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Our Research Publications

Below is a selection of our previous publications and media coverage.
Full list of our publications is available on Google Scholar, ORCID, and ResearchGate.

Previous Work
Postdoctoral
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Abstract
Decision-making requires flexibility to rapidly switch one’s actions in response to sensory stimuli depending on information stored in memory. We identified cortical areas and neural activity patterns underlying this flexibility during virtual navigation, where mice switched navigation toward or away from a visual cue depending on its match to a remembered cue. Optogenetics screening identified V1, posterior parietal cortex (PPC), and retrosplenial cortex (RSC) as necessary for accurate decisions. Calcium imaging revealed neurons that can mediate rapid navigation switches by encoding a mixture of a current and remembered visual cue. These mixed selectivity neurons emerged through task learning and predicted the mouse’s choices by forming efficient population codes before correct, but not incorrect, choices. They were distributed across posterior cortex, even V1, and were densest in RSC and sparsest in PPC. We propose flexibility in navigation decisions arises from neurons that mix visual and memory information within a visual-parietal-retrosplenial network.

Predoctoral
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Abstract
Decision-making requires flexibility to rapidly switch one’s actions in response to sensory stimuli depending on information stored in memory. We identified cortical areas and neural activity patterns underlying this flexibility during virtual navigation, where mice switched navigation toward or away from a visual cue depending on its match to a remembered cue. Optogenetics screening identified V1, posterior parietal cortex (PPC), and retrosplenial cortex (RSC) as necessary for accurate decisions. Calcium imaging revealed neurons that can mediate rapid navigation switches by encoding a mixture of a current and remembered visual cue. These mixed selectivity neurons emerged through task learning and predicted the mouse’s choices by forming efficient population codes before correct, but not incorrect, choices. They were distributed across posterior cortex, even V1, and were densest in RSC and sparsest in PPC. We propose flexibility in navigation decisions arises from neurons that mix visual and memory information within a visual-parietal-retrosplenial network.

Mind Reading from a Single Neuron! (Audio recommended)
Example trial with neural recording from a parietal neuron. After the monkey’s eye position (yellow dot) fixates on the central white dot, two red choice targets appear, with the left target in the neuron’s Response Field. Shapes appear sequentially until the monkey initiates a saccade. Action potentials are indicated by audible clicks and tick marks above the graph, which displays cumulative evidence associated with each new shape (white horizontal line segments).
In the 1st movie, the cumulative evidence initially fluctuates around zero, then shifts toward the left target, reflected by increased neural firing as the monkey selects Tin. In the 2nd movie, the cumulative evidence initially favored the left target but then reversed to favor the right target. Reflecting this pattern, the firing rate increased initially but then diminished until the monkey chose the right target.

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Abstract

Many decisions benefit from the accumulation of evidence obtained sequentially over time. In such circumstances, the decision-maker must balance speed against accuracy, while considering the cost associated with the passage of time. A neural mechanism to achieve this balance is to accumulate evidence and to terminate the deliberation when enough evidence has accrued. To accommodate time costs, it has been hypothesized that the criterion to terminate a decision may become lax as a function of time. Here we tested this hypothesis by manipulating the cost of time in a perceptual choice–reaction time (RT) task. Human participants (both sexes) discriminated the direction of motion in a dynamic random-dot display, which varied in difficulty across trials. Unbeknownst to the participants, halfway through the experiment, we increased the time pressure by canceling a small fraction of trials, mimicking a broken fixation, if they had not made a decision by a provisional deadline. This subtle manipulation led participants to make faster but less accurate decisions. Choice and RT were well explained by a bounded evidence-accumulation process. We developed a novel computational method to estimate the time-dependent changes in the stopping bounds directly from the participants’ RT and choice data. Our analysis revealed that the bounds decline as a function of time, and that this decline is steeper following the time–cost manipulation. The time-varying decision bounds approximate an optimal stopping policy, although the specific bound shape is idiosyncratic across individuals.

Dissertation

Department of Psychology

Florida State University

1107 W Call Street, Tallahassee, FL 32306-4301

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