2. ELECTROPHYSIOLOGY OF THE RETINA
35
of analysis of the electroretinogram (ERG) into three components by
Granit (1933) using the cat retina has now been generalized to all the
vertebrates. The ERG represents a sum of electrical activities in individual retinal cells, whereas the optic nerve activity represents their
integrated result. These two electrical phenomena were therefore utilized
for the study of retinal mechanisms and of information sent to the brain
along the optic nerve (Adrian and Matthews, 192%; Granit, 1933).
A striking advance was made when the microdissection technique
was introduced into this research field by Hartline (1935, 1938); th' IS was
rapidly followed by the use of the microelectrode technique by Granit
and Svaetichin (1939). These two techniques made it possible to record
the impulse discharge in single ganglion cells (or in single optic nerve
fibers) in response to a variety of photic stimulations, which differ in
intensity, wavelength, area, pattern, and so forth.
The microelectrode technique has the additional advantage that
recordings can be made from within the retinal tissue. The depth recording of the ERG with microelectrodes advanced intraretinally served for
more direct localization of the ERG components into retinal layers and
for recording potentials at the electrode tip. Since the first use of this
method (Tomita, 1950), it has now developed into the technique of
intracellular recording from single retinal cells to be described later. It
should be emphasized that many of the recent important contributions
in the field of electrophysiology of the vertebrate retina have been accomplished by the application of these microtechniques to fish retinas.
Readers who are interested in more background information should refer
to Granit (1947, 1962) and Brindley (1960).
11. ELECTRORETINOGRAM
A. Electroretinogram as a Mass Response
As early as 1865 Holmgren discovered that a pair of electrodes, one
on the cornea and the other on the back of the eye, would record a weak
electrical change when the retina is illuminated by light. This response,
now generally known as the electroretinogram or ERG, can also be obtained from the eye with its anterior half removed, or from the retina
isolated completely from the rest part of the eye. Two ERG recordings
from the same eye of the carp but at different adaptation states are illustrated in Fig. 2. The upper tracing is from the eye which has been
dark-adapted ( scotopic) and the lower after light adaptation ( photopic),
35
of analysis of the electroretinogram (ERG) into three components by
Granit (1933) using the cat retina has now been generalized to all the
vertebrates. The ERG represents a sum of electrical activities in individual retinal cells, whereas the optic nerve activity represents their
integrated result. These two electrical phenomena were therefore utilized
for the study of retinal mechanisms and of information sent to the brain
along the optic nerve (Adrian and Matthews, 192%; Granit, 1933).
A striking advance was made when the microdissection technique
was introduced into this research field by Hartline (1935, 1938); th' IS was
rapidly followed by the use of the microelectrode technique by Granit
and Svaetichin (1939). These two techniques made it possible to record
the impulse discharge in single ganglion cells (or in single optic nerve
fibers) in response to a variety of photic stimulations, which differ in
intensity, wavelength, area, pattern, and so forth.
The microelectrode technique has the additional advantage that
recordings can be made from within the retinal tissue. The depth recording of the ERG with microelectrodes advanced intraretinally served for
more direct localization of the ERG components into retinal layers and
for recording potentials at the electrode tip. Since the first use of this
method (Tomita, 1950), it has now developed into the technique of
intracellular recording from single retinal cells to be described later. It
should be emphasized that many of the recent important contributions
in the field of electrophysiology of the vertebrate retina have been accomplished by the application of these microtechniques to fish retinas.
Readers who are interested in more background information should refer
to Granit (1947, 1962) and Brindley (1960).
11. ELECTRORETINOGRAM
A. Electroretinogram as a Mass Response
As early as 1865 Holmgren discovered that a pair of electrodes, one
on the cornea and the other on the back of the eye, would record a weak
electrical change when the retina is illuminated by light. This response,
now generally known as the electroretinogram or ERG, can also be obtained from the eye with its anterior half removed, or from the retina
isolated completely from the rest part of the eye. Two ERG recordings
from the same eye of the carp but at different adaptation states are illustrated in Fig. 2. The upper tracing is from the eye which has been
dark-adapted ( scotopic) and the lower after light adaptation ( photopic),