Barzykowski and Moulin (B&M) provide us with an overview of two related processes and provide significant detail of the psychological mechanisms. While the authors touch on the underlying neural correlates (e.g., cortical midline structures, medial-temporal), more detail as to the proximate brain mechanisms would further convince readers of their claims. Further, but not addressed here, the authors leave the readers wanting a deeper evolutionary, ultimate perspective and we look forward to papers that address evolutionary, comparative, and genetic examinations of these two memory phenomena.

As elucidated by B&M, oddities of human cognition often provide significant insight into the mechanistic functions of the brain, which in turn provides knowledge about the phenomena themselves. Both involuntary autobiographical memories (IAMs) and déjà vu are two such examples. IAMs are spontaneously recalled without conscious effort (Berntsen, Reference Berntsen2021), are often triggered by elements of the environment that correspond to a previous event (Berntsen, Reference Berntsen2009), and are typically unpleasant, and as such, they are one of the main symptoms of posttraumatic stress disorder (PTSD). B&M note that IAMs are a feature of normal functioning cognitive processes, and it is the frequency and intensity (rather than their existence) that warrants a PTSD diagnosis (Rasmussen & Berntsen, Reference Rasmussen and Berntsen2011). In contrast to IAMs, déjà vu is categorized as any erroneous subjective perception that a currently experienced event is similar to an indeterminate past occurrence (Sno & Linszen, Reference Sno and Linszen1990). Episodes of déjà vu originate from a memory error that is often influenced by feelings of fluency and familiarity, thus affecting memory retrieval (Illman, Butler, Souchay, & Moulin, Reference Illman, Butler, Souchay and Moulin2012).

However, the authors may wish to consider a bigger role for “the self” in these processes, as evidence from neuroscience guides us to think higher order “meta” processes may distinguish these memory deviations. Metacognition, as defined here, refers to the capacity to keep track of and regulate one's own cognitive processes (Fleur, Bredeweg, & van den Bos, Reference Fleur, Bredeweg and van den Bos2021). The link between déjà vu and the sensation of foreboding may be explained by the metacognitive bias initiated by the experience itself (Cleary & Claxton, Reference Cleary and Claxton2018). In brief, IAMs typically have a reduction of metacognitive processes when compared to déjà vu which involves a sense of seeing oneself as an agent in the experience. We derive this notion from neurological studies in both normals and patients.

In terms of neural correlates, IAMs typically activate the left angular gyrus, posterior midline, visual cortex, hippocampus, and parahippocampal cortex (Berntsen, Reference Berntsen2021). Contrary to IAMs, the medial prefrontal cortex is engaged during déjà vu. As a further distinction between IAMs and déjà vu, and likely more important in terms of the behavioral differences, the right hemisphere appears active during bouts of déjà vu (Vlasov, Chervyakov, & Gnezditskii, Reference Vlasov, Chervyakov and Gnezditskii2013). The right frontal cortex and temporal parietal junction are active in normals during tasks that involve self-awareness (Morita et al., Reference Morita, Saito, Ban, Shimada, Okamoto, Kosaka and Naito2018) and disruption of the right hemisphere disrupts self-awareness (Keenan, Nelson, O'Connor, & Pascual-Leone, Reference Keenan, Nelson, O'Connor and Pascual-Leone2001).

Déjà vu is but one of many perturbations that involves the right frontal/temporal regions and the self. While déjà vu involves a brief narrative clip, significant neural damage can lead to truly devastating disorders. The occurrence of hallucinations in which a location has been duplicated, or exists in two different places, is known as reduplicative paramnesia, which is a rare illness seen in neurological patients (Borghesani, Monti, Fortis, & Miceli, Reference Borghesani, Monti, Fortis and Miceli2019). An example of reduplicative paramnesia involved a 70-year-old woman, who presented to her local emergency room, and was found to have a right temporal meningioma. In the days prior to her craniotomy, she had been able to recount “her two houses.” She was aware she owned an apartment in Rome, yet in the previous month, her single apartment had “become” two interchangeable homes, with identical floors, addresses, and furniture (Gerace & Blundo, Reference Gerace and Blundo2013). Capgras syndrome, also referred to as the delusion of doubles, is defined by the patient's mistaken conviction that an exact duplicate has taken the place of a person of significance (Shah, Jain, & Wadhwa, Reference Shah, Jain and Wadhwa2022). Within the disorder, the delusion typically involves the afflicted person assuming their close friend or relative has disappeared. The impersonator remains without name and identity, and is viewed pejoratively (Barrelle & Luauté, Reference Barrelle and Luauté2018). Fregoli syndrome is defined as the irrational mistaken identification of known individuals posing as others, as well as unfamiliar strangers and/or casual acquaintances identified as a different but known individual (Langdon, Connaughton, & Coltheart, Reference Langdon, Connaughton and Coltheart2014). The disorder has frequently been linked to Capgras syndrome in the past; however, the two have distinct defining features (Mojtabai, Reference Mojtabai1994).

There are numerous other, similar disorders of misidentification of self and other (Feinberg & Keenan, Reference Feinberg and Keenan2005). We believe, like B&M, the distinction between IAMs and déjà vu provide insights into human cognition that reach beyond the phenomena themselves. Here we hope to have elucidated a number of proximate reasons for such a distinction. However, we believe that the role of the self may play a larger role than posited by B&M. Neuroimaging demonstrates that déjà vu activates regions associated with self-awareness and we believe this is one of the cases where neuroscience can help to clarify a psychological debate.