What do the hospital mean by someone having slow brain activity?

[bingbong4]

My partner who is 6 weeks into a coma had a brain scan to check for epilepsy. it came back clear from epilepsy but we were told that he has slow brain activity.

[fity123r]

hi my husband has a hypoxic brain injury last year thats what the doctors said to me to that his brain has slow activity but i really dont know what that means myself and i really would want some in this forum to give a rough idea what that means

apart from that my husbands scans wer clear but lata had aggresive outburts no sleeping in the night or sleeping more than 18hrs