1. ANATOMY AND PHYSIOLOGY OF THE CENTRAL NERVOUS SYSTEM
43
and Davidson, 1966). However, the units whose axons make up the
tectal commissure did respond to the general level of illumination. The
units were inhibited by light and discharged regularly in the dark,
During dark adaptation, the units whose axons were in the tectal commissure were spontaneously active and discharged at a regular rate which
vari6.d widely from unit to unit. Sudden increase in the general level of
room illumination inhibited the discharge rate and was followed by a
rebound acceleration at light- offset. Similar response characteristics have
been found during cellular recordings of tectal units ( Cronly-Dillon,
1964; Jacobson and Gaze, 1964; Mark and Davidson, 1966).
Every conimissural fiber was a slowly adapting unit which gal7e a
prolonged off rcsponse (Mark and Davidson, 1966). Units with this characteristic were found most frequently in layer D (Jacobson and Gaze,
1961) of the optic tectum which was located in the zone of central gray
matter that contains the cell bodies of origin of the tectal commissure
( Ariens Kappers et al., 1960). There were no on unit responses recorded
from conimissural axons. The interocular exchange between the two
tectal hemispheres is soniehow involved in the perceptual mechanism
which is related to fine pattern vision in the fish (Mark and Davidson,
1966).
F. The Optic Tectum and Learning
Using crucian carp, Carassius carassius, Bianki (1960, 1961, from
Bianki and Deniina, 1964) found that animals trained to react to light
or sound stimuli still respond appropriately after the tectal hemispheres
are separated by a longitudinal midline incision. However, the animals
wcre unable to distinguish the positions of the light (spatial orientation)
after sectioning of the optic tectum. The animals also appeared to have
difficulties in locating the position of the sound stimulus. No similar
disturbance in behavior was found after midline incision of the cerebellum. In another series of experiments crucian carp, Carassius carassius,
and carp, Cyprinus carpio, were trained to respond to light or sound by
swimming to one side of an aquarium ( Bianki and Demina, 1964).
Following acquisition of the task one-half of the optic tectum, right or
left, was removed. It was found that within the first 3 days postoperatively, removal of the optic tectum had no effect on the ability of the
animals to give a positive response to thc onsct of light. Approximately
21 days postoperatively the animals started to lose their ability to
spatially orient the stimuli in the testing apparatus. This removal of the
optic tectum had no effect on the animal’s ability to make a brightness
43
and Davidson, 1966). However, the units whose axons make up the
tectal commissure did respond to the general level of illumination. The
units were inhibited by light and discharged regularly in the dark,
During dark adaptation, the units whose axons were in the tectal commissure were spontaneously active and discharged at a regular rate which
vari6.d widely from unit to unit. Sudden increase in the general level of
room illumination inhibited the discharge rate and was followed by a
rebound acceleration at light- offset. Similar response characteristics have
been found during cellular recordings of tectal units ( Cronly-Dillon,
1964; Jacobson and Gaze, 1964; Mark and Davidson, 1966).
Every conimissural fiber was a slowly adapting unit which gal7e a
prolonged off rcsponse (Mark and Davidson, 1966). Units with this characteristic were found most frequently in layer D (Jacobson and Gaze,
1961) of the optic tectum which was located in the zone of central gray
matter that contains the cell bodies of origin of the tectal commissure
( Ariens Kappers et al., 1960). There were no on unit responses recorded
from conimissural axons. The interocular exchange between the two
tectal hemispheres is soniehow involved in the perceptual mechanism
which is related to fine pattern vision in the fish (Mark and Davidson,
1966).
F. The Optic Tectum and Learning
Using crucian carp, Carassius carassius, Bianki (1960, 1961, from
Bianki and Deniina, 1964) found that animals trained to react to light
or sound stimuli still respond appropriately after the tectal hemispheres
are separated by a longitudinal midline incision. However, the animals
wcre unable to distinguish the positions of the light (spatial orientation)
after sectioning of the optic tectum. The animals also appeared to have
difficulties in locating the position of the sound stimulus. No similar
disturbance in behavior was found after midline incision of the cerebellum. In another series of experiments crucian carp, Carassius carassius,
and carp, Cyprinus carpio, were trained to respond to light or sound by
swimming to one side of an aquarium ( Bianki and Demina, 1964).
Following acquisition of the task one-half of the optic tectum, right or
left, was removed. It was found that within the first 3 days postoperatively, removal of the optic tectum had no effect on the ability of the
animals to give a positive response to thc onsct of light. Approximately
21 days postoperatively the animals started to lose their ability to
spatially orient the stimuli in the testing apparatus. This removal of the
optic tectum had no effect on the animal’s ability to make a brightness