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1528 Neuronal activities of cerebellar dentate nucleus and globus pallidus during sequential motor task
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1527
REVERSIBLE BLOCKADE OF EXTERNAL V E R S I V E EYE D E V I A T I O N .
GLOBUS
PALLIDUS INDUCES
CONTRA-
MAKOTO KATO, OKIH1DE HIKOSAKA Lab. of Neural Control, Natl. Inst. for Physiol. Sci., Myodaiii, Okazaki 444, Japan In basal ganglia, oculomotor signals are mediated by neurons in the substantia nigra pars reticulata (SNr) that exert tonic inhibition on the superior colliculus (SC). The SNr is under the control of the striatum (1) directly and (2) indirectly through the external segment of the globus pallidus (GPe) and the subthalamic nucleus (STN). We previously found neurons in the GPe that carried non-specific visual/oculomotor signals. The net action of the GPe on the SC is thought to be facilitatory because two inhibitory connections are interposed (GPe-STN and SNr-SC). We thus expected that local blockade of the GPe would lead to suppression of contralateral saccades and consequently ipsilateral gaze shift. However, we found the opposite effects. Within 20 min to I hr after injection of muscimol (1-5 l.tg in 1 pl saline), the eye became deviated to the direction contralateral to the injection site. The eye position in horizontal direction was virtually locked to 20-25 ° from the midline in either light or darkness. The monkey was thus unable to fixate a central spot. Eye movements in vertical direction appeared relatively unimpaired. Task-related saccades were examined when. the effects were milder; contralateral saccades tended to be slow and hypometric, whereas ipsilateral saccades tended to be hypometric. Deficits in vision or attention were not detected using an attention task. The function of the GPe now needs to be reconsidered.
1528 N E U R O N A L ACTIVITIES OF CEREBELLAR DENTATE N U C L E U S A N D GLOBUS PALLIDUS DURING SEQUENTIAL M O T O R TASK. HAJIME MUSHIAKE 1 A N D P.L. STRICK 2 Dept. Physiology of T o h o k u University 1 (151) VA Medical Center 800 Irving Ave. Syracuse, NY 13210-2799, U.S.A. 2 We trained three monkeys(Macaca Nemestrina) to p e r f o r m sequential pointing m o v e m e n t with right h a n d u n d e r two conditions: Tracking and Remembered. The m o n k e y faces a panel with five pairs of LED and buttons in a row. In Tracking task, the m o n k e y has to touch three buttons w h e n their LED are illuminated.
In R e m e m b e r e d task, after a delay period, the m o n k e y
is required to touch three buttons in the sequence indicated b y LEDs in the preceding instruction period. We m a d e single unit recording f r o m Dentate Nucleus(DN) and Globus Pallidus(GP). These neurons s h o w e d a Task- d e p e n d e n t activities, b u t patterns of activity of GP neurons were different from those of D N neurons.
1 529
CLINICAL SIGNIFICANCE OF THE PALLIDO-RETICULO-SPINALPATHWAY PROPOSED BY EXPERIENCE OF POSTEROVENTRAL PALLIDOTOMY IN PATIENTS WITH MOVEMENT DISORDERS. FU_M!_QSH_IMA, SHUJI SAKATA, MOTOHIRO KATO, Clinical Neurophysiology, Neurological Institute, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan
Electrocoagulations restricted to the posteroventral part of the internal pallidum were made in 32 patients with movement disorders including Parkinson's disease with main signs of gait and postural abnormalities and idiopathic dystonia which did not respond to VL thalamotomy performed previously. As well as rigidity, negative signs of Parkinson's disease including bradykinesia, frozen gait and postural abnormalities were improved immediately after pallidotomy, however, tremor was ceased several months after surgery. Dystonic contractions uot improved by thalamotomy were markedly decreased by the pallidotomy. These clinical findings indicate that mechanism of posteroventral pallidotomy does not involve in the pallido-thalamo-cortical pathway but in the descending pallido-reticulo-spinal pathway. Microrecording techniques revealed the markedly hyperactive neurons in the internal pallidum in Parkinsonian patients and the unusual pallidal neurons activated by non-specific voluntary movements in dystonic patients. Mechanism underlying the movement disorders will be discussed based on these physiological findings.
