Biomedical Engineering Reference
In-Depth Information
Laser
light
fluorescent
light
fluorescent
molecule
out
Cell
Membrane
in
Ion
Channel
current
Figure 10.1:
Molecular binding of a fluorescent molecule to the cell membrane.
F
LQ
F
RXW
/LJKWIUHTXHQF\
Figure 10.2:
Left: Example absorption (dotted) and emitted spectra for a fluorescent molecule. Right:
Example of proportionality between
V
m
and emitted light intensity.
to examine populations of neurons, an individual neurons or even regions of a single neuron. Lastly, new
dyes have been discovered that are dependent on
Ca
2
+
]
[
instead of
V
m
, opening up the potential to better
understand bursting and synaptic transmission.
The are, however, a number of disadvantage of optical mapping. First, the equipment is more
expensive than using Ag-AgCl electrodes. Second, the dye itself is somewhat toxic and therefore can not
be used for long periods of time or in humans. Third, as light can only penetrate a short distance into
tissue, optical imaging is generally limited to thin slices of tissue. Lastly, the response times of fluorescent
dyes are orders of magnitude slower than electrodes.Therefore, resolving fast propagation can be difficult.
