Talk abstracts > Philippe Domenech (ICM, Paris)

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Philippe Domenech - ICM, Paris

Friday, June 2^nd

Talk Session 3: Electrophysiology of decision-making

10h30 - 11h

 Exploring the cortico-subcortical dynamic of task switching with human intracranial EEG

The ability to strategically switch between rules in response to changing environmental demands critically depend on the dorsomedial prefrontal cortex (dmPFC) and the basal ganglia. However, the precise neural implementations of such higher-order cognitive control processes, as well as its tempo-frequential dynamic, remain unclear. I will discuss key results from two studies reporting on local field potential recordings in patients performing variants of a task-switching paradigm. In a first study, we recorded the hyperdirect medio-prefrontal-subthalamic pathway in the dmPFC (in drug-resistant epileptic patients) and in the subthalamic nucleus (STN; in drug-resistant OCD patients). We fitted a hierarchical drift-diffusion model to patients’ choice behavior and found that task-switching was associated with a shift in the starting point of evidence accumulation (z), effectively disentangling rule switches from the selection of the new response. At the neural level, we found that theta band (5-10 Hz) activity increased first in the dmPFC and then in the STN during task switching. Furthermore, dmPFC also encoded preemptively the likelihood of switch in the beta band. An initially counter-intuitive finding was that temporally delayed and excessive levels of theta activity led to premature responding and switching errors. However, using a hierarchical neural drift diffusion model provided a mechanistic explanation of these observations, as trial-by-trial fluctuations in theta power negatively correlated with the subjects’ starting point parameter. In a second study, we recorded local field potentials in a large group of drug-resistant epileptic patients (n=26) performing a variant of the task-switching task that specifically disentangled rule switch from response remapping. We confirmed in this independent sample the specific role of increased dmPFC theta activity for switching between rules and characterized a prefrontal network whose theta activity reflected rule switches, such as the orbito-frontal cortex that anticipated successful switches or the anterior-dorsal insula and the inferior operculum. Together, these findings illustrate a versatile mechanism through which dmPFC can rapidly activate the STN, earlier in the decision process than previously thought, to overcome pre-established choices and allow time for flexible task-set reconfiguration, by shaping prefrontal theta dynamic.