In her research to understand the basis of behavioral learning, Sascha du Lac exemplifies the modern systems neuroscientist.
Behavioral learning is an intricate process that requires the signaling circuitry among neurons to form the new pathways that etch memories in the brain. To learn new motor skills, for example, humans and other mammals need to detect errors in motor performance and modify subsequent movements to reduce or eliminate mistakes. This is why repetition is as essential for the violinist performing a concerto as it is for the gymnast executing a triple somersault.
Du Lac has designed a bold and daring research plan to understand the cellular and molecular changes that underpin a specific type of learning: how the brain learns to stabilize an image on the retina and compensate for head movement. This is called the vestibular-ocular reflex or VOR, and it's what enables the gymnast to nail that triple somersault while maintaining a perfect sense of where the ground is in relation to her body.
In studies of mice, du Lac is analyzing how "motor memories" are maintained in the neural circuitry that subserves the VOR. Her studies have concentrated on cells called flocculus target neurons (FTNs), which are located in the brainstem and lie downstream of the output cells of the cerebellum, called Purkinje cells. How and why FTNs are critical in maintaining motor memories have yet to be determined.
To advance these studies, du Lac has developed transgenic mice with fluorescent marker genes that enable identification of Purkinje cells and FTNs. By studying the electrophysiological properties of these cells, she is discovering how those properties enable learning-related plasticity. She also conducts eye-movement studies in normal and genetically altered mice to explore the cellular mechanisms of VOR.
In future work, du Lac plans to manipulate molecular and genetic components of the eye-movement circuitry in specific populations of neurons, to test their roles in learning and memory storage. She is also planning molecular studies to understand how connections among neurons change during neural plasticity. And, by manipulating the activity of specific subsets of neurons with inserted transgenes, she hopes to unravel the cellular mechanisms that transform experience into adaptive changes in performance.
Scientists who are knowledgeable about her research view du Lac as poised to make the links across levels of analysis to provide a plausible explanation, in terms of molecules, cells, and circuits, for one form of behavioral learning.
