title: Effects of simulated microgravity on brain plasticity: a startle reflex habituation study.
abstract: There is limited but increasing evidence that space environment, namely weightless condition, may affect astronauts' cerebral neurotransmitters and cognitive performance. The present experiment hypothesized that learning and brain plasticity are affected by simulated microgravity condition. To this aim, 22 male subjects matching astronauts' characteristics were divided in two groups, Head-Down Bed Rest (HDBR) and Sitting Control. After 3-h bed rest (or sitting condition) subjects started a picture viewing task during which 30 acoustic startle probes (100 dBA loudness), divided into three consecutive blocks, were delivered through headphones while startle reflex amplitude was measured from the EMG of the orbicularis oculi muscle. Habituation analysis of the startle reflex showed a normal reflex inhibition across blocks in sitting controls and no habituation in HDBR subjects. Results point to a microgravity-induced lack of startle reflex plasticity in subjects matching astronauts, a learning deficit which may affect the success of long-term space missions.
authors.affiliation: Department of General Psychology, University of Padova, 35131 Padova, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Messerotti Benvenuti
authors.forename: Marta
authors.initials: M
authors.lastname: Bianchin
authors.forename: Alessandro
authors.initials: A
authors.lastname: Angrilli
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D000704:Analysis of Variance; D001921:Brain / Q000502:physiology*; D004576:Electromyography / Q000379:methods; D005072:Evoked Potentials, Auditory / Q000502:physiology; D006185:Habituation, Psychophysiologic / Q000502:physiology*; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology; D013216:Reflex, Startle / Q000502:physiology*; D014893:Weightlessness; D018474:Weightlessness Simulation / Q000379:methods; D055815:Young Adult