1. ANATOMY AND PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM
51
The Purkinje cells within this area take various forms in different
species of fish. The more evolved fish demonstrate the most complex
dendritic patterns of these extraordinary nerve cells ( Nieuwenhuys,
1967a; Nieuwenhuys and Nicholson, 1967).
B. Deficit Function
Extensive work on the cerebellum has demonstrated that this portion
of the brain is involved in several functions. Earlier work resulted in
different deficits from similar cerebelIar lesions. After partial or extensive
removal of the cerebellum, these ranged from no deficit in equilibrium,
swimming, courtship, spawning, or parental behavior to severe impairment in swimming movements and sexual behavior (Aronson, 1963;
Healey, 1957). In addition, cerebellar ablation had differential effects
on the ability of operated animals to learn to respond to both light and
sound stimuli.
In recent studies complete removal of the body of the cerebellum of
the dogfish ( a selachian) resulted in a decrease in motor activity,
changes in sensory functions, and marked reduction in activity of the
fish when attempts were made to capture it (Karamyan, 1956). Ablation
of the entire cerebellum resulted in complete loss of locomotion in the
dogfish; however, recovery of function appeared within S-8 hr but the
recovered pattern of swimming was aberrant. In addition to general
locomotor effects, gill movements were disturbed, the animals did not
respond to pain stimuli, and the animals flexed toward the point of
stimulation. The dogfish appeared disoriented in space and often leaped
out of the aquarium. In skates, total removal of the cerebellum did not
appear to result in any motor disorders (Karamyan, 1956). Th‘ is was
linked with the fact that removal of the cerebellum did not result in
degeneration of layers in the optic tectum. Karamyan’s work suggests
a difference in extent of sensory or motor disorder after cerebellum
ablation in dogfish and skates.
In teleosts (goldfish and carp; Karamyan, 1956) complete removal of
the cerebellum resulted in an initial loss of muscle tonus followed by a
spontaneous recovery of function within 4 8 hr; however, the operation
invariably resulted in death. The fish were hypersensitive to touch or
pain and ipsiversive circular motions were often evident. Reaction to
auditory and visual stimuli disappeared completely. Removal of only the
body of the cerebellum resulted in less severe disordcrs in carp than in
goldfish; howevcr, there appeared to be severe motor and sensory disorders in both species. The histological findings showed degenerative
51
The Purkinje cells within this area take various forms in different
species of fish. The more evolved fish demonstrate the most complex
dendritic patterns of these extraordinary nerve cells ( Nieuwenhuys,
1967a; Nieuwenhuys and Nicholson, 1967).
B. Deficit Function
Extensive work on the cerebellum has demonstrated that this portion
of the brain is involved in several functions. Earlier work resulted in
different deficits from similar cerebelIar lesions. After partial or extensive
removal of the cerebellum, these ranged from no deficit in equilibrium,
swimming, courtship, spawning, or parental behavior to severe impairment in swimming movements and sexual behavior (Aronson, 1963;
Healey, 1957). In addition, cerebellar ablation had differential effects
on the ability of operated animals to learn to respond to both light and
sound stimuli.
In recent studies complete removal of the body of the cerebellum of
the dogfish ( a selachian) resulted in a decrease in motor activity,
changes in sensory functions, and marked reduction in activity of the
fish when attempts were made to capture it (Karamyan, 1956). Ablation
of the entire cerebellum resulted in complete loss of locomotion in the
dogfish; however, recovery of function appeared within S-8 hr but the
recovered pattern of swimming was aberrant. In addition to general
locomotor effects, gill movements were disturbed, the animals did not
respond to pain stimuli, and the animals flexed toward the point of
stimulation. The dogfish appeared disoriented in space and often leaped
out of the aquarium. In skates, total removal of the cerebellum did not
appear to result in any motor disorders (Karamyan, 1956). Th‘ is was
linked with the fact that removal of the cerebellum did not result in
degeneration of layers in the optic tectum. Karamyan’s work suggests
a difference in extent of sensory or motor disorder after cerebellum
ablation in dogfish and skates.
In teleosts (goldfish and carp; Karamyan, 1956) complete removal of
the cerebellum resulted in an initial loss of muscle tonus followed by a
spontaneous recovery of function within 4 8 hr; however, the operation
invariably resulted in death. The fish were hypersensitive to touch or
pain and ipsiversive circular motions were often evident. Reaction to
auditory and visual stimuli disappeared completely. Removal of only the
body of the cerebellum resulted in less severe disordcrs in carp than in
goldfish; howevcr, there appeared to be severe motor and sensory disorders in both species. The histological findings showed degenerative