Functional cognitive disorders: update on diagnostic status

Towards a neural network hypothesis for functional cognitive disorders: an extension of the Overfitted Brain Hypothesis

Introduction: Whilst the empirical understanding of functional cognitive disorders (FCD) has advanced in recent years, theoretical and conceptual models have evolved more slowly. Existing frameworks for FCD are based on models of other functional neurological disorders or of metacognitive processes and are recognised to lack mechanistic precision.Methods: In this article, a novel application to FCD of Hoel's Overfitted Brain Hypothesis of the evolved function of dreaming is attempted.Results: This posits that the empirically observed sleep disturbance in FCD entails impaired dreaming which causes the brain to be overfitted and hence unable to generalise appropriately, producing mismatch between memory expectations and memory performance.Conclusions: This formulation of FCD is based on considerations derived from the study of neural networks and shares commonalities with Bayesian models of functional neurological disorders. Additionally, it has implications for future hypothesis-driven research in FCD and suggests a pragmatic basis for management strategies.

Functional Cognitive Disorders (FCD): How Is Metacognition Involved?

Functional cognitive disorders (FCD) have become a subject of increasing clinical interest in recent years, in part because of their high prevalence amongst patients attending dedicated memory clinics. Empirical understanding of FCD based on observational studies is growing, suggesting a relationship to other functional neurological disorders (FND) based on shared phenomenology. However, understanding of FCD at the theoretical level has been lacking. One suggestion has been that FCD are disorders of metacognition, most usually of metamemory. In this article, a brief overview of these constructs is presented along with existing evidence for their impairment in FCD. Previous adaptations of theoretical models of FND to accommodate FCD are reviewed. A novel application to FCD of Nelson and Narens’ monitoring and control model of metamemory is then attempted, positing an improper setting of the monitoring function, with examples of ecological relevance. Formulation of FCD in light of a metacognitive model of anosognosia is also considered. Although lacking mechanistic and neuroanatomical sophistication, this metacognitive formulation of FCD may give pointers for future hypothesis-driven research and a pragmatic basis for management strategies.

Michael Faraday's "loss of memory" revisited

In the mid-1970s, the psychiatrist Edward Hare published two accounts of Michael Faraday's memory symptoms, based upon which he suggested the diagnostic possibilities of an amnesic syndrome related to a transient ischemic attack in the vertebrobasilar cerebrovascular system. This article revisits the contemporary evidence of Faraday's letters and the notes of his physician, Peter Mere Latham, and considers subsequent responses to and shortcomings of Hare's analysis. In light of more recent conceptualizations of memory disorders, a new formulation for Faraday's memory symptoms is suggested: namely, that he manifested a functional cognitive disorder.