B. Wright, Kamal Sen, William Bialek, A. Doupe
In nature, animals encounter high dimensional sensory stimuli that have complex statistical and dynamical structure. Attempts to study the neu- ral 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 ana- lyzed 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 with- out 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 be- ing 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
% extra information. Thus, single central auditory neurons can pro-
vide an informative representation of naturalistic sounds, in which spike timing may play a signiﬁcant role.