v V. S. Ramachandran presents a number of cases where consciousness is affected by damage to the body. Some of these cases are described online at:
v http://www.pbs.org/wgbh/nova/mind/
v The entire video transcript is also online as is a paper Rama.. wrote on these topics..
v Discoveries in the 19th century led to a deeper understanding of localization of brain functions Ð especially contralateral connections between cerebral hemispheres and body movements. Working on birds and dogs, then apes and finally humans -- a similar pattern of sensory-motor correlations were obtained.
v http://human-nature.com/mba/chap7.html
v There's simplistic but cute animated sensori-motor homunculus at:
v www.cs.uta.fi/~jh/homunculus.html
v and PBS has a similar Penfield based demonstration
v www.pbs.org/wgbh/nova/mind/probe.html
v (Its simplistic in that there are not sharp "edges" separating one area from another but instead a neuron population gradient -- in the center of an area for example, most neurons serve such and such a function. This may help explain the "phantom" phenomenon.)
v Ramachandran suggests phantoms result from sensory neurons being stimulated by neighboring neurons with inputs from other body areas, e.g. cheek input stimulates arm receptors.
v Seeing without awareness? Rama's suggestion is that two visual pathways are operative in normal humans Ð the most recent and significant one is accompanied by awareness as it functions. The older pathway, carrying less detailed information, is not accompanied by awareness.
v (An alternative possibility is that small populations of neurons remain active, but in insufficient numbers to attain consciousness. And of course there is the old idea of "hysterical blindness" where there is no actual physiological deficit. This isn't a possibility here.)
Graham Brown's phenomenal experience appears to be quite different from one visual field to the other and suggests what we independently know, that various visual features are processed in parallel and reassembled or bound together to provide the normal visual experience. Hence his damaged field "senses" movement but not form.
v I imagine these arise for diverse reasons; one of them suggested and confirmed by Rama and his "mirror box."
Visual Neglect
(inattention to the left -- in this case -- visual field) This patient also doesn't "see" the neglected field in her imagination as reflected her drawings.
v
Jean Marie Joseph
Capgras ,(1873-1950)
French psychiatrist.
v
The delusion that a
close relative or friend has been replaced by an impostor, an exact double,
despite recognition of familiarity in appearance and behaviour.
v
J. M. J. Capgras, Jean
Reboul-Lachaux (1923) L'illusion des "sosies" dans un dŽlire
systŽmatisŽ chronique. Bulletin de la SociŽtŽ clinique de
mŽdecine mentale, 6-16.
v
This would be an example
of a brain injury "unbinding" an essential component of recognition
of objects.
epilepsy, temporal lobes and God
(seizures and emotional salience of objects, a tendency to attribute cosmic significance to everything! Brain regions in temporal lobes conducive to religion? Since this video, there has been a lot of research on this and controversial interpretations of the data.)
v
Fritsch and Hitzig, Uber
die elektrische Erregbarkeit des Grosshirns, Arch. f. Anat., Physiol. und wissenschaftl. Mediz.,
Leipzig, 37, 1870, 300-321.
v
(cited in Young, R. M.
1970 online :
v
http://human-nature.com/mba/chap7.html
v
Penfield, W., & Roberts, L. (1959). Speech and
brain mechanisms. Princeton, NJ:
Princeton University Press.
v
Wessinger, C. M., Fendrich, R., & Gazzaniga, M.
(1997). Islands of residual vision in hemianopic patients. Journal of cognitive
neuroscience, 9(2), 203-221.
v (presents an alternative account of blindsight to that presented by Ramachandran. Both are plausible as far as I can tell.)
