Although the use of all modalities of evoked potentials (EPs) and cognitive/event-related evoked potentials (ERPs) has a successful history, with ERPs even being able to signal cognitive deficits in psychiatric and neurological patients (Mathalon et al., 2000; Huang et al., 2011; Zhanga et al., 2021; Olichney et al., 2022), some of their potential applications are still limited. One of the reasons for this limitation is the lack of easily transportable inexpensive equipment. As a result, patients who could benefit from these examinations often do not undergo them. Furthermore, electrophysiological examinations in psychiatric patients are complicated because they usually require an accompanying person, who may not be available for repeated visits to mostly dislocated specialized labs. In addition, these patients may feel uncomfortable in an unfamiliar environment with many cables, some of which are connected to their head, due to their tendency to be anxious – e.g. in schizophrenia (Achim et al., 2011; Braga et al., 2013), where the need for ERP testing is quite high (because an objective detection of cognitive changes is a good marker of development of schizophrenia – Higuchi et al., 2021). Also, in children (e.g. with anxiety and depressive disorders, ADHD, and autism spectrum disorders), a more convenient ERP examination could help to gain a better insight into their cognitive functions (Berchio and Micali, 2022). Our intention was to try to implement an ERP examination of psychiatric patients in an environment familiar to the patient, such as their standard outpatient setting, hospital room, or home. Since the use of portable devices can improve accessibility and use of the electrophysiological methods, we have recently developed a portable device for visual evoked potentials (VEPs) and ERPs examination called “VEPpeak” (Fig. 1) (Kuba et al., 2023; https://www.veppeak.com). The device has a built-in color LED visual stimulator (Fig. 2), enabling a broad spectrum of visual stimulations, including various cognitive stimuli.

In this pilot study, we tested the applicability of the VEPpeak with visual event-related potentials (ERPs - P300 wave) in 15 twice-examined control subjects and in 31 schizophrenia patients. We started testing intentionally with these patients because it seems that their potential cognitive deficit can be detected through changes in P300 wave parameters (Javitt, 2015; Lee and Kim, 2022), and also that the effect of antipsychotic therapy can be verified this way (e.g. Korostenskaja and Kähkönen, 2009; Park et al., 2010). In addition, there are increasing attempts to predict the development of schizophrenia in at-risk individuals (Van der Stelt et al., 2005; Niznikiewicz, 2019; Oribe et al., 2020; Higuchi et al., 2021), and reduced and delayed P300 appears to be a promising diagnostic tool not only in schizophrenia but also in other psychiatric disorders such as obsessive-compulsive disorder (Kim et al., 2003; Raggi et al., 2021).

Although many of the clinical and neuropsychological correlates of P300 changes are unknown (Nieman et al., 2002), some of them appear to be already ascribed to specific characteristics of schizophrenia (Mori et al., 2007) or considered intermediate phenotypes (Winterer et al., 2003; Flint et al., 2014).

Our laboratory specializes in the visual modality of evoked potentials, so we chose the visual variant of the P300, even though it is a less used modality compared to the auditory ERP (about 2 - 3 times more studies are dealing with auditory ERP/P300 in schizophrenia according to the records in WOS). As to literature data and our own experience, standard VEP stimuli (flash, pattern-related) activate primary visual cortical areas and may not display significant changes in psychiatric disorders, for which mainly ERPs are recommended (Berchio and Micali, 2022). Because of this and also to avoid prolonging the examination and potentially reducing patients' concentration, we did not combine ERP testing with an examination of VEPs in this study.

This study aims to assess the feasibility of recording reproducible and robust visual ERPs using a portable VEPpeak device in psychiatric patients. The goal is to determine whether this portable tool can be used for prospected standard monitoring of cognitive changes in psychiatric patients and objective detection of pharmacotherapeutic effects. The cited literature points to the potential benefits of a portable device in enabling large-scale screening of changes in visual cognitive processing by simple testing of P300 parameters in various patient groups, especially with schizophrenia. We would like to motivate interested laboratories to help expand the validation of the utility of the portable VEP device in psychiatry (multiple VEPpeak prototypes are available for free loan).