Early visual, processing deficits in schizophrenia: impaired PI generationrevealed by high-density electrical mapping

Integrity of early visual sensory processing in schizophrenia was assessed using the well characterized PI and NI components of the visual evoked pote ntial (VEP) as our dependent measures. VEPs were recorded in response to su ccessively less fragmented line drawings of common objects. PI amplitudes w ere significantly reduced across all stimulus conditions for patients versu s controls. Further, this decrement was relatively greater at parieto-occip ital than occipito-temporal electrode sites. No differences in NI amplitude were found. The finding of PI deficits in patients, particularly over dors al scalp, supports the view that schizophrenia is associated with impairmen t of early dorsal visual stream processing. On the other hand, the finding of normal NI amplitudes in patients suggests that early stages of ventral s tream processing may be relatively more intact. These results imply that th e cognitive impairment seen in schizophrenia is not just due to deficits in higher order aspects of cognition but also encompasses significant deficit s in early sensory processing. NeuroReport 12:3815-3820 (C) 2001 Lippincott Williams & Wilkins.