Schizophrenia Bulletin Advance Access published online on January 31, 2008
Schizophrenia Bulletin, doi:10.1093/schbul/sbm146
Impaired Prepulse Inhibition and Prepulse-Elicited Reactivity but Intact Reflex Circuit Excitability in Unmedicated Schizophrenia Patients: a Comparison With Healthy Subjects and Medicated Schizophrenia Patients
2 University Hospital of Psychiatry Zurich, PO Box 1931, CH-8032 Zurich, Switzerland
3 Laboratory of Behavioural Neurobiology, ETH Zurich, Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland
4 Psychiatric Services of Aargau Canton, Department of Research, PO Box 298, CH-5201 Brugg, Switzerland
1 To whom correspondence should be addressed; tel: +41-44-3822407, fax: +41-44-384-2499, e-mail: csomor{at}bli.uzh.ch.
Deficient sensorimotor gating as indexed by prepulse inhibition (PPI) of the startle response has been reported repeatedly in patients suffering from schizophrenia. According to the widely accepted "protective hypothesis," PPI reflects the protection of ongoing information processing against interference by other stimuli. Alternatively, it has been proposed that PPI might be regulated by startle reflex circuit excitability. In the present study, we evaluated these 2 conceptually divergent approaches underlying the regulation of PPI. To this end, we assessed sensorimotor gating as indexed by PPI, the reactivity to the prepulse-alone stimulus indexed as prepulse-elicited reactivity (PPER), and acoustic blink reflex excitability in terms of paired pulse suppression (PPS) within a single recording session in 13 unmedicated and 24 medicated (11 first break) schizophrenia patients in comparison to 43 healthy control subjects. The results showed that PPI was significantly reduced in unmedicated, but not in medicated schizophrenia patients. Furthermore, unmedicated patients could be distinguished from the medicated patients and control subjects in terms of PPER. In contrast to PPI, PPS did not differ between patients and control subjects. These findings are in line with the "protective hypothesis" of PPI and indicate that reduced sensorimotor gating in schizophrenia patients might be based on a reduced perception and/or processing of the prepulse stimulus. The extent to which PPER may or may not be causally associated with sensorimotor gating in schizophrenia has to be further investigated in human and animal studies.
Keywords: schizophrenia / prepulse inhibition / prepulse-elicited reaction / paired pulse suppression / reflex excitability / human