The different faces of one's self: an fMRI study into the recognition of current and past self-facial appearances

Abstract

Mirror self-recognition is often considered as an index of self-awareness. Neuroimaging studies have identified a neural circuit specialised for the recognition of one's own current facial appearance. However, faces change considerably over a lifespan, highlighting the necessity for representations of one's face to continually be updated. We used fMRI to investigate the different neural circuits involved in the recognition of the childhood and current, adult, faces of one's self. Participants viewed images of either their own face as it currently looks morphed with the face of a familiar other or their childhood face morphed with the childhood face of the familiar other. Activity in areas which have a generalised selectivity for faces, including the inferior occipital gyrus, the superior parietal lobule and the inferior temporal gyrus, varied with the amount of current self in an image. Activity in areas involved in memory encoding and retrieval, including the hippocampus and the posterior cingulate gyrus, and areas involved in creating a sense of body ownership, including the temporo-parietal junction and the inferior parietal lobule, varied with the amount of childhood self in an image. We suggest that the recognition of one's own past or present face is underpinned by different cognitive processes in distinct neural circuits. Current self-recognition engages areas involved in perceptual face processing, whereas childhood self-recognition recruits networks involved in body ownership and memory processing.

Figure 1

Stimuli. Each stimulus was a morph that contained different percentages of the participants’ own face. There were two sets of morphs: one set were morphs between the participants’ current facial appearance and the appearance of a personally familiar other (a). The second set of morphs were between the participants’ childhood face and the childhood face of the same personally familiar other (b). Participants were presented with one morphed image on each trial, or a scrambled image. The morphed images in this figure are of two of the experimenters, used for illustrative purposes only.

Figure 2

Behavioural results. Percentage of “self” responses for each of the current and childhood stimuli. Error bars depict the between-subject standard error of the mean.

Figure 3

fMRI results. Current self: Activity shown in (a) the Superior Parietal Lobule (SPL) and (c) in the Inferior Occipital Gyrus (IOG) – putatively in the Occipital Face Area (OFA) - that varied with the amount of current self present in the morphed stimuli; activity in these regions did not vary with the amount of childhood self in the stimuli. Peristimulus time histogram (PSTH) plots of activity from the peak voxel in the SPL (b) and the IOG (d) time-locked to the stimuli containing current facial appearances. Childhood self: Activity shown in (e) the Hippocampus and (g) the Inferior Parietal Lobule (IPL) that varied with the amount of childhood self present in the morphed stimuli.; activity in these regions did not vary with the amount of current self in morphed stimuli. PSTH plots of activity from the peak voxel in the Hippocampus (f) and the IPL (h) time-locked to the stimuli containing childhood facial appearances. Conjunction: Activity shown in the Inferior Frontal Gyrus (IFG) (i) that varied with both the amount of childhood and current self in the morphed stimuli. PSTH plots of activity from the peak IFG voxel, time-locked to (j) the current stimuli and (k) the childhood stimuli. The current and childhood self data in the PSTHs are plots of activity evoked by the stimuli containing 100% and 80% “self”, and the current and childhood other data are plots of the activity evoked by the stimuli containing 0% and 20% “self”.