1527
REVERSIBLE BLOCKADE OF EXTERNAL V E R S I V E EYE D E V I A T I O N .
GLOBUS
PALLIDUS INDUCES
CONTRA-
MAKOTO KATO, OKIH1DE HIKOSAKA Lab. of Neural Control, Natl. Inst. for Physiol. Sci., Myodaiii, Okazaki 444, Japan In basal ganglia, oculomotor signals are mediated by neurons in the substantia nigra pars reticulata (SNr) that exert tonic inhibition on the superior colliculus (SC). The SNr is under the control of the striatum (1) directly and (2) indirectly through the external segment of the globus pallidus (GPe) and the subthalamic nucleus (STN). We previously found neurons in the GPe that carried non-specific visual/oculomotor signals. The net action of the GPe on the SC is thought to be facilitatory because two inhibitory connections are interposed (GPe-STN and SNr-SC). We thus expected that local blockade of the GPe would lead to suppression of contralateral saccades and consequently ipsilateral gaze shift. However, we found the opposite effects. Within 20 min to I hr after injection of muscimol (1-5 l.tg in 1 pl saline), the eye became deviated to the direction contralateral to the injection site. The eye position in horizontal direction was virtually locked to 20-25 ° from the midline in either light or darkness. The monkey was thus unable to fixate a central spot. Eye movements in vertical direction appeared relatively unimpaired. Task-related saccades were examined when. the effects were milder; contralateral saccades tended to be slow and hypometric, whereas ipsilateral saccades tended to be hypometric. Deficits in vision or attention were not detected using an attention task. The function of the GPe now needs to be reconsidered.
1528 N E U R O N A L ACTIVITIES OF CEREBELLAR DENTATE N U C L E U S A N D GLOBUS PALLIDUS DURING SEQUENTIAL M O T O R TASK. HAJIME MUSHIAKE 1 A N D P.L. STRICK 2 Dept. Physiology of T o h o k u University 1 (151) VA Medical Center 800 Irving Ave. Syracuse, NY 13210-2799, U.S.A. 2 We trained three monkeys(Macaca Nemestrina) to p e r f o r m sequential pointing m o v e m e n t with right h a n d u n d e r two conditions: Tracking and Remembered. The m o n k e y faces a panel with five pairs of LED and buttons in a row. In Tracking task, the m o n k e y has to touch three buttons w h e n their LED are illuminated.
In R e m e m b e r e d task, after a delay period, the m o n k e y
is required to touch three buttons in the sequence indicated b y LEDs in the preceding instruction period. We m a d e single unit recording f r o m Dentate Nucleus(DN) and Globus Pallidus(GP). These neurons s h o w e d a Task- d e p e n d e n t activities, b u t patterns of activity of GP neurons were different from those of D N neurons.
1 529
CLINICAL SIGNIFICANCE OF THE PALLIDO-RETICULO-SPINALPATHWAY PROPOSED BY EXPERIENCE OF POSTEROVENTRAL PALLIDOTOMY IN PATIENTS WITH MOVEMENT DISORDERS. FU_M!_QSH_IMA, SHUJI SAKATA, MOTOHIRO KATO, Clinical Neurophysiology, Neurological Institute, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812, Japan
Electrocoagulations restricted to the posteroventral part of the internal pallidum were made in 32 patients with movement disorders including Parkinson's disease with main signs of gait and postural abnormalities and idiopathic dystonia which did not respond to VL thalamotomy performed previously. As well as rigidity, negative signs of Parkinson's disease including bradykinesia, frozen gait and postural abnormalities were improved immediately after pallidotomy, however, tremor was ceased several months after surgery. Dystonic contractions uot improved by thalamotomy were markedly decreased by the pallidotomy. These clinical findings indicate that mechanism of posteroventral pallidotomy does not involve in the pallido-thalamo-cortical pathway but in the descending pallido-reticulo-spinal pathway. Microrecording techniques revealed the markedly hyperactive neurons in the internal pallidum in Parkinsonian patients and the unusual pallidal neurons activated by non-specific voluntary movements in dystonic patients. Mechanism underlying the movement disorders will be discussed based on these physiological findings.