|Budget Amount *help
¥19,300,000 (Direct Cost : ¥19,300,000)
Fiscal Year 1994 : ¥3,900,000 (Direct Cost : ¥3,900,000)
Fiscal Year 1993 : ¥15,400,000 (Direct Cost : ¥15,400,000)
Evoked potential (EP) is a cortical response that occurs within 500 ms when sensory stimulus is presented to a person. Considering the mechanism of its generation, it reflects the primary sensory information processing in the brain. Measuring and analyzing EPs enables us to understand the relation between the sensory information in the environment and the person's response without leading him to evaluation.
First of all, effect of attention on perception of sound was studied with measurement and analysis of auditory evoked potentials (AEPs). AEPs are characteristic movements of potential in brain waves that are evoked by auditory stimulus within 500 msec, and of which later elements are said to be concerned with advanced psychological process of perception. Two experiments were made. In the first experiment, AEPs to 6 intensities of constant interval pink noise as auditory stimulus were recorded from vertex under eye-closed condition, and in the second, AEPs to 4 intensities of random i
nterval pink noise were also recorded from vertex under eye-opened condition. In each experiment, 3 hearing conditions which had differences in attention to stimulus were set up. Response latencies to characteristic peak in later elements of AEPs that were called N1, P2, and N2 components and response amplitudes of N1-P2 and P2-N2 components were analyzed. Results of these two experiments showed that intensity of stimulus affected both response latencies and response amplitudes, that attention to stimulus affected response amplitudes of P2-N2 components, and that the character of interstimulus interval affected response latencies of N1 and P2 components. Considering that AEPs objectively suggest perception of sound, these results indicate that very low level sound of 33 dBA is also perceived under the condition of working with little attention to sound, and that predictability and attention make different perception of sound.
Furthermore, to obtain some suggestions about effects of habituation on perception of noise, effects of habituation to noise stimuli on auditory evoked potentials (AEPs) that reflect the auditory information processing in the central nervous system are analyzed. In the experiment, pink noise of 33,40,50,70 dB (A) was repeatedly presented to subjects through loudspeaker in the soundproof room. One trial at each sound pressure level (SPL) took about ten minutes. Subjects were indicated to listen to noise stimuli (Condition (A)), or to do the calculation task without attention to noise (Conditon (B)). AEPs were measured from a subject at first, middle and latter part of a trial. The analysis reveals that response quantity of processing that corresponds to perceptual quantity is affected by intensity, attention, habituation to auditory information, and their interaction. Habituation only occurs at 70 dB (A) in the processing when auditory stimuli are not attended to, however it occurs at 50 dB (A) and above when it is listened to with attention.