Research lines

  • The neural circuitry of expectation during decision making tasks

    In this project, funded by the European Research Council (ERC-2015-CoG - 683209_PRIORS), we aim to characterize the neural basis of expectation, an instrumental aspect of perception, and its impact on perceptual decisions. In particular, we investigate which areas of the brain process previous experiences to generate predictive biases, which are the algorithms used in this computation and how these algorithms could be implemented by neuronal circuits. We are interested in the extent to which the representation of the sensory environment is modulated by expectation and in particular whether stimulus-evoked neural responses in early sensory areas are affected but expectation signals or by the previous history of stimuli, choices and rewards. To this end, we train rats in two-alternative forced task (2AFC) in which the weight and direction of expectation priors together with the ambiguity of an auditory stimulus are systematically manipulated. We characterize the impact of these priors on behavior while simultaneously record the spiking activity of neurons in the auditory cortex, prefrontal areas and the striatum. We also use pharmacological and optogenetic experiments to determine the role of different brain areas in the various aspects of the task. We combine our experiments with statistical models to quantitatively describe both the behavior and the activity of neural populations. The project is done in collaboration with Alex Hyafil (CRM, Barcelona) and David Robbe (INMED, Marseille).

  • The dynamics of sensory evidence integration during perceptual decision making

    During perceptual discrimination task sensory information must be transformed into decision evidence and then temporally integrated in order to yield choices. We are interested in several aspects of this process: what causes the trial-to-trial response variability ubiquitous to this kind of tasks? Is the neural variability found in sensory areas introducing variability (i.e. noise) in the decision process? does the behavioral variability instead mainly reflects the dynamics of latent variables yet to be characterized? How are prior expectations integrated with the stimulus evidence? How can we design a biophysically realistic model that carries out the integration and categorization of evidence? To answer these questions we perform psychophysical experiments in humans and rodents and combined them with the analysis of latent variable dynamic models (e.g. diffusion models) as well as biophysically-inspired neural network models. We also perform electrophysiology recordings during the perceptual task which allow us to characterize the circuit mechanisms underlying the integration process. In particular we are interested in comparing categorization dynamics (such as those obtained using attractor models) with other standard models such as the drift diffusion model. Moreover, we aim to extend this type of models with urgency dynamics and experimentally determine the factors that modulate these urgency signals. Finally we are also interested in the interaction between the process of decision evidence integration and the planning and execution of the motor response (is there a bidirectional interaction? are the two processes carried out in separate circuits? ). The project is done in collaboration with Alex Roxin (CRM, Barcelona), Klaus Wimmer (CRM, Barcelona), Alex Hyafil (CRM, Barcelona) and Tobias Donner (Univ. of Hamburg).

  • The neural circuitry of Working Memory (WM): memory interference and disease-mediated deficits

    Working memory is the cognitive function describing the maintenance and processing of information in the brain during brief periods of time. The brain areas involved in this function and the underlying circuit mechanisms are still not entirely understood. In this project we aim to characterize the neural circuit dynamics underlying simple WM tasks carried out by mice. We investigate the factors that can limit the accuracy of WM: can previously stored memoranda interfere with the current content of WM? Is this interaction a bug or a feature? Can the accuracy of WM only decrease with the delay duration (e.g. diffusion ) or there can be other temporal dependencies (e.g. when retrieval occurs at unexpected times)? To what extent is the maintenance of memories decoupled from future motor plans? To address these questions we have designed a 2AFC auditory delayed-response task and a parametric visuospatial WM task in mice. Animals performed the task in high throughput computer-controlled set-up that generate very large data sets. We then combine recordings during the task using wide-field Calcium imaging or electrophysiology with a fine statistical characterization of the behavior and its relation to neural activity. Finally, we investigate how WM is altered in a mouse model of anti-NMDAr encephalopathy in order to understand the role of NMDAr during WM and to mechanistically characterize the executive deficits observed in patients during the period of disease recovery. The project is done in collaboration with Albert Compte (IDIBAPS), Josep Dalmau (ICREA/IDIBAPS) and Pablo Jercog (IDIBAPS).