William Spain M.D.
Professor, with Neurology
M.D. Columbia College of Physicians and Surgeons, 1977
Properties of Neocortex
What am I? Where am I? Who am I? Time, Space and Consciousness - the pursuit of science and the folly of art. A reminder lest we lose sight of the "big questions" in our daily labors on form and function. The lab? It deals with both of those issues (form and function). Will the results shed light on consciousness? Doubtful, but lets keep our minds open for possible connections. After tabling the quest for a complete understanding of consciousness, I have settled to the more pragmatic task of studying the mechanisms by which central neurons code information under normal conditions and how those processes are altered in neurological disease. To that end, my lab is identifying the rules for transducing synaptic input into frequency-coded trains of action potentials in neocortical neurons and brainstem auditory relay neurons. Because those neurons perform different functions, their transduction mechanisms contrast sharply. For example, the cortical Betz cells provide the primary motor output to brainstem and spinal cord. Cortical integrative processes converge on Betz cells; thus, they sit in a position critical for the summing of cortical commands prior to relay to lower centers. Accordingly, they are designed primarily as temporal integrators. In contrast, auditory relay neurons enable the coding of sound location via the difference in the time of arrival of sound at the two ears. The neurons preserve precise timing information by phase-locking to sound of a given frequency and by acting as coincidence detectors. Thus, the auditory relay neurons must (and indeed do) possess membrane properties that differ from the cortical neurons. By learning as much as possible about the different types of neuronal building blocks and their relation to one another, we are gaining insight into how the brain processes information.