Superdave, let me sum it up, and if one disagrees then they are completely misinformed, basically what I'm saying is this is the answer to your question.
Just how bad is herb on the brain?
Its not bad at all. Any information saying that herb has a negative effect on the brain was put out and funded by the government. A while back studies were done on monkeys(1950's I believe) where they were given huge amounts of herb, the carcinogens and smoke alone would cause any man(or animal) to become "out of it" or "dazed", anyway, from this experiment the govt. exploited the results which were backed by NO scientific evidence whatsoever and said "marijuana kills brain cells", herb has nothing to do with brain cells whatsoever.
Also, if one is stupid or slow when High then that person was already stupid or slow, herb enhances, not the opposite, herb is not supposed to be used to get stoned and retarded, its intent by God was to help your thoughts elevate to a different plane of thinking, if those who use it and abuse it for personal and party purposes then the negative results they receive, whether it be sleepiness or slowness, are well deserved. peace