Yuri Imaizumi’s research while affiliated with University of Tsukuba and other places

Inhibitory interneurons are fundamental constituents of cortical circuits that process information to shape economic behaviors. However, the role of inhibitory interneurons in this process remains elusive at the core cortical reward-region, orbitofrontal cortex (OFC). Here, we show that presumed parvalbumin-containing GABAergic interneurons (fast-spiking neurons, FSNs) cooperate with presumed regular-spiking pyramidal neurons (RSNs) during economic-values computation. While monkeys perceived a visual lottery for probability and magnitude of rewards, identified FSNs occupied a small subset of OFC neurons (12%) with high-frequency firing-rates and wide dynamic-ranges, both are key intrinsic cellular characteristics to regulate cortical computation. We found that FSNs showed higher sensitivity to the probability and magnitude of rewards than RSNs. Unambiguously, both neural populations signaled expected values (i.e., probability times magnitude), but FSNs processed these reward's information strongly governed by the dynamic range. Thus, cooperative information processing between FSNs and RSNs provides a common cortical framework for computing economic values.

Neural dynamics reflect canonical computations that relay and transform information in the brain. Previous studies have identified the neural population dynamics in many individual brain regions as a trajectory geometry in a low-dimensional neural space. However, whether these populations share particular geometric patterns across brain-wide neural populations remains unclear. Here, by mapping neural dynamics widely across temporal/frontal/limbic regions in the cortical and subcortical structures of monkeys, we show that 10 neural populations, including 2,500 neurons, propagate visual item information in a stochastic manner. We found that the visual inputs predominantly evoked rotational dynamics in the higher-order visual area, the TE and its downstream striatum tail, while curvy/straight dynamics appeared more frequently downstream in the orbitofrontal/hippocampal network. These geometric changes were not deterministic but rather stochastic according to their respective emergence rates. These results indicated that visual information propagates as a heterogeneous mixture of stochastic neural population signals in the brain.

Neural population dynamics provide a key computational framework for understanding information processing in the sensory, cognitive, and motor functions of the brain. They systematically depict complex neural population activity, dominated by strong temporal dynamics as trajectory geometry in a low-dimensional neural space. However, neural population dynamics are poorly related to the conventional analytical framework of single-neuron activity, the rate-coding regime that analyzes firing rate modulations using task parameters. To link the rate-coding and dynamic models, we developed a variant of state-space analysis in the regression subspace, which describes the temporal structures of neural modulations using continuous and categorical task parameters. In macaque monkeys, using two neural population datasets containing either of two standard task parameters, continuous and categorical, we revealed that neural modulation structures are reliably captured by these task parameters in the regression subspace as trajectory geometry in a lower dimension. Furthermore, we combined the classical optimal-stimulus response analysis (usually used in rate-coding analysis) with the dynamic model and found that the most prominent modulation dynamics in the lower dimension were derived from these optimal responses. Using those analyses, we successfully extracted geometries for both task parameters that formed a straight geometry, suggesting that their functional relevance is characterized as a unidimensional feature in their neural modulation dynamics. Collectively, our approach bridges neural modulation in the rate-coding model and the dynamic system, and provides researchers with a significant advantage in exploring the temporal structure of neural modulations for pre-existing datasets.

Research in the multidisciplinary field of neuroeconomics has mainly been driven by two influential theories regarding human economic choice: prospect theory, which describes decision-making under risk, and reinforcement learning theory, which describes learning for decision-making. We hypothesized that these two distinct theories guide decision-making in a comprehensive manner. Here, we propose and test a decision-making theory under uncertainty that combines these highly influential theories. Collecting many gambling decisions from laboratory monkeys allowed for reliable testing of our model and revealed a systematic violation of prospect theory's assumption that probability weighting is static. Using the same experimental paradigm in humans, substantial similarities between these species were uncovered by various econometric analyses of our dynamic prospect theory model, which incorporates decision-by-decision learning dynamics of prediction errors into static prospect theory. Our model provides a unified theoretical framework for exploring a neurobiological model of economic choice in human and nonhuman primates.