^A A lot of processing is done in the retina as well. This book, however, is not about how the brain processes sensory information, and so I won’t go into those details, but a good resource for anyone who is interested is the recent textbook by Chaudhuri.

^B Psychophysics is the study of the timing of perceptual responses.

^C At the time, only one neuron could be recorded at a time. Georgopoulos and his colleagues trained the monkey so well that each reach from center out was almost exactly the same motion. Recording one or two neurons per day, they then combined all of the reaches the monkey made over the course of several years to create a “pseudo-ensemble” of thousands of neurons. Their experiments have more recently been replicated using smaller sets (dozens) of simultaneously recorded neurons, but the conclusions have not changed.²⁸

^D This mental rotation by the monkey between the immediate reaction of reaching to the cue and the later correction to reach 90 degrees off from it is a special case of the issue we discussed in Chapter 10 that the brain first plans the quick and obvious reaction but can correct it if given time.³¹

^E There is some evidence, for example, that giving some of these patients a rhythm to work with (e.g., through music) can renormalize motion. Sometimes the presence of visual cues is enough to re-enable motion. For example, placing a stick across a patient’s path can force the patient to step over the stick and get started walking again. This is shown very nicely in the movie Awakenings, in which the doctor has the floor painted with black and white squares, which allows the patient, “Rose,” to walk to the window.⁴⁰

^F The brain does not have any local, internal pain sensors, so it is possible to use local anesthesia to silence the sensors in the skin and then manipulate the brain of the patient, while the patient is awake and on the table. I have seen this done during a deep-brain-stimulation surgery in which deep-brain stimulation electrodes were being implanted. The patient was calm and comfortable and chatted with the doctors as they implanted the electrodes in his brain. Most lesion surgeries (e.g., for epilepsy) are done on awake patients, so that surgeons can determine the role of the structures they are removing to make sure they do not remove anything critical (to avoid the tragedy of H.M.).