The goal of research in the Sawtell laboratory is to forge detailed links between the properties of neural circuits and their functions. Our studies of weakly electric fish have shown how a specific form of synaptic plasticity operating within a well-characterized cerebellum-like circuit functions to predict and cancel out sensory inputs generated by the animal’s own behavior. Such a process could allow behaviorally relevant sensory inputs, e.g. those generated by predators or prey, to be processed more effectively. This work provides a mechanistic account of how copies of motor commands are transformed into specific predictions of sensory events as well as insights into the function of the cerebellar granular layer. A tight coordination of experimental and theoretical approaches is a key aspect of the lab’s approach. Experimental work involves intra- and extracellular recordings from identified neuron classes in awake, behaving fish. Theoretical work is performed in collaboration with Larry Abbott’s group at the Center for Theoretical Neuroscience at Columbia University.
Cerebellum-like circuits similar to those in electric fish are also present at the initial stage of mammalian auditory processing in a structure known as the dorsal cochlear nucleus. An additional goal of the lab is to test the hypothesis that the dorsal cochlear nucleus functions to predict and cancel self-generated sounds. Cerebellum-like circuits in fish and mammals provide a unique opportunity for a comparative study of neural circuit function because they evolved independently and exhibit both striking similarities and differences in their circuitry and cellular physiology. Future studies will also take advantage of powerful genetic tools available in mice for linking adaptive sensory processing in the dorsal cochlear nucleus to aspects of the underlying circuitry, including specific sites and mechanisms of synaptic plasticity and neuromodulation.
Intriguingly, several lines of evidence suggest that the cerebellum itself is involved in generating predictions of the sensory consequences of motor commands, similar to those described in electric fish. Such predictions may be important not only for sensory processing and perception but also for motor, emotional, and cognitive functions. A long-term goal of research in the Sawtell lab is to extend studies of sensory predictions in cerebellum-like structures to the cerebellum itself in both electric fish and mice. Weakly electric mormyrid fish may provide a unique opportunity in this regard because they possess a massively hypertrophied cerebellum, larger for their brain and body size than that found in any other vertebrate species.