Evidence and implications of abnormal predictive coding in dementia

Abstract

The diversity of cognitive deficits and neuropathological processes associated with dementias has encouraged divergence in pathophysiological explanations of disease. Here, we review an alternative framework that emphasises convergent critical features of cognitive pathophysiology. Rather than the loss of “memory centres” or “language centres”, or singular neurotransmitter systems, cognitive deficits are interpreted in terms of aberrant predictive coding in hierarchical neural networks. This builds on advances in normative accounts of brain function, specifically the Bayesian integration of beliefs and sensory evidence in which hierarchical predictions and prediction errors underlie memory, perception, speech and behaviour. We describe how analogous impairments in predictive coding in parallel neurocognitive systems can generate diverse clinical phenomena, including the characteristics of dementias. The review presents evidence from behavioural and neurophysiological studies of perception, language, memory and decision-making. The re-formulation of cognitive deficits in terms of predictive coding has several advantages. It brings diverse clinical phenomena into a common framework; it aligns cognitive and movement disorders; and it makes specific predictions on cognitive physiology that support translational and experimental medicine studies. The insights into complex human cognitive disorders from the predictive coding framework may therefore also inform future therapeutic strategies.

Noradrenergic deficits contribute to apathy in Parkinson’s disease through the precision of expected outcomes

“…However, we cannot comment directly on the exact algorithmic underpinnings of Bayesian perceptual inference in our experiment [ 105 ]. Following hierarchical models of predictive coding, one could decompose behaviour in our experiment into predictions at multiple levels of abstraction, from low-level proprioceptive predictions for movement to high-level multi-modal, domain-general beliefs [ 46 , 106 – 111 ]. Future work is needed to address how such a framework can accommodate the various stages of information processing that are thought to be involved in effort- and reward-based decision-making [ 112 – 114 ], including the weighting of action policies [ 13 , 15 , 53 ], initiating and sustaining an action [ 115 ], and evaluating and learning from the action outcomes.…”

Causal Evidence for the Multiple Demand Network in Change Detection: Auditory Mismatch Magnetoencephalography across Focal Neurodegenerative Diseases

“…The detection of sensory regularities is a fundamental neurocognitive process across the lifespan. However, the ability to detect a change or deviation from such regularities changes with age ( De Kerangal et al, 2021 ), and in many neurologic and psychiatric disorders ( Kocagoncu et al, 2020 ). This impaired ability to recognize and adapt to unexpected events and environmental changes is proposed to be a core feature of dementia ( Goto et al, 2014 ; Lee et al, 2016 ), but its behavioral assessment is complicated by more general dementia-related impairments, such as problems with working memory and concentration.…”

Neurophysiological consequences of synapse loss in progressive supranuclear palsy

“…We probed the cortical circuits using responses evoked in the roving auditory mismatch paradigm. Such tasks and change detection paradigms have been used to study many forms of dementia, ageing and other neurological diseases [51][52][53][54] . This paradigm reliably evokes signals in temporal, parietal and frontal regions 55 .…”