Impairments in generation of early-stage transient visual evoked potentials to magno- and parvocellular-selective stimuli in schizophrenia

Abstract

Objective-Patients with schizophrenia demonstrate significant impairments of early visual processing, potentially implicating dysfunction of the magnocellular visual pathway. The present study evaluates transient visual evoked potential (tVEP) responses to stimuli biased toward the magnocellular (M) or parvocellular (P) systems in patients with schizophrenia vs. normal volunteers first to evaluate relative contributions of M and P systems to specific tVEP components in schizophrenia and, second, to evaluate integrity of early M and P processing in schizophrenia.Methods-Seventy-four patients with schizophrenia and schizoaffective disorder were compared with 59 control subjects using separate stimuli to assess the tVEP response to M, P and mixed M/P conditions. Stimuli were biased toward M vs. P processing by manipulation of chromatic and achromatic contrast. C1, P1, N1 and P2 components were compared between patients and controls. All subjects showed 20/32 vision or better.Results-Waveforms were obtained to low contrast (M), chromatic contrast (P) and high contrast (mixed M/P) stimuli in both patients and controls. C1 was present to P and mixed M/P stimuli. Patients showed a significant reduction in amplitude and an increase in latency of the C1 component. P1 was elicited primarily by M and mixed M/P stimuli, whereas N1 was elicited primarily by P and mixed M/P stimuli. Patients showed reductions in both P1 and N1 amplitudes across conditions. However, only reductions in P1 amplitude survived covariation for between group differences in visual acuity. Further, P1 amplitude reductions in the M condition correlated with a proxy measure of global outcome.Conclusions-M-and P-selective stimuli elicit differential components of the tVEP. Patients with schizophrenia show significant reductions in response even to simple visual stimuli. Deficits, particularly within the M system, may correlate significantly with global outcome and level of community functioning.Significance-Whereas deficits in high-order cognitive processing have been extensively documented in schizophrenia, integrity of early-stage sensory processing has been studied to a lesser degree. The present findings suggest that deficits in early-stage visual processing are significantly

Visual sensory processing deficits in Schizophrenia and their relationship to disease state

“…Schechter et al [56] in an investigation aimed at parsing the Magnocellular and Parvocellular contributions to visual system functioning in schizophrenia also found the P1 deficit in patients. They then found significant correlation of the P1 deficit with global outcome and community functioning measures using the Independent Living Scale (ILS) [39].…”

“…It is worth noting here that DUP measures are notoriously difficult to obtain and standardise and it was simply not possible to include accurate estimates of this measure in our calculations. With few studies actually correlating VEP measures to symptom and functional outcome scales [16,56], we also sought to examine the relationship between the P1 deficit and clinical features of schizophrenia as measured by the brief psychiatric rating scale (BPRS) [51] and the scale for the assessment of negative symptoms (SANS) [2].…”

Encoding vs. retention: Differential effects of cue manipulation on working memory performance in schizophrenia

“…In particular, with regard to the disinhibitory deficits, it remains to be determined whether patients solely lack the frontal inhibitory mechanisms needed to maintain the negative response bias produced by the invalid cue, or whether they fail as well to adequately decode the information content of the cue stimuli. In schizophrenia, visual processing deficits have been increasingly documented over recent years Schechter et al, 2005), raising the possibility that sensory deficits may contribute to impaired overall performance in this task.…”

Dissecting the cellular contributions to early visual sensory processing deficits in schizophrenia using the VESPA evoked response

“…Visual evoked potential (VEP) studies have consistently demonstrated that patients with schizophrenia exhibit relatively severe deficits in early visual sensory processing, as indexed by a robust decrement in amplitude of the occipital P1 component (e.g., Foxe et al, 2001Foxe et al, , 2005Butler et al, 2001Butler et al, , 2007Doniger et al, 2002; Available online at www.sciencedirect.com Spencer et al, 2003;Schechter et al, 2005;Haenschel et al, in press). Concomitant structural deficits have also been shown in the visual sensory pathways (Butler et al, 2006).…”