An evolutionary theory of schizophrenia: Cortical connectivity, metarepresentation, and the social brain

Abstract

Schizophrenia is a worldwide, prevalent disorder with a multifactorial but highly genetic aetiology. A constant prevalence rate in the face of reduced fecundity has caused some to argue that an evolutionary advantage exists in unaffected relatives. Here, I critique this adaptationist approach, and review – and find wanting – Crow's “speciation” hypothesis. In keeping with available biological and psychological evidence, I propose an alternative theory of the origins of this disorder. Schizophrenia is a disorder of the social brain, and it exists as a costly trade-off in the evolution of complex social cognition. Paleoanthropological and comparative primate research suggests that hominids evolved complex cortical interconnectivity (in particular, frontotemporal and frontoparietal circuits) to regulate social cognition and the intellectual demands of group living. I suggest that the ontogenetic mechanism underlying this cerebral adaptation was sequential hypermorphosis and that it rendered the hominid brain vulnerable to genetic and environmental insults. I argue that changes in genes regulating the timing of neurodevelopment occurred prior to the migration of Homo sapiens out of Africa 100,000–150,000 years ago, giving rise to the schizotypal spectrum. While some individuals within this spectrum may have exhibited unusual creativity and iconoclasm, this phenotype was not necessarily adaptive in reproductive terms. However, because the disorder shared a common genetic basis with the evolving circuitry of the social brain, it persisted. Thus schizophrenia emerged as a costly trade-off in the evolution of complex social cognition.

Extrapolating brain development from experimental species to humans

“…the faster a species lived, the faster it would die. But although life span is not unrelated to metabolism (Economos, 1981), the rate of living theory remains controversial (Burns, 2004) and is generally discounted (Lints, 1989). …”

A Probabilistic Framework to Infer Brain Functional Connectivity from Anatomical Connections

“…Recently, it has been suggested that consciousness depends on the brain's ability to integrate information among different thalamo-cortical areas [8]. Disruption in cortical connectivity has been also implicated in a number of disorders and pathologies, such as schizophrenia [3], autism [21], brain trauma [23] and so on. As a result there is a shift of research attention from localised brain function to network organization and dynamics.…”

Using SDRT to Analyze Pathological Conversations: Logicality, Rationality, and Pragmatic Deviances

“…Since some schizophrenic disorders are likely to be accounted for by explanations of an evolutionary nature, at least as far as language [10], reasoning [8,9], and social behavior [5] are concerned, we can expect that the study of such pathological interactions will tell us something about the rationality of the cognitive processes listed above. Indeed, the manifestation of the disorder during interactions and the need to maintain the link cause the schizophrenic interlocutor to adopt a compensatory management strategy.…”