Distribution of bilateral forelimb outputs in the motor cortex of the neonatally hemidecorticated rat

S1.58 DISTRIBUTION

279

NEONATALLY

OF BILATERAL

FORELIMB

HEMIDECORTICATED

OUTPUTS

IN THE

MOTOR CORTEX

OF THE

RAT.

KOICHI FUJIMURA Dept. of Physiology,

After unilateral examined

Nagasaki

ablation

by intracortical

University,

of the sensorimotor microstimulation

recording from distal forelimb the latency of ipsilateral although

the difference

ipsilateral

EMG responses

280

12-4, Nagasaki

rats, the reorganization

hemisphere

response

of the corticospinal

Bilateral forelimb responses

and ipsilateral

responses

forelimb

system was (EMG)

were common,

in the neonatal

muscles

In a few small sites, the latency of ipsilateral

of ipsilateral

852-8523

of the lesioned rat with electromyogram

being longer than that of contralateral

in the latency between contralateral

or the threshold

dominant

cortex in neonatal in the unablated

muscles under ketamine anesthesia.

bilateral response in the control animal. the contralateral,

School of Medicine. Sakamoto-1Chome

was smaller

usually

lesioned rat, than that of

response was shorter than that of

was lower than the contralateral.

The incidence

of such a

site tended to be higher in the rostra1 part of forelimb motor area (RFA) than the caudal part (CFA).

LOCAL CIRCUIT IN THE CEREBRAL CORTEX: PROJECTION NEURONS

INPUTS TO CORTICOSPINAL

TAKESHI KANEKO’, TOMOKO SEGAWA’, NOBORU MIZUNO’ ‘Dept. of Morphological Brain Science, Graduate School of Medicine, Kyoto Univ., Kyoto 606-850 1, *Tokyo Metropolitan Institute for Neuroscience, Tokyo 183-8526 Connections from pyramidal neurons to corticospinal neurons in the rat motor cortex were examined by combining intracellular staining with Golgi-like retrograde labeling of corticofugal neurons. Tetramethylrhodamine-dextran amine (TMR-DA) was injected into the corticospinal tract at the upper cervical level. Three days after the injection, neurons in the motor cortex were examined by intracellular recording using brain slices. After injection of biocytin, the slices were fixed and processed for further staining. Biocytininjected neurons were visualized black by the ABC method with DAB/nickel reaction, and TMR-DA was stained red by the PAP method with the anti-TMR antibody and TAPMlp-cresol reaction. Varicosities of axon collaterals of pyramidal neurons in the deep part of layer III and layer V were apposed more frequently to dendrites of corticospinal neurons than those in other layers. These results indicate that cortical motor output neurons mainly receive information from pyramidal cells in the deep part of layer III.

281

POOR PERFORMANCE TEMPORARILY MOVEMENT LEARNING.

RIEKO OSU’ and MITSUO

INCREASES

STIFFNESS

DURING

MULTIJOINT

ARM

KAWATO’,2

‘Kawato Dynamic Brain Proj. ERATO JST, ‘ATR Human Information Soraku-gun, Kyoto 619-0288

Processing

Res. Labs., Hikaridai,

Seika-cho,

Motor learning is associated with a change in stiffness, which temporarily increases and decreases, but in the long term decreases with the improvement of performance. We focused on the short term interaction between joint stiffness and performance during the learning of multijoint arm movements. Subjects were instructed to move a hand together with a reference hand trajectory that moved from an initial position to a final position. The relationship between joint torque and the EMG of six muscles was used to estimate the relative joint stiffness value. RMS error between the reference and the actual hand trajectory was used to determine performance error. The moving average (3-5 trials) of joint stiffness showed a positive correlation in the 3-6 trials preceding performance error. The results suggest that the poor performance increases future stiffness while good performance decreases it, and support the idea that active stiffness control can facilitate motor learning.