Catching the imposter in the brain: The case of Capgras delusion

The misidentification syndromes and source memory deficits with their neuroanatomical correlates from neuropsychological perspective

The suggested model is discussed with reference to two clinical populations with memory disorders - patients with misidentification syndromes and those with source memory impairment, both of whom may present with (broadly conceived) déjà vu phenomenon, without insight into false feeling of familiarity. The role of the anterior thalamic nucleus and retrosplenial cortex for autobiographical memory and familiarity is highlighted.

Transforming Social Perspectives with Cognitive Maps

Growing evidence suggests that cognitive maps represent relations between social knowledge similar to how spatial locations are represented in an environment. Notably, the extant human medial temporal lobe literature assumes associations between social stimuli follow a linear associative mapping from an egocentric viewpoint to a cognitive map. Yet, this form of associative social memory doesn't account for a core phenomenon of social interactions in which social knowledge learned via comparisons to the self, other individuals, or social networks are assimilated within a single frame of reference. We argue that hippocampal-entorhinal coordinate transformations, known to integrate egocentric and allocentric spatial cues, inform social perspective switching between the self and others. We present evidence that the hippocampal formation helps inform social interactions by relating self versus other social attribute comparisons to society in general, which can afford rapid and flexible assimilation of knowledge about the relationship between the self and social networks of varying proximities. We conclude by discussing the ramifications of cognitive maps in aiding this social perspective transformation process in states of health and disease.

What is Capgras delusion?

INTRODUCTION

Capgras delusion is sometimes defined as believing that close relatives have been replaced by strangers. But such replacement beliefs also occur in response to encountering an acquaintance, or the voice of a familiar person, or a pet, or some personal possession. All five scenarios involve believing something familiar has been replaced by something unfamiliar.

METHODS

We evaluate the proposal that these five kinds of delusional belief should count as subtypes of the same delusion.

RESULTS

Personally familiar stimuli activate the sympathetic nervous system (SNS) much more strongly than unfamiliar stimuli. In Capgras delusion, this difference is absent, prompting the delusional idea that a familiar person is actually a stranger. We suggest this absence of an effect of familiarity on SNS response will occur in all five scenarios and will prompt the idea that the familiar has been replaced by the unfamiliar.

CONCLUSIONS

We propose that: (a) all five scenarios be referred to as subtypes of Capgras delusion; (b) in all five, ideas about replacement are prompted by weakness of SNS responses to familiar stimuli; (c) this is insufficient to generate delusion. For a delusional idea to become a belief, a second factor (impaired hypothesis evaluation) must also be present.

Anatomical and neurophysiological basis of face recognition

Face recognition is a highly developed and efficient human function that involves multiple neural networks. A main pathway links the occipital cortex, where an occipital face area (OFA) has been identified, to a fusiform face area (FFA) in the fusiform gyrus, which plays a critical role in face recognition. This core pathway deals with invariant aspects of the face. Another pathway, including the superior temporal sulcus, is involved in the perception of more changeable aspects of the face such as gaze orientation, face expression and lip movements. It has been defined by some authors as a "third pathway of visual recognition", i.e. a lateral pathway in addition to the "what" and "where" pathways. It deals with sociocognitive aspects of face perception. Many other accessory functional systems are connected to the core system of visual recognition to act in concert with it: the intraparietal sulcus (for the management of spatial attention), the primary auditory cortex (prelexical perception of speech), the amygdala, the insula and the limbic system (perception of emotions), the anterior temporal pole (access to the identity of the individual, his name, biographical information), etc. Functional brain imaging has made remarkable progress in the understanding of face perception, which in the early years was limited to the description of single cases of brain-damaged patients. This progress has made it possible to better analyse the many face recognition disorders, sometimes subtle, other times confusing, observed in human pathology.

Clinical Lycanthropy, Neurobiology, Culture: A Systematic Review

Background: Culture can affect psychiatric disorders. Clinical Lycanthropy is a rare syndrome, described since Antiquity, within which the patient has the delusional belief of turning into a wolf. Little is known on its clinical or therapeutic correlates. Methods: We conducted a systematic review (PRISMA) on PubMed and Google Scholar, until January 2021. Case reports, data on neurobiological hypotheses, and cultural aspects were included. Language was not restricted to English. Results: Forty-three cases of clinical lycanthropy and kynanthropy (delusion of dog transformation) were identified. Associated diagnoses were: schizophrenia, psychotic depression, bipolar disorder, and other psychotic disorders. Antipsychotic medication may be an efficient treatment for this rare transnosographic syndrome. In case of depression or mania, the treatment included antidepressants or mood regulators. The neuroscientific hypotheses include the conception of clinical lycanthropy as a cenesthopathy, as a delusional misidentification of the self-syndrome, as impairments of sensory integration, as impairments of the belief evaluation system, and right hemisphere anomalies. Interestingly, there is a clinical overlap between clinical lycanthropy and other delusional misidentification syndromes. Clinical lycanthropy may be a culture-bound syndrome that happens in the context of Western cultures, myths, and stories on werewolves, and today's exposure to these narratives on cultural media such as the internet and the series. We suggest the necessity of a cultural approach for these patients' clinical assessment, and a narrative and patient-centered care. Conclusions: Psychiatric transtheoretical reflections are needed for complementaristic neurobiological and cultural approaches of complex delusional syndromes such as clinical lycanthropy. Future research should include integrative frameworks.