My intuition was very wrong. I thought that the greyness of depression was part of a change in the process of constructing consciousness that reduced the vividness of experience. A recent post in Discovery Magazine by E. Strickland (here) points to two papers which put the dulling of experience near the sense organ level rather than the consciousness level.
Here is a bit from the abstracts of these papers:
Biol Psychiatry. 2010 Jul 15;68(2):205-8. Epub 2010 Mar 31 Seeing gray when feeling blue? Depression can be measured in the eye of the diseased Bubl, Kern, Ebert, Bach, Tebartz van Elst.
Everyday language relates depressed mood to visual phenomena. Previous studies point to a reduced sensitivity of subjective contrast perception in depressed patients. One way to assess visual contrast perception in an objective way at the level of the retina is to measure the pattern electroretinogram (PERG). To find an objective correlate of reduced contrast perception, we measured the PERG in healthy control subjects and unmedicated and medicated patients with depression…Unmedicated and medicated depressed patients displayed dramatically lower retinal contrast gain. We found a strong and significant correlation between contrast gain and severity of depression. This marker distinguishes most patients on a single-case basis from control subjects. A receiver operating characteristic analysis revealed a specificity of 92.5% and a sensitivity of 77.5% for classifying the participants correctly.
And doi:10.1016/j.neuroscience.2010.05.012 Reduced olfactory bulb volume and olfactory sensitivity in patients with acute major depression Negoias, Croy, Gerber, Puschmann, Petrowski, Joraschky, Hummel.
The purpose of this study was to assess olfactory function and olfactory bulb volume in patients with acute major depression in comparison to a normal population. Twenty-one patients diagnosed with acute major depressive disorder and 21 healthy controls matched by age, sex and smoking behavior participated in this study. Olfactory function was assessed in a lateralized fashion using measures of odor threshold, discrimination and identification. Olfactory bulb volumes were calculated by manual segmentation of acquired T2-weighted coronal slices according to a standardized protocol. Patients with acute major depressive disorder showed significantly lower olfactory sensitivity and smaller olfactory bulb volumes. Additionally, a significant negative correlation between olfactory bulb volume and depression scores was detected. Their results provide the first evidence, to our knowledge, of decreased olfactory bulb volume in patients with acute major depression. These results might be related to reduced neurogenesis in major depression that could be reflected also at the level of the olfactory bulb.
It is a good thing to have my intuitions shown to be very wrong every now and then. Keeps me honest and on my toes. I will have to be careful about thinking that one of the minor reasons for consciousness is to supply vividness to our experiences to engage and entertain us. Forget that idea unless there is some evidence for it.