FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

Stimulus information coded by spike timing
Collaborators: M. N. Havenith, S. Yu, J. Biederlack, N-H. Chen, W. Singer, D. Nikolić
The synchronized activity of cortical neurons often features spike delays of several milliseconds.
Usually, these delays are considered too small to play a role in cortical computations. We used
simultaneous recordings of spiking activity from up to 12 neurons to show that, in the cat visual
cortex, the pairwise delays between neurons form a preferred order of spiking, called firing sequence.
This sequence spans up to 15 ms and is referenced not to external events but to the internal cortical
activity (e.g., beta/gamma oscillations). Most importantly, the preferred sequence of firing changed
consistently as a function of stimulus properties. During beta/gamma oscillations, the reliability of
firing sequences increased and approached that of firing rates. This suggests that, in the visual system,
short-lived spatio-temporal patterns of spiking defined by consistent delays in synchronized activity
occur with sufficient reliability to complement firing rates as a neuronal code.
Figure: A network of time delays extracted from all possible pairwise cross correlations computed for seven
multi-units. Example cross-correlo-grams are shown on the bottom. The time delays on the edges are in
milliseconds and have the property of additivity.
Related publication in 2011:
M. N. Havenith, S. Yu, J. Biederlack, N-H. Chen, W. Singer and D. Nikolić, Synchrony makes
neurons fire in sequence – and stimulus properties determine who is ahead, Journal of Neuroscience,
31, 8570-8584 (2011).
71