| Research Abstract |
(1) Behavioral studies on habituation and reinforced learning in the feeding behavior.
Neonatal chicks peck at small and conspicuous objects. This action is innate and not requiring postnatal experiences, which however drastically change the preferences of the pecking action. In this study, habituation to neutral stimuli and reinforced one-trial learning were examined in this study.
The pecking action showed a strong habituation for stimulus object that was repeatedly presented, irrespectively of where the interval was short (5min) or long (1 hour). The habituated response was not observed when an object of the same size, shape but of sifferenent color was presented, indicating that the memory content was mainly its color. The passive avoidance learning reinforced by aversive taste, on the other hand, was formed after a single experience of pecking a bitter object, and the accompanying memory content covered not only the color, but also its shape and procedure of the object presentation.
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The same object could thus be stored in different manners in the central nervous system, and the neural mechanisms underlying these two forms of memory should be analyzed.
(2) Neurological studies on causal relationships between immediate early gene (c-fos) and LTP.
Expression of immediate early gene (c-fos) in a hyperstriatal region (IMHV) has been shown to correlate significantly with the strength of learming accomplished in the imprinting paradigm (McCabe and Horn 1994). Long-term potentiation (LTP) of synaptic transmission, on the other hand, has been assumed to constitute the cellular basis of memory formation (Matsushima and Aoki 1995). In this study, the causal relationships between the c-fos expression and LTP has been analyzed.
Experimental condition sufficient for inducing LTP in the local synaptic transmission (5Hzx300pulses) failed to enhance the c-fos expression. Conversely, those slices where endogenous expression of c-fos was high, the conditioning electrical stimulation failed to induce LTP.Furthermore, an antagonist of GABA-A receptors (biuculline) locked the LTP,while the c-fos expression was somewhat enhanced.
Both of the c-fos expression and the synaptic LTP are plastic process which depend on the preceding neural activities, however, the underlying cellular mechanisms proved to be distinct. Rather, the c-fos expression tended to negatively correlated with the LTP.The molecular cascades for these processes remains to be unraveled, particularly in relation to the sensitive period of the filial learning. Less
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