Papers by kimberly obando
Neuron
Flexible decision-making requires animals to forego immediate rewards (exploitation) and try nove... more Flexible decision-making requires animals to forego immediate rewards (exploitation) and try novel choice options (exploration) to discover if they are preferable to familiar alternatives. Using the same task and a partially observable Markov decision process (POMDP) model to quantify the value of choices, we first determined that the computational basis for managing explore-exploit tradeoffs is conserved across monkeys and humans. We then used fMRI to identify where in the human brain the immediate value of exploitative choices and relative uncertainty about the value of exploratory choices were encoded. Consistent with prior neurophysiological evidence in monkeys, we observed divergent encoding of reward value and uncertainty in prefrontal and parietal regions, including frontopolar cortex, and parallel encoding of these computations in motivational regions including the amygdala, ventral striatum, and orbitofrontal cortex. These results clarify the interplay between prefrontal and motivational circuits that supports adaptive explore-exploit decisions in humans and nonhuman primates.
SummaryHumans and other animals often make the difficult decision to try new options (exploration... more SummaryHumans and other animals often make the difficult decision to try new options (exploration) and forego immediate rewards (exploitation). Novelty-seeking is an adaptive solution to this explore-exploit dilemma, but our understanding of the neural computations supporting novelty-seeking in humans is limited. Here, we presented the same explore-exploit decision making task to monkeys and humans and found evidence that the computational basis for novelty-seeking is conserved across primate species. Critically, through computational model-based decomposition of event-related functional magnetic resonance imaging (fMRI) in humans, these findings reveal a previously unidentified cortico-subcortical architecture mediating explore-exploit behavior in humans.
Journal of Neurotrauma, 2021
Apathy is a common and impairing sequela of traumatic brain injury (TBI). Yet, little is known ab... more Apathy is a common and impairing sequela of traumatic brain injury (TBI). Yet, little is known about the neural mechanisms determining which patients do or do not develop apathy post-TBI. Here we aimed to elucidate the impact of TBI on motivational neural circuits, and how this shapes apathy over the course of TBI recovery. Resting-state functional magnetic resonance imaging (rsfMRI) data were collected in patients with subacute mild TBI (N=44), chronic mild-to-moderate TBI (N=26), and non-brain-injured control participants (CTRL; N=28). We measured ventromedial prefrontal cortex (vmPFC) functional connectivity (FC) as a function of apathy, using an a priori vmPFC seed adopted from a motivated decision making study in an independent TBI study cohort. Patients reported apathy using a well-validated tool for assaying apathy in TBI. vmPFC-to-wholebrain FC was contrasted between groups, and we fit regression models with apathy predicting vmPFC FC. Subacute and chronic TBI caused increased apathy relative to CTRL, replicating prior work suggesting that apathy has an enduring impact in TBI. vmPFC was functionally connected to the canonical default network, and this architecture did not differ between subacute TBI, chronic TBI, and CTRL groups. Critically, in TBI, increased apathy scores predicted decreased vmPFC-dorsal anterior cingulate cortex (dACC) FC. Lastly, we subdivided the TBI group based on patients above versus below the threshold for "clinically-significant apathy," finding that TBI patients with clinically-significant apathy demonstrated comparable vmPFC-dACC FC to CTRLs, whereas TBI patients with subthreshold apathy scores demonstrated vmPFC-dACC hyperconnectivity relative to both CTRLs and patients with clinically-significant apathy. Post-TBI vmPFC-dACC hyperconnectivity may represents an adaptive compensatory response, helping to maintain motivation and enabling resilience to the development of apathy after neurotrauma. Given the role of vmPFC-dACC circuits in value-based decision making, rehabilitation strategies designed to improve this ability may help to reduce apathy and improve functional outcomes in TBI.
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Papers by kimberly obando