Kensaku Miyamoto

Studies on the Neural Basis of Behavior by Continuous Frequency Analysis of EEG

Publisher Summary This chapter discusses the studies on the neural basis of behavior by continuous frequency analysis of Electroencephalography (EEG). A number of electroencephalographic studies have been reported that aimed to clarify the neural mechanisms that control conditioned behavior. In some experiments, intracerebral stimulation was used as the conditioned stimulus, as the indifferent tracer stimulus to follow the input, or to influence the conditioned response. The component at 9.5 c/s driven by the reticular stimulation, showed a marked increase in amplitude just before the lever-pressing in the frontal Lead on both sides. The EEG component of the stimulation frequency in the hippocampal lead was replaced by an enhancement of the component at 7–8 c/s because of the hippocampal arousal pattern at that time. The changes of the temporo-occipital and occipito-frontal EEGs correlated with the “switch-off behavior” resembled those of the hippocampal EEG. It is found that when the EEG changes correlated with the switch-off behavior driven by the brain-stem stimulation were compared to those of the spontaneous lever-pressing, a similarity was found in the hippocampus.

A Study on the Invasive Hippocampal θ-Waves to the Cortex

Publisher Summary This chapter presents the experiments that are designed to investigate: (1) general features of the cortical “iso-hippocampal rhythm” (IHR), (2) the cortical distribution of the IHR, (3) conditions for the appearance of the cortical IHR, and (4) the cortical excitability during the IHR. The chapter uses the term IHR to denote the activity of extra-hippocampal structures which continues at least for 2 sec at frequencies of the θ of 4-7 c/sec and waxes and wanes in synchrony with the θ-waves of the hippocampus. The IHR activity could appear spontaneously, but it is much easier to induce it by the arousal stimulation. The IHRs presented in the chapter are mainly obtained by the electrical stimulation of the brain stem structures. One of the electrographic arousal states is characterized by cortical desynchronization and hippocampal synchronization. It is reported by Yoshii and associates that the cortical desynchronization sometimes contains a well-developed activity at the frequency-band corresponding to the hippocampal θwaves. The cortical activity with IHR is supposed to be moderately aroused and excludes the indifferent impulses coming to the cortex for inducing the correct performance in the conditioned and learned behavior.

Neural coding of speech sound in the telencephalic auditory area of the mynah bird

SummaryThe responses of neurons in field L in the auditory neostriatum of the mynah bird, Gracula religiosa, were recorded during presentation of intact or manipulated mimic voices. A typical mimic voice ‘konnichiwa’ elicited responses in most of the neurons. Neurons in the input layer (L2) of field L showed many peaks on peristimulus time histograms while those in other layers (L1 and L3) exhibited only one or two peaks. Several neurons in L1 and L3 responded only to the affricative consonant /t∫/ in the intact mimic voices. They did not respond to the affricative consonant in the isolated segment or to the one in the playbacked voice in reverse. Forty-five percent of the neurons (33/ 73) decreased in firing rates at the affricative consonant in the isolated segment compared with in the intact voice. Some of these neurons, in which neither the affricative consonant in the isolated segment nor bursts of noise alone elicited responses, exhibited clear phasic responses to /t∫/ in the case when bursts of noise with particular central frequencies preceded the affricative consonant. The responsiveness of these neurons appears to receive temporal facilitation. These results suggest that these neurons code the temporal relationship of speech sound.

The effect of changes in visible area on facial recognition.

The proportion of a human face which needs to be visible for correct identification was investigated. Photographs of familiar public faces were presented under two conditions: (i) the facial photographs were original photographs with local information; and (ii) the facial photographs were blurred, with high spatial frequencies removed and with no local information. Subjects could scan the face as they wished through a moveable window generated by a TV system and had to identify the depicted person as quickly as possible. Window size was varied systematically. The main study showed that, in spite of including only its local features, a familiar facial photograph could be perfectly identified when the visual window covered one-fifth of the whole face, and that a global image of the whole face was obtained when nearly half of the whole face was processed simultaneously. The structure of the memory image of the face is discussed in the light of the results obtained.