bluelogo.gif (1643 bytes)
Gatsby Computational Neuroscience Unit
Alexandra House, 17 Queen Square, LONDON, WC1N 3AR, UK
Tel: +44 (0) 20 7679 1176, Fax +44 (0) 20 7679 1173, admin@gatsby.ucl.ac.uk, www.gatsby.ucl.ac.uk

 

home
people
research
annual report
publications
seminars
travel
vacancies
the greater gatsby
search
ucl

 

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.