Optical imaging of neural activity to vocalized sounds in the guinea‐pig auditory cortex

Spatiotemporal neural activity in response to vocalized sounds (calls) was investigated in the auditory cortex of anesthetized guinea pigs using an optical imaging technique with a voltage‐sensitive dye (RH795). Guinea‐pig calls were recorded digitally and presented to the ear from a loudspeaker located contralaterally to the recording cortex. Pure tone (PT), click (CLK), and white noise (WN) stimuli were used for comparison. The response in the primary (AI) and dorsocaudal (DC) fields of the auditory cortex to a PT appeared at the stimulus onset and in the corresponding frequency band, followed by nonsimultaneous lateral inhibition in the adjacent frequency bands. The responses to CLK and WN stimuli appeared in a wide area of the fields corresponding to the wide frequency components of the stimuli. The response to calls changed spatially and temporally because the components’ frequencies changed over time. Strong responses occurred in the frequency bands corresponding to prominent instantaneous frequency...