Welcome to the IBRO 2023 Interactive Programme

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Short-term memory is central to cognition, allowing behavior to be decoupled from the immediate world. In this talk, I will discuss the neural dynamics that support short-term memory. Using large-scale recordings in monkeys and mice, we have found short-term memory representations are distributed across the brain. Short-term memory involves the interactions of multiple brain regions, including sensory and associative areas. Furthermore, the neural representation of the content of short-term memory changes over time, moving between different ‘subspaces’ of the neural population. These dynamics may play a critical role in sustaining memory representations and protecting them from interference from new sensory inputs.

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Neural mechanisms for flexible decision-making at single-cell and neuronal circuit levels

Yanhe Liu, Yuan Zhang, Yu Xin, Jie Du, Jingwei Pan and Ning-long Xu

Making flexible decisions in a dynamic environment is a powerful capacity of the mammalian brain. Despite decades of research at the behavioral and cognitive levels, the biological mechanisms implementing computations underlying flexible decision-making remain largely unknown. Here we developed an inferece-based flexible decision-making task in mice and combined in vivo two-photon imaging, large-scale neurophysiological recording and circuit manipulations to investigate the computational mechanisms underlying flexible decision-making at both single-neuron and brain-wide circuit levels. Subcelullar dendritic imaging shows that dendritic and somatic compartments of projection-defined layer 5 pyramidal neurons in auditory cortex differentially represent sensory, choice and task-rule information, revealing a single-neuron computational mechanism for flexible decision-making. Cross-brain region circuit analyses show that the orbitofrontal-sensory cortical circuits implement a rule-inference algorithm to confer high flexibility in rule-switching decision-making behavior. Using brain-wide electrophysiology, we further show that the representations of key task variables are widely distributed across brain regions. Our findings provide new insights to the neuronal and circuit mechanisms implementing computations for flexible decision-making.

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The ability of the mammalian central nervous system to constantly adapt motor commands and optimise behaviour according to the context does not only rely on the efficient analysis of the incoming sensory flow. The cerebral cortex is indeed thought to compute, based on past experience, a dynamic model of our interactions with our environment, allowing to anticipate future sensory inputs. Sensory perception would therefore imply a continuous comparison of the expected sensory inputs with those actually received. The error signals generated in case of deviation between these two types of information would allow a readjustment of the current motor commands, as well as an update of the internal model, which is key to optimize future behaviour.

Several experimental studies invite us to think that cortical primary sensory areas, which receive both bottom up projections carrying sensory information from the periphery, and top-down projections from higher order and motor areas, are likely to play a key role in these predictive processes.

Because the sense of touch particularly relies on efficient sensorimotor integration, we use the tactile whisker system of mice as a model to try revealing signals linked to the prediction of sensory inputs (rather than the sensory inputs per se) in the primary somatosensory cortex of mice engaged in sensorimotor tasks by introducing deviances between expected and received sensory inputs.

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