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The Contribution of Subcortical Structures in Cognition and Language
Brain and Cognition 40, 287–288 (1999) Article ID brcg.1999.1081, available online at http://www.idealibrary.com on
INTRODUCTION The Contribution of Subcortical Structures in Cognition and Language It has been recognized for some time that subcortical structures, including the basal ganglia, play an important role in a wide range of cognitive and motor behaviors. The neuroanatomy and physiology of these structures have been intensively studied and there are an increasing number of investigations exploring and defining their functional implications. In general, experimental data and clinical observations from from both animal and human studies have clearly revealed the implication of these structures in motor behavior. The basal ganglia, for example, are involved in the organization and control of voluntary movements as well as in the inhibition of involuntary movements (Graybiel, Aosaki, Flaherty, & Kimura, 1994; Marsden, 1982). It has also been shown that damage to these subcortical structures and perturbation of the fronto-striatal projections may also rise to cognitive deficits, especially in attention, memory, and language as well as in such executive functions as ability to initiate and plan behavior programs (Brown & Marsden, 1988; Cohen, Bouchard, Scherzer, & Whitaker, 1994; Cummings, 1993; Eslinger & Grattan, 1993). Finally, their influence on the regulation of affect and personality has also been revealed (e.g., Mega & Cummings, 1994). The subcortical structures, through multiple direct and indirect projections with the rest of the brain, are therefore implicated in the functional aspects of a rather large repertoire of behaviors. It is, however, in the area of motor behavior that their involvement has been best described. In clinical settings, motor disorders are frequently seen following subcortical damage of vascular or traumatic origin. Indeed, movement disorders are some of the most salient symptoms of neurodegenerative disease of the basal ganglia. A number of diseases (e.g., Parkinson’s disease,) can thus be used as models of functional disorders to better understand the role of these structures in motor, cognitive, and linguistic berhavior. In this special issue, we explore and further define the role of these subcortical structures in language and cognition. Each of the six contributions focuses on the interaction between motor function and a specific characteristic of cognitive or linguistic function. Be´dard, Pilon, Dubois, Duchesne, Masson, and Agid have investigated 287 0278-2626/99$30.00
Copyright 1999 by Academic Press All rights of reproduction in any form reserved.
288
INTRODUCTION
the cognitive and neuropsychological effects of anticholinergic treatments in Parkinson’s disease. They show how cholinergic blockade may exacerbate a range of cognitive deficits characteristic of the executive dysfunctions associated with the subcortico-frontal syndrome. Merians, Clark, Poizner, Jacobs, Adair, Macauley, Gonzalez Rothi, and Heilman present evidence of how praxic behavior in corticobasal degeneration, a disorder characterized by both basal ganglia and cortical dysfunction, differs from apraxia following left-parietal damage. Jacobs, Adair, Macauley, Gold, Gonzalez Rothi, and Heilman also present case studies of patients with corticobasal degeneration. They suggest that manifestations of ideomotor apraxia are primarily associated with difficulty in performing skilled movements and that the representations of these movements appear spared. The other three contributions focus more specifically on language and speech following subcortical damage. Kegl, Cohen, and Poizner present and highlight the similarities and distinctions between the two modalities of speech and sign in PD, in an attempt to better comprehend the impingements of the disease on language production. Grossman specifically focuses on sentence processing difficulty in PD and suggests how degradation of the dopaminergic projection system may disrupt the fronto-striatal network. Finally, Crosson reviews a number of case studies to illustrate how the thalamic nuclei and systems actively participate in lexical–semantic functions. Taken together, the articles in this special issue suggest that these subcortical structures are integrated in a mosaic of complex networks linking sensorimotor and associative areas as well as thalamic nuclei to frontal and prefrontal cortex. It would thus appear that subcortical dysfunctions may contribute to the genesis of deficits, whose manifestations can similarly be observed in various areas of behavior, such as in motricity and cognition. REFERENCES Brown, R. G., & Marsden, C. D. 1988. Internal versus external cues and the control of attention in Parkinson’s disease. Brain, 111, 323–345. Cohen, H., Bouchard, S., Scherzer, P., & Whitaker, H. A. 1994. Language and verbal reasoning in Parkinson’s disease. Neuropsychiatry, Neuropsychology and Behavioral Neurology, 7, 166–175. Cummings, J. L. 1993. Frontal-subcortical circuits and human behavior. Archives of Neurology, 50, 873–880. Eslinger, P. J., & Grattan, L. M. 1993. Frontal lobe and frontal–striatal substrates of different forms of human cognitive flexibility. Neuropsychologia, 31, 17–28. Graybiel, A. M., Aosaki, T., Flaherty, A. W., & Kimura, M. 1994. The basal ganglia and adaptive motor control. Science, 265, 1826–1831. Marsden, C. D. 1982. The mysterious motor functions of the basal ganglia. Neurology, 32, 514–539. Mega, N. S., & Cummings, J. L. 1994. Frontal–subcortical circuits and neuropsychiatric disorders. Journal of Neuropsychiatry and Clinical Neurosciences, 6, 358–370. Henri Cohen and Judy Kegl
