The past two decades have advanced our knowledge on brain circuits involved in regulating emotion and motivation. In the tightly interconnected circuitry formed by the amygdala, prefrontal cortex, striatum and mesencephalic dopamine neurons, single-neuron activity patterns correlating to salient behavioral events such as reward, actions and stimuli predictive of reward have been identified. When considering that such single-neuron information must be processed together with massive signaling by surrounding neurons, the question arises how neural populations in a target structure may filter out and respond to relevant information. The first part of this seminar will be dedicated to the question, how groups of neurons code emotionally relevant information (particularly information concerning the expectation of an upcoming reward). We will also ask how fast such a code is sculpted during learning. To investigate this, we conducted ensemble recordings in the orbitofrontal cortex of rats engaged in an olfactory learning task. The second part of the seminar will be devoted to neural processes operating after learning has occurred in a behaviorally active state: during off-line processing periods such as sleep. Current evidence suggests that particularly slow-wave sleep is important for (declarative) memory consolidation. Here we will examine whether motivationally valuable information in ventral striatal ensembles in rat brain is `replayed´, and how such replay is coordinated with reactivation of spatial-contextual information in the hippocampus. These findings strongly suggest a neural mechanism for storing place-reward associations.
Cyriel M.A. Pennartz
Cognitive & Systems Neuroscience
University of Amsterdam, SILS Center for Neuroscience, Faculty of Science.