0
b
Fig. 30. ( A ) Multiple exposures of responses recorded in a group A2 motoneuron
during quiet sounds in vicinity of preparation. ( B ) Responses recorded in cell body
of group A2 motoneuron during spinal cord stimulation below the level of the
recording. a, Stimulus below threshold for excitation of either Mauthner axon; b,
stimulus at threshold for excitation of ipsilateral Mauthner axon; and c, as b, but
preceded by a stimulus applied to contralateral Mauthner axon. Upper trace: response
of excitatory Mauthner cell. Second trace: response of inhibitory Mauthner cell.
Third trace: motonenron response at high gain. Bottom trace: motoneuron response
at low gain. Note that response in a is subthreshold for firing the motoneuron, and
that this is obscured by the full response in b. In c the inhibition prevents the full
responses but does not affect the subthreshold response. Clearly the latter was initiated near the recording electrode, while the inhibition was exerted at a point
remote from this (probably mainly on the ventral dendrite near the point of initiation
of the response to Mauthner axon excitation). Calibrations: vertical, top and second
traces, 2 mV, third traces, 1.25 mV, bottom traces, 20 mV; horizontal, 2.0 msec.