelerated decline of episodic memory in the incident Alzheimer's disease group from 6 to 3 years before diagnosis. These results indicate that Alzheimer's disease is characterized by a long preclinical period during which episodic memory deficits are detectable. The magnitude of these deficits appears to be quite stable, at least up to 3 years before diagnosis. This may reflect the fact that those biological events that eventually result in clinically diagnosed Alzheimer's disease e.g. the appearance of amyloid plaques and neurofibrillary tangles) accumulate at a relatively slow rate. (+info)