Gating neuronal activity in the brain Cellular and network processing of propagating activity in the perirhinal–entorhinal cortex

The research described in this dissertation offers insight in how transmission of neuronal activity is regulated in the perirhinal-entorhinal cortex, a brain area involved in memory processing. The perirhinal-entorhinal cortex is anatomically separated into an input and output network via the superficial and deep layers, respectively. This separation promotes that cortical activity is transmitted through the PER-LEC superficial layers towards the hippocampus for further processing. Via the activation of deep layer inhibitory interneurons, the output pathway of the hippocampus is blocked when activity is transmitted towards the hippocampus.
It is known that emotion can modulate memory storage and retrieval, which increases the chances for survival. The amygdala, a structure involved in emotion, can modulate the transmission of activity through the perirhinal-entorhinal cortical network and herewith regulate memory formation. Although it has long been thought that synaptic input from the LA and cortex mainly interacted on the excitatory synaptic responses, we showed in this dissertation that modulation of inhibition probably plays a crucial role in the regulation of transmission by the amygdala. Co-activation of the amygdala induced prompter action potential firing of the inhibitory neurons, which probably ensures synchronization of firing of principal neurons. This synchronization caused by emotional modulation is suggested to ensure efficient and time-delimited information transmission to the projection areas.