Audition: Spike Timing

Like a computer, the brain uses digital signals, but its all-or-nothing spikes occur at anytime, whereas the computer waits for its clock to tick or tock first. The brainís digital-amplitudeñanalog-time hybrid is unique, and nowhere is the analog-time dimension exploited more exquisitely than in the auditory system. Even though a spike lasts for a millisecond, barn owls can catch mice in the dark by resolving microsecond time differences between sounds arriving at the two ears!

Photo of a brain
The Patch-Clamp Physiologists eavesdrop on the electrical life of cells using the patch-clamp (right); it mimicks the effect of synaptic transmission (left). The cell's behavior is described using batteries, variable resistors, and a capacitor (overlaid), primitives borrowed from electrical engineers that are readily assembled on a chip—we use transistors in place of resistors. [John Wittig 2004]
From its detection in the ear to its perception in the cortex, sound is encoded precisely.

Sound is separated into its constituent tones by the cochlea, a spiral structure in the inner ear. The cochlea's basilar membrane vibrates at its base when stimulated by high frequencies and vibrates Ventral and dorsal cochlear nucleus Cells in the ventral cochlear nucleus are primarily innervated by auditory nerve fibers and rely on intrinsic membrane properties for information processing. In contrast, cells in the dorsal cochlear nucleus receive multi-modal inputs (even non-auditory) and rely on local networks to process information. at its apex when stimulated by low frequencies; the location progresses logarithmically along the length of this tapered structure as frequency drops. This place-code is complemented by a time-code. At each point in time, the basilar membrane's.

displacement is encoded