Conference Agenda

Self-recognition is possible from minimal kinematic cues. We have recently identified frontoparietal nodes of the Action Observation Network (AON) preferentially engaged by minimal kinematic cues from actions of the self (Kadambi et al., 2025). Here, we investigate whether this ability to infer self-identity from movement relates to motor imagery ability—an index of motor simulation—and its corresponding neural basis. Using multivariate decoding and functional localizer analyses, we examined self-recognition performance across core nodes of the AON (Inferior Parietal Lobules, IPL; Inferior Frontal Gyri, IFG; Extrastriate Body Area, EBA; Superior Temporal Sulci, STS) and measured their relationships with motor imagery ability. Self-specific decoding emerged in the IFG and IPL, while the EBA decoded between all identities (self, friend, stranger). The IPL and EBA were functionally connected during self-recognition and their decoding accuracy was associated with motor imagery. These findings suggest a relationship between motor imagery and self-action recognition, at least for minimal kinematic cues, that emerges from interactions between IPL and EBA, expanding our understanding of cortical systems relevant to both.

Introduction: Episodic memory retrieval is often accompanied by autonoetic consciousness (ANC) — the vivid feeling of mentally re-experiencing past events. However, the neural mechanisms underlying this phenomenological experience are still poorly understood. The hippocampus is central to memory retrieval, coordinating the reactivation of cortical regions which were involved during event encoding. Such reinstatement effects have been shown to take place in sensory cortices (auditory, visual) but the specific role of motor inputs in ANC remains unknown. In the present study we investigated whether motor signals and their cortical representation, generated by movements at encoding, are reinstated at retrieval and whether this contributes to ANC.

Methods: 54 participants encoded real-life-like events in a 3D immersive mixed reality environment, performing motor actions. The following day participants came back and were asked to freely retrieved each of these events while their brain (study 1, n=30, fMRI), or muscle (study 2, n=24, EMG) activity was being recorded.

Results: We observed memory-related activations in regions such as the hippocampus, parahippocampus, and critically, the motor cortex. Additionally, activity in motor areas was linked to the intensity of participants’ re-experiencing of events. We also showed that hippocampus to motor cortex functional connectivity was enhanced during free retrieval. Finally, we observed motor reinstatement at the peripheral level, with EMG ongoing activity of a muscle being higher during retrieval of episodes which engaged that particular muscle at encoding.

Conclusion: This study underscores the role of motor context in the phenomenology of ANC, highlighting the enacted nature of memory retrieval.

As a 2-dimensional system, the skin shows certain analogies with the external environment. Both contain boundaries and landmarks, and both can be navigated. We here tested whether the brain mechanisms known to encode our trajectories in external space, i.e. grid-cells, can also encode the trajectory of a stimulus travelling across the skin.

In this fMRI experiment, the experimenter drew lines on the back of the participants' hands (n=29). We then looked for the BOLD signature characteristic of grid cells (Doeller et al 2008). We initially found no grid cells in the entorhinal cortex, the region typically showing grid cell activity during spatial navigation. However, tactile perception is known to exhibit distortions related to the oval shape of tactile receptive fields (Longo & Haggard 2011), a property known as tactile distance anisotropy. After distorting the stimulation space according to each individual’s level of tactile anisotropy, measured in a separate task, we found the characteristic signature of grid cells in the entorhinal cortex. In the somatosensory cortex, we also observed the signature of grid cells for the anisotropic space, as well as for the original non-deformed stimulation space but less robustly.

These results demonstrate that the cognitive mechanisms used for encoding external space are also used for encoding skin space, a space that is directly experienced from the inside, here navigated by an external agent. This grid code is constrained by the properties of the tactile system, suggesting that it corresponds to a sensory grid code.

Inferences about the neural bases of subjective experience often rely on reports that participants express whilst performing a task. However, different studies suggest that reports bias such inferences, contaminating the neural correlates of consciousness. More recently, no-report paradigms have been developed but the involvement of attention in such tasks remains unknown.

Here, 32 adults were presented with 60 EEG frequency-tagging sequences composed of various images presented at 6 Hz and all degraded to a supraliminal contrast. In these sequences, male or female faces were also tagged at the specific frequency of 1.2 Hz. Concurrently, participants were asked to detect the color change of a fixation cross on the images to monitor their attention. At the end of each sequence, participants were instructed to estimate the subjective visibility of the faces (using the Perceptual Awareness Scale - PAS), to categorise their gender (measure of objective visibility), and to assess their confidence in this categorisation (measure of metacognition).

Mixed-effect models revealed that the signal-to-noise ratio (SNR) at the face frequency increased linearly with PAS and confidence. Conversely, the SNR at the image frequency reflecting attentional processes only increased with confidence. This was confirmed by the concurrent attentional task where performance only increased with confidence, but not with PAS.

Overall, this data shows that frequency-tagging is sensitive to subjective experience in the absence of reports during the sequence presentation. They also suggest that attentional processes are less involved in subjective visibility than in metacognition.

Cyclic variations of baroreceptor activity (BRA) across the cardiac (systole/ diastole) and respiratory (inhalation/ exhalation) can modulate cortical excitability and so influence perceptual awareness.

To determine how these bodily signals modulate awareness-related brain activity, we presented visual stimuli at the discrimination threshold and compared ERPs and their intracranial sources when subjects correctly identified the stimuli with and without awareness as a function of the cardiac and respiratory phases. The earliest marker of awareness was the P1 (90-120 ms) for low BRA (diastole/ inhalation) and the VAN (250-350 ms) for high BRA (systole/ exhalation). Moreover, activity spread from the primary visceral cortex (posterior insula) to parietal cortices during high and from associative interoceptive centers (anterior insula) to the prefrontal cortex during low BRA indicating that bodily signals modulate the pathway to awareness.

Respiration can affect awareness both directly through the entrainment of cortical activity by the mechanical stimulation of the olfactory bulb (OB) and indirectly through respiratory sinus arrythmia, which is partly modulated by BRA. To determine the mechanism underlying the influence of respiratory phase on awareness, we repeated the experiment during oral breathing when OB stimulation is greatly reduced, and BRA is preserved. Here, the P1 component was not modulated by awareness, but the P3a was obtained when BRA is low indicating an interaction between OB stimulation and BRA: only when both OB stimulation is present and BRA is low, the P1 the earliest ERP component modulated by awareness, revealing a complex interplay between bodily signals and awareness-related brain activity.