The ultimate purpose of the proposed study is to increase our understanding of how the motor cortex controls movements and subsequently to contribute toward the better treatment of human motor dysfunctions.
The specific aim during the coming years is to elucidate the neuronal mechanisms of how peripheral sensory input contribute to the smooth execution of voluntary movements. It has been shown that there are closed loop circuits between the motor cortex and the periphery and each loop is specific for a particular muscle. It has recently been shown that these circuits play an important role during voluntary movements. As for the neuronal mechanisms of these circuits, we have proposed that each loop circulates impulses before and during the movements to increase the excitability of neurons related to each loop, i.e., preferential bias theory. This hypothesis will be examined through chronic and acute experiments. Chronic experiments will be carried out using cynomolgus monkeys. They will be trained to pick up food pellet from rotating food board. Then a closed chamber will be installed over the motor cortex and activity of motor cortical neurons will be studied before and during the pick-up movements. Distribution of preferentially biased neurons in relation to location of regular movement related neurons will be examined. Effect of interruption of the loop circuits to these preferential bias will also be examined. Acute experiments will be carried out using cats. It has been shown that peripherally evoked activity of motor cortical neurons is modified by the input from the sensory cortex. The mode of modification will be studied by delivering conditioning and testing stimuli to the sensory cortex and the thalamus. The effect of conditioning stimuli will be examined using monosynaptic PSPs elicited by the test stimuli as indicators. Various combinations of conditioning and test stimuli will be used.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
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Neurology B Subcommittee 1 (NEUB)
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Rockefeller University
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New York
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Miyashita, E; Keller, A; Asanuma, H (1994) Input-output organization of the rat vibrissal motor cortex. Exp Brain Res 99:223-32
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Kaneko, T; Caria, M A; Asanuma, H (1994) Information processing within the motor cortex. II. Intracortical connections between neurons receiving somatosensory cortical input and motor output neurons of the cortex. J Comp Neurol 345:172-84
Kaneko, T; Caria, M A; Asanuma, H (1994) Information processing within the motor cortex. I. Responses of morphologically identified motor cortical cells to stimulation of the somatosensory cortex. J Comp Neurol 345:161-71
Keller, A; Asanuma, H (1993) Synaptic relationships involving local axon collaterals of pyramidal neurons in the cat motor cortex. J Comp Neurol 336:229-42
Pavlides, C; Miyashita, E; Asanuma, H (1993) Projection from the sensory to the motor cortex is important in learning motor skills in the monkey. J Neurophysiol 70:733-41
Keller, A; Arissian, K; Asanuma, H (1992) Synaptic proliferation in the motor cortex of adult cats after long-term thalamic stimulation. J Neurophysiol 68:295-308
Asanuma, H; Keller, A (1991) Neuronal mechanisms of motor learning in mammals. Neuroreport 2:217-24
Keller, A; Miyashita, E; Asanuma, H (1991) Minimal stimulus parameters and the effects of hyperpolarization on the induction of long-term potentiation in the cat motor cortex. Exp Brain Res 87:295-302
Iriki, A; Pavlides, C; Keller, A et al. (1991) Long-term potentiation of thalamic input to the motor cortex induced by coactivation of thalamocortical and corticocortical afferents. J Neurophysiol 65:1435-41

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