Researchers recently published a study in Proceedings of the National Academy of Sciences of the United States of America that found supplementation with vitamin D improved hippocampal-dependent learning and memory as well as hippocampal synaptic functioning in rats.
The hippocampus is a structure in the brain that plays important roles in converting short-term memory into long-term memory as well as in spatial memory and navigation. Humans have two hippocampi, one on each side of the brain.
Synapses are structures in the nervous system that allow a neuron to pass an electrical or chemical signal to another cell (neural or otherwise). It is widely accepted that synapses play a crucial role in the formation of memory.