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Biomedical subjects

T Ohi

Publications and source records attributed to T Ohi.

At least 73 records · Page 4Linked to original sources
PubMed1981

[Effects of bilateral mammillary bodies destruction on lever pressing for food reward in the rabbit (author's transl)].

Effects for continuous reinforcement (CRF) learning and differential reinforcement of low rate (DRL) learning for food in the rabbit by bilateral mammillary bodies destruction were examined with the Skinner box. There was no marked changes in general behavior, except a tendency to freezing by a sign of somebody and sounds. In CRF learning a delay in the start of bar pressing was thought to be due to a decrease in exploratory behavior and a decrease of the number of bar pressing may be due either to a delay of adaptation to a new environment, or to an impediment of learning by the decrease in rewarding effects. The acquisition of DRL learning was affected, but the retention of that was not. DRL learning has been generally remarked to be chiefly consisted of motivation and temporal discrimination. In our study, however, there was no remarkable changes in motivation itself and temporal discrimination was not affected at all. It was concluded that the impediment of acquisition depended upon a general decrease in cerebral rewarding effects.

Animals↗
PubMed1980

Afferent artery and the site of neck of anterior communicating aneurysms.

The relationship between the afferent artery and the site of aneurysmal neck and hemodynamics in the anterior part of the circle of Willis was investigated from surgical and angiographic findings in 213 patients with anterior communicating artery aneurysms. An afferent artery was limited to the dominant A1 in about 95% of them. The neck of an aneurysm was more than three times greater at the bifurcation of the dominant A1 and the anterior communicating artery than at the bifurcation of the non-dominant A1 and the anterior communicating artery.

Cerebrovascular Circulation↗
PubMed1980

[Electrical activity of the dorsal hippocampus during DRL learning in the rabbit (author's transl)].

The change of electrical activity of the dorsal hippocampus during differential reinforcement of low rate (DRL) learning was examined in six rabbits. Bipolar electrodes were implanted stereotaxically into the dorsal hippocampus (3 mm posterior to bregma, 4-4.5 mm lateral and 7-7.5 mm ventral from bregma). After completion of continuous reinforcement learning, the animals learned DRL on a 10 sec. schedule. Rhythmic theta waves (6-8 Hz, 0.6-1.5 mV) were predominant in the early sessions of the DRL schedule. With further sessions, regular theta waves decreased and desynchronized waves or slightly irregular theta waves increased especially during the 10 second waiting period. Contrary to the report of Bennett et al., synchronized waves were always seen from 1-2 sec. before lever-press until completing of lever-press. Moreover, these preceding synchronized waves became more pronounced and of higher frequencies (8-10 Hz.) as learning proceeded. These high frequency regular waves (alpha-bursts) were seen in 5.6-35.8% of reinforced lever-press in the 10th session, and 79.5-93.8% in the 60th session. Alpha bursts were sometimes seen after 8-9 sec. waiting in the later sessions, but never seen within five secs.. During the extinction of DRL learning, the occurrence rate of alpha-bursts on adequate but non-rewarded lever-pressing decreased. These results cannot be explained satisfactorily in terms of an association between synchronized waves and voluntary movement. Frequency increase was seen when rabbits expected reinforcement after waiting for about 10 sec. or more. These results indicate that frequency increase of hippocampal synchronized waves is seen in association with higher central processing, most likely with memory.

Alpha Rhythm↗
PubMed1979

Angiographic study of cerebral vasospasm following rupture of intracranial aneurysms: Part I. Time of the appearance.

An investigation of the time of appearance of vasospasm as seen angiographically after the onset of subarachnoid hemorrhage was carried out on 797 cases of intracranial saccular aneurysm in which operations were performed. It has been reported that vasospasm often occurs early after the onset of subarachnoid hemorrhage. With only one subarachnoid hemorrhage, vasospasm occurred within three days after the hemorrhage in only 4.2% of the 120 cases in this study. The appearance of vasospasm was most frequently seen angiographically between ten and 17 days. During this period vasospasm was seen in 49.1% of 116 cases. In those cases with a subarachnoid hemorrhage one to 17 days before the last one, vasospasm within three days after the last hemorrhage was seen in 38.7% of 62 cases. During the period between ten and 17 days after the last hemorrhage, vasospasm was seen in only 20% of 25 cases. The preceding subarachnoid hemorrhage, which had occurred between one and 17 days before the last hemorrhage, seemed to be responsible for the high rate of vasospasm within three days after the last hemorrhage, and the low rate of vasospasm in the period between ten and 17 days after the last hemorrhage.

Brain↗