Physiology 3120 Lecture Notes - Lecture 11: Partial Seizure, Somatotopic Arrangement, Magnetic Resonance Imaging

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Hore Lecture 11
1.a) electrically stimulate the motor cortex
b) magnetically stimulate motor cortex so that the rapidly changing magnetic fields induces a
current on the motor cortex
2. a) too much electricity will destroy neurons
b) different chemicals destroys neurons
3. a) record at a single neuron to see changes with different types of movements
b) evoked potentials in somatosensory cortex lecture
d) PET scan is Positron Emission Tomography where inject radioactive substance and record the
blood flow due to the positrons that come out of that area
e) functional MRI (Magnetic Resonance Imaging) is very popular nowadays where the increased
activity in a specific part of the brain at a specific time is related to the oxygenation from the
blood coming from that specific area
-so applying stimulus to a certain part of the motor cortex will cause movement in certain body
-electrically stimulate leg portion of right precentral gyrus  see flexion of left leg
-stick in microelectrode in arm portion of right precentral gyrus  move around left arm to
induce extracellular currents from neurons that fire APs that will be recorded
-say motor epilepsy focused in right leg portion of precentral gyrus  left leg twitches first, then
trunk twitches, then arm twitches then fingers twitch then face twitches
so area of twitch starts at the focus of the epilepsy and then moves to other parts of the body
according to somatotopic map = Jacksonian March of epilepsy
-motor cortex has LOW threshold
-apply low electrical stimulation in motor cortex to get movement
-apply the same low electrical stimulation in somatosensory cortex, will get tingling
sensation but no movement
3. stick in microelectrode into motor cortex to stimulate neurons for a few seconds at very low
levels, purposeful movements can be produced ie: brings hand to mouth and opens mouth
-so although stimulating just one area of the motor cortex, there is one purposeful movement
in many different muscles
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