K. Wimmer 1,2, M. Stimberg 1,2 R. Martin 1,2, J. Schummers 3,4 , M.
Sur 3,4 and K. Obermayer1,2
1Dept of Computer Science and Electrical Engineering, Berlin Univ of Technology,
Berlin, Germany
2Bernstein Center for Computational Neuroscience, Berlin Univ of Technology, Berlin, Germany
3Dept of Brain and Cognitive Sciences, Massachusetts Inst of Technology, Cambridge MA, USA
4Picower Center for Learning and Memory, Massachusetts Inst of Technology, Cambridge MA, USA
The time course of orientation tuned responses in primary visual cortex (V1) can provide insight into the circuitry underlying tuning. While several models of orientation tuning in V1 have been proposed, most of the research focused on the steady-state behavior of the simulated networks. Here, we characterize the temporal response dynamics of a large-scale network using forward- and reverse-correlation analysis of the responses to time-varying stimuli. The network is composed of more than 20000 excitatory and inhibitory Hodgkin-Huxley neurons whose orientation preferences depend on the location of the neurons in an artificial orientation map. Varying both the strength of the excitatory and inhibitory recurrent connections, we assess implications for the response dynamics. Our findings confirm previous results regarding the likely operating regime of V1 [1]: The model operates in a balanced regime in which recurrent excitation and inhibition together with feedforward input lead to sharp spike tuning irrespective of the position of a neuron in the orientation preference map. Interestingly, this map-location invariance also holds for the mean temporal response. The variance of responses may, however, correlate with differences in properties between orientation domains and pin-wheel centers [1], as observed in recent experimental findings regarding the temporal response dynamics of V1 neurons. [1] Mariņo, J. et al., Nat Neurosci 8, 194ff (2005).