Localization and Elimination of Attentional Dysfunction in Schizophrenia During Visual Search

One turn at a time: Behavioral and ERP evidence for two types of rotations in the classical mental rotation task

We perform mental rotations in many everyday situations, such as reading a map or following furniture assembling instructions. In a classical mental rotation task, participants are asked to judge whether a rotated stimulus is presented in its mirrored form or its canonical form. Previous results have indicated a degree effect: RT is longer as the angle of rotation increases, and this effect is traditionally explained by arguing that this judgment requires rotating the stimulus back to its upright form. Importantly, in half of the trials, the stimuli are rotated on both the page plane and mirror plane. Namely, we argue that in previous research the task actually involved two different rotation processes. To provide a clear dissociation between these two rotations, we collected EEG data and used the Contralateral Delay Activity (CDA) as an indicator of visual working memory (VWM) load. The results of Experiment 1 suggested different VWM involvement according to the degrees rotations when the item was not mirrored, such that the CDA amplitude generally increased as the degree of rotation was higher. Mirrored trials were all at ceiling in terms of CDA, regardless of their rotation degree. Experiment 2 showed increased CDA amplitude uniquely related to the flip rotation. Thus, we provided ERP evidence that the canonical mental rotation task involves two types of rotations that can be dissociated based on the load they imposed on VWM.

Altered Visuospatial Processing in Schizophrenia: An Event-related Potential Microstate Analysis Comparing Patients with and without Hallucinations with Healthy Controls

Patients with schizophrenia present with various symptoms related to different domains. Abnormalities of auditory and visual perception are parts of a more general problem. Nevertheless, the relationship between the lifetime history of auditory verbal hallucination (AVH), one of the most prevalent symptoms in schizophrenia, and visuospatial deficits remains unclear. This study aimed to investigate differences in hemispheric involvement and visuospatial processing between healthy controls (HCs) and schizophrenia patients with and without AVHs. HCs (N = 20), schizophrenia patients with AVH (AVH group, N = 16), and schizophrenia patients without hallucinations (NH group, N = 10) participated in a 4-choice reaction task with lateralized stimuli. An event-related potential (ERP)-microstate approach was used to analyze ERP differences between the conditions and groups. The schizophrenia patients without hallucinations had slower responses than the HCs. An early visual N1 contralateral to stimulation side was prominent in all groups of participants but with decreased amplitude in the patients with schizophrenia, especially in the AVH group over the right hemisphere. The amplitude of P3b, a cognitive evaluation component, was also decreased in schizophrenia. Compared to AVH and HC groups, the patients in the NH group had altered microstate patterns: P3b was replaced by a novelty component, P3a. Although the difference between both patient groups was only based on the presence of AVHs, our findings indicated that patients had specific visuospatial deficits associated with a lifetime history of hallucinations: patients with AVHs showed early visual component alterations in the right hemisphere, and those without AVHs had more prominent visuospatial impairment.

Targeting cognition in schizophrenia through transcranial direct current stimulation: A systematic review and perspective

Cognitive deficits are a fundamental feature of schizophrenia for which currently no effective treatments exist. This paper examines the possibility to use transcranial direct current stimulation (tDCS) to target cognitive deficits in schizophrenia as evidence from studies in healthy participants suggests that tDCS may improve cognitive functions and associated neural processes. We carried out a systematic review with the following search terms: 'tDCS', 'electric brain stimulation', 'schizophrenia', 'cognitive', 'cognition' until March 2019. 659 records were identified initially, 612 of which were excluded after abstract screening. The remaining 47 articles were assessed for eligibility based on our criteria and 26 studies were excluded. In addition, we compared several variables, such as online vs. offline-stimulation protocols, stimulation type and intensity on mediating positive vs. negative study outcomes. The majority of studies (n = 21) identified significant behavioural and neural effects on a range of cognitive functions (versus n = 11 with null results), including working memory, attention and social cognition. However, we could not identify tDCS parameters (electrode montage, stimulation protocol, type and intensity) that clearly mediated effects on cognitive deficits. There is preliminary evidence for the possibility that tDCS may improve cognitive deficits in schizophrenia. We discuss the rationale and strength of evidence for using tDCS for targeting cognitive deficits in schizophrenia as well as methodological issues and potential mechanisms of action.

Relationship between MEG global dynamic functional network connectivity measures and symptoms in schizophrenia

An investigation of differences in dynamic functional network connectivity (dFNC) of healthy controls (HC) versus that of schizophrenia patients (SP) was completed, using eyes-open resting state MEG data. The MEG analysis utilized a source-space activity estimate (MNE/dSPM) whose result was the input to a group spatial independent component analysis (ICA), on which the networks of our MEG dFNC analysis were based. We have previously reported that our MEG dFNC revealed that SP change between brain meta-states (repeating patterns of network correlations which are allowed to overlap in time) significantly more often and to states which are more different, relative to HC. Here, we extend our previous work to investigate the relationship between symptomology in SP and four meta-state metrics. We found a significant correlation between positive symptoms and the two meta-state metrics which showed significant differences between HC and SP. These two statistics quantified 1) how often individuals change state and 2) the total distance traveled within the state-space. We additionally found that a clustering of the meta-state metrics divides SP into groups which vary in symptomology. These results indicate specific relationships between symptomology and brain function for SP.

Mechanisms Underlying Visuospatial Working Memory Impairments in Schizophrenia

Working memory deficits are observed in the vast majority of individuals diagnosed with schizophrenia and those at risk for the disorder. Working memory impairments are present during the prodromal stage and persist throughout the course of schizophrenia. Given the importance of cognition in functional outcome, working memory deficits are an important therapeutic target for schizophrenia. This chapter examines mechanisms underlying working memory deficits in schizophrenia, focusing on the roles of perception and attention in the encoding process. Lastly, we present a comprehensive discussion of neural oscillation and internal noise in the context of the etiology of working memory deficits in schizophrenia and introduce noninvasive treatment strategies that could improve encoding processes.