The Shallow Cognitive Map Hypothesis: A Hippocampal framework for Thought Disorder in Schizophrenia

Abstract

Memories are not formed in isolation. They are associated and organized into relational knowledge structures that allow coherent thought. Failure to express such coherent thought is a key hallmark of Schizophrenia. Here we explore the hypothesis that thought disorder arises from disorganized Hippocampal cognitive maps. In doing so, we combine insights from two key lines of investigation, one concerning the neural signatures of cognitive mapping, and another that seeks to understand lower-level cellular mechanisms of cognition within a dynamical systems framework. Specifically, we propose that multiple distinct pathological pathways converge on the shallowing of Hippocampal attractors, giving rise to disorganized Hippocampal cognitive maps and driving thought disorder. We discuss the available evidence at the computational, behavioural, network and cellular levels. We also outline testable predictions from this framework including how it could unify major chemical and psychological theories of schizophrenia and how it can provide a rationale for understanding the aetiology and treatment of the disease.

Spatiotemporal Precision of Neuroimaging in Psychiatry

“…This finding is consistent with a theory of reduced synaptic gain in schizophrenia, which is thought to significantly impact synaptic plasticity and attractor dynamics within hippocampus (90)(91)(92). This points to a link between an observable cognitive process (impaired structural inference, possibly manifesting as incoherent thought) and a previously unobservable neurophysiological process (replay of an inferred cognitive map in hippocampus) that might guide prognosis, as well as pharmacological and therapeutic treatment (90).…”

“…After completing a task in which the temporal order of a stimulus sequence needs to be inferred, even though the "true" order is never experienced, patients with schizophrenia show weaker evidence for reorganisation of ordered state reactivation during rest compared with healthy controls, an effect that localises to hippocampus and corresponds with behaviour (78). This finding is consistent with a theory of reduced synaptic gain in schizophrenia, which is thought to significantly impact synaptic plasticity and attractor dynamics within hippocampus (90)(91)(92). This points to a link between an observable cognitive process (impaired structural inference, possibly manifesting as incoherent thought) and a previously unobservable neurophysiological process (replay of an inferred cognitive map in hippocampus) that might guide prognosis, as well as pharmacological and therapeutic treatment (90).…”

Cognitive impairment in schizophrenia: aetiology, pathophysiology, and treatment

“…At a higher level, a 'cognitive map' refers to the concept that accumulated knowledge and experiences are linked in an organised structure that allows for subsequent novel inferences. Disruption to the architecture of cognitive maps schizophrenia may potentially provide a framework to account for problems in executive functioning and general reasoning abilities [270]. A key consideration in terms of the inferential reasoning supported by a cognitive map is how easily separate memories can be linked: too high a barrier and no connections can be made; too low and entirely unrelated memories may be inappropriately linked.…”

“…Impairment in this process of memory linkage has recently been demonstrated in schizophrenia [271]. As inhibitory signalling is crucial for appropriate memory separation [272], disinhibition could promote the aberrant associations and working memory deficits that are evident in people with schizophrenia [270].…”

Thoughts falling apart: disorganized schizotypy specifically predicts both psychotic- and stress-reactivity in daily life

“…Relatedly, one may speculate about the mechanisms mediating the association. One possibility might be that disorganization captures the phenomenological aspects of inefficient top-down control by the prefrontal cortex (Thomas et al, 2021) and/or incoherent cognitive maps in the hippocampus (Musa et al, 2022). In individuals showing increased disorganization and related behavioral signs (i.e.…”