Speaker: Dr. Ilvana Dzafic
25th June 2020
Recent theories in computational psychiatry propose that unusual perceptual experiences and delusional beliefs may emerge as a consequence of aberrant inference and disruptions in sensory learning. The current study investigates this theory by exploring sensory learning and inference on sound regularities; we examine if alterations are specific to schizophrenia spectrum disorders, or occur as psychotic phenomena intensify (even non-clinical population).
We recruited 66 participants: 22 schizophrenia spectrum inpatients, 22 non-psychotic inpatients and 22 non-clinical controls. Participants completed an auditory oddball task with volatility manipulated. We recorded neural responses with electroencephalography and behaviorally measured errors to inferences on the probability of sounds. Furthermore, we explored neural dynamics using Dynamic Causal Modelling (DCM).
Attenuated prediction error was specifically observed in the schizophrenia spectrum group, with reductions in MMN in stable, and P300 in volatile contexts. Greater errors in behaviour were observed across all participants that reported more psychotic-like experiences. DCM revealed that impaired behaviour was associated with decreased intrinsic connectivity in the inferior frontal gyri (IFG) and left primary auditory cortex (A1). People who experienced more hallucinations and psychotic-like symptoms had increased top-down and decreased bottom-up and intrinsic connectivity within the IFG.
The findings provide evidence that reduced prediction errors show specificity to the schizophrenia spectrum, but deficits in behaviour and brain connectivity are aligned on the full psychosis continuum. Along the continuum, psychotic experiences were related to an aberrant interplay between top-down, bottom-up and intrinsic connectivity in the IFG during sensory uncertainty. These findings provide novel insights into psychosis pathophysiology.
Ilvana completed her undergraduate in Psychology and her PhD in cognitive neuroscience, she is currently a postdoc in the Garrido lab. She is investigating different mental health conditions, such as schizophrenia and anxiety. She uses neuroimaging techniques, fMRI and EEG, as well as the predictive coding framework, to explore why some people develop psychiatric symptoms. She is also exploring if psychosis is on a continuum, which extends into the non-clinical, so-called “healthy” population.