[12] The ability of such hemianopic subjects to become consciously aware of stimuli presented to their blind field is also commonly referred to as "residual" or "degraded" vision.
[5][11][6] Blindsight may be thought of as a converse of the form of anosognosia known as Anton syndrome, in which there is full cortical blindness along with the confabulation of visual experience.
Furthermore, under certain experimental conditions, she could detect a variety of visual stimuli, such as the presence and location of objects, as well as shape, pattern, orientation, motion, and color.
Subjects who had suffered damage to their visual cortices due to accidents or strokes reported partial or total blindness.
This suggests that perceptual awareness is modular and that—in sighted individuals—there is a "binding process that unifies all information into a whole percept", which is interrupted in patients with such conditions as blindsight and visual agnosia.
Another explanation for the phenomenon of blindsight is that even though the majority of a person's visual cortex may be damaged, tiny islands of functioning tissue remain.
[27] More recently, with the demonstration of a direct input from the LGN to area V5 (MT),[28][29][30][31] which delivers signals from fast moving stimuli at latencies of about 30 ms,[32][33] another explanation has emerged.
[36] The pulvinar nucleus of the thalamus also sends direct, V1 by-passing, signals to V5[37] but their precise role in generating a conscious visual experience of motion has not yet been determined.
Evidence of blindsight can be indirectly observed in children as young as two months, although there is difficulty in determining the type in a patient who is not old enough to answer questions.
[38] In a 1995 experiment, researchers attempted to show that monkeys with lesions in or even wholly removed striate cortexes also experienced blindsight.
The monkeys were placed in front of a monitor and taught to indicate whether a stationary object or nothing was present in their visual field when a tone was played.
The monkeys performed very similar to human participants and were unable to perceive the presence of stationary objects outside of their visual field.
To do this, researchers used another standard test for humans which was similar to the previous study except moving objects were presented in the deficit visual field.
[40] Several years later, another study compared and contrasted the data collected from monkeys and that of a specific human patient with blindsight, GY.
By comparing the test results of both GY and the monkeys, the researchers concluded that similar patterns of responses to stimuli in the "blind" visual field can be found in both species.
[41] Lawrence Weiskrantