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George E. Carvell, PhD, PT   University of Pittsburgh
The movie shows a blindfolded rat palpating (whisking) a textured surface (1/4 inch mesh screen). Extracellular microelectrode recordings were made from the right trigeminal ganglion, as well as electromyographic (EMG) recordings from the mystacial pad muscles that move the right whiskers. Action potentials of several individual trigeminal neurons innervating whisker follicles can be seen in the top trace of the oscilloscope screen; EMG (low gain) is displayed as the bottom trace. If you look closely at the upper trace of  the oscilloscope inset you should be able to distinguish at least two different waveforms corresponding to two trigeminal ganglion neurons.
 
ACTION POTENTIAL: RECORDING NEURONAL APs in the Intact Brain
BC&P Box 4.1 Fig A p. 75
  Neuroscientists record extracellular action potentials to learn about the functional properties of individual neurons and populations of neurons within a particular area of the nervous system. Experiments may address questions regarding responsiveness to sensory inputs, production of motor patterns, or task-related activity of neurons in behaving animals. Such recordings are rarely done in human subjects for obvious reasons. However, some investigators do record from selected brain areas when this information is vital to neuro-surgeons who will remove specific brain areas that are thought to be the source of intractable seizures.
  While intracellular recordings can be done in the intact brain (with great difficulty) most intracellular recordings are done with brain slices in a well-controlled environment to record membrane potentials & APs.
Intracellular Recording
Extracellular Recording
PLAY THE MOVIE: Right Audio = Spikes,  Left Audio = EMG