Abstract
Spatial navigation involves neural computations in distributed regions of the brain. Little is known about how activity across cortical regions is coordinated when animals navigate novel spatial environments or how that coordination changes as environments become familiar. We recorded mesoscale calcium (Ca2+) dynamics across large swathes of the dorsal cortex in male mice solving the Barnes maze, a 2D spatial navigation task where mice used random, serial, and spatial search strategies to navigate to the goal. Cortical dynamics exhibited patterns of repeated calcium activity with rapid and abrupt shifts between cortical activation patterns at sub-second time scales. When mice used serial or spatial search strategies to navigate to the goal, the frontal regions of the cortex were reliably activated for prolonged durations of time (> 1s) shortly after trial initiation. These frontal cortex activation events coincided with mice approaching the edge of the maze from the center and were preceded by temporal sequences of cortical activation patterns that were distinct for serial and spatial search strategies. In serial search trials, frontal cortex activation events were preceded by activation of the posterior regions of the cortex followed by lateral activation of one hemisphere. In spatial search trials, frontal cortical events were preceded by activation of posterior regions of the cortex followed by broad activation of the lateral regions of the cortex. Our results suggest that different sequences of cortical state activations precede goal-directed navigation in spatial versus serial strategies, with exploratory analysis identifying state 3 as potentially important in spatial search.
Significance statement
Spatial navigation involves neural computations in many brain regions. Little is known about how activity across cortical regions is coordinated across different brain regions. Using a miniaturized microscope, we imaged neural activity from most of the cortical surface in freely moving mice as they navigated a maze. Mice placed at the center of a well-lit environment try to find an escape goal along the edge of the maze. Initially, subjects search randomly, but with experience, they learn to go directly to the goal. We found that mesoscale cortical activity dynamics were different for different navigation strategies used by the mice, indicating distinct sets of brain-wide circuits are engaged based on the behavioral strategies used to solve the maze.