Longitudinal metabolic changes in the thalamus of macaque brain during 42-day head down tilt

Basic changes in environmental conditions are fundamental to understanding brain mechanisms. several studies have reported impairment of central nervous processes during weightlessness. in this study,neurobiological alterations during 6°head down tilt (hdt) were investigated longitudinally using non-invasive proton magnetic resonance spectroscopy (1h mrs) at 3t in region related to cognitive and movement,such as the thalamus. scans were performed in five rhesus monkeys before hdt and at 7,21 and 42 days after hdt. spectra were processed using lc model. statistical analysis of the data obtained demonstrated no significant difference in the bilateral thalamus of macaques. our mrs data showed reduced n-acetylaspartate (naa) (p<0.05) glutamate/glutamine (glx) (p<0.05) and elevated myo-inositol (mi) (p<0.05) in the bilateral thalamus during hdt,and all metabolites approached their baseline levels by the fourth scan. these results demonstrate that metabolic changes occur in the thalamus during hdt in rhesus monkeys. the 1h mrs detection of ongoing neuro chemical changes induced by hdt,especially in the thalamus,may contribute to reduce motor control abilities and multiple executive functions in astronauts in a microgravity environment. copyright 2016 zoological society of pakistan.