Sensorimotor gating deficits and hypofrontality in schizophrenia.

Patients with schizophrenia exhibit (a) deficient sensorimotor gating as indexed by impaired prepulse inhibition (PPI) of the startle eyeblink reflex suggesting abnormal automatic information processing and (b) abnormal attentional modulation of PPI suggesting impaired controlled information processing. Here we test the hypothesis of deficient attentional modulation of PPI in schizophrenia as a defect in the interrelationship between frontal lobe functions of planning and executive action and posterior function of processing of sensory stimulation using positron emission tomography (PET). Consistent with the literature, our findings indicate that unmedicated schizophrenia patients exhibit lower frontal/occipital ratios (termed "hypofrontality") compared with healthy controls (n=15 in each group) during a standard tone-length-judgment (attention-to-prepulse) task. Moreover, better attentional modulation of PPI was associated with higher frontal/occipital ratios in the control, but not the patient group. These findings extend animal models to humans by demonstrating the importance of frontal and occipital lobe coordination in the modulation of PPI.