Carvell, PhD, PTUniversity
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 ofthe 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
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
to record membrane potentials & APs.
THE MOVIE: Right Audio = Spikes,Left Audio = EMG