TOSHIAKI J . HARA
98
trophysiological analysis of the messages conveyed in the olfactory tract.
As already stated above, the first electrophysiological investigation of
this kind was that by Adrian and Ludwig (1938). Similar findings were
reported for catfish by Boudreau (1962) who recorded summated activity
of the olfactory tract and showed that the increases in tract activity were
produced by various chemicals in extremely dilute concentrations. Acetic
acid and butyric alcohol remained effective at concentrations of lo-’’ M
and
M , respectively; at higher concentrations they depressed activity.
Electrical properties of the olfactory tract were studied by analyzing
compound action potential induced by electrical stimulation in the burbot
Lota lota and in some species of the orders Anacanthini and Ostariophysi
(Doving and Gemne, 1965; Doving, 1967). The compound action potential of the olfactory tract had three components with different conduction
velocities ranging from 0.25 to 5.5 meters/sec at 10°C. Generally, the
third component which showed the lowest conduction velocity was
present in the medial bundle of the tract. This component, probably nonmyelinated, might be responsible for connecting the olfactory system with
the hypophysis ( Kandel, 1964; Jasinski et al., 1966, 1967). Furthermore,
the activity of single fibers in the olfactory tract was influenced by stimulating the olfactory epithelium with various chemical solutions in the
burbot when efferent inflow was eliminated by sectioning the olfactory
tract. Most of the chemicals evoked both excitatory and inhibitory types
of response in different individual units. Slow rate of adaptation of the
activity of the secondary neurons to continuous stimulation was observed;
this confirmed earlier findings in catfish by Adrian and Ludwig (1938).
Similar effects on the spontaneous firing of single fibers in the olfactory
tract to afferent olfactory stimulation were obtained by Nanba et al.
(1966) in Abramis and Carmsius. Recently, Westerman and Wilson
(1968) reported the conduction velocity averaging 0.6 meters/sec in the
lateral olfactory tract of the carp.
The demonstration that afferent nerve impulses in the olfactory system can be directly controlled by influences originating in the central
nervous system has been one of the most interesting developments in
physiology of the olfactory system. The action is mediated by way of the
“centrifugal” fiber system, part of which has long been known anatomically ( Sheldon, 1912; Allison, 1953; Kappers et al., 1960; Aronson, 1963).
Section of the ipsilateral olfactory tract caused a marked augmentation
of the induced response of the olfactory bulb to NaCl infusion (Hara
and Gorbman, 1967; Fig. 7). In the preparation sectioned at the midbrain-hindbrain level ( ceroeau isole‘), cutting the olfactory tract eliminated the similar NaC1-induced bulbar response ( Oshima and Gorbman,
1966a). Bulbar potential waves evoked by electrical stimulation of the
98
trophysiological analysis of the messages conveyed in the olfactory tract.
As already stated above, the first electrophysiological investigation of
this kind was that by Adrian and Ludwig (1938). Similar findings were
reported for catfish by Boudreau (1962) who recorded summated activity
of the olfactory tract and showed that the increases in tract activity were
produced by various chemicals in extremely dilute concentrations. Acetic
acid and butyric alcohol remained effective at concentrations of lo-’’ M
and
M , respectively; at higher concentrations they depressed activity.
Electrical properties of the olfactory tract were studied by analyzing
compound action potential induced by electrical stimulation in the burbot
Lota lota and in some species of the orders Anacanthini and Ostariophysi
(Doving and Gemne, 1965; Doving, 1967). The compound action potential of the olfactory tract had three components with different conduction
velocities ranging from 0.25 to 5.5 meters/sec at 10°C. Generally, the
third component which showed the lowest conduction velocity was
present in the medial bundle of the tract. This component, probably nonmyelinated, might be responsible for connecting the olfactory system with
the hypophysis ( Kandel, 1964; Jasinski et al., 1966, 1967). Furthermore,
the activity of single fibers in the olfactory tract was influenced by stimulating the olfactory epithelium with various chemical solutions in the
burbot when efferent inflow was eliminated by sectioning the olfactory
tract. Most of the chemicals evoked both excitatory and inhibitory types
of response in different individual units. Slow rate of adaptation of the
activity of the secondary neurons to continuous stimulation was observed;
this confirmed earlier findings in catfish by Adrian and Ludwig (1938).
Similar effects on the spontaneous firing of single fibers in the olfactory
tract to afferent olfactory stimulation were obtained by Nanba et al.
(1966) in Abramis and Carmsius. Recently, Westerman and Wilson
(1968) reported the conduction velocity averaging 0.6 meters/sec in the
lateral olfactory tract of the carp.
The demonstration that afferent nerve impulses in the olfactory system can be directly controlled by influences originating in the central
nervous system has been one of the most interesting developments in
physiology of the olfactory system. The action is mediated by way of the
“centrifugal” fiber system, part of which has long been known anatomically ( Sheldon, 1912; Allison, 1953; Kappers et al., 1960; Aronson, 1963).
Section of the ipsilateral olfactory tract caused a marked augmentation
of the induced response of the olfactory bulb to NaCl infusion (Hara
and Gorbman, 1967; Fig. 7). In the preparation sectioned at the midbrain-hindbrain level ( ceroeau isole‘), cutting the olfactory tract eliminated the similar NaC1-induced bulbar response ( Oshima and Gorbman,
1966a). Bulbar potential waves evoked by electrical stimulation of the