Cognitive/Neural Compensatory Mechanisms in Schizophrenia: Reaction Times-Brain Activity Correlates

Abstract

Abstract Cognitive deficiency in schizophrenia (SZ) was found to be associated with decreased PFC activity compared to healthy controls (HC). Other studies referred to increased / intact patterns of PFC activity. Parallel to those inconsistent neuroimaging findings, schizophrenia patients also showed increased intra-individual reaction times variability (RT_IIV). In the current work, we suggested that inconsistent findings in schizophrenia neuroimaging literature are driven by their increased RT-IIV. We hypothesized that performance with increased reaction times in SZ patients reflects compensatory cognitive/neural mechanisms. To address that general hypothesis, we conducted three studies as follow: 1. Activation likelihood Estimation (ALE) meta analysis of (90 fMRI studies in SZ); In that study we were first concerned with extracting the most consistent neuroimaging findings in the previous SZ literature. Second, we conducted ALE analyses within two categories: experiment with impaired RT (effect sizes > 0.3) vs. experiments with unimpaired RT (effect sizes <0.3); 2. In the second study, we investigated RT_IIV coefficients during AX task performance in four groups, SZ patients (N= 20), SZ.R (N= 33), HC subjects (N =21), HC.R (N= 23). We hypothesized that SZ patients and their relatives would show increased RT_IIV relative to HC within the probe and the cue conditions. 3. In our main study, fMRI study, we tested BOLD response across three levels of RT (slow, medium and fast). We hypothesized that SZ patients and their relatives will show more VLPFC activity during the slow trials than the faster trials relative to HC- reflecting slow reactive compensatory mechanisms.