S165

1530 ANALYSIS OF SMOOTH PURSUIT EYE MOVEMENTS (SPEM) IN SCHIZOPHRENICS: A COMPARISON WITH THE ANTISACCADE TASK. JUNKQ FUKUSHIMA I, KIKURO FUKUSHIMA 2,

IColI. Medical Techno!, 2Dept. Phvsiol. Sch. Ned., HQkkaido Univ., Sapporo 060 Janan. We reported the specific abnormalities in the antisaccade task in many

schizophrenics, similar to those of the patients with localized frontal cortical lesions, and suggested the frontal dysfunction in schizophrenics. Recent studies reported an involvement of the frontal eye field in SPEM also. We, therefore, studied open loop- and closed loop- gain of SPEM, and compared the results with those in the antisaccade task in the same schizophrenic patients. A target for SPEM was presented by a laser-beam, and moved horizontally at 5 and i0 deg/s in step-ramp and triangular fashions. Eye movements were recorded by infrared oculography. Open loop gain was calculated at the beginning of SPEM in the step-ramp condition. Closed loop gain was analyzed according to "time-weighted average gain" method.

The schizophrenics as a whole revealed significantly lower gain in both open loop- and closed loop- conditions, compared to age-matched normal controls. The values of open loop gain were positively correlated with those of closed loop gain. However, individual patients showed a wide variability; although majority of them showed lower closed loop gain, open loop gain was normal in about 60 % of them despite that all of them showed abnormalities in the error rates and/or latencies in the antisaccade- task. These results suggest more factors must be considered in the abnormalities of SPEM in schizophrenics.

1 5 3 1 NEURAL CONNECTIONS OF THE ANTERIOR MOTOR THAIAMIC NUCLEI IN MACAQUE MONKEYS, KATSUMA NAKANO, TETSURO KAYAHARA, YUKIHIKO YASUI AND YASUO

HASEGAWA, D e p a r t m e n t o f Ana tomy , Facul _ty o f Medic ine , Mie Univers iW, Tsu, Mie 514 , J a p a n

To a s c e r t a i n t he n e u r a l c o n n e c t i o n s o f t h e a n t e r i o r p a r t s o f m o t o r t h a l a m i c nuc le i , w e c o n d u c t e d r e t r o g r a d e a n d a n t e r o g r a d e s tud i e s us ing v a r i o u s t r ace r s . T h e r e su l t s i n d i c a t e t h a t t h e c a u d a l a n d v e n t r o l a t e r a l 2 / 3 pa r t s o f t he m e d i a l pa l l ida l s e g m e n t (GPm) p r o j e c t to l a m i n a I in m o t o r a r e a v ia n u c l e u s ven t r a l i s l a te ra l i s p a r s ora l is (VLo); t h e r o s t r a l a n d d o r s o m e d i a l p a r t s o f t h e GPm to l a m i n a I in the a r c u a t e p r e m o t o r a n d s u p p l e m e n t a r y m o t o r a r e a s v i a n u c l e u s v e n t r a l i s a n t e r i o r p a r s p r inc ipa l i s (VApc); t h e n u c l e u s v e n t r a l i s a n t e r i o r p a r s m a g n o c e l l u l a r i s (VAmc) r e c e i v e s i n p u t s f r o m r o s t r a l a n d c a u d o l a t e r a l p a r t s o f t h e s u b s t a n t i a n i g r a p a r s r e t i c u l a t a (SNr) a n d p r o j e c t s to l a m i n a I in t h e p r e f r o n t a l c o r t e x ; a n d t h e n u c l e u s v e n t r a l i s l a te ra l i s p a r s med ia l i s (VLm) rece ives i n p u t s f r o m t h e v e n t r o m e d i a l p o r t i o n o f t h e SNr a n d t h e v e n t r o m e d i a l p a r t o f t h e n u c l e u s d e n t a t u s as wel l as t h e v e n t r a l p a r t o f t h e n u c l e u s i n t e r p o s i t u s pos t e r io r .

1 5 3 2 FIELD POTENTIAL CHANGE IN THE PREFRONTAL CORTEX OF THE LEFT HEMISPHERE DURING LEARNING PROCESS OF REACTION-TIME HAND MOVEMENT WITH COMPLEX TONE IN THE

MONKEY. HISAE GEMBA 1, NAOKI MIKP AND KAZUO SASAKI 2, ~Dept. of Integrative Brain Science, Fae. of Medicine, Kyoto Univ., Kyoto 606 and ~Dept. of Integrative PhysioloFy, National Institute for Physiological Sciences, Okazaki 444, Japan

Field potentials were recorded with electrodes chronically implanted on the surface and at a depth of 2.0-3.0 mm in respective cortical areas of a monkey. Potentials associated with hand movements in response to auditory stimuli (monkey vocalization and buzzer sound) were observed during the learning process of the movement. On the ftrst training day, potentials appeared in the prefrontal and premotor cortices, and then became less marked on the following days. When surface-negative, depth-positive potentials (at a latency of about 80 ms) appeared in the rostral bank of inferior limb of arcuate sulcus of the left cerebral hemisphere in 5-7 days of training, and became gradually larger, the monkey began to respond to the stimulus with the movement. As the potential in the prefrontal cortex and the cerebellar-mediated potential in the motor cortex gradually increased with further training, the movement became shorter and less variable in reaction time.(1). It took 2-3 weeks for three naive m~akeys to achieve the movement, which was shorter than the movement with pure tone (1). This suggests that monkeys can more easily learn the movement with complex than pure tone. It is also suggested that the prefrontal cortex contributes more actively to the learning of the movement with complex than pure tone. Meaningful sounds for monkeys appear to be composed of tones of various frequencies. In contrast, the rostral bank of inferior limb of arcuate sulcus in the fight cerebral hemisphere was scarcely changed in its potentials during the learning process of the movement with complex tone. The bank potential in the fight hemisphere seemed rather to be associated with different brain functions from the learning of the movement (2). These findings suggest functional differences between the prefrontal cortices of the left and right hemispheres in monkeys.

1.Gemba & Sasaki, Exp. Brain Res. (1988) 70: 43-49. 2.Gemba & Sasaki, Jpn. J. Physiol. Suppl. 43 (1993) in press