## 3 The Mechanisms Behind Broken MNs in ASD and Schizophrenia
### Mu Rhythm Suppression in Schizophrenia
\(Mu\) suppression was measured through an EEG task, in which the participants were presented with a clip containing short sequences involving white background, biological motion with social inferences, and white visual noise. The study recruited 30 participants: 15 drug-naive or drug-free patients with schizophrenia at the early stages of the illness, and 15 controls with no record of neuropsychiatric disorder, matched on age, sex and educational level. According to the results, the level of \(mu\) rhythm suppression over the sensorimotor cortex (SMC) among patients with schizophrenia and healthy controls presented significant deviations, which as interpreted as an indicator for the MNS dysfunction. In addition, the findings highlighted a significant negative correlation between \(mu\) suppression over the right sensorimotor cortex (rSMC) and the thought disturbance cluster on PANSS (Positive and Negative Syndrome Scale) [74]. Thought disorder refers to cognitive discrepancies that attenuate communication, language and thought [75]. [PERSON] et al. 's [73] results link irregularities in the function of the MNS to cognitive deficits in patients with schizophrenia. Differences in research outcomes across studies may be attributed to differences in study design, population samples, and/or the tasks administered to measure the suppression of the \(mu\) wave. [PERSON] et al. [76] conducted an analysis of relevant studies in order to investigate the activation of MNs in schizophrenia and ASD by measuring deviations in \(mu\) rhythm suppression during the observation of biological motion. For their analysis, they selected three groups of participants: individuals with high-functioning ASD, individuals with schizophrenia in the early stages of psychosis (EP) that had active negative symptoms, and a group of controls with no clinical diagnoses. The authors examined neural commonalities between the disorders that might stem from the negative symptoms of schizophrenia. The studies selected had all used EEG during the observation of biological motion. The analysis involved four conditions: baseline/ball condition [77], moving hand condition [77], social interactive condition [78] and a biological motion/point light display animation [79]. The results indicated that reactions to the observation of biological movement resulted in crucially reduced \(mu\) rhythm suppression in both clinical groups(i.e., individuals with ASD and individuals with early psychosis experiencing negative symptoms) as opposed to the healthy control group. For the EP group, the findings showed that individuals that exhibited more severe negative symptoms demonstrated less \(mu\) suppression. As mentioned before, negative symptoms in schizophrenia correspond to impairments in social cognition and executive functioning. [PERSON] et al. 's [PERSON] et al. 's [PERSON] et al. (2018) study has highlighted the similarities between ASD and schizophrenia with respect to dysfunctional neural mechanisms associated with impaired socio-cognitive performance. The relationship between \(mu\) rhythm suppression and degree of severity of symptoms in schizophrenia has also been a fruitful area of research. For instance, [PERSON] et al. [PERSON] et al. (2018) tested 20 first-episode psychosis patients with schizophrenia for Event Related Desynchronisation (ERD) of \(mu\) waves, comparing their performance to 12 healthy controls. Their findings demonstrated that reduced \(mu\) suppression was associated with more severe negative symptoms and poorer social functioning in first-episode psychosis patients, further implying that deficits with respect to \(mu\) suppression may be related to the social and cognitive impairments observed in the early stages of schizophrenia. Similarly, the objective of the study by [PERSON] et al. [PERSON] et al. (2018) was to explore the connection among MN function, psychosis and empathic processes in patients with schizophrenia, by measuring \(mu\) rhythm suppression and its correlation with empathy and psychotic episodes.