In your phase: neural phase synchronisation underlies visual imagery of faces

Abstract

Mental imagery is the process through which we retrieve and recombine information from our memory to elicit the subjective impression of “seeing with the mind’s eye”. In the social domain, we imagine other individuals while recalling our encounters with them or modelling alternative social interactions in future. Many studies using imaging and neurophysiological techniques have shown several similarities in brain activity between visual imagery and visual perception, and have identified frontoparietal, occipital and temporal neural components of visual imagery. However, the neural connectivity between these regions during visual imagery of socially relevant stimuli has not been studied. Here we used electroencephalography to investigate neural connectivity and its dynamics between frontal, parietal, occipital and temporal electrodes during visual imagery of faces. We found that voluntary visual imagery of faces is associated with long-range phase synchronisation in the gamma frequency range between frontoparietal electrode pairs and between occipitoparietal electrode pairs. In contrast, no effect of imagery was observed in the connectivity between occipitotemporal electrode pairs. Gamma range synchronisation between occipitoparietal electrode pairs predicted subjective ratings of the contour definition of imagined faces. Furthermore, we found that visual imagery of faces is associated with an increase of short-range frontal synchronisation in the theta frequency range, which temporally preceded the long-range increase in the gamma synchronisation. We speculate that the local frontal synchrony in the theta frequency range might be associated with an effortful top-down mnemonic reactivation of faces. In contrast, the long-range connectivity in the gamma frequency range along the fronto-parieto-occipital axis might be related to the endogenous binding and subjective clarity of facial visual features.

Towards a view from within: The contribution of Francisco Varela to the study of consciousness

“…However, the evidence still supports the claim that phase synchronisation may play an important role in neuronal communication between distant brain regions (Arnulfo et al, 2020;Misselhorn et al, 2019), which in turn may be necessary for selective attention (Doesburg et al, 2008;Rohenkohl et al, 2018) and visual integration (Uhlhaas et al, 2009). Recently, for instance, we found that the act of imagining faces is accompanied by long-range gammaband phase synchronisation (Figure 2), arguably due to visual binding of facial features (Canales-Johnson et al, 2021). Participants had to study different celebrities' faces prior to the task.…”

Neural and behavioural dynamics of the individual and collective self(s)

“…While they responded to sentences, reaction times and EEG activity were measured. EEG neural dynamics recorder was used to obtain ERPs and weighted symbolic mutual information (wSMI, in the way proposed by Canales-Johnson et al, 2020, 2021; Imperatori et al, 2019a; King et al, 2013). We predict that if they are independent of each other, Neural information (wSMI) would be greater for stimuli for the collective self vs. individual self.…”

Towards a view from within: The contribution of Francisco Varela to the study of consciousness

“…However, the evidence still supports the claim that phase synchronisation may play an important role in neural communication between distant brain regions (Arnulfo et al, 2020; Misselhorn et al, 2019), which in turn may be necessary for selective attention (Doesburg et al, 2008; Rohenkohl et al, 2018) and visual integration (Uhlhaas et al, 2009). Recently, for instance, we found that the act of imagining faces is accompanied by long-range gamma-band phase synchronisation (Figure 2), arguably due to visual binding of facial features (Canales-Johnson et al, 2021b). Participants had to study different celebrities’ faces prior to the task.…”