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Switching on to the basal ganglia and cognition
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Switching on to the basal ganglia and cognition In addition to the well-known contribution of the basal ganglia to motoric function, evidence is accumulating that suggests that these subcortical structures also play an important role in more cognitive operations. For example, neuropsychological, behavioural and functional neuroimaging evidence suggests that the basal ganglia is implicated in the cognitive processes that are required when a change or switch in the behavioural set that governs behaviour is required. Patients with Parkinson’s disease, in which the functions of the basal ganglia are disrupted by dopamine deficiency, are impaired
on tasks that measure the ability to switch attentional set in this manner. However, switching deficits have not been observed when a Posner spatialcueing paradigm is used to examine switching time in Parkinson’s disease. Hayes et al.1 present evidence that suggests that this apparent conflict can be resolved by a consideration of the precise form of the switch that is required. Thus, when subjects were asked to switch their response from one stimulus dimension (colour) to another (shape), or when the subjects were required to switch from one sequence of key presses (three key presses in one
Cerebral organization of language It is well known that areas in the left hemisphere of the brain are specialized for the processing of language. An interesting question is to what extent this specialization is innate or influenced by experience. To address this issue, Neville et al.1 conducted a functional magnetic resonance imaging study in which subjects read sentences of English in one condition, and saw sentences signed in American Sign Language (ASL) in another. Three subject groups were tested: (1) (monolingual) native speakers of English; (2) hearing bilinguals who had both English and ASL as their native languages; and (3) deaf, native ASL signers who had learned (written) English at a later age, and scored only moderately on tests of English grammar.
While the subjects were processing their native language, either ASL or English, the ‘classical’ language areas in the left hemisphere showed activation on fMRI. However, the deaf subjects did not show activation in these areas when confronted with written English. This suggests that the age at which the language is learned, or at least the level of proficiency acquired, plays a role in the recruitment of these left brain areas. Furthermore, hearing as well as deaf, native ASL signers also showed activation of areas in the right hemisphere. This suggests that the modality of the language (spoken versus signed) also has an effect on the organization of language in the brain.
Attention to faces in the fusiform gyrus Face recognition represents one of the most expert skills of the human visual/ memory system. It has been proposed to rely on a highly specific, modular system distinct from the system(s) involved in recognition of other objects. A recent imaging study has shown face-specific activations in the ventral occipitotemporal pathway, in particular, in the fusiform gyrus1. In this blocked-design functional magnetic resonance imaging study, the authors investigate whether fusiform gyrus activity in response to faces is modulated by attention. They show that the same stimuli containing a pair of houses plus a pair of faces activate face-specific fusiform areas more strongly when the task focuses subjects’ attention on faces relative to houses. Consequently, this study supports the
Reference 1 Wojciulik, E., Kanwisher, N. and Driver, J. (1998) Covert visual attention modulates face-specific activity in the human fusiform fMRI
study
J.
Reference 1 Hayes, A.E. et al. (1998) Toward a functional analysis of the basal ganglia J. Cog. Neurosci. 10, 178–198
This fMRI study confirms what has been known for some time from lesion and EEG studies. Although it is an interesting finding that experience and/or proficiency in a language affects the cerebral organization of its processing, the study does not answer the more burning questions neurolinguists ask, such as which sub-processes of language processing (e.g. lexical processing, syntactic processing, semantic processing or further sub-processes thereof) are, or could be, subserved by which brain areas? And how exactly does experience or proficiency play a role in the cerebral specialization of each of these sub-processes? The neuroimaging of language processing clearly still has a long way to go. Reference 1 Neville, H.J. et al. (1998) Cerebral organization for language in deaf and hearing subjects: biological constraints and effects of experience Proc. Natl. Acad. Sci. U. S. A. 95, 922–929
Would you like to contribute to Monitor?
idea that fusiform gyrus activation in response to faces is not merely driven by the visual characteristics specific to these stimuli relative to other objects, but is also modulated by attentional processes. This result has implications for a strictly modular view of the facerecognition system. Because it shows that face-specific fusiform gyrus activations are not purely automatic and unmodulated, this study throws doubt on such a strict modular view of face recognition.
gyrus:
order) to another (same three key presses in a different order) the patients with Parkinson’s disease were slower than the age-matched control subjects. Importantly, these differences were greater than those seen during nonswitch trials. Subsequent experiments suggest that the switching impairment is related to the dopamine systems in the Parkinson’s patients. The authors discuss the results in the context of ‘executive’ switching and a conceptual framework that suggests that the switching deficits also underlie the motor disturbances observed in Parkinson’s disease.
Neurophysiol.
79,
The Monitor section of Trends in Cognitive Sciences provides a summary of recently published papers that may be of interest to scientists across the broad spectrum of cognitive sciences. A typical Monitor contribution has a short introduction that sets the scene, a description of the approach taken, the key results obtained, the conclusions reached and their implications. If you think that you could write all this within 200–250 clear and concise words then get in touch with the Editor ([email protected]), as we are always on the lookout for suitable writers. Regular contributors can expect to receive a free subscription to Trends in Cognitive Sciences.
