Valérian Chambon

Sense of agency

What is the sense of agency? The term ‘sense of agency’ refers to the experience of controlling ones own actions, and, through them, events in the outside world. Most of us have the feeling that we are in control of what we are doing most of the time: this is the normal sense of agency.

The role of configural information in facial emotion recognition in schizophrenia

The schizophrenia deficit in facial emotion recognition could be accounted for by a deficit in processing the configural information of the face. The present experiment was designed to further test this hypothesis by studying the face-inversion effect in a facial emotion recognition task. The ability of 26 schizophrenic patients and 26 control participants to recognize facial emotions on upright and upside-down faces was assessed. Participants were told to state whether faces expressed one of six possible emotions (happiness, anger, disgust, fear, sadness, neutrality) in two sessions, one with upright faces and the other with upside-down faces. Discriminability and the decision criterion were computed. The results indicated that the schizophrenic patients were impaired in upright facial emotion discrimination by comparison with the controls. They also exhibited an inversion effect similar to the controls. However, whereas controls tended to adopt a more conservative criterion for all emotions and a liberal criterion for neutrality when the faces were upside-down, schizophrenic patients presented a decision criterion pattern that was similar for the two orientations and similar to controls in upside-down emotion recognition. The lack of a decision criterion shift was associated with positive symptoms such as delusions, hallucinations, and bizarre behavior. Moreover, positive and negative symptoms were associated with inversion effect on discriminability; the more severe the symptoms, the weaker the inversion effect. We conclude that individuals with schizophrenia do process the configural information of the face. However, further investigations are needed to assert whether this information is of good quality in schizophrenia.

Priming of actions increases sense of control over unexpected outcomes

Sense of agency (SoA) refers to the feeling that we are in control of our own actions and, through them, events in the outside world. SoA depends partly on retrospectively matching outcomes to expectations, and partly on prospective processes occurring prior to action, notably action selection. To assess the relative contribution of these processes, we factorially varied subliminal priming of action selection and expectation of action outcomes. Both factors affected SoA, and there was also a significant interaction. Compatible action primes increased SoA more strongly for unexpected than expected outcomes. Outcome expectation had strong effects on SoA following incompatible action priming, but only weak effects following compatible action priming. Prospective and retrospective SoA may have distinct and complementary functions.

TMS stimulation over the inferior parietal cortex disrupts prospective sense of agency

Sense of agency refers to the feeling of controlling an external event through one’s own action. On one influential view, sense of agency is inferred after an action, by “retrospectively” comparing actual effects of actions against their intended effects. However, it has been recently shown that earlier processes, linked to action selection, may also contribute to sense of agency, in advance of the action itself, and independently of action effects. The inferior parietal cortex (IPC) may underpin this “prospective” contribution to agency, by monitoring signals relating to fluency of action selection in dorsolateral prefrontal cortex (DLPFC). Here, we combined transcranial stimulation (TMS) with subliminal priming of action selection to investigate the causal role of these regions in the prospective coding of agency. In a first experiment, we showed that TMS over left IPC at the time of action selection disrupts perceived control over subsequent effects of action. In a second experiment, we exploited the temporal specificity of single-pulse TMS to pinpoint the exact timing of IPC contribution to sense of agency. We replicated the reduction in perceived control at the point of action selection, while observing no effect of TMS-induced disruption of IPC at the time of action outcomes.

Changing ideas about others’ intentions: updating prior expectations tunes activity in the human motor system

Predicting intentions from observing another agent’s behaviours is often thought to depend on motor resonance – i.e., the motor system’s response to a perceived movement by the activation of its stored motor counterpart, but observers might also rely on prior expectations, especially when actions take place in perceptually uncertain situations. Here we assessed motor resonance during an action prediction task using transcranial magnetic stimulation to probe corticospinal excitability (CSE) and report that experimentally-induced updates in observers’ prior expectations modulate CSE when predictions are made under situations of perceptual uncertainty. We show that prior expectations are updated on the basis of both biomechanical and probabilistic prior information and that the magnitude of the CSE modulation observed across participants is explained by the magnitude of change in their prior expectations. These findings provide the first evidence that when observers predict others’ intentions, motor resonance mechanisms adapt to changes in their prior expectations. We propose that this adaptive adjustment might reflect a regulatory control mechanism that shares some similarities with that observed during action selection. Such a mechanism could help arbitrate the competition between biomechanical and probabilistic prior information when appropriate for prediction.

Focal versus distributed temporal cortex activity for speech sound category assignment

Significance When listening to speech, phonemes are represented in a distributed fashion in our temporal and prefrontal cortices. How these representations are selected in a phonemic decision context, and in particular whether distributed or focal neural information is required for explicit phoneme recognition, is unclear. We hypothesized that focal and early neural encoding of acoustic signals is sufficiently informative to access speech sound representations and permit phoneme recognition. We tested this hypothesis by combining a simple speech-phoneme categorization task with univariate and multivariate analyses of fMRI, magnetoencephalography, intracortical, and clinical data. We show that neural information available focally in the temporal cortex prior to decision-related neural activity is specific enough to account for human phonemic identification. Percepts and words can be decoded from distributed neural activity measures. However, the existence of widespread representations might conflict with the more classical notions of hierarchical processing and efficient coding, which are especially relevant in speech processing. Using fMRI and magnetoencephalography during syllable identification, we show that sensory and decisional activity colocalize to a restricted part of the posterior superior temporal gyrus (pSTG). Next, using intracortical recordings, we demonstrate that early and focal neural activity in this region distinguishes correct from incorrect decisions and can be machine-decoded to classify syllables. Crucially, significant machine decoding was possible from neuronal activity sampled across different regions of the temporal and frontal lobes, despite weak or absent sensory or decision-related responses. These findings show that speech-sound categorization relies on an efficient readout of focal pSTG neural activity, while more distributed activity patterns, although classifiable by machine learning, instead reflect collateral processes of sensory perception and decision.

