Sum of the Parts: Musings on the Function of the Hippocampo-Entorhinal System. NaK Group September 24, 2003. “Computational models of the hippocampal region: linking incremental and episodic memory”. MA Gluck, M Meeter and C.E. Myers TRENDS in Cognitive Sciences June 2003.
September 24, 2003
MA Gluck, M Meeter and C.E. Myers
TRENDS in Cognitive Sciences
JJ Chrobak, A Lorincz and G Buzsaki
Theta Waves cortex system”
Seen during exploration, sensory input, etc.
EC Layer II and III neurons fire in theta-modulated gamma freq, projecting to the dentate, CA3, CA1, and the subiculum
Dentate and CA1 neurons also independently fire theta-modulated gamma as they receive EC input
EC Layers V and IV are relatively quiet
Thought to allow EC neurons to alter synaptic connectivity in the hippo
Seen during consummatory behaviors, sitting quietly, etc.
EC Layers V and IV neurons fire 140-200 Hz as they receive sharp waves from the hippo (originating primarily in CA3)
This discharge coincides with neocortical activity (perirhinal and medial prefrontal cortexes)
EC Layers II and III do not increase their firing rates
Thought to allow hippo neurons to alter connectivity of neocortical neuronsTheta and Sharp Waves
“Novelty” (error)-detecting “reconstruction network” cortex system”
Neocortical patterns are primarily projected to the hippo via Layer III
The hippo reconstructs the neocortical template in order to optimize the pattern into temporal sequences
Layer II compares neocortical inputs and feedback inputs from the hippocampus
Primary input from the neocortex and Layer V-transformed output from the hippocampus is compared by Layer II
Layer II “calculates” error or novelty, and this is sent to the DG and CA3, where alterations (plasticity) occur in the CA3 network
If there is no novelty, then the hippocampus simply reproduces previously stored patterns
This will continue until the error is minimizedWorking Together: EC-Hippocampal Cooperation