Research

As shown in the above diagram, our department is studying the neural control of eye and hand movements.
We focus on saccadic eye movements and dexterous hand movements, especially precision grip. We study the structure and functions of the neural circuits and functional recovery after lesion of a particular component of the circuits, as summarized in the figure. As for the detail;
@ We study the local circuits of the superior colliculus by using in vitro slice preparations obtained from rodents.
Selected papers;
Original papers
Kaneda K, Isa K, Yanagawa Y, Isa T (2008) Nigral inhibition of GABAergic neurons in mouse superior colliculus. Journal of Neuroscience, 28: 11071-11078.
Phongphanphanee P, Kaneda K, Isa T (2008) Spatio-temporal profiles of field potentials in mouse superior colliculus analyzed by multichannel recording. Journal of Neuroscience, 28: 9309-9318.
Kaneda K, Phongphanphanee P, Katoh T, Isa K, Yanagawa Y, Obata K, Isa T (2008) Regulation of burst activity through pre- and postsynaptic GABAB receptors in mouse superior colliculus. Journal of Neuroscience, 28:816-827.
Lee PH*, Sooksawate T*, Yanagawa Y, Isa K, Isa T**, Hall WC** (2007) Identity of a pathway for saccadic suppression. Proceedings of National Academy of Sciences, USA 104: 6824-6827.
Endo T, Yanagawa Y. Obata K, Isa T (2005) Nicotinic acetylcholine receptor subtypes involved in facilitation of GABAergic inhibition in mouse superficial superior colliculus. Journal of Neurophysiology, 94:3893-3902.
Saito Y, Isa T (2003) Local excitatory network and NMDA receptor activation generate a synchronous and non-linear bursting command from the superior colliculus. Journal of Neuroscience, 23:5854-5864.
Saito Y, Isa T (1999) Electrophysiological and morphological properties of neurons in the rat superior colliculus. I. Neurons in the intermediate layer. Journal of Neurophysiology 82: 754-767.
Isa T, Endo T, Saito Y (1998) The visuo-motor pathway in the local circuit of the rat superior colliculus. Journal of Neuroscience 18: 8496-8504.
Reviews:
Isa T, Hall WC (2009) Exploring the superior colliculus in vitro. Journal of Neurophysiology (review), 102: 2581-2593.
Sakatani T, Isa T (2008) Superior colliculus and saccade generation in mice. In gEyes, Retina and Visual System of the Mouseh (eds Calupa Leo.M. & Willliams R), MIT Press, pp233-244.
Isa T & Sparks D (2006) Microcircuit of the Superior Colliculus: A Neuronal Machine that Determines Timing and Endpoint of Saccadic Eye Movements. Background paper for 93rd Dahlem Workshop on Microcircuits; The interface between Neurons and Global Brain Function, pp1-34.
Isa T (2002) Intrinsic processing in the mammalian superior colliculus. Current Opinion in Neurobiology, 12:668-677.
Isa T, Saito Y (2001) The direct visuo-motor pathway in mammalian superior colliculus; novel perspective on the interlaminar connection. Neuroscience Research, (update article) 41: 107-113.

A We study the behaviors and electrophysiology of macaque monkeys with unilateral lesion of the primary visual cortex (V1), an animal model of blindsight to obtain insights of functional recovery after the loss of conscious vision.
Selected papers:
Original papers
Yoshida M, Takaura K, Kato R, Ikeda T, Isa T (2008) Striate cortical lesions affect deliberate decision and control of saccade: implication for blindsight. Journal of Neuroscience, 28: 10517-10530.
Reviews:
Isa T, Yoshida M. (2009) Saccade control after V1 lesion revisited. Current Opinion in Neurobiology, in press.

B We study the organization of the corticospinal tract, especially their control of spinal cord interneurons, using electrophysiological and neuroanatomical tracing techniques.
Selected papers;
Original papes
Isa T, Ohki Y, Seki K, Alstermark B (2006) Properties of propriospinal neurons in the C3-C4 segments mediating disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey. Journal of Neurophysiology, 95: 3674-3685.
Alstermark B, Ogawa J, Isa T (2004) Lack of monosynaptic corticomotoneuronal excitation in the adult rat: fast disynaptic excitation is mediated via reticulospinal neurones and slow polysynaptic excitation via segmental interneurons. Journal of Neurophysiology, 91:1832-1839.
Alstermark B, Isa T, Ohki Y, Saito Y. (1999) Disynaptic pyramidal excitation in forelimb motoneurons mediated via C3-C4 propriospinal neurons in the macaca fuscata. Journal of Neurophysiology, 82: 3580-3585.
Reviews
Isa, T., Ohki, Y., Alstermark, B., Pettersson, L-G., Sasaki, S (2007) Direct and indirect cortico-motoneuronal pathways and control of hand/arm movements. Physiology, 22: 145-152.
Alstermark, B. Isa, T., Pettersson, L-G., Sasaki, S (2007) The C3-C4 propriospinal system in the cat and monkey; a spinal premotoneuronal centre for voluntary motor control. Acta.Physiol. Scand., 189: 123-140.
Pettersson L.-G.., Alstermark, B., Blagovechtchenski, E., Isa, T., Sasaski, S(2007) Skilled digit movements in feline and primate ? descending control and motor recovery after spinal cord injuries. Acta Physiol. Scand., 189: 141-154.
Alstermark B, Isa T (2002) Premotoneuronal and direct corticomotoneuronal control in the cat and macaque monkey. In gMovement and Sensationh (eds. Gandevia S, Proske U), Adv Exp Med Biol. 2002; 508: 281-297.

C We study the functional recovery after lesion of the corticospinal tract at the C4/C5 level of the cervical spinal cord. We especially focused on the reorganization of the cortical circuitries using PET.
Selected papers:
Original papers;
Higo N, Nishimura Y, Murata Y, Oishi T, Saito K, Takahashi M, Tsuboi F, Isa T (2009) Increased expression of the growth-associated protein-43 gene in the sensorimotor cortex of the macaque monkey after lesioning of the lateral corticospinal tract. Journal of Comparative Neurology, 516: 493-506.
Nishimura Y, Morichika Y, Isa T (2009) A common subcortical oscillatory network contributes to recovery after spinal cord injury. Brain,132: 709-721.
Nishimura Y, Onoe T, Morichika Y, Perfiliev S, Tsukada H, Isa T (2007) Time-dependent central compensatory mechanism of finger dexterity after spinal-cord injury. Science, 318: 1150-1155.
Sasaki S, Isa T, Pettersson L-G, Alstermark B, Naito K, Yoshimura K, Seki K, Ohki Y (2004) Dexterous finger movements in primate without monosynaptic corticomotoneuronal excitation. Journal of Neurophysiology, 92:3142-3147.
Reviews;
Nishimura Y, Isa T (2009) Compensatory changes at the cerebral cortical level
after spinal cord injury. The Neuroscientist, 15: 436-444.

D We are performing the basic studies on the brain-machine interfaces, especially to utilize the subdural ECoG (electro-corticogram) signals for high-performance BMIs. We are also exploring the methods to utilize the sensory-feedback signals for accurate control of neuroprosthesis.

E We are also developing the techniques to introduce particular genes in the monkey neocortex and other CNS regions with viral vectors to obtain clear-cut methodology for analysis of integrative brain functions and also for the analysis of molecular basis of higher and cognitive brain functions unique to the primates




Prof. Tadashi Isa
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