Neural coding of prior expectations in hierarchical intention inference

The ability to infer other people’s intentions is crucial for successful human social interactions. Such inference relies on an adaptive interplay of sensory evidence and prior expectations. Crucially, this interplay would also depend on the type of intention inferred, i.e., on how abstract the intention is. However, what neural mechanisms adjust the interplay of prior and sensory evidence to the abstractness of the intention remains conjecture. We addressed this question in two separate fMRI experiments, which exploited action scenes depicting different types of intentions (Superordinate vs. Basic; Social vs. Non-social), and manipulated both prior and sensory evidence. We found that participants increasingly relied on priors as sensory evidence became scarcer. Activity in the medial prefrontal cortex (mPFC) reflected this interplay between the two sources of information. Moreover, the more abstract the intention to infer (Superordinate > Basic, Social > Non-Social), the greater the modulation of backward connectivity between the mPFC and the temporo-parietal junction (TPJ), resulting in an increased influence of priors over the intention inference. These results suggest a critical role for the fronto-parietal network in adjusting the relative weight of prior and sensory evidence during hierarchical intention inference.

The influence of prior reputation and reciprocity on dynamic trust-building in adults with and without autism spectrum disorder

The present study was designed to investigate the effects of reputational priors and direct reciprocity on the dynamics of trust building in adults with (N = 17) and without (N = 25) autism spectrum disorder (ASD) using a multi-round Trust Game (MTG). On each round, participants, who played as investors, were required to maximize their benefits by updating their prior expectations (the partners positive or negative reputation), based on the partners directed reciprocity, and adjusting their own investment decisions accordingly. Results showed that reputational priors strongly oriented the initial decision to trust, operationalized as the amount of investment the investor shares with the counterpart. However, while typically developed participants were mainly affected by the direct reciprocity, and rapidly adopted the optimal Tit-for-Tat strategy, participants with ASD continued to rely on reputational priors throughout the game, even when experience of the counterparts actual behavior contradicted their prior-based expectations. In participants with ASD, the effect of the reputational prior never disappeared, and affected judgments of trustworthiness and reciprocity of the partner even after completion of the game. Moreover, the weight of prior reputation positively correlated with the severity of the ASD participants social impairments while the reciprocity score negatively correlated with the severity of repetitive and stereotyped behaviors, as measured by the Autism Diagnostic Interview-Revised (ADI-R). In line with Bayesian theoretical accounts, the present findings indicate that individuals with ASD have difficulties encoding incoming social information and using it to revise and flexibly update prior social expectations, and that this deficit might severely hinder social learning and everyday life interactions.

Trading off the cost of conflict against expected rewards

Value-based decision-making involves trading off the cost associated with an action against its expected reward. Research has shown that both physical and mental effort constitute such subjective costs, biasing choices away from effortful actions, and discounting the value of obtained rewards. Facing conflicts between competing action alternatives is considered aversive, as recruiting cognitive control to overcome conflict is effortful. Yet, it remains unclear whether conflict is also perceived as a cost in value-based decisions. The present study investigated this question by embedding irrelevant distractors (flanker arrows) within a reversal-learning task, with intermixed free and instructed trials. Results showed that participants learned to adapt their choices to maximize rewards, but were nevertheless biased to follow the suggestions of irrelevant distractors. Thus, the perceived cost of being in conflict with an external suggestion could sometimes trump internal value representations. By adapting computational models of reinforcement learning, we assessed the influence of conflict at both the decision and learning stages. Modelling the decision showed that conflict was avoided when evidence for either action alternative was weak, demonstrating that the cost of conflict was traded off against expected rewards. During the learning phase, we found that learning rates were reduced in instructed, relative to free, choices. Learning rates were further reduced by conflict between an instruction and subjective action values, whereas learning was not robustly influenced by conflict between one’s actions and external distractors. Our results show that the subjective cost of conflict factors into value-based decision-making, and highlights that different types of conflict may have different effects on learning about action outcomes.

203 – How cognitive control is implemented in the prefrontal cortex of patients with schizophrenia

Background: Deficits of cognitive control (the ability to coordinate thoughts and actions in relation with internal goals) are incriminated to be at the core of the severe and multiple cognitive deficits observed in schizophrenia. The lateral prefrontal cortex was often cited to be responsible for these deficits. However, until now, researchers failed in identifying the precise functional architecture of schizophrenias cognitive control. Recently, Koechlin et al. showed that the lateral prefrontal cortex (LPFC) is organized as a cascade of executive processes, from premotor to anterior prefrontal areas, that control behavior according to distinct information: sensory information, contextual information (i.e. present perceptual context) and episodic information (i.e. temporal episode in which stimuli occur) respectively. This study aimed at determining which levels of cognitive control are specifically impaired and which prefrontal area is dysfunctional in schizophrenia. Methods: We used functional magnetic resonance imagery to investigate the cerebral correlates of the contextual and episodic controls in 15 schizophrenic patients and 14 control subjects. Results: In normal subjects, as expected, contextual control was only subserved by caudal LPFC, whereas episodic control was subserved by the rostral LPFC. In schizophrenic patients, although a significant increase of error rates compared to controls, the same pattern of prefrontal cortex activations was observed. However, controls recruited bilateral caudal LPFC to a significantly greater extent than patients when subjects had to control contextual information. Conclusions: Our study demonstrates that episodic and contextual controls are specifically impaired in schizophrenia. This impairment is specifically associated with a caudal LPFC dysfunction. These results allow a better understanding of the pathophysiology of some symptoms of schizophrenia.