The contribution of oscillatory synchrony in the primate amygdala-prefrontal pathway to aversive learning remains largely unknown. We found increased power and phase synchrony in the theta range during aversive conditioning. The synchrony was linked to single-unit spiking and exhibited specific directionality between input and output measures in each region. Although it was correlated with the magnitude of conditioned responses, it declined once the association stabilized. The results suggest that amygdala spikes help to synchronize ACC activity and transfer error signal information to support memory formation.

Cortical activity is determined by the balance between excitation and inhibition. To examine how shifts in brain activity affect this balance, we recorded spontaneous excitatory and inhibitory synaptic inputs into layer 4 neurons from rat somatosensory cortex while altering the depth of anesthesia. The rate of excitatory and inhibitory events was reduced by ϳ50% when anesthesia was deepened. However, whereas both the amplitude and width of inhibitory synaptic events profoundly increased under deep anesthesia, those of excitatory events were unaffected. These effects were found using three different types of anesthetics, suggesting that they are caused by the network state and not by local specific action of the anesthetics. To test our hypothesis that the size of inhibitory events increased because of the decreased rate of synaptic activity under deep anesthesia, we blocked cortical excitation and replayed the slow and fast patterns of inhibitory inputs using intracortical electrical stimulation. Evoked inhibition was larger under low-frequency stimulation, and, importantly, this change occurred regardless of the depth of anesthesia. Hence, shifts in the balance between excitation and inhibition across distinct states of cortical activity can be explained by the rate of inhibitory inputs combined with their short-term plasticity properties, regardless of the actual global brain activity.

SummaryThe contribution of oscillatory synchrony in the primate amygdala-prefrontal pathway to aversive learning remains unknown. We found increased power and phase synchrony in the theta range during aversive conditioning. The synchrony was linked to single-unit spiking and exhibited specific directionality between input and output measures in each region. Although it was correlated with the development of conditioned responses, it declined once the association stabilized. The results suggest that amygdala spikes aid to synchronize ACC activity and transfer error-signal information to support memory formation.

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A very-large-scale integration field-programmable mixed-signal array specialized for neural signal processing and neural modeling has been designed. This has been fabricated as a core on a chip prototype intended for use in an implantable closed-loop prosthetic system aimed at rehabilitation of the learning of a discrete motor response. The chosen experimental context is cerebellar classical conditioning of the eye-blink response. The programmable system is based on the intimate mixing of switched capacitor analog techniques with low speed digital computation; power saving innovations within this framework are presented. The utility of the system is demonstrated by the implementation of a motor classical conditioning model applied to eye-blink conditioning in real time with associated neural signal processing. Paired conditioned and unconditioned stimuli were repeatedly presented to an anesthetized rat and recordings were taken simultaneously from two precerebellar nuclei. These paired stimuli were detected in real time from this multichannel data. This resulted in the acquisition of a trigger for a well-timed conditioned eye-blink response, and repetition of unpaired trials constructed from the same data led to the extinction of the conditioned response trigger, compatible with natural cerebellar learning in awake animals.