Aphasia

http://www.merck.com/mmpe/sec16/ch210/ch210d.html

Nope, no body language:
Receptive (sensory, or Wernicke's) aphasia is inability to comprehend words or to recognize auditory, visual, or tactile symbols.
Nor would he recognize a McDonalds symbol if he was hungry, lol

As my neuro proffesor said, you can't have a drug magically target specific neurons in a specific part of the brain and on a specific side.
(This is true for most of the brain and/or peripheral neurons where the receptors are basically the same. There are exceptions in areas such as parts of the brain stem, where the neurons are unique. For example- a plant toxin causes a Parkinson-like disease in Horses by targeting an area with a really complicated name. Don't ask me for a human example- I'm a vet student )

May I suggest dysarthria(found on above link) - your baddies could inject something into those muscles, or hit him or anything.

If you want to get creative, have them use a special devise to punch through his skull and inject a drug locally to that area of his brain. Also, this could leave him with some residual damage from the invasiveness...
Course, this is getting more serious...

And for those curious, back to the horse example:
This plant (Yellow Star Thistle) is toxic to horses in large amounts, causing equine nigropallidal encephalomacia ("chewing disease"). The first signs of poisoning are an inability to eat or drink as the muscles of the lips, face, and tongue become stiff and swollen, giving the horse a fixed expression. Poisoning eventually results in permanent brain damage, and severely affected animals eventually die of thirst and starvation. Sheep, cows and other livestock are not affected

Good question!
Christina

I strongly recommend the neurological case studies of Oliver Sacks (The Man Who Mistook His Wife For A Hat, etc. ) for research into neuro conditions. Gorgeous mixture of the literary and the medical - research will never be so much fun.

Aphasias vary enormously. As language production and comprehension centres are somewhat separate it is entirely possible to understand language perfectly but be unable to produce it. And it is 100% possible, in fact common, to ben utterly unable to understand speech but perfectly able to understand symbols and body language.

I think the term "aphasia" is used to cover a variety of symptoms related to speaking and understanding speech. I know that my grandmother had "aphasia" after her stroke. She could understand other people perfectly, but would become very frustrated when she was trying to make herself understood.

Maybe your imaginary drug could mimic those symptoms.

She could speak, and it got better with practice. However, certain words eluded her. You could tell that she knew the concept that she was trying to convey, but the word was "on the tip of her tongue" yet just out of reach-- very frustrating.

For her, she got certain words mixed up. For example, she couldn't remember my name, so she would call me "Jimmy" -- my father's name, because she could remember that I was his oldest daughter. She might be able to name every flower in the garden, but struggle for 5 minutes to come up with the word for sock, only to end up with "shoe" or "glove". Her word substitutions were always related in some way.

She understood body language perfectly and would often use it as a substitute. For example, she would mimic rocking a baby if she couldn't remember the word "baby", or she would twirl her finger at her temple for "crazy" as a way of conveying her own frustration with an uncooperative brain.

I've had aphasia with some of my migraines. It's a pretty interesting experience - but definitely not one I'd care to repeat. Sometimes, I lost the ability to tell time, other times, I couldn't understand anything written, other times I couldn't understand spoken English, sometimes a combination thereof. I don't remember whether nonverbal worked or not - I suspect not, but could have been just as much a part of pain and not wanting to bother with the effort combined with holing up in a dark room.


ETA: My short term memory is also crapped when I have migraines. During the worst ones, I don't remember anything for days on either side of the migraine and including the migraine. Huge chunks of time gone.