OneHalfGiraffe

I would suspect that because this person understands language and can express it with signs better than speech, there is a slight disconnect in the language and motor areas. Specifically, there is a region called Broca's area that is involved in verbal fluency (like recall and production) and it interacts with the motor centers of the tongue and mouth, which may explain why this person struggles with producing words. There are two parts of Broca's area numbered 44 and 45 which do different things. Area 44 is involved in processing of sounds and language production while area 45 is involved in verbal memory. As for this person's ASL efficiency, I wonder if his hand motor centers are more effective than his mouth and tongue centers in relaying thought. ASL is also considered to be less difficult a language than English because it omits articles, etc. and the sentence structure is less complicated, so maybe he finds cutting out some of these words and structuring them differently to be easier, which would increase verbal recall. There is also a school in Canada that works with people that have a variety of disorders and it may be of help to you or this person: http://www.arrowsmithschool.org/arrowsmithprogram/index.html.

1. Amplitude The intensity of a stimulus affects the frequency of the action potential. So, a weak stimulus like 20 mV will cause a small frequency, or a low number of action potentials whereas a strong stimulus like 60 mV will cause a large frequency, or a high number of action potentials. Note that the size of the action potential does not become larger with a strong stimulus; rather, the intensity of the stimulus is related to the frequency of action potentials. This is known as the rate law. Yes, action potentials follow the "all-or-nothing" principle where the signal is either too weak or strong enough to cause a neuron to fire. If the stimulus is strong enough to reach the threshold, then a neuron will fire. The frequency of the action potential is not dependent on the stimulus, you are correct, and this is because the amount of excitation beyond the threshold does not cause a neuron to fire any differently than it would if there were just enough excitability to reach the threshold. It's the number of times a neuron fires in a specific time period that's important, not the intensity of the stimulus. So if you were to measure the number of action potentials that occurred during a 3 second period at 20, 40 and 60 mV, you would want to count the number of times the neuron fired which would determine if the stimulus was weak or strong. In summary, the intensity of a stimulus affects the frequency of the action potential up to the point where it meets the threshold (all-or-nothing), causes the neuron to fire, and the weaker/stronger the stimulus the less/more times the neuron will fire (rate law). 2. Electrode This site may answer your questions regarding number and placement of electrodes: http://www.medicine.mcgill.ca/physio/vlab/CAP/recording.htm Hope this helps!