SA70. Cognitive Correlates of Visual Cortical Plasticity in Schizophrenia

Abstract

Background: The amount of improvement that people with schizophrenia (SZ) show after a cognitive remediation intervention may depend on the integrity of basic plasticity mechanisms. However, to date it has been difficult to assess cortical plasticity in vivo in humans. Recently, various electroencephalogram (EEG) paradigms have been developed to noninvasively evaluate visual plasticity in humans. In SZ, there has been only 1 published report that used a visual plasticity paradigm (Cavus et al., 2012), which revealed short-term (i.e., up to 4 minutes) enhancement of the N1b visual evoked potential (VEP) component after high-frequency visual tetanization. However, the sample size in that study was relatively modest (n = 19), and correlates to important aspects of functioning were not explored. In the current study, we examined visual plasticity in a large sample of SZ and its cognitive, functional, and clinical correlates. Methods: Sixty-four SZ completed EEG and performance-based measures, as part of an ongoing cognitive remediation study, at baseline before remediation began. Participants were assessed on the visual plasticity paradigm, neurocognition (MCCB), functional capacity (UPSA), and community functioning (Role Functioning Scale) as well as clinical symptoms (BPRS and SANS). For the plasticity paradigm, we assessed VEPs prior (baseline) to 2 minutes of high-frequency stimulation (HFS; i.e., tetanization), and 2–4, 4–6, and 20–22 minutes after HFS (Post-1, Post-2, and Post-3, respectively). Results: We noted 2 time windows in which VEPs were modified after HFS (i.e., larger negative or positive amplitudes compared to baseline): an early time window (150–235 ms) and a late time window (250–400 ms). Compared to baseline, there was an enhanced negativity in the early time window at Post-1 (P = .001) and Post-2 (P = .007) but not at Post-3. Additionally, there was an enhanced positivity in the late time window at Post-2 (P < .001) and Post-3 (P = .02). The increased negativity at Post-2 in the early time window was significantly correlated with a lower MCCB composite score (P = .009), whereas the increased positivity at Post-2 and Post-3 in the later time window was correlated with a higher MCCB composite score (P = .001 and .02, respectively). Conclusion: Results suggest that after visual HFS, SZ patients exhibit short-term plasticity (increased negativity) that lasts for approximately 6 minutes and long-term plasticity (enhanced positivity) that lasts up to 22 minutes after HFS. Although short-term plasticity showed an inverse relationship with cognition, long-term plasticity was related to better cognitive performance suggesting that this aspect of plasticity supports learning and memory.