Spike timing

Spike timing in the auditory nerve carries information about important acoustic features. This comes about because auditory-nerve-fiber spikes are "phase locked" to low-frequency components of incoming acoustic signals. For low-frequency pure-tone stimuli, the instantaneous spike probability is a well-modulated function of the stimulus phase. Similar temporal coding occurs for second-order statistics (i.e., modulation frequency) of complex sounds. Temporal spike codes are extremely important in audition, which is an incredibly "fast" sense compared to the other senses such as vision. Auditory neurons can discriminate inter-aural time differences as low as 10 µs. That's 100 times shorter than the duration of a spike!

Video 1: Phase-locked spikes in the ventral cochlear nucleus

(Some of) our (broad) questions in spike timing

• How does "enhanced" phase locking emerge (in various brainstem nuclei)?
• How are temporal codes "transformed" at more central processing sites?
• Does well-timed inhibition play a role in brainstem processing of acoustic signals?

Further reading

• Johnson DH (1980). The relationship between spike rate and synchrony in responses of auditory-nerve fibers to single tones. The Journal of the Acoustical Society of America 68: 1115–1122.

• Joris PX et al. (2004). Neural processing of amplitude-modulated sounds. Physiological Reviews 84: 541-577.

• Henry KS, Heinz MG (2012). Diminished temporal coding with sensorineural hearing loss emerges in background noise. Nature Neuroscience 15: 1362–1364.