My senior project studies the effects of impaired long-term depression on cerebellar learning. The cerebellum is a brain structure present in mammals, at the back of the brain, and is thought to be heavily involved in motor learning and coordination.
Previous work has shown that the cerebellum is critical for two reflexes: the vestibulo-ocular and optokinetic reflexes. The optokinetic reflex (OKR) is the tendency of the eyes to follow objects moving in the visual field. The vestibulo-ocular reflex (VOR) is eye movement in the opposite direction of head motion. For example, rotating the head horizontally to the left results in compensating eye movements moving the eyes to the right, so that the eyes remain fixed on a single point. Try it! Place your finger in front of your face, and rotate your head to the left while fixing your gaze on your finger. Your eyes have to rotate in the direction opposite of head motion so that your gaze remains fixed on the same point.
Aside from encoding these reflexes, the cerebellum can help us learn to change these reflexes in certain ways. We try to increase the vestibulo-ocular reflex, so that the eye moves more in the direction opposite to its head motion. This is measured by a really cool setup featuring a sensor above the eye and a magnet placed beneath the conjunctiva of the eye. The magnet moves with the eye, and the sensor on the top of the head head detects the changes in magnetic fields as a result of the movement. Thus, we can track the eye movements in response to various stimuli.
The cerebellum learns primarily through the process of long-term depression (the opposite of long-term potentiation). Learning occurs in the cerebellar cortex, and connections that produce errors in movements are depressed (hence, long-term depression), leaving only the connections that produce desired movements. My project studies how impairing this learning process — LTD, that is — affects behavioral performance, that is, the speed of learning.