Hirohiko Ohta

Specific cholinergic destruction in the basal magnocellular necleus and impaired passive avoidance behavior of rodents

A nerve growth factor (NGF)-diphtheria toxin conjugate (NGDT) was found to selectively abolish or depress the activity of NGF receptor-bearing cholinergic neurons of the basal magnocellular nucleus (BMN). Bilateral cortical injections of NGDT impaired the retention of passive avoidance behavior in mice. A memory deficit was also revealed when cortical injections of NGDT were administered after the acquisition of a passive avoidance response. Thus, retrograde destruction of BMN cholinergic neurons by the cortical injection of NGDT interfered with both learning and memory processes. The animal model outlined here should be useful in analyzing the pathogenesis of Alzheimers disease and the functions of the cholinergic system in the BMN.

Learning Set Formation in Ring-Tailed Lemurs (Lemur catta)

Following the study on nocturnal slow lorises ( Nycticebus coucang ), the visual discrimination learning set was tested on diurnal ring-tailed lemurs ( Lemur catta )

Learning Set Formation in Slow Lorises (Nycticebus coucang)

In primates, learning set formation has been reported in various simian species, but in only few prosimian species. The formation of visual discrimination learning set was tested on a nocturnal prosimian species, slow lorises (Nycticebus coucang). Their performance was higher than that of some New World monkeys. This confirmed the suggestion from the data on black lemurs (Lemur macaco) that there is an overlap between prosimians and simians in learning set ability.

Learning Set Formation in Common Tree Shrews (Tupaia glis)

Following the studies on slow lorises (Nycticebus coucang) and ring-tailed lemurs (Lemur catta), the visual discrimination learning set was tested on diurnal comm

Learning Set Formation in Thick-Tailed Bush Babies (Galago crassicaudatus) and Comparison of Learning Ability among Four Species

Following the studies on Nycticebus coucang, Lemur catta and Tupaia glis, the Visual Discrimination Learning Set was tested on the nocturnal pr

Age Change in Learning Ability of Japanese Monkeys (Macaca Fuscata) Measured by the Transfer Index

To examine the developmental change in learning 26 Japanese monkeys at five ages, 1, 2, 3, 5, and over 7 years old, were given two sorts of discrimination-reversal problems differing in prereversal acquisition, one at 67% and the other at 80%. Transfer Index was estimated. With a shift in acquisition from 67% to 80%, the Transfer Indexes were maintained in the 1-, 2-, and 3-yr. groups but declined in the 5-yr. and the adult groups. The results suggest some critical point in learning by Japanese monkeys.

Volumetric comparisons on some nuclei in the cerebellar complex of prosimians

Seven measurements were performed on the cerebellar complex of 30 specimens, covering three species each of Cheirogaleidae, Lemuridae and Indriidae, and Daubentonia, and three each of Lorisinae, Galaginae, and Tarsius. The items measured were the volume of the medial (CM), interposed (CI), and lateral (CL) cerebellar nuclei, ventral pons (Vpo), inferior olivary principal (OLIPr) and accessory (OLIAc) nuclei, and the vestibular nuclear complex (VES). The raw data for these measurements were previously reported [Matano et al., Folia Primatol 44:171–181, 182–203, 1985; 47:189–203, 1986; Matano, Anthropol Soc Nippon 100:69–82, 1992]. For this paper, the relative size of each nucleus was expressed in terms of size indices based upon?the allometric line obtained by reduced major axis analysis?and comparisons between species within family or subfamily?were made. Lemur showed one of the highest cerebellar complex indices and Lepilemur one of?the lowest. Generally, the three cerebellar nuclei (CM,?CI, and CL) were enlarged to the same extent in each species. Only?Daubentonia showed higher size indices of CL, Vpo,?and OLIPr than of CM and OLIAc. Characteristics of the?cerebellar complex enlargement of Tarsius were comparable to those of prosimians. The VES indices for non‐leaping Lorisinae?were markedly lower than those for the actively leaping Galago?and Tarsius. Am. J. Primatol. 48:31–48, 1999.

Acquisition and transfer of visual Go/No-go discrimination by a chimpanzee

An adolescent female chimpanzee was trained to press a key in the presence of a computer-graphic geometric figure (“Go” stimulus) within 5 sec and not to press the key during 5-sec presentations of another figure (“No-go” stimulus) with food reinforcement. In the acquisition training, the accuracy of performance increased primarily as a result of learning to inhibit key presses in No-go trials. The chimpanzee acquired this “Go/No-go” visual discrimination task in 1,260 trials. She was then given 14 successive transfer problems. The results for these problems suggested that learning-set formation and repeated use of the same discriminative stimuli both influenced transfer to new problems.

Developmental change in subjective probability during adolescence.

The developmental change in subjective probability during adolescence, an important period for establishing the probability concept, was investigated. 75 Japanese adolescents, from 12 to 23 yr. of age, were asked to make probability judgments for a lottery under 15 conditions. Analysis showed that with increase in age their subjective probability came closer to the objective probability. Discussion of these results took into consideration recent studies on the development of the concept of probability.

DECISION MAKING WITH PROBABILITY FORECASTS OF RAINFALL

Decision making with probability forecasts of rainfall was investigated experimentally by considering three variables, i.e., the rainfall probability, the duration of being away from home, and the outdoor weather condition. 274 Japanese college students were asked to make decisions on the necessity for person A to take an umbrella with him under 16 different conditions. Analysis showed obviously that the necessity tended to increase as probability of rainfall rose, as duration became longer, and also as the outdoor weather was cloudy rather than clear. Discussion of these results considered recent studies of decision making and subjective probability.