The mirror mechanism in schizophrenia: A systematic review and qualitative meta-analysis

Abstract

BackgroundMirror neuron system (MNS) consists of visuomotor neurons that are responsible for the mirror neuron activity (MNA), meaning that each time an individual observes another individual performing an action, these neurons encode that action, and are activated in the observer's cortical motor system. Previous studies report its malfunction in autism, opening doors to investigate the underlying pathophysiology of the disorder in a more elaborate way and coming up with new rehabilitation methods. The study of MNA function in schizophrenia patients has not been as frequent and conclusive as in autism. In this research, we aimed to evaluate the functional integrity of MNA and the microstructural integrity of MNS in schizophrenia patients.MethodsWe included case-control studies that have evaluated MNA in schizophrenia patients compared to healthy controls using a variety of objective assessment tools. In August 2022, we searched Embase, PubMed, and Web of Science for eligible studies. We used an adapted version of the NIH Quality Assessment of Case-Control Studies tool to assess the quality of the included studies. Evidence was analyzed using vote counting methods of the direction of the effect and was tested statistically using the Sign test. Certainty of evidence was assessed using CERQual.ResultsWe included 32 studies for the analysis. Statistical tests revealed decreased MNA (p = 0.002) in schizophrenia patients. The certainty of the evidence was judged to be moderate. Investigations of heterogeneity revealed a possible relationship between the age and the positive symptoms of participants in the included studies and the direction of the observed effect.DiscussionThis finding contributes to gaining a better understanding of the underlying pathophysiology of the disorder by revealing its possible relation to some of the symptoms in schizophrenia patients, while also highlighting a new commonality with autism.Systematic review registrationPROSPERO identifier: CRD42021236453.

Bottom-up and top-down contributions to impaired motion processing in schizophrenia

“…Dysfunctional MNS activity has been associated with social cognitive impairments across neuropsychiatric disorders (reviewed in Chan and Han 2020; Jeon and Lee 2018). In Sz, studies have reported reduced MNS activation during action observation (Mehta et al 2014;Valizadeh et al 2022), in association with impaired TOM performance (Choe et al 2018) and negative symptom severity (Schilbach et al 2016). In recent studies (Martinez et al 2018;Martinez et al 2019;Martínez et al 2022), we have observed reduced MT+ activation in Sz in response to simple motion stimuli which correlate with reduced FER to static emotional faces (Martinez et al 2018), suggesting a potential involvement of MT+ deficits even to static-only stimuli.…”

Disrupted third visual pathway function in schizophrenia: Evidence from real and implied motion processing

“…These include the middle frontal gyrus (MFG), sensorimotor cortex (SMC), supplementary motor area (SMA), posterior superior temporal sulcus (pSTS) and the putamen ( Bonini, 2017 , Caspers et al, 2010 , Errante and Fogassi, 2020 , Ferrari et al, 2017 , Molenberghs et al, 2012 ). Disrupted MNS activity during action observation/imitation has been reported in several neuropsychiatric disorders (reviewed in Chan and Han, 2020 , Jeon and Lee, 2018 ) including Sz ( Brown et al, 2016 , Mehta et al, 2014b , Thakkar et al, 2014 , Valizadeh et al, 2022 ). In Sz, altered MNS activity has also been associated with impaired TOM performance ( Choe et al, 2018 ) and greater symptom severity ( Mehta et al, 2014a , Saito et al, 2018 , Schilbach et al, 2016 ).…”