58
JERALD J . BERNSTEIN
could be expected, there was a decrease in latency of response as more
afferent channels were activated. Units discharging trains of spikes show
the effect of summation of the excitatory influences on the dendritic field.
The receptive fields of the reticuloniotor cells were mapped (Restieaux and Satchell, 1958). These afferent fields were grouped into four
types of reticulomotor neuron responses: one group of neurons had a
receptive field which could be excitcd by stroking of the skin over any
part of the body; a second group had receptive fields which were limited
to the region anterior to the posterior margin of the pectoral fins and
could also be activated from the stimulation of the ophthalmic and
hyomandibular nerves; a small number of units had an extremely
restricted field and only responded to stimulation of the ophthalmic
nerve or stroking of the surface of the snout; however, the large majority
of reticulomotor neurons had receptive fields which werc limited to the
region anterior to the pectoral fins and responded to stimulation of the
ophthalmic and hyomandibular ncrves. Afferent nerve fibers were also
found to innervate the reticuloniotor cells from the optic tectum, since
stimulation of the optic tectum resulted in the discharge of thcse cells
with latencies similar to thosc found from the afferent input derived
from stimulation of the ophthalmic nerve ( Restieaux and Satchell, 1955).
There was a balance of excitatory and inhibitory afferent input into
the reticulomotor system which was partially correlated with asymmetry
of the bilateral affcrent input. Units were excited and discharged with
ipsilateral stimulation of the left Ophthalmic nerve but were inhibited by
a synchronous contralateral stimulation of the right ophthalmic nerve.
The contralateral area of inhibition corresponded to the ipsilateral arca
of excitation. The integration of afferent sensory information of the body
and its resolution into a pattern of reticulomotor discharges appear to
be the function of the reticulomotor system within the brain stem of
the shark. The reticulomotor nerve fibers distribute information from
the brain stem to the motor neuron pool of the trunk and tail. This
information is carried in the rcticulospinal systcm within the spinal cord
(Restieaux and Satchell, 1958).
D. Taste
Electrophysiological studies have revealed that some fish possess
chemoreceptors which respond to the four classic types of taste quality,
i.e., sweet, salty, sour, and bitter. Howcver, the stimulation effcct of sapid
substances on fish chemoreceptors was relative to the species of animal
utilized and not to the substance tested (Bardach and Casc, 1965;
JERALD J . BERNSTEIN
could be expected, there was a decrease in latency of response as more
afferent channels were activated. Units discharging trains of spikes show
the effect of summation of the excitatory influences on the dendritic field.
The receptive fields of the reticuloniotor cells were mapped (Restieaux and Satchell, 1958). These afferent fields were grouped into four
types of reticulomotor neuron responses: one group of neurons had a
receptive field which could be excitcd by stroking of the skin over any
part of the body; a second group had receptive fields which were limited
to the region anterior to the posterior margin of the pectoral fins and
could also be activated from the stimulation of the ophthalmic and
hyomandibular nerves; a small number of units had an extremely
restricted field and only responded to stimulation of the ophthalmic
nerve or stroking of the surface of the snout; however, the large majority
of reticulomotor neurons had receptive fields which werc limited to the
region anterior to the pectoral fins and responded to stimulation of the
ophthalmic and hyomandibular ncrves. Afferent nerve fibers were also
found to innervate the reticuloniotor cells from the optic tectum, since
stimulation of the optic tectum resulted in the discharge of thcse cells
with latencies similar to thosc found from the afferent input derived
from stimulation of the ophthalmic nerve ( Restieaux and Satchell, 1955).
There was a balance of excitatory and inhibitory afferent input into
the reticulomotor system which was partially correlated with asymmetry
of the bilateral affcrent input. Units were excited and discharged with
ipsilateral stimulation of the left Ophthalmic nerve but were inhibited by
a synchronous contralateral stimulation of the right ophthalmic nerve.
The contralateral area of inhibition corresponded to the ipsilateral arca
of excitation. The integration of afferent sensory information of the body
and its resolution into a pattern of reticulomotor discharges appear to
be the function of the reticulomotor system within the brain stem of
the shark. The reticulomotor nerve fibers distribute information from
the brain stem to the motor neuron pool of the trunk and tail. This
information is carried in the rcticulospinal systcm within the spinal cord
(Restieaux and Satchell, 1958).
D. Taste
Electrophysiological studies have revealed that some fish possess
chemoreceptors which respond to the four classic types of taste quality,
i.e., sweet, salty, sour, and bitter. Howcver, the stimulation effcct of sapid
substances on fish chemoreceptors was relative to the species of animal
utilized and not to the substance tested (Bardach and Casc, 1965;