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Abstract Background and Hypothesis Corollary discharge mechanism suppresses the conscious auditory sensory perception of self-generated speech and attenuates electrophysiological markers such as the auditory N1 Event-Related Potential (ERP) during Electroencephalographic (EEG) recordings. This phenomenon contributes to self-identification and seems to be altered in people with schizophrenia. Therefore, its alteration could be related to the anomalous self-experiences (ASEs) frequently found in these patients. Study Design To analyze corollary discharge dysfunction as a possible substrate of ASEs, we recorded EEG ERP from 43 participants with schizophrenia and 43 healthy controls and scored ASEs with the ‘Inventory of Psychotic-Like Anomalous Self-Experiences’ (IPASE). Positive and negative symptoms were also scored with the ‘Positive and Negative Syndrome Scale for Schizophrenia’ (PANSS) and with the ‘Brief Negative Symptom Scale’ (BNSS) respectively. The N1 components were elicited by two task conditions: (1) concurrent listening to self-pronounced vowels (talk condition) and (2) subsequent non-concurrent listening to the same previously self-uttered vowels (listen condition). Study Results The amplitude of the N1 component elicited by the talk condition was lower compared to the listen condition in people with schizophrenia and healthy controls. However, the difference in N1 amplitude between both conditions was significantly higher in controls than in schizophrenia patients. The values of these differences in patients correlated significantly and negatively with the IPASE, PANSS, and BNSS scores. Conclusions These results corroborate previous data relating auditory N1 ERP amplitude with altered corollary discharge mechanisms in schizophrenia and support corollary discharge dysfunction as a possible underpinning of ASEs in this illness.

Introduction The combination of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) enables direct interaction with the brain while recording the resulting neural activity, offering a unique opportunity to understand the brain's functional dynamics. In this study, TMS–EEG was employed to examine the effects of TMS on functional network connectivity through graph theory parameters. Methods A total of 29 healthy controls underAuthor: Please check funding information and confirm its correctness.went a single‐pulse TMS–EEG protocol targeting the dorsolateral prefrontal cortex. Three graph theory parameters summarizing functional network properties (i.e., connectivity strength, clustering coefficient, and characteristic path length) were analyzed before and after TMS application. Results TMS‐single pulse administration over the dorsolateral prefrontal cortex of healthy controls was associated with a significant increase in connectivity strength and clustering coefficient, and a significant decrease in the characteristic path length parameters. These changes are consistent with a shift towards a small‐world network organization. Conclusion These findings provide insight into the neurophysiological mechanisms underlying TMS‐induced changes and could have potential therapeutic implications. TMS was associated with a modulation of functional network connectivity. TMS modulation effects seem to reflect a change into a small‐world organization. EEG‐based brain graphs contribute to understand TMS neurophysiological basis.

Abstract Background and Hypothesis Altered brain activity preceding behavior may reflect a reduced ability to suppress the sensory consequences of self-generated actions in schizophrenia. The corollary discharge (CD) mechanism has been proposed to underlie this process. In the present study, we investigated CD by analyzing the readiness potential (RP) and its relationship to auditory N1 suppression in patients with schizophrenia compared to healthy controls (HCs). We also examined the association between RP activity and anomalous self-experiences (ASEs). Study Design Event-related potentials were recorded from 48 patients with schizophrenia and 55 HCs during a vocalization paradigm including talk and listen conditions. RP amplitude and N1 suppression were quantified as the amplitude difference between listen and talk conditions. Regression analyses assessed the relationship between these components within each group and examined associations between RP and N1 amplitudes and ASEs, measured using the Inventory of Psychotic-Like Anomalous Self-Experiences (IPASE) scale, in the schizophrenia group. Study Results In the talk condition, HCs showed greater RP amplitude compared with the listen condition, a difference that was absent in the schizophrenia group. In HCs, this RP increase was followed by suppression of the N1 component. A significant correlation between RP amplitude and N1 suppression was observed in HCs but not in patients. Importantly, reduced N1 suppression in patients with schizophrenia was associated with higher IPASE scores. Conclusions These findings suggest that schizophrenia involves impairments in early cortical processes related to efference copy and corollary discharge mechanisms, reflected in reduced RP amplitude and the lack of coupling with N1 suppression. Such alterations may contribute to deficits in sensory prediction and to anomalous self-experiences in schizophrenia.

