Multi-unit peristimulus time (MU-PST) histograms were recorded in the gerbil inferior colliculus (IC) in response to tone burst stimuli, Histograms were collected every 100 μm as the recording electrode was advanced along the tonotopic axis of the central nucleus of the IC. Space/time maps of neural activity were constructed from these data, In most of our sample the pattern of response changed systematically as the stimulating frequency was increased in octave steps. At low frequencies (< 500 Hz) the pattern of response was broadly distributed spatially and phase-locked to the stimulus frequency. At higher frequencies (> 1 kHz) the pattern of response was more localized and showed no evidence of phase locking. The location of the maximum response to tones from 1 to 32 kHz moved ventrally along the tonotopic axis at an approximate rate of 230 μm/stimulus octave. The patterns Of response were localized near stimulus threshold and spread over a larger region as level increased. This method of collecting and displaying multiunit response maps provides an overview of ensemble activity that allows concurrent observation of spatial and temporal variations in activity patterns. The quantitative analysis of components of MU-PST Maps are consistent with trends illustrated with single-unit tuning and level functions. This perspective of IC activity suggests potential processing mechanisms that are congruent with single-unit reconstructions.
Bibliographical noteFunding Information:
We appreciate the editorial help of Monita Chattewrjee and Honor O'Malley. Supported by research grants number RO1 NS19518 (D.M.H.) R01 DC 01526-04 (R.V.S.) from the National Institute on Deafness and Other Communication Disorders, National Institutes of Health, the Deafness Research Foundation (D.M.H.), and the Boys Town National Institute (R.V.S. and E.C.), who provided partial support for the data analysis. We thank Joseph Santos-Sacchi and Barbara Wendt Harris for their continued support of this project. Portions of this report have been reported in abstract ( Harris and Lambert, 1986 ; Harris et al. 1987, 1990 ).
- Central auditory system
- Inferior colliculus
- Neural map
- Sensory coding