9422392 Ribak One of the parts of the brain important for learning in mammals is called the hippocampus, lying deep beneath the cererbral hemispheres. The hippocampus contains a curled formation called the dentate gyrus, which has three layers of nerve cells, or neurons. These neurons have characteristic shapes and some of their connections are known to form particular local circuits. The basket cells, granule cells, mossy cells and mossy fibers form circuits that are believed to underlie the functions of spatial learning. The postnatal development of the functional connections within these circuits are important to know if we are to understand the role of the hippocampus in early learning. This collaborative work by an electron microscopist and a neurophysiologist examines the ultrastructure of synapses (the functional cellular connections) between particular classes of neurons and the membrane properties of those neurons. Documenting changes in these structural and functional features during development will allow a better understanding of how the hippocampus begins to function during early learning. The results will be important not only for understanding brain development, but also for psychological studies on learning.
