The Journal of Neuroscience, October 15, 2001, 21(20):8136-8144
1 W. M. Keck Center for Integrative Neuroscience
and University of California San Francisco/Berkeley Bioengineering
Group, San Francisco, California 94143, 2 Helen Wills
Neuroscience Institute, University of California, Berkeley, California
94720, and 3 Department of Electrical and Computer
Engineering, Bioengineering, University of Connecticut, Storrs,
Connecticut 06269
Action potentials are a universal currency for fast information
transfer in the nervous system, yet few studies address how some spikes
carry more information than others. We focused on the transformation of
sensory representations in the lemniscal (high-fidelity) auditory
thalamocortical network. While stimulating with a complex sound, we
recorded simultaneously from functionally connected cell pairs in the
ventral medial geniculate body and primary auditory cortex. Thalamic
action potentials that immediately preceded or potentially caused a
cortical spike were more selective than the average thalamic spike for
spectrotemporal stimulus features. This net improvement of thalamic
signaling indicates that for some thalamic cells, spikes are not
propagated through cortex independently but interact with other inputs
onto the same target cell. We then developed a method to identify the
spectrotemporal nature of these interactions and found that they could
be cooperative or antagonistic to the average receptive field of the
thalamic cell. The degree of cooperativity with the thalamic cell
determined the increase in feature selectivity for potentially causal
thalamic spikes. We therefore show how some thalamic spikes carry more receptive field information than average and how other inputs cooperate
to constrain the information communicated through a cortical cell.
Key words: convergence; information; receptive field; feature selectivity; medial geniculate; auditory cortex