FACILITATORY NEURAL DYNAMICS FOR PREDICTIVE EXTRAPOLATION A Dissertation by HEE

Facilitatory Neural Dynamics for Predictive Extrapolation. (August 2006) Heejin Lim, B.S., Keimyung University; M.S., Keimyung University Chair of Advisory Committee: Yoonsuck Choe Neural conduction delay is a serious issue for organisms that need to act in real time. Perceptual phenomena such as the flash-lag effect (FLE) suggest that the nervous system may have mechanisms to compensate for delay. In motion FLE, the position of a moving object is perceived to be ahead of a brief flash when they are actually co-localized. Motion extrapolation hypothesis suggests that FLE may be due to an extrapolation process in the nervous system that counters the effects of neural conduction delay. However, the precise neural mechanism for extrapolation has not been fully investigated. One potential neural mechanism for delay compensation can be found in dynamic synapses. Dynamic synapses, facilitating or depressing, have drawn much attention due to their implicated functional role in memory and temporal information processing. The main hypothesis of this dissertation is that facilitating synapses, with their dynamic sensitivity to the rate of change in input, may also play an important role in compensating for neural delay. To test this hypothesis, I developed the Facilitatory Activation Model (FAM), a model based on firing rate neurons, and tested it in motion FLE. The computational results were consistent with human data. The model was further extended to account for a peculiar behavior not fully explainable by extrapolation alone: the lack of FLE at motion termination or motion reversal points.