| How the brain is able to maintain short-term memory is an unanswered question. The neural correlate of short-term memory is persistent discharge in the absence of continued stimulus. This thesis describes the study of one model system of persistent activity, the goldfish oculomotor neural integrator that integrates (in the calculus sense) transient saccadic and vestibular signals into permanent changes in eye position.;We use in vivo whole-cell intracellular recordings of integrator neurons in awake goldfish to temporally resolve individual excitatory postsynaptic potentials (EPSPs). We discovered that the EPSP rate increases with average membrane potential and eye position. The EPSPs also form a frothy fluctuation that constitutes a significant fraction of the total membrane voltage. This suggests that network mechanisms play a substantial if not dominant role in the operation of these neurons. But contrary to predictions of existing neural integration network models, individual EPSPs do not appear to possess long time constants that were critical to network stability and tuning.;We present numeric models that show how under some regimes, neurons may be more responsive to fast fluctuation inputs than slow constant inputs.;These results motivate the theoretical studies of a new class of neural integrator models that are characterized by fluctuation dominated spike dynamics. |
