@article {69611, title = {Sub-threshold neuronal activity and the dynamical regime of cerebral cortex.}, journal = {Nat Commun}, volume = {15}, year = {2024}, month = {2024 Sep 11}, pages = {7958}, abstract = {

Cortical neurons exhibit temporally irregular spiking patterns and heterogeneous firing rates. These features arise in model circuits operating in a {\textquoteright}fluctuation-driven regime{\textquoteright}, in which fluctuations in membrane potentials emerge from the network dynamics. However, it is still debated whether the cortex operates in such a regime. We evaluated the fluctuation-driven hypothesis by analyzing spiking and sub-threshold membrane potentials of neurons in the frontal cortex of mice performing a decision-making task. We showed that while standard fluctuation-driven models successfully account for spiking statistics, they fall short in capturing the heterogeneity in sub-threshold activity. This limitation is an inevitable outcome of bombarding single-compartment neurons with a large number of pre-synaptic inputs, thereby clamping the voltage of all neurons to more or less the same average voltage. To address this, we effectively incorporated dendritic morphology into the standard models. Inclusion of dendritic morphology in the neuronal models increased neuronal selectivity and reduced error trials, suggesting a functional role for dendrites during decision-making. Our work suggests that, during decision-making, cortical neurons in high-order cortical areas operate in a fluctuation-driven regime.

}, keywords = {Action Potentials, Animals, Cerebral Cortex, Decision Making, Dendrites, Frontal Lobe, Male, Membrane Potentials, Mice, Mice, Inbred C57BL, Models, Neurological, Neurons}, issn = {2041-1723}, doi = {10.1038/s41467-024-51390-x}, url = {https://doi.org/10.1038/s41467-024-51390-x}, author = {Amsalem, Oren and Inagaki, Hidehiko and Yu, Jianing and Svoboda, Karel and Darshan, Ran} } @article {68786, title = {Distributing task-related neural activity across a cortical network through task-independent connections.}, journal = {Nature Communications}, volume = {14}, year = {2023}, month = {2023 May 18}, pages = {2851}, abstract = {

Task-related neural activity is widespread across populations of neurons during goal-directed behaviors. However, little is known about the synaptic reorganization and circuit mechanisms that lead to broad activity changes. Here we trained a subset of neurons in a spiking network with strong synaptic interactions to reproduce the activity of neurons in the motor cortex during a decision-making task. Task-related activity, resembling the neural data, emerged across the network, even in the untrained neurons. Analysis of trained networks showed that strong untrained synapses, which were independent of the task and determined the dynamical state of the network, mediated the spread of task-related activity. Optogenetic perturbations suggest that the motor cortex is strongly-coupled, supporting the applicability of the mechanism to cortical networks. Our results reveal a cortical mechanism that facilitates distributed representations of task-variables by spreading the activity from a subset of plastic neurons to the entire network through task-independent strong synapses.

}, keywords = {Action Potentials, Models, Neurological, Neurons, Synapses}, issn = {2041-1723}, doi = {10.1038/s41467-023-38529-y}, author = {Kim, Christopher M and Finkelstein, Arseny and Chow, Carson C and Svoboda, Karel and Darshan, Ran} } @article {49449, title = {Idiosyncratic choice bias in decision tasks naturally emerges from neuronal network dynamics.}, journal = {Nature Human Behavior}, volume = {3}, year = {2019}, month = {2019 Sep 02}, pages = {1190-1202}, abstract = {

Idiosyncratic tendency to choose one alternative over others in the absence of an identified reason, is a common observation in two-alternative forced-choice experiments. It is tempting to account for it as resulting from the (unknown) participant-specific history and thus treat it as a measurement noise. Indeed, idiosyncratic choice biases are typically considered as nuisance. Care is taken to account for them by adding an ad-hoc bias parameter or by counterbalancing the choices to average them out. Here we quantify idiosyncratic choice biases in a perceptual discrimination task and a motor task. We report substantial and significant biases in both cases. Then, we present theoretical evidence that even in idealized experiments, in which the settings are symmetric, idiosyncratic choice bias is expected to emerge from the dynamics of competing neuronal networks. We thus argue that idiosyncratic choice bias reflects the microscopic dynamics of choice and therefore is virtually inevitable in any comparison or decision task.

