Expert: Harriet B Jacobster, Au.D. - 6/17/2008

Question
QUESTION: Hi Harriet.
I realize it's not your area of specialization, but maybe as a doctor you will know the answer. I wanted to ask this question to a neurologist, but haven't found any of them available on this site.

So, my question.
Is it always that first an intent appears in our brain, i.e., we have an intent of opening the door, and only later an impulse is sent into the muscles to perform this activity? Is it always the case, that first an impulse from the brain must be sent so that our body could do any activity? Even when we walk, does the brain have to continuously keep sending signals to our muscles in the legs so that we could take a single step. It seems to me that walking is done without thinking about it, but I may be wrong. Perhaps each time I take a step, even though I do not think about it, the brain sends impulses to the muscles so that I could do it. Do you have any thoughts on this?

Thanks

ANSWER: Hi Luke...
Yes, this is out of my area of expertise; however, I do know a little about this.  There is an "arc," as it were, that occurs when performing most conscious actions.  In the example you gave, the thought is to move the leg, the leg moves, and then there is feedback to the brain on the movement. The brain monitors the movement and then a command is sent for the next movement. This arc continues until the action is complete.  In a normal person, this all feels as if you are doing it without thinking; however, it is a very complex thought process.  Ask anyone who has to learn to walk again after an injury.  
For more in depth information, check out "efferent" and "afferent" nervous systems as well as "proprioception."
It's interesting stuff...have fun.
Harriet B. Jacobster, AuD
Board Certified Doctor of Audiology

---------- FOLLOW-UP ----------

QUESTION: Hello Harriet. Thank you for your answer.
Just for the sake of clarification, I have a short follow-up.
You wrote: ....the thought is to move the leg, the leg moves....

How is that possible that a thought moves anything. When I think of my hand lifting up it does not lift. In my opinion there is a thought and after that we send a signal, an impulse to our muscles in the leg and only then it lifts up or we take a step. Just thinking about it doesn't do anything. Do you agree?

All the best

Answer
Luke,
Yes, you are, in a sense, correct.  I tried to simplify the process. In "normal" people, the thoughts are translated into the impulse, whether it be neural, muscular or both.  However, just as a sidebar, there is a lot of research being conducted using monkeys and brain-computer interfaces.  By using just their "thought," the monkeys are able to move a robotic arm.  This research will be especially valuable for people with movement disorders, such as spinal cord injury, Parkinson's disease, etc.
It really is interesting stuff.  
Harriet B. Jacobster, AuD
Board Certified in Audiology