16
JERALD J. BERNSTEIN
contralateral olfactory bulb. In addition, the patterns of electrical stimulation of the contralateral olfactory bulb to both the physiologically and
electrically induced discharges were depressed when the anterior commissure of the telencephalon was electrically stimulated (Hara and
Gorbman, 1967). This confirms electrophysiologically the earlier neuroanatomical observation that interbulbar connections carrying olfactory
information are mediated through the anterior commissure ( Nieuwenhuys, 1967b).
Stimulation of the posterior portion of the telencephalon produced
characteristic changes in the synchronous electrical activity of the olfactory bulb (Hara and Gorbman, 1967). These changes varied with changing frequencies of stimulation. Stimulation of the anterior part of the
telencephalon only slightly depressed the intrinsic electrical activity of
the bulb and then only at high frequencies and intensities of stimulation.
Stimulation of the preoptic area of the diencephalon facilitated responses
in the ipsilateral bulb. It would appear that the neurons of the preoptic
nucleus were directly affected by stimulation of the olfactory bulb.
These data indicate that there are olfactory centrifugal systems that
exert a tonic inhibitory influence upon the olfactory bulb of the goldfish.
This influence is mediated along centrifugal nerve fiber bundles in the
medial olfactory tract. The results of the telencephalic stimulation studies
strongly suggest that the bulb can be influenced by activity .originating
in the ipsilateral hemisphere. There is central regulation of afferent transmission within the nervous system of fish (central control of periphery).
This appears to be a common mode of neural integration (Hara and
Gorbman, 1967).
The electrophysiological properties of the nerve fibers of the olfactory tract of the burbot, Lota, were studied by Doving and Gemne
(1965, 1966). The rostra1 portion of the olfactory tract was stimulated
and potentials recorded from the transected caudal stump. The action
potentials of each of four classes of nerve fibers showed two initial components and a third late component. Three components were evident in
the action potentials recorded from the olfactory tract nerve fibers. These
components varied in conduction velocity and refractory period in the
medial and lateral divisions of the olfactory tract. The units recorded
from thc olfactory tract had a mean absolute refractory period of 3.7
msec. The relative refractory period for the units are 16-20 msec for the
first component, 28-39 msec for the second component, and about 120
msec for the third component. Neurons in the olfactory bulb were found
to be spontaneously active and effcrent impulses could be evoked by
stimulation of the ipsi- and contralateral olfactory tracts (Doving and
Gemne, 1966). The postetanic potentiation of the response together with
other evidence in the burbot indicate that as in the goldfish (Hara and
JERALD J. BERNSTEIN
contralateral olfactory bulb. In addition, the patterns of electrical stimulation of the contralateral olfactory bulb to both the physiologically and
electrically induced discharges were depressed when the anterior commissure of the telencephalon was electrically stimulated (Hara and
Gorbman, 1967). This confirms electrophysiologically the earlier neuroanatomical observation that interbulbar connections carrying olfactory
information are mediated through the anterior commissure ( Nieuwenhuys, 1967b).
Stimulation of the posterior portion of the telencephalon produced
characteristic changes in the synchronous electrical activity of the olfactory bulb (Hara and Gorbman, 1967). These changes varied with changing frequencies of stimulation. Stimulation of the anterior part of the
telencephalon only slightly depressed the intrinsic electrical activity of
the bulb and then only at high frequencies and intensities of stimulation.
Stimulation of the preoptic area of the diencephalon facilitated responses
in the ipsilateral bulb. It would appear that the neurons of the preoptic
nucleus were directly affected by stimulation of the olfactory bulb.
These data indicate that there are olfactory centrifugal systems that
exert a tonic inhibitory influence upon the olfactory bulb of the goldfish.
This influence is mediated along centrifugal nerve fiber bundles in the
medial olfactory tract. The results of the telencephalic stimulation studies
strongly suggest that the bulb can be influenced by activity .originating
in the ipsilateral hemisphere. There is central regulation of afferent transmission within the nervous system of fish (central control of periphery).
This appears to be a common mode of neural integration (Hara and
Gorbman, 1967).
The electrophysiological properties of the nerve fibers of the olfactory tract of the burbot, Lota, were studied by Doving and Gemne
(1965, 1966). The rostra1 portion of the olfactory tract was stimulated
and potentials recorded from the transected caudal stump. The action
potentials of each of four classes of nerve fibers showed two initial components and a third late component. Three components were evident in
the action potentials recorded from the olfactory tract nerve fibers. These
components varied in conduction velocity and refractory period in the
medial and lateral divisions of the olfactory tract. The units recorded
from thc olfactory tract had a mean absolute refractory period of 3.7
msec. The relative refractory period for the units are 16-20 msec for the
first component, 28-39 msec for the second component, and about 120
msec for the third component. Neurons in the olfactory bulb were found
to be spontaneously active and effcrent impulses could be evoked by
stimulation of the ipsi- and contralateral olfactory tracts (Doving and
Gemne, 1966). The postetanic potentiation of the response together with
other evidence in the burbot indicate that as in the goldfish (Hara and