Last update: 08/12/2009

Long-lasting context dependence constrains neural encoding models in rodent auditory cortex

Asari, H. and Zador, A.M.

Acoustic processing requires integration over time. We have used in vivo intracellular recording to measure neuronal integration times in anesthetized rats. Using natural sounds and other stimuli, we found that synaptic inputs to auditory cortical neurons showed a rather long context-dependence, up to four seconds or longer (~1 s), even though sound-evoked excitatory and inhibitory conductances per se rarely lasted longer than ~100 ms. Thalamic neurons showed only a much faster form of adaptation with a decay constant <100 ms, indicating that the long-lasting form originated from presynaptic mechanisms in the cortex, such as synaptic depression. Restricting knowledge of the stimulus history to only a few hundred milliseconds reduced the predictable response component to about half of that of the optimal infinite-history model. Our results demonstrate the importance of long-range temporal effects in auditory cortex, and suggest a potential neural substrate for auditory processing that requires integration over time scales of seconds or longer, such as stream segregation.

Poster: Computational and Systems Neuroscience (COSYNE) 2006, Salt Lake City, Utah.
Poster: Gordon Research Conference (Sensory coding and the natural environment), Big Sky, Montana, 2006.
Poster (446KB, PDF): Computational and Systems Neuroscience (COSYNE) 2007, Salt Lake City, Utah.
Preprint (4.9MB, PDF): J. Neurophys. 2009; 102(5): 2638-2656.
See also my dissertation (Chapter 3).