The Department of Biomedicine

BBB seminar: Marianne Hafting Fyhn

The role of perineuronal nets in cortical plasticity and remote memory storage

Marianne Hafting Fyhn
Department of Biosciences and Centre for Integrative Neuroplasticity (CINPLA), University of Oslo

Compared to our knowledge of the molecular mechanisms underlying learning and memory encoding and consolidation, far less is known about remote memory storage. Recently, it was proposed that the specialized extracellular matrix structures called perineuronal nets (PNNs) may be a physical framework for long term memory storage. Their mesh like structure, tightly enwrapping and stabilizing synaptic connections and a composition of molecules with very slow turnover rates, point in this direction but remains to be tested. Moreover, the late postnatal appearance of the PNNs in the brain, overlapping with the closure of the period of heightened plasticity in the juvenile brain, further support a role for these structures to limit adult brain plasticity but how they affect information processing remains unknown.

In this seminar data will be presented, where, for the first time, we have investigated the role of PNNs in remote visual fear memories. Recent evidence indicates that over time, visual fear memories become dependent on the lateral part of the secondary visual cortex (V2L), suggesting that secondary sensory cortices may be pivotal in long term memory storage. Degrading the PNNs in V2L prior to the remote memory retrieval test selectively disrupted the visual fear memory. The findings were supported by simultaneous electrophysiological recordings from V2L and the basolateral amygdala, critical during learning of the task, during memory recall in animals with intact and abolished PNNs in the V2L. It will be shown that the PNNs may stabilize neural networks and perhaps limit cortical plasticity through modification of inhibition.

Chairperson: Clive R. Bramham <clive.bramham@uib.no>, Department of Biomedicine