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WORKSHOP ON:
CENTRAL PROBLEMS IN SINGLE CELL COMPUTATION
16-18 September 2002
By invitation only
Venue
B10 Seminar Room, Alexandra House, 17 Queen Square, London, WC1N 3AR
| Stochastic integration in neocortical
pyramidal neurons in vivo |
| A. Destexhe, Unite de
Neuroscience Integratives et Computationnelles, CNRS, Gif-sur-Yvette, France |
| Little is known about the integrative properties
of central neurons during active states in vivo, despite its functional importance. Here
we investigated the integrative properties of neocortical pyramidal neurons in which in
vivo conditions were simulated based on intracellular recordings. Neocortical neurons
recorded from cat parietal cortex during active states, before and after microperfusion of
TTX, show that synaptic background activity accounts for a strong (3-5 fold) decrease of
input resistance, a depolarization of approx. 15 mV, and large-amplitude membrane
potential fluctuations (std. dev.of approx 3-4 mV). Recording of miniature events in the
same cells allowed us to estimate the conditions of release (conductance, frequency,
random nature) at excitatory and inhibitory synapses corresponding to active states in
vivo. In a second phase, we evaluated the impact of synaptic background activity on
integrative properties. We show that high-conductance fluctuations induce a stochastic
state in which dendrites are fast-conducting and have facilitated initiation and
forward-propagation of Na+-dependent spikes. The probability of evoking a somatic spike is
independent of the location of the synaptic input, and is modulable by network activity.
Thus, models predict that the integrative mode of neocortical neurons in vivo should be
stochastic, fast-conducting, and optimized to process synaptic inputs at high temporal
resolution, independently of their position in the dendrites. |
| Joint work with M. Rudolph (CNRS) and D.
Pare (Rutgers University) Supported by CNRS and NIH |
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