Structure and flexibility in cortical representations of odour space

The cortex organizes sensory information to enable discrimination and generalization1-4. As systematic representations of chemical odour space have not yet been described in the olfactory cortex, it remains unclear how odour relationships are encoded to place chemically distinct but similar odours, such as lemon and orange, into perceptual categories, such as citrus5-7. Here, by combining chemoinformatics and multiphoton imaging in the mouse, we show that both the piriform cortex and its sensory inputs from the olfactory bulb represent chemical odour relationships through correlated patterns of activity. However, cortical odour codes differ from those in the bulb: cortex more strongly clusters together representations for related odours, selectively rewrites pairwise odour relationships, and better matches odour perception. The bulb-to-cortex transformation depends on the associative network originating within the piriform cortex, and can be reshaped by passive odour experience. Thus, cortex actively builds a structured representation of chemical odour space that highlights odour relationships; this representation is similar across individuals but remains plastic, suggesting a means through which the olfactory system can assign related odour cues to common and yet personalized percepts

Examination of targeted, activity-dependent spinal stimulation in a rat model of spinal cord injury

Thesis (Master's)--University of Washington, 2023Spinal cord injuries (SCIs) cause debilitating motor and sensory impairments that can significantly impact patients’ quality of life. Although an estimated 300,000 people in the United States are living with a spinal cord injury, there are few available treatments for chronic injuries beyond physical and occupational therapy. Even after injury, the spinal cord has an innate ability for plasticity that can promote spontaneous recovery and be harnessed with therapeutic interventions to improve functional outcomes for patients. Previous work has shown that targeted, activity-dependent electrical stimulation of the spine in an animal model improves functional outcomes greater than open-loop electrical stimulation or physical retraining alone. However, the mechanism by which this targeted stimulation works and whether it is promoting plasticity in particular descending pathways remains unclear. We hypothesized that this therapy paradigm targets descending cortical projections to the spinal cord and that electrophysiological recordings of the motor cortex and anatomical tracing of this corticospinal tract would reveal changes after injury and with therapy. Unfortunately, we were unable to answer these questions, but new knowledge of technical limitations will hopefully provide a baseline for future pursuance of this research