Reduced learning rate and E/I imbalance drive Peripersonal Space boundaries expansion in Schizophrenia

Abstract

AbstractBackground and HypothesisAbnormalities in the encoding of the space close to the body, named peripersonal space (PPS), is thought to play a crucial role in the disruption of the bodily self observed in schizophrenia (SCZ). Empirical evidence indicates a narrower extension of the PPS in SCZ compared to controls but preserved plasticity of the PPS. Computational studies suggest that increased excitation of sensory neurons could explain the smaller PPS observed in SCZ. However, it is unclear why SCZ patients preserve PPS plasticity and how such an excitation imbalance influences learning during the extension of the PPS boundaries.Study DesignWe hypothesise that Hebbian plasticity can account for PPS expansion after active tool use training, which occurs in spite of E/I imbalance and reduced synaptic density. Using simulations in a SCZ network model, we explored the effects of such impairments on PPS plasticity and fitted the model to behavioural data before and after a training routine.Study ResultsWe found that increased excitation of sensory neurons does not impede the expansion of PPS and could explain a sharper demarcation of PPS boundaries after training. In addition, we found that a reduction in the learning rate is required to reproduce the post-training PPS representation of SCZ patients.ConclusionsWe discuss how the neural mechanisms behind the plasticity of PPS in the SCZ spectrum are related to the core pathophysiology of the disease.