title: 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.
  
  
  CONCLUSIONS
  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 related to overall clinical outcome in schizophrenia. Further, between-group differences in visual acuity may influence VEP results, even for subjects with 'normal' vision (20/32 or better).
authors.affiliation: Nathan Kline Institute, Program in Cognitive Neuroscience and Schizophrenia, Orangeburg, NY 10962, USA.
authors.forename: Isaac
authors.initials: I
authors.lastname: Schechter
authors.forename: Pamela D
authors.initials: PD
authors.lastname: Butler
authors.forename: Vance M
authors.initials: VM
authors.lastname: Zemon
authors.forename: Nadine
authors.initials: N
authors.lastname: Revheim
authors.forename: Alice M
authors.initials: AM
authors.lastname: Saperstein
authors.forename: Maria
authors.initials: M
authors.lastname: Jalbrzikowski
authors.forename: Roey
authors.initials: R
authors.lastname: Pasternak
authors.forename: Gail
authors.initials: G
authors.lastname: Silipo
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Javitt
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D014150:Antipsychotic Agents / Q000627:therapeutic use; D020532:Basal Nucleus of Meynert / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D004569:Electroencephalography; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000503:physiopathology / Q000523:psychology; D012559:Schizophrenia / Q000188:drug therapy / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D016896:Treatment Outcome; D014795:Visual Pathways / Q000502:physiology*
chemical_list: D014150:Antipsychotic Agents