Tactile prepuff inhibition of startle in children with Tourette's syndrome: in search of an "fMRI-friendly" startle paradigm.

BACKGROUND: Functional magnetic resonance imaging (fMRI) studies in neuropsychiatric populations will be enhanced by "on-line" tasks that assess brain activation linked to neurocognitive and psychophysiological functions. In some cases, task modifications may be required for use in an fMRI environment. Prepulse inhibition (PPI) of the startle reflex is an operational measure of sensorimotor gating that is deficient in specific neuropsychiatric disorders, including schizophrenia, Huntington's disease, and Tourette's syndrome (TS). This study examined whether a modified "fMRI-friendly" PPI paradigm is suitable for use in children and adequately sensitive to detect PPI deficits in TS.

METHODS: Bilateral eyeblink PPI was measured in children using chin air puffs to elicit startle and prepuffs to the dorsal hand surface as inhibiting stimuli. This paradigm involved no metallic objects or acoustic stimuli, making it suitable for an fMRI environment that is magnetically sensitive and acoustically complex. Children were also assessed in a "standard" acoustic PPI paradigm.

RESULTS: Robust startle was elicited via either puffs or noise bursts, and these responses were inhibited by prepuffs and prepulses, respectively. Compared to control subjects, children with TS exhibited comparable startle magnitude and habituation but significantly reduced prepuff inhibition and acoustic PPI.

CONCLUSIONS: Sensorimotor gating can be assessed in an "fMRI-friendly" paradigm that detects inhibitory deficits in TS.