To assess early consequences of severe traumatic brain injury (TBI) we used lateral fluid percussion model (3-4 atm) in male Sprague-Dawley rats. To evaluate symptoms of anxiety light-dark box and elevated plus-maze tests were used; to estimate global brain function and sleep disturbances electrocorticogramms (ECoG) were recorded prior TBI and during acute posttraumatic period (first week after injury). Our results suggest that during acute posttraumatic period rats demonstrate symptoms of anxiety associated with reduced percentage of REM-sleep as well as its decreased frequency and amplitude.