The reflection of retinal light response information onto the superior colliculus in the rat.
BACKGROUND
The functional principles of mediation of retina-encoded visual information through the optic nerve to the superior colliculus (SC) of the contralateral brain hemisphere were investigated in non-drugged and unrestrained albino rats by considering the following issues: (1) the type of information transmitted, (2) the response components of the retina and SC involved in encoding the transmitted information, and (3) the timing of related processes.


METHODS
The field potential responses for different intensities of flashes, under different background illuminations, were simultaneously recorded from the sclera area of the eye and the optic layer of the contralateral SC.


RESULTS
It was found that the b-wave crest of the retinal electroretinogram (ERG) and the peak-1 or peak-2 of the SC correlate by their amplitude, while the a-wave trough of the retinal ERG and the peak-1 of the SC correlate by their latency. The values of these mutually correlating response components were invariably determined by the given light response bias of the retina (photoreceptors), the change in the photon flux of the light stimulus and, obviously, the change in the wavelength of the light stimulus. The a-wave trough, peak-1, b-wave crest and peak-2 were invariably induced in this time-order.


CONCLUSIONS
The data suggest that the information properties of (a) intensity, (b) presentation time and, obviously, (c) colour of the light stimulus, such as are shed on the retina, and information about the light response bias of the retina are mediated correlatively and quantitatively to the cell network system of the SC through the optic nerve. These processes must happen during the a-to-b-wave phases of the ERG. The data indicate that the random-type variations in the activity of the related cellular systems may actually be harnessed in mediating the defined information properties of the visual stimulus from the retina to the SC of the brain through the optic nerve. This study shows a method of measuring the function of the optic nerve.
Valjakka
Antti
A
Department of Pharmaceutics, University of Kuopio, P.O. Box 1627, Kuopio 70211, Finland. anttivaljakka@dnainternet.net
D000818:Animals; D004596:Electroretinography; D005071:Evoked Potentials / Q000502:physiology; D008027:Light; D008297:Male; D009900:Optic Nerve / Q000502:physiology*; D010775:Photic Stimulation; D051381:Rats; D012160:Retina / Q000528:radiation effects*; D013477:Superior Colliculi / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology