Analysis of Abnormal Motor Patterns in Patients with Schizophrenia

Significance statement

The ability to suppress the brain’s responses to sensory repercussions that are due to their own actions is common in humans (many other animals). It is accomplished by the nervous system with corollary discharge that produces an efference copy of the expected sensory consequences. Schizophrenia effects 1% of people across the globe. It is difficult for patients to differentiate between external and internally generated stimulus. Therefore, studying corollary discharge and its relationship to symptoms might allow us to better understand the problems faced by patients. 

Abstract

Movements induce sensory inputs which can hinder our capability to respond (Example - something hits us) is indistinguishable from the input that is caused by outside agents (Example - in the manner of something, hits you). It is important for the nervous system to distinguish amid the two signals. These signals are called corollary discharge and concern sensory processing. The system that allows animals to predict feelings, suppress responses to self-generated sensations, and therefore processing sensations economically and proficiently gets stimulated by the succeeding motor action resulting in corollary discharge of the expected stimuli in sensory cortex. Schizophrenic patients show less evidence of pre-talking and repression of the speech sound, considering dysfunctionality of corollary discharge. Our data set includes 26 patients [22 healthy (HC), 23 schizophrenics, and 3 schizoaffective (SZ)], we asked if patterns emerge as seen in speaking that would generalize the reaction to pressing a button to hear a tone. Increase in electrical activity of the brain (lateralized readiness potential) was estimated by comparing the neural activity from the right and left hemisphere. In healthy controls, the auditory N100 [N: negative] component was suppressed when pressing a button to produce a tone but was not compressed while passive listening. This was not evident in patients with schizophrenia. There was no difference in the P200 [P: positive] ERP component between the HC and SZ group. The negative ERP component (lateralized readiness potential) was greater in HC than SZ.

Data

The data set is taken from the Kaggle. Funding for the study procedures came from National Institute of Mental Health, NIMH project number (R01MH058262). The derived data includes ERP from 9 electrode sites. The size of the data is 2 gigabytes.

Introduction

The language capacity of non-human primates is different from that of modern humans (Bickerton, 1990). The genetic etiology of schizophrenia in the aspect of language is of importance (Crow, 1997). Psychotic symptoms characterize schizophrenia as patient’s experience misperceive circumstances and sensations. Patients inhibit the basic inability to make valid predictions about expected sensations and experiences towards these dispositions. The unconscious prediction arising from the normal neural functioning of healthy people facilitate the process of sensations, experiences as to accurately distinguish the expected from the unexpected (DeLisi, 2001). A broad range of experiments on analysis of predictive abnormalities in schizophrenia has been conducted to understand the failure of corollary discharge. Patients passively receive input from external sources to make predictions about patterns. Studies show that patients adjust actions and predictions appropriately due to mechanics of corollary discharge (Feinberg, 1978). Research is accumulating that schizophrenia is a dysfunction of efference copy/corollary discharge systems that normally allow us to unconsciously identify and disregard feelings resulting from our very own activities.

This dysfunction may give rise to refined but pervasive sensory/perceptual aberrations in schizophrenic patients, changing their interactions with their own overt and covert activities, as well as their interactions with the surroundings, it could also add to symptoms such as hallucinations and delusions, and could disrupt the drive to connect with people and activities. Abnormalities of predictive coding in schizophrenia have been reported across a wide selection of experimental paradigms, from those targeted at examining failures to draw out guidelines from environmental habits of events to prospects targeted at understanding failures of efference copy and corollary release systems (Langdon R, 1999). Studies of rule extraction typically require patients passively obtaining input from external sources and making predictions about habits or breaks. Studies of efference copy and corollary release mechanisms require patients actively making their own sensory activities and predictions correctly. The latter signifies a paradigm change from the original stimulus-response procedure, for learning normal and pathological brain function, to a lot more interactive response-stimulus approach. The suppression of sensory signals is prompted by efferent signals (Voss, 2006). Differentiation between efference copy and corollary discharge is vital as some investigators choose one to describe both. An efference copy of the preceding plan is sent to the sensory cortex generating corollary discharge of the expected move. Real sensations are subtracted from the expected sensations generating net suppression (Grossberg, 2000). Net suppression depends on the match between expected and experienced situations. Thus, corollary discharge and efference copy of a prediction system are critical to survival. Vocalization has been studied across the animal kingdom in a variety of species, from monkeys (Christenson, 2007) and insects to human (Ford, 2007). Auditory responsiveness is suppressed when the animal is producing the sound in all the cases. This is consistent with non-invasive human electrophysiological studies. The event-related EEG based studies on N100 shows increased activity in auditory areas during speech, but the activity is lower during speaking when recorded sounds are played back (Christoffels, 2007). We have found that in schizophrenic patients there is a reduction of N100 suppression.

Results

N100 amplitude

The significant condition X group proves that N1 was suppressed during button tone in HC compared with play tone in both the groups. The group effect in each condition was taken into consideration but it was insignificant. At FCz N100 is the largest.