Biology Reference
In-Depth Information
Presupposing that rod signals had access to all three cone
pathways of normal trichromatic colour processing, and that rod
and cone signals acted with the same sign on shared neurons, they
attempted to explain these different rod-hue biases on the assump-
tion that the green rod-hue bias resulted from a stronger rod influence
on M-cone pathways than on L-cone pathways, while the blue and
short-wave red rod-hue biases resulted from a relatively strong
rod input into S-cone pathways, i.e. pathways to small bistratified
ganglion cells (Buck,
2004
).
The basic assumption that rod and cone signals may mimic
and reinforce each other was found to be consistent with a wide
variety of psychophysical studies and also to be consistent with
more recent anatomical and neurophysiological evidence indicating
that rod signals, both through the primary and secondary pathway,
are transferred to the cone pathway via gap junctions (see Fig. 10.1).
Since gap junctions are sign-conserving synapses, signals from rods
will tend to enhance cone signals both through the primary and
secondary rod pathway (Daw
et al
.,
1990
).
Interestingly, the finding that the rod signals are transferred
to cone pathways provides strong evidence that the cone receptor
systems preceded the rod system in the evolutionary process and that
the rod system simply utilized the already existing cone pathway in
order to convey their information to the brain.
14.5. Contribution of J. L. Nerger and
co-workers
In a series of papers at the turn of the twentieth century, Nerger,
Volbrecht and co-workers investigated the effect of rod activity on
the unique hues of the spectrum; the pure blue, green and yellow (see
Nerger
et al
.,
1995
,
1998
; Volbrecht
et al
.,
2000
). The measurements
were made both during the cone plateau period when presumably
only cones were activated and in a dark-adapted state when both rods
and cones were activated.
The results showed that the added rod activity in the
dark-adapted state may change the spectrum locus of all three unique
