9. THE MAUTHNER CELL
M c e l l Spike
Eye muscle EMG
279
-L??
l e f t
right
V
a
right l e f t
-v
l e f t
right "7J"c
right
l e f t
Fig. 9. Responses recorded extracellularly and simultaneously from both Mauthner
cells in brain and both right and left retro-orbital muscle. Corresponding records are
alongside each other. Calibrations: vertical, 2 mV; horizontal, 1 msec for M cell
records, and 2 msec for muscle records. a and b show responses when only one
Mauthner axon was excited and c when both were excited simultaneously.
free-swimming fish produced by a sudden blow to the fish tank or
by a sudden change of illumination (caused, for example, by passing
the hand between a light source and the tank).
When EMGs or ventral root records are inspected it is found that
there is also an output from the spinal cord on the opposite side to
that of the excited Mauthner axon (Figs. 8 and 11). The contralateral
excitatory response is smaller than the ipsilateral one and it comes
about 1-3 msec later. However, the overall movement is to the ipsilateral
side, i.e., that of the excited Mauthner axon; the report to the contrary
by Retzlaff (1957) is in error. The contralateral response, therefore,
may have a role concerned with stabilization and possibly the bringing
about of a brisk end to the swiveling movement of the animal. Its initiation relative to that of the ipsilateral excitation is discussed later (Section VI, E ) ,
B. The Inhibition of the Response
Consider now what happens when both Mauthner cells are synchronously excited. This can certainly be done orthodromically by appropri-
M c e l l Spike
Eye muscle EMG
279
-L??
l e f t
right
V
a
right l e f t
-v
l e f t
right "7J"c
right
l e f t
Fig. 9. Responses recorded extracellularly and simultaneously from both Mauthner
cells in brain and both right and left retro-orbital muscle. Corresponding records are
alongside each other. Calibrations: vertical, 2 mV; horizontal, 1 msec for M cell
records, and 2 msec for muscle records. a and b show responses when only one
Mauthner axon was excited and c when both were excited simultaneously.
free-swimming fish produced by a sudden blow to the fish tank or
by a sudden change of illumination (caused, for example, by passing
the hand between a light source and the tank).
When EMGs or ventral root records are inspected it is found that
there is also an output from the spinal cord on the opposite side to
that of the excited Mauthner axon (Figs. 8 and 11). The contralateral
excitatory response is smaller than the ipsilateral one and it comes
about 1-3 msec later. However, the overall movement is to the ipsilateral
side, i.e., that of the excited Mauthner axon; the report to the contrary
by Retzlaff (1957) is in error. The contralateral response, therefore,
may have a role concerned with stabilization and possibly the bringing
about of a brisk end to the swiveling movement of the animal. Its initiation relative to that of the ipsilateral excitation is discussed later (Section VI, E ) ,
B. The Inhibition of the Response
Consider now what happens when both Mauthner cells are synchronously excited. This can certainly be done orthodromically by appropri-