The brain is smart enough to structurally stabilize neuronal networks shaped during learning, which is fundamental for long-term memory storage.
In the mature brain such stabilization is mediated by the so-called extracellular matrix (ECM) by enwrapping the synaptic contacts between neurons like a protective nutshell. Such stability might come with the costs of a lesser degree of freedom when it comes to life-long memory reformations and relearning processes.
In a recent study, researchers from the Leibniz Institute for Neurobiology in Magdeburg, tried to tackle this question. They trained adult Mongolian gerbils in a cognitively demanding auditory reversal learning task. The animals had to discriminate between two sound signals, which were associated with either escaping a foot shock by a compartment change in the test chamber or stay to avoid it. After animals performed the task well, i.e. acquired an established memory of the stimulus contingencies, those were reversed from one day to the other.
The researchers found that a local weakening of the structurally rigid ECM by injection of a degrading enzyme in auditory cortex of the gerbils specifically accelerated the strategy changes required for such reversal learning. Importantly, it neither affected general sensory learning nor erased already established, learned memory traces.
Thus, the flexible modulation of the ECM in the mature brain might promote the cognitive flexibility that can build on learned behaviors and allows for an enhanced activity-dependent memory re-formation. The study has further promising implications to develop new tools for guided neuroplasticity where the opened "window of opportunities"Â where increased brain rewiring could occur has therapeutic potential, for instance in stroke therapies, neuroprosthetic applications and others.