}, doi = {10.1101/284877}, author = {Lebovich, Lior and Darshan, Ran and Lavi, Yoni and Hansel, David and Loewenstein, Yonatan} } @article {49448, title = {Strength of correlations in strongly recurrent neuronal networks.}, journal = {Physical Review X}, year = {2018}, month = {2018 Sep 17}, pages = {031072}, abstract = {

Spatiotemporal correlations in brain activity are functionally important and have been implicated in perception, learning and plasticity, exploratory behavior, and various aspects of cognition. Neurons in the cerebral cortex are strongly interacting. Their activity is temporally irregular and can exhibit substantial correlations. However, how the collective dynamics of highly recurrent and strongly interacting neurons can evolve into a state in which the activity of individual cells is highly irregular yet macroscopically correlated is an open question. Here, we develop a general theory that relates the strength of pairwise correlations to the anatomical features of networks of strongly coupled neurons. To this end, we investigate networks of binary units. When interactions are strong, the activity is irregular in a large region of parameter space. We find that despite the strong interactions, the correlations are generally very weak. Nevertheless, we identify architectural features, which if present, give rise to strong correlations without destroying the irregularity of the activity. For networks with such features, we determine how correlations scale with the network size and the number of connections. Our work shows the mechanism by which strong correlations can be consistent with highly irregular activity, two hallmarks of neuronal dynamics in the central nervous system.

}, doi = {10.1103/PhysRevX.8.031072}, author = {Darshan, Ran and van Vreeswijk, Carl and Hansel, David} } @article {49003, title = {A canonical neural mechanism for behavioral variability.}, journal = {Nature Communications}, volume = {8}, year = {2017}, month = {2017 May 22}, pages = {15415}, abstract = {

The ability to generate variable movements is essential for learning and adjusting complex behaviours. This variability has been linked to the temporal irregularity of neuronal activity in the central nervous system. However, how neuronal irregularity actually translates into behavioural variability is unclear. Here we combine modelling, electrophysiological and behavioural studies to address this issue. We demonstrate that a model circuit comprising topographically organized and strongly recurrent neural networks can autonomously generate irregular motor behaviours. Simultaneous recordings of neurons in singing finches reveal that neural correlations increase across the circuit driving song variability, in agreement with the model predictions. Analysing behavioural data, we find remarkable similarities in the babbling statistics of 5-6-month-old human infants and juveniles from three songbird species and show that our model naturally accounts for these {\textquoteright}universal{\textquoteright} statistics.

}, issn = {2041-1723}, doi = {10.1038/ncomms15415}, author = {Darshan, Ran and Wood, William E and Peters, Susan and Leblois, Arthur and Hansel, David} } @inbook {49450, title = {Basal ganglia: songbird models}, booktitle = {Encyclopedia of Computational Neuroscience}, year = {2015}, pages = {356-61}, abstract = {

Songbirds produce complex vocalizations, a behavior that depends on the ability of juveniles to imitate the song of an adult. Song learning relies on a specialized basal ganglia-thalamocortical loop. Several computational models have examined the role of this circuit in song learning, shedding light on the neurobiological mechanisms underlying sensorimotor learning.

}, author = {Leblois, Arthur and Darshan, Ran} } @article {49004, title = {Interference and shaping in sensorimotor adaptations with rewards.}, journal = {PLoS Computational B2014-01-09iology}, volume = {10}, year = {2014}, month = {2014 Jan}, pages = {e1003377}, abstract = {

When a perturbation is applied in a sensorimotor transformation task, subjects can adapt and maintain performance by either relying on sensory feedback, or, in the absence of such feedback, on information provided by rewards. For example, in a classical rotation task where movement endpoints must be rotated to reach a fixed target, human subjects can successfully adapt their reaching movements solely on the basis of binary rewards, although this proves much more difficult than with visual feedback. Here, we investigate such a reward-driven sensorimotor adaptation process in a minimal computational model of the task. The key assumption of the model is that synaptic plasticity is gated by the reward. We study how the learning dynamics depend on the target size, the movement variability, the rotation angle and the number of targets. We show that when the movement is perturbed for multiple targets, the adaptation process for the different targets can interfere destructively or constructively depending on the similarities between the sensory stimuli (the targets) and the overlap in their neuronal representations. Destructive interferences can result in a drastic slowdown of the adaptation. As a result of interference, the time to adapt varies non-linearly with the number of targets. Our analysis shows that these interferences are weaker if the reward varies smoothly with the subject{\textquoteright}s performance instead of being binary. We demonstrate how shaping the reward or shaping the task can accelerate the adaptation dramatically by reducing the destructive interferences. We argue that experimentally investigating the dynamics of reward-driven sensorimotor adaptation for more than one sensory stimulus can shed light on the underlying learning rules.

}, keywords = {Adaptation, Physiological, Algorithms, Biomechanical Phenomena, Brain, Computational Biology, Computer Simulation, Feedback, Sensory, Humans, Learning, Models, Neurological, Movement, Neuronal Plasticity, Neurons, Psychomotor Performance, Reproducibility of Results, Reward, Rotation, Synapses}, issn = {1553-7358}, doi = {10.1371/journal.pcbi.1003377}, author = {Darshan, Ran and Leblois, Arthur and Hansel, David} }