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Abstract:
In nature, animals encounter high dimensional sensory stimuli
that have complex statistical and dynamical structure. Attempts
to study the neural coding of these natural signals face
challenges both in the selection of the signal ensemble and in
the analysis of the resulting neural responses. For zebra
finches, naturalistic stimuli can be defined as sounds that they
encounter in a colony of conspecific birds. We assembled an
ensemble of these sounds by recording groups of 10-40 zebra
finches, and then analyzed the response of single neurons in the
songbird central auditory area (field L) to continuous playback
of long segments from this ensemble. Following methods developed
in the fly visual system, we measured the information that spike
trains provide about the acoustic stimulus without any
assumptions about which features of the stimulus are relevant.
Preliminary results indicate that large amounts of information
are carried by spike timing, with roughly half of the information
accessible only at time resolutions better than 10 ms; additional
information is still being revealed as time resolution is
improved to 2 ms. Information can be decomposed into that carried
by the locking of individual spikes to the stimulus (or
modulations of spike rate) vs. that carried by timing in spike
patterns. Initial results show that in field L, temporal patterns
give at least ≅20% extra information. Thus, single central
auditory neurons can provide an informative representation of
naturalistic sounds, in which spike timing may play a significant
role.
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