# Somatosensory Mismatch Response in Patients with Cerebral Palsy
## 1 Introduction
found a negative component peaking at approximately 60 ms (N60) and a large positive peak at around 100-200 ms (P150) [7]. In most cases, sMMN appeared over the frontocentral regions [6; 11]. In addition to MMN, a later negative mismatch-related ERP component is often observed in both auditory [24; 25; 26] and somatosensory [21] oddball paradigms and is referred to as late discriminative negativity (LDN). Generally, LDN is observed at around 400 ms, following MMN [27]. Although less is known about LDN, its amplitude is typically higher in infants and children, but it has also been observed in adults [24; 28]. Irrespective of the modalities of mismatch-related ERP components, they are widely used for monitoring treatment adequacy in cognitive-impairment-related diseases like schizophrenia, Alzheimer's, and vascular dementia [23; 29; 30]. While the potential uses of mismatch responses are noteworthy, studies involving patients with cerebral palsy (CP) are generally lacking to date, and to our knowledge. CP leads to a movement disorder caused by nonprogressive damage in the developing brain during early childhood. The movement disorder associated with CP is classified into three types: spasticity, dyskinesia, and ataxic CP. Depending on the extent of the brain damage, patients with CP may also exhibit additional symptoms such as cognitive, communicative, and/or behavioral deficits. CP is mainly characterized by motor abnormalities. Any correctly initiated movement requires an intact sensory motor system. Therefore, it is evident and supported by research also that somatosensory dysfunction plays a crucial role in movement control in the case of CP. Furthermore, children with CP often have difficulties processing somatosensory information, which can also lead to difficulties in learning and movement execution. For example, in the case of hemiplegia, the hand on the less affected side may process touch differently than the one on the more affected side. This difference in sensory information processing is frequently manifested in more pronounced disparities in movement execution and strength between the two sides of the body [31; 32; 33]. Mismatch-related ERP responses have the potential to serve as a valuable tool for probing the neural mechanisms underlying somatosensory processing in patients with CP. By studying those, researchers and clinicians can gain insights into the nature of sensory abnormalities. Knowledge of the sensory process can help to develop different therapies tailored to the problem. For instance, [PERSON] et al. [34] demonstrated that the cerebellum plays a role in the automatic detection of changes in somatosensory input. Their study not only validated the reliability of somatosensory mismatch negativity (sMMN) recordings but also suggested that individuals with cerebellar damage might experience difficulties in processing incoming somatosensory information in the cortex. Conducting ERP experiments would be particularly suitable for patients with CP, including young adults, considering potential challenges in concentration and attention span during tasks [35; 36]. Mismatch-related ERP responses, in particular, provide an opportunity to look at cognitive processing even when a patient faces concentration deficit, as the patient does not need to focus on the task. The appearance of mismatch-related responses in the EEG allows one to detect changes related to sensory or cognitive processes in the brain. In this study, we chose an adult population of patients with CP who were able to read and had sufficient concentration. Our goal was to assess the tolerability of the EEG cap preparation. Additionally, we aimed to know whether it was feasible to derive any mismatch-related ERP responses at all in the case of CP with our experimental protocol (i.e., can the participants perform the tasks?).