Biology Reference
In-Depth Information
23
Rushton and Barlow compared
As can be seen, the theories of light and dark adaptation proposed
by Rushton and Barlow disagreed both with regard to the site of the
gain-determining mechanisms and the question of whether light and
dark adaptation were equivalent.
In the 1965 version, Rushton held that the two processes were
controlled in an AGC pool located centrally to the photoreceptors,
while in the 1972 version he suggested that dark adaptation mainly
occurred in the receptors and light adaptation in horizontal cells.
In both versions he held that light and dark adaptation were quite
different processes.
The noise theory of Barlow, on the other hand, presumed that
light- and dark-adaptation processes were equivalent and located
mainly in the receptors - that light adaptation mainly resulted from
statistical fluctuation of photons of the background light, while dark
adaptation was controlled by photon-like events, possibly originating
from photoproducts as a stream of events fluctuating randomly like
the photons.
