We designed a new multi-unit acquisition system for free-moving animal which breaks through the constraint of conventional multi-unit recording systems. To release those animals from thick electronic wires while experiments, the IrDA infrared data communication, field programmable analog array-MPAA020 and 16bit micro processor-H8 were used for the design. We summarized the related works for multi-unit recording techniques and pointed out the defects of those old techniques. Then the design of the system were introduced. In the result of the paper, we checked the fidelity of recorded neural activity and the reliability of the data transmission.
We investigated the dynamic interaction in the guinea pig auditory cortex induced by a combination of acoustic and hippocampal CA1 stimuli by means of the optical imaging method. First: Single acoustic stimulus induced a regular response lasting 100 ms in the auditory cortex. Second: Single hippocampal stimulus induced no activities in the auditory cortex. Third: Combination of acoustic-hippocampal stimulus induced a different type of activity comparing with the first one. The effect of hippocampus made quicker response moving from the high frequency area to the low area that dynamically modifies the response in the cortex which seems to have another functional connection in the cortex.
Recently, it is sometimes discussed that cortical neurons perform some sort of coincidence detection. This paper proposes a new model for a functional coincidence detector by using neural cells with long membrane time constants. The basic idea is a combinational use of an excitatory output cell and an inhibitory intermediate cell, both of which have common external inputs. The intermediate cell converts an external input into an inhibitory signal and passes it to the output cell with a certain delay time. The delay time performs as a time window of the coincidence detection. Since one external input causes a pair of excitatory input and delayed inhibitory input of the output cell, only coincidental external inputs within the time window can raise the membrane potential of the output cell.