Role of biophysical specialization in cholinergic modulation in neurons ofthe ventral cochlear nuclei

In contacting arrays of different types of neurons whose axons have differi ng targets in the brain stem, the auditory pathway is subdivided into paral lel ascending pathways, each of which carries a different type of informati on. Several distinct arrays of neurons in the ventral cochlear nuclei have anatomical and biophysical specializations which enable them to extract dif fering facets of acoustic information and to convey it up the auditory path way. T stellate cells have higher input resistances and have lower firing t hresholds than bushy or octopus cells, enabling their firing to be modulate d by small currents. Cholinergic currents, driven by neurons in the ventral nucleus of the trapezoid body that are likely to include medial olivocochl ear efferents, excite T stellate cells, but have subtle effects on the firi ng of bushy cells, and have no detectable influence on octopus cells and D stellate cells. We suggest that cholinergic excitation of T stellate cells contributes toward shifting their acoustic dynamic ranges and increasing th e encoding of spectral peaks in noisy conditions and in awake animals. Copy right (C) 2001 S. Karger AG, Basel.