LIMBO: Dynamics

info time scalesThe aim is to understand the origin of the time scales for neural information representation and processing, and to relate them to underlying biophysical parameters [3] and to experimental observations [2]. Following the original analysis [1] which linked the most important of these time scales to synaptic conductance inactivation times, extensive simulations needed to be carried out to validate and extend theoretical results [4]. These have revealed a conflict between dynamical stability and memory capacity, which is avoided only if inhibition is of a sufficiently multiplicative nature [5]. Moreover the time for collective information retrieval has been confirmed, but only when mean-field dynamics prevails, to be linearly related to synaptic conductance inactivation times, and only weakly dependent on firing rates and membrane time constants [6]. The applicability of the mean-field approximation is limited, as evident from the picture: at (partial) cue onset the network slowly enters the correct basin of attraction, with slow mean-field dynamics paced by synaptic inactivation, whereas at cue removal the network abruptly jumps to the recurrent attractor state (in this case much more correlated to the memory than the partial cue), with a rapid transition that mean-field cannot describe.


While simulations use simplified stimuli with instantaneous onset, data recorded from IT neurons has indicated what are the relevant time scales with natural visual stimuli [6]. The simple S+F model used to describe spike counts can be used as a basis for to model the effects of associative plasticity on feed-forward synapses [7].


A collaboration with Marco Canepari has focused instead on single synapses with highly stochastic release, relating the time for effective integration of presynaptic spike trains to quantal parameters and their modulation [8].

Two more recent lines of research involve convergent dynamics in IT (AAA, AT, see cortical attractors) and latching dynamics in Potts networks (ER, EK, AT, see latching & language).


  1. AT, Network 4:259-284 (1993)
  2. MJ Tovee, ET Rolls, AT & RP Bellis, J Neurophysiol 70:640-654 (1993)
  3. AT, ET Rolls & MJ Tovee, in Neurobiology: Ionic Channels, Neurons and the Brain, NATO ASI Vol A 289:371-382 (1996)
  4. AT, ET Rolls & M Simmen, Physica D 107:392-400 (1997)
  5. FPB & AT, Neural Comp 10:431-450 (1998)
  6. AT, SP, ET Rolls, MCA Booth & EA Wakeman, Neural Comp 11:601-631 (1999)
  7. GS & AT, Neural Comp 12:1773-1787 (2000)
  8. M Canepari & AT, Network 12:175-198 (2001)

Last updated 06/07/08. Back to LIMBO, CNS, SISSA.