Murat Okatan

Murat Okatan

School/Degree: Boston University, Ph.D.
Lab Position:Post Doctoral Research Associate

Research Interests:

  • Hippocampal-prefrontal interactions during reinforcement learning and action selection.
  • Multielectrode recording of ensemble neural spiking activity.
  • Point process network likelihood models of ensemble neural spiking activity.
  • Joint probability models of ensemble spiking activity and behavior.

Experimental and computational investigation of reward-related activity in the hippocampus and its functional role in learning, memory, and decision making

We use multi-electrode recording to capture the spike trains of rat hippocampal neurons while the animal performs a reinforcement learning task with dynamic reward schedule, and develop statistical models to explain the observed spiking activity as a function of task-relevant covariates, including reward-related processes. We have developed a conditional spatial goal selection task to cue rats to choose one of the arms of a T-maze in search of food reward. In post-learning sessions, reward magnitude is varied during the course of a session to determine whether and how this impacts hippocampal neural spiking activity. Our preliminary data show that a substantial percentage of hippocampal neurons change their firing rate with changing reward magnitude, in positive or negative correlation, and that the change in the firing rate of some neurons exhibits a backward shift relative to the time of reward with increasing trial number during the session. We develop point process likelihood models to explore the functional role of this reward-modulated backward shift in neural activity, and consider the possibility that it may be the signature of a learning process that is similar to a well-known machine learning algorithm called the Temporal Difference learning algorithm. We expect our results to advance our understanding of the computational mechanisms underlying the formation of hippocampal memory representations and their relation to the reward and decision making systems of the brain.

Okatan M. Correlates of Reward-Predictive Value in Learning-Related Hippocampal Neural Activity. HIPPOCAMPUS 19:487-506 (2009)PDF

Okatan, M.; Komorowski, R.; Eichenbaum, H.B.; Reward-predictive value in learning-related hippocampal neural activity. Bioengineering Conference, 2009 IEEE 35th Annual Northeast, 3-5 April 2009, Digital Object Identifier 10.1109/NEBC.2009.496772 PDF