Neurons (nerve cells) communicate through a process in which one cell stimulates another with an electric pulse transmitted by secreting special chemicals called neurotransmitters into the synapse (gap) between the cells. Learning and memory are influenced by changes in the strength of these synaptic connections and by alterations in the excitability of neurons (how readily they produce an electrochemical response). Abnormalities in the regulation of neuronal excitability give rise to neurological diseases including epilepsy and psychiatric diseases such as schizophrenia. Dr. Brian MacVicar is studying two aspects of synaptic transmission: mechanisms that regulate neuronal excitability and mechanisms that influence synaptic plasticity (the ability of neurons to adapt the way they communicate with each other). In one series of experiments, he is examining cells that surround neurons in the brain to determine if they influence neuronal activity through the regulation of blood flow or other mechanisms. He is also studying how past synaptic experience modifies activity in dendrites, the part of the neuron that receives synaptic transmissions. This research into how brain activity is regulated will contribute to improved understanding of many aspects of neuroscience, including stroke, mental illness and learning and memory.