Vestibulo-ocular signal transformation in frequency-tuned channels.

Self-generated locomotor activity is accompanied by head movements that cause retinal image displacements with a resultant degradation of visual information processing. To maintain visual acuity, retinal image drift must be counteracted by dynamic compensatory gaze adjustments that derive to a large extent from vestibulo-ocular reflexes (VOR). During head motion, vestibular signals code a wide frequency range from static head position to high acceleration profiles during rapid head turns. This large dynamic range suggests that the sensory-motor transformation occurs in parallel, yet complementary frequency-tuned pathways. In fact, the classic "three-neuronal" VOR pathway is composed of distinct functional subgroups of cells with different intrinsic properties and response dynamics at each synaptic level. This generates sets of neuronal filters that are ideal for particular frequency ranges and signaling patterns, respectively. In second-order vestibular subgroups, different filter functions, and hence a different synaptic processing is facilitated by a coadaptation of intrinsic membrane and emerging network properties. The consecutive assembly and sequential connectivity of pre- and postsynaptic neuronal elements with corresponding physiological properties, generates parallel pathways that allow for separate coding of different dynamic head-motion components during locomotor activity.