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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
Multiplicative computation in a
looming-sensitive neuron |
Fabrizzio Gabbiani, Division
of Neuroscience, Baylor College of Medicine |
Multiplicative operations are thought to play
an important role in the processing of sensory stimuli in many systems. Yet, how
multiplication is implemented biophysically remains largely unknown. We investigated an
identified neuron (the LGMD of locusts) whose output firing rate can be described by a
multiplication between two postsynaptic inputs, excitatory and inhibitory, converging onto
its dendritic tree. In addition, a potentially important presynaptic inhibitory component
has been identified. Selective activation and inactivation of pre- and post-synaptic
inhibition suggest that postsynaptic inhibition plays a predominant role and that
multiplication is implemented within the neuron itself. Pharmacological experiments and
measurements of firing rate versus membrane potential revealed that sodium channels act
both to temporally advance the response of the LGMD and to map membrane potential to
firing rate in a nearly exponential manner. These results are consistent with an
implementation of multiplication based on dendritic subtraction of two converging inputs
followed by active exponentiation. |
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