Excitatory and inhibitory tonotopic bands in chinchilla inferior colliculus revealed by c-fos immuno-labeling

- We report a protocol for c-fos immuno-labeling in inferior colliculus of chinchilla.
- Tonotopic bands of labeled cells are present following pure tone sound stimulation.
- Multi-unit recordings in inferior colliculus confirm tonotopic arrangement of bands.
- Regions of decreased cell labeling flank tonotopic bands: potential inhibitory region.
- Spatial patterns of c-fos labeling match unit lateral inhibition.

We describe in detail a reliable experimental protocol for c-fos immuno-labeling of patterns of neural activation in the chinchilla (chinchilla laniger). We report on resting-level neural activity in inferior colliculus (IC) of auditory midbrain, and on tonotopic bands present following 90 min of pure-tone sound stimulation. Neurons activated by 6-kHz sound stimulation lay ventro-medial to those activated at 2 kHz. This is consistent with the known tonotopic organization of IC, and verified in the present report by multi-unit neuron response recordings in central nucleus of IC. Of particular interest, we observe a significant reduction in cell labeling adjacent to the tonotopic bands, and suggest that such decreases represent inhibitory regions. C-fos-labeled bands and lateral regions of reduced labeling resemble excitatory and lateral-inhibitory response areas of IC neurons.