Medication status affects the relationship of symptoms to prepulse inhibition of acoustic startle in schizophrenia.

Inhibition of the acoustic startle response by a smaller preliminary nonstartling stimulus is termed prepulse inhibition (PPI). Schizophrenia patients have impairments in PPI that may not fully normalize even when they are clinically stable on medication, particularly typical antipsychotics. There is evidence that more severe symptoms are associated with more severe PPI abnormalities, but the effect of antipsychotics on this relationship is not clear.

The effects of a subanesthetic dose of ketamine on verbal memory in normal volunteers.

Rationale: N-methyl-D: -aspartate (NMDA) glutamate receptor antagonists have been reported to induce schizophrenia-like symptoms in humans, including memory impairments. Although the NMDA receptor has been shown to impair memory acquisition by disrupting long-term potentiation (LTP), limited research has been done on studying the effects of NMDA antagonists on the post-LTP cascade of events implicated in consolidation as measured by administering the drug after the initial learning experience.

Objective: The purpose of this experiment was to examine the effect of ketamine on mental status and to identify NMDA antagonist-induced memory deficits by comparing the recall performance of items presented both immediately before and during ketamine infusion.

Menstrual cycle phase effects on prepulse inhibition of acoustic startle.

Prepulse inhibition (PPI) represents an attenuation of the startle reflex following the presentation of a weak prepulse at brief intervals prior to the startle eliciting pulse. It has been shown that increases in striatal dopamine levels decrease PPI; because dopamine release is sensitive to estrogen, it is likely that PPI varies across the menstrual cycle. Cross-sectional studies looking at estrogen effects suggest that this may be true.

Effect of treatment status on prepulse inhibition of acoustic startle in schizophrenia.

Rationale: The acoustic startle response is inhibited when the startling stimulus is preceded by a weaker non-startling acoustic stimulus. This phenomenon, termed prepulse inhibition of acoustic startle (PPI), is impaired in schizophrenics compared to normal controls. To date, there is conflicting evidence regarding whether PPI impairments improve with antipsychotic treatment.