INTRODUCTION The Contribution of Subcortical Structures in Cognition and Language It has been recognized for some time that subcortical structures, including the basal ganglia, play an important role in a wide range of cognitive and motor behaviors. The neuroanatomy and physiology of these structures have been intensively studied and there are an increasing number of investigations exploring and defining their functional implications. In general, experimental data and clinical observations from from both animal and human studies have clearly revealed the implication of these structures in motor behavior. The basal ganglia, for example, are involved in the organization and control of voluntary movements as well as in the inhibition of involuntary movements (Graybiel, Aosaki, Flaherty, & Kimura, 1994; Marsden, 1982). It has also been shown that damage to these subcortical structures and perturbation of the fronto-striatal projections may also rise to cognitive deficits, especially in attention, memory, and language as well as in such executive functions as ability to initiate and plan behavior programs (Brown & Marsden, 1988; Cohen, Bouchard, Scherzer, & Whitaker, 1994; Cummings, 1993; Eslinger & Grattan, 1993). Finally, their influence on the regulation of affect and personality has also been revealed (e.g., Mega & Cummings, 1994). The subcortical structures, through multiple direct and indirect projections with the rest of the brain, are therefore implicated in the functional aspects of a rather large repertoire of behaviors. It is, however, in the area of motor behavior that their involvement has been best described. In clinical settings, motor disorders are frequently seen following subcortical damage of vascular or traumatic origin. Indeed, movement disorders are some of the most salient symptoms of neurodegenerative disease of the basal ganglia. A number of diseases (e.g., Parkinson’s disease,) can thus be used as models of functional disorders to better understand the role of these structures in motor, cognitive, and linguistic berhavior. In this special issue, we explore and further define the role of these subcortical structures in language and cognition. Each of the six contributions focuses on the interaction between motor function and a specific characteristic of cognitive or linguistic function. Be´dard, Pilon, Dubois, Duchesne, Masson, and Agid have investigated 287 0278-2626/99$30.00
Copyright 1999 by Academic Press All rights of reproduction in any form reserved.
288
INTRODUCTION
the cognitive and neuropsychological effects of anticholinergic treatments in Parkinson’s disease. They show how cholinergic blockade may exacerbate a range of cognitive deficits characteristic of the executive dysfunctions associated with the subcortico-frontal syndrome. Merians, Clark, Poizner, Jacobs, Adair, Macauley, Gonzalez Rothi, and Heilman present evidence of how praxic behavior in corticobasal degeneration, a disorder characterized by both basal ganglia and cortical dysfunction, differs from apraxia following left-parietal damage. Jacobs, Adair, Macauley, Gold, Gonzalez Rothi, and Heilman also present case studies of patients with corticobasal degeneration. They suggest that manifestations of ideomotor apraxia are primarily associated with difficulty in performing skilled movements and that the representations of these movements appear spared. The other three contributions focus more specifically on language and speech following subcortical damage. Kegl, Cohen, and Poizner present and highlight the similarities and distinctions between the two modalities of speech and sign in PD, in an attempt to better comprehend the impingements of the disease on language production. Grossman specifically focuses on sentence processing difficulty in PD and suggests how degradation of the dopaminergic projection system may disrupt the fronto-striatal network. Finally, Crosson reviews a number of case studies to illustrate how the thalamic nuclei and systems actively participate in lexical–semantic functions. Taken together, the articles in this special issue suggest that these subcortical structures are integrated in a mosaic of complex networks linking sensorimotor and associative areas as well as thalamic nuclei to frontal and prefrontal cortex. It would thus appear that subcortical dysfunctions may contribute to the genesis of deficits, whose manifestations can similarly be observed in various areas of behavior, such as in motricity and cognition. REFERENCES Brown, R. G., & Marsden, C. D. 1988. Internal versus external cues and the control of attention in Parkinson’s disease. Brain, 111, 323–345. Cohen, H., Bouchard, S., Scherzer, P., & Whitaker, H. A. 1994. Language and verbal reasoning in Parkinson’s disease. Neuropsychiatry, Neuropsychology and Behavioral Neurology, 7, 166–175. Cummings, J. L. 1993. Frontal-subcortical circuits and human behavior. Archives of Neurology, 50, 873–880. Eslinger, P. J., & Grattan, L. M. 1993. Frontal lobe and frontal–striatal substrates of different forms of human cognitive flexibility. Neuropsychologia, 31, 17–28. Graybiel, A. M., Aosaki, T., Flaherty, A. W., & Kimura, M. 1994. The basal ganglia and adaptive motor control. Science, 265, 1826–1831. Marsden, C. D. 1982. The mysterious motor functions of the basal ganglia. Neurology, 32, 514–539. Mega, N. S., & Cummings, J. L. 1994. Frontal–subcortical circuits and neuropsychiatric disorders. Journal of Neuropsychiatry and Clinical Neurosciences, 6, 358–370. Henri Cohen and Judy Kegl