How hardwired is the brain? Technological advances provide new insight into brain malleability and neurotransmission.

Any discussion of the impact of nutrition and environment on the brain is based on the premise that the brain is malleable, but just how malleable is this most complex of all organs? And to what extent does the term "malleability" extend beyond subtle functional changes into the realms of morphology and connectivity? Recent methodological advances have provided new insight into these issues and have revealed synapse populations that turn over at high rates and synaptic receptors that are continuously on the move. The unveiling of this unsuspected structural plasticity has prompted new research on a class of enzymes (matrix metalloproteinases) that regulate the physical constraints imposed by extracellular matrix molecules. The realization that the brain is more "softwired" than previously anticipated emphasizes the relevance of current endeavors to explore the impact of nutrition and exercise on brain function and structure.