Biol Psychiatry
May 25, 2018
Philipp Sterzer, Rick A. Adams, Paul Fletcher et al.
901 citations
Psychosis may stem from altered predictive coding in the brain, where prior beliefs are combined with sensory signals to interpret the world. The canonical account suggests that weakened prior beliefs relative to sensory data lead to maladaptive inferences. However, evidence is mixed: some studies find weakened priors, others stronger priors. Hallucinations and delusions may involve distinct predictive coding alterations. Challenges include non-uniform deficits across sensory modalities, hierarchical processing where lower and higher levels interact non-linearly, and the role of active inference—anticipating how actions affect sensations. Considering these complexities could reconcile conflicting findings and yield a more comprehensive framework for psychosis.
Frontiers in Human Neuroscience
December 22, 2016
Philipp Sterzer, Aaron Mishara, Martin Voss et al.
78 citations
Thought insertion in schizophrenia may arise from altered Bayesian inference within the predictive coding framework. Early 20th-century phenomenological accounts by the Heidelberg School described thought insertion as a self-disturbance involving disrupted inner connectedness of thoughts, which become sensory and feel inserted. Mescaline was used as a model psychosis to explore these mechanisms. The authors propose that reduced precision of context-dependent predictions, relative to sensory precision, increases prediction-error signals for internal events like thoughts. This aberrant salience, analogous to that proposed for external events, leads individuals to interpret thoughts as inserted by an alien agent, similar to delusion formation from aberrant sensory salience.
Schizophrenia Bulletin
July 21, 2023
Predrag Petrović, Philipp Sterzer
42 citations
Delusions in psychotic disorders are hard to reconcile with the predictive processing (PP) framework, which suggests psychosis involves reduced weighting of prior beliefs relative to sensory data—yet delusions are highly resistant to change. This paradox can be resolved by a hierarchical PP model: reduced weighting of low-level priors may be compensated by increased influence of higher-order beliefs, including delusional beliefs, which then shape perception and resist contradictory evidence. A review of experimental evidence supports decreased weighting of low-level priors and increased weighting of high-level priors in both delusional and delusion-prone individuals. The prefrontal cortex is highlighted as a neural basis for this increased weighting of high-level priors, with clinical implications discussed.
Frontiers in Psychology
April 8, 2021
Heiner Stuke, Elisabeth Kress, Veith Weilnhammer et al.
41 citations
People with stronger tendencies toward hallucinations and delusions are more likely to perceive faces in visual noise and to detect invisible direct gaze, supporting the theory that psychosis involves overweighing high-level prior expectations over sensory evidence. In 39 healthy individuals varying in psychosis proneness, the tendency to see faces in noise correlated with hallucination proneness (r = 0.50) and delusion proneness (r = 0.46). The tendency to detect invisible direct gaze also correlated with hallucination proneness (r = 0.43) but not conclusively with delusion proneness. These findings suggest that overly strong priors for socially meaningful stimuli may represent an early processing alteration in psychosis.
Brain : a journal of neurology
May 13, 2025
Veith Weilnhammer, Marcus Rothkirch, Deniz Yilmaz et al.
11 citations
Perception normally balances external sensory signals with internal predictions based on prior knowledge. In a double-blind, placebo-controlled, cross-over experiment with healthy participants, the N-methyl-D-aspartate receptor (NMDAR) antagonist S-ketamine shifted perception toward the external mode, favoring sensory input over prior knowledge. A case-control study found that people with paranoid schizophrenia, a condition linked to NMDAR hypofunction, also spend more time in the external mode. This NMDAR-dependent shift suggests that schizophrenia symptoms may arise from recurring disconnections between perception and prior knowledge about the world.
Philosophy and the Mind Sciences
April 19, 2022
Joshua M. Martin, Philipp Sterzer
7 citations
Psychedelics may help treat mental health conditions by changing how people think about themselves, but the context in which they are taken plays a crucial role. A commentary on Chris Letheby's 'Philosophy of Psychedelics' argues that a person's mindset and physical surroundings during a psychedelic experience shape which new self-conceptions they discover. This aligns with the REBUS model, where relaxing strong prior beliefs makes the brain more sensitive to incoming sensory information. A supportive environment and positive state of mind make beneficial changes in self-understanding and long-term well-being more likely. This view largely agrees with Letheby but questions his idea that psychedelics create a 'level cognitive playing field' where all self-related hypotheses are equally probable.
Current biology : CB
July 12, 2021
Veith Weilnhammer, Merve Fritsch, Meera Chikermane et al.
Inferior frontal cortex plays a causal role in resolving perceptual ambiguities, thereby determining what is consciously experienced. Computational modeling and two fMRI experiments showed that this region detects conflicts caused by ambiguous sensory information. Disrupting inferior frontal cortex activity with transcranial magnetic stimulation slowed the updating of conscious experience in response to such conflicts. These findings indicate that prefrontal cortex is not merely involved in introspection or action but actively contributes to shaping the contents of consciousness.
NeuroImage
May 1, 2018
Gregor Wilbertz, Madhura Ketkar, Matthias Guggenmos et al.
Combining eye-tracking and functional magnetic resonance imaging (fMRI) improves the ability to decode which of two alternating perceptions a person is experiencing while viewing a bistable visual motion stimulus. Twenty participants viewed a plaid pattern that induces spontaneous perceptual switches and reported their perceptions. Using a support vector machine, multivoxel pattern analysis of fMRI data alone achieved 86% accuracy, eye-tracking alone 88% accuracy, and the combined approach reached 91% accuracy. This suggests that integrating brain and eye signals can reduce reliance on active verbal reports, which can confound studies of conscious perception, and may enable more effective no-report paradigms for investigating the neural correlates of consciousness.