Schizophrenia has been associated with a reduced task-related modulation of cortical activity assessed through electroencephalography (EEG). However, to the best of our knowledge, no study so far has assessed the underpinnings of this decreased EEG modulation in schizophrenia. A possible substrate of these findings could be a decreased inhibitory function, a replicated finding in the field. In this pilot study, our aim was to explore the association between EEG modulation during a cognitive task and the inhibitory system function in vivo in a sample including healthy controls and patients with schizophrenia. We hypothesized that the replicated decreased task-related activity modulation during a cognitive task in schizophrenia would be related to a hypofunction of the inhibitory system. For this purpose, 27 healthy controls and 22 patients with schizophrenia (including 13 first episodes) performed a 3-condition auditory oddball task from which the spectral entropy modulation was calculated. In addition, cortical reactivity—as an index of the inhibitory function—was assessed by the administration of 75 monophasic transcranial magnetic stimulation single pulses over the left dorsolateral prefrontal cortex. Our results replicated the task-related cortical activity modulation deficit in schizophrenia patients. Moreover, schizophrenia patients showed higher cortical reactivity following transcranial magnetic stimulation single pulses over the left dorsolateral prefrontal cortex compared to healthy controls. Cortical reactivity was inversely associated with EEG modulation, supporting the idea that a hypofunction of the inhibitory system could hamper the task-related modulation of EEG activity.

Aiming at discerning potential biotypes within the psychotic syndrome, we have recently reported the possible existence of two clusters or biotypes across schizophrenia and bipolar disorder characterized by their cognitive performance using the Brief Assessment of Cognition in Schizophrenia (BACS) instrument and validated with independent biological and clinical indexes (Fernández-Linsenbarth et al. in Schizophr Res 229:102–111, 2021). In this previous work, the group with larger cognitive deficits (N = 93, including 69 chronic schizophrenia, 17 first episodes (FE) of schizophrenia and 7 bipolar disorder patients) showed smaller thalamus and hippocampus volume and hyper-synchronic electroencephalogram than the group with milder deficits (N = 105, including 58 chronic schizophrenia, 25 FE and 22 bipolar disorder patients). We predicted that if these biotypes indeed corresponded to different cognitive and biological substrates, their adaptation to real life would be different. To this end, in the present work we have followed up the patients’ population included in that work at 1st and 3rd years after the date of inclusion in the 2021 study and we report on the statistical comparisons of each clinical and real-life outcomes between them. The first cluster, with larger cognitive deficits and more severe biological alterations, showed during that period a decreased capacity for job tenure (1st and 3rd years), more admissions to a psychiatric ward (1st year) and a higher likelihood for quitting psychiatric follow-up (3rd year). Patients in the second cluster, with moderate cognitive deficits, were less compliant with prescribed treatment at the 3rd year. The differences in real-life outcomes may give additional external validity to that yielded by biological measurements to the described biotypes based on neurocognition.

Introduction Recent studies support the identification of valid subtypes within schizophrenia and bipolar disorder using cluster analysis. Our aim was to identify meaningful biotypes of psychosis based on network properties of the electroencephalogram. We hypothesized that these parameters would be more altered in a subgroup of patients also characterized by more severe deficits in other clinical, cognitive, and biological measurements. Methods A clustering analysis was performed using the electroencephalogram‐based network parameters derived from graph‐theory obtained during a P300 task of 137 schizophrenia (of them, 35 first episodes) and 46 bipolar patients. Both prestimulus and modulation of the electroencephalogram were included in the analysis. Demographic, clinical, cognitive, structural cerebral data, and the modulation of the spectral entropy of the electroencephalogram were compared between clusters. Data from 158 healthy controls were included for further comparisons. Results We identified two clusters of patients. One cluster presented higher prestimulus connectivity strength, clustering coefficient, path‐length, and lower small‐world index compared to controls. The modulation of clustering coefficient and path‐length parameters was smaller in the former cluster, which also showed an altered structural connectivity network and a widespread cortical thinning. The other cluster of patients did not show significant differences with controls in the functional network properties. No significant differences were found between patients´ clusters in first episodes and bipolar proportions, symptoms scores, cognitive performance, or spectral entropy modulation. Conclusion These data support the existence of a subgroup within psychosis with altered global properties of functional and structural connectivity. In this study, our aim was to contribute to a better understanding of the biological heterogeneity in psychoses. For this purpose, we conducted a cluster analysis to identify patients’ subgroups based on the characteristics of their functional network, assessed wit electroencephalogram (EEG) data and methods derived from graph‐theory. Our cluster analysis yielded a two‐cluster solution, where one cluster showed significant alterations in their functional network and a significantly altered structural connectivity network with a widespread cortical thinning, and the other cluster showed a normal functional network.