| PURPOSE |
Deegan and Jacobs worked with bushbabies, which have
a very interesting visual history. Because this animal is nocturnal,
it was previously thought that it only contained rods. However, an
experiment in 1968 proved differently - Dodt found that the spectrum of
color that the bushbaby could see was much higher. These scientists
used a noninvasive electrophysiological technique, electroretinogram (ERG)
flicker photometry to examine the number of cone types in the bushbaby
retina and to assess these spectral properties. |
| PROCEDURE |
To do this, the bushbabies (Otelemur crassicaudatus)
were anesthetized and presented with stimuli. The ERG recorded retinal
potentials of the animals from light pulses produced. In this way
the scotopic spectral sensitivity and the photopic spectral sensitivity
could be determined. |
| RESULTS |
The results of this experiment are shown below.
On the left is a graph of the effects of chromatic adaption
on ERG equations. Because the relative sensitivity does not change
as a function of adaptation condition, it follows that the eye has only
one type of cone pigment.
The graph on the right shows the scotopic spectral sensitivity
function. This graph is used to determine the maximum wavelength
of light that the bushbaby can detect. It is from this information
that Deegan and Jacobs could make conclusions.
Because there is a clear shift from the scotopic to the
photopic sensitivity, bushbabies can be said to have only dichromatic color
vision. |
courtesy Deegan and Jacobs
|
courtesy Deegan and Jacobs
|