1574–1578
Copyright © 1998, Elsevier Science Ltd. All rights reserved. 1364-6613/98/$19.00 Trends in Cognitive Sciences – Vol. 2, No. 6,
June 1998
205
Switching on to the basal ganglia and cognition In addition to the well-known contribution of the basal ganglia to motoric function, evidence is accumulating that suggests that these subcortical structures also play an important role in more cognitive operations. For example, neuropsychological, behavioural and functional neuroimaging evidence suggests that the basal ganglia is implicated in the cognitive processes that are required when a change or switch in the behavioural set that governs behaviour is required. Patients with Parkinson’s disease, in which the functions of the basal ganglia are disrupted by dopamine deficiency, are impaired
on tasks that measure the ability to switch attentional set in this manner. However, switching deficits have not been observed when a Posner spatialcueing paradigm is used to examine switching time in Parkinson’s disease. Hayes et al.1 present evidence that suggests that this apparent conflict can be resolved by a consideration of the precise form of the switch that is required. Thus, when subjects were asked to switch their response from one stimulus dimension (colour) to another (shape), or when the subjects were required to switch from one sequence of key presses (three key presses in one
Cerebral organization of language It is well known that areas in the left hemisphere of the brain are specialized for the processing of language. An interesting question is to what extent this specialization is innate or influenced by experience. To address this issue, Neville et al.1 conducted a functional magnetic resonance imaging study in which subjects read sentences of English in one condition, and saw sentences signed in American Sign Language (ASL) in another. Three subject groups were tested: (1) (monolingual) native speakers of English; (2) hearing bilinguals who had both English and ASL as their native languages; and (3) deaf, native ASL signers who had learned (written) English at a later age, and scored only moderately on tests of English grammar.
While the subjects were processing their native language, either ASL or English, the ‘classical’ language areas in the left hemisphere showed activation on fMRI. However, the deaf subjects did not show activation in these areas when confronted with written English. This suggests that the age at which the language is learned, or at least the level of proficiency acquired, plays a role in the recruitment of these left brain areas. Furthermore, hearing as well as deaf, native ASL signers also showed activation of areas in the right hemisphere. This suggests that the modality of the language (spoken versus signed) also has an effect on the organization of language in the brain.
Attention to faces in the fusiform gyrus Face recognition represents one of the most expert skills of the human visual/ memory system. It has been proposed to rely on a highly specific, modular system distinct from the system(s) involved in recognition of other objects. A recent imaging study has shown face-specific activations in the ventral occipitotemporal pathway, in particular, in the fusiform gyrus1. In this blocked-design functional magnetic resonance imaging study, the authors investigate whether fusiform gyrus activity in response to faces is modulated by attention. They show that the same stimuli containing a pair of houses plus a pair of faces activate face-specific fusiform areas more strongly when the task focuses subjects’ attention on faces relative to houses. Consequently, this study supports the
Reference 1 Wojciulik, E., Kanwisher, N. and Driver, J. (1998) Covert visual attention modulates face-specific activity in the human fusiform fMRI
study
J.
Reference 1 Hayes, A.E. et al. (1998) Toward a functional analysis of the basal ganglia J. Cog. Neurosci. 10, 178–198
This fMRI study confirms what has been known for some time from lesion and EEG studies. Although it is an interesting finding that experience and/or proficiency in a language affects the cerebral organization of its processing, the study does not answer the more burning questions neurolinguists ask, such as which sub-processes of language processing (e.g. lexical processing, syntactic processing, semantic processing or further sub-processes thereof) are, or could be, subserved by which brain areas? And how exactly does experience or proficiency play a role in the cerebral specialization of each of these sub-processes? The neuroimaging of language processing clearly still has a long way to go. Reference 1 Neville, H.J. et al. (1998) Cerebral organization for language in deaf and hearing subjects: biological constraints and effects of experience Proc. Natl. Acad. Sci. U. S. A. 95, 922–929
Would you like to contribute to Monitor?
idea that fusiform gyrus activation in response to faces is not merely driven by the visual characteristics specific to these stimuli relative to other objects, but is also modulated by attentional processes. This result has implications for a strictly modular view of the facerecognition system. Because it shows that face-specific fusiform gyrus activations are not purely automatic and unmodulated, this study throws doubt on such a strict modular view of face recognition.
gyrus:
order) to another (same three key presses in a different order) the patients with Parkinson’s disease were slower than the age-matched control subjects. Importantly, these differences were greater than those seen during nonswitch trials. Subsequent experiments suggest that the switching impairment is related to the dopamine systems in the Parkinson’s patients. The authors discuss the results in the context of ‘executive’ switching and a conceptual framework that suggests that the switching deficits also underlie the motor disturbances observed in Parkinson’s disease.
Neurophysiol.
79,
The Monitor section of Trends in Cognitive Sciences provides a summary of recently published papers that may be of interest to scientists across the broad spectrum of cognitive sciences. A typical Monitor contribution has a short introduction that sets the scene, a description of the approach taken, the key results obtained, the conclusions reached and their implications. If you think that you could write all this within 200–250 clear and concise words then get in touch with the Editor ([email protected]), as we are always on the lookout for suitable writers. Regular contributors can expect to receive a free subscription to Trends in Cognitive Sciences.
1574–1578
Copyright © 1998, Elsevier Science Ltd. All rights reserved. 1364-6613/98/$19.00 Trends in Cognitive Sciences – Vol. 2, No. 6,
June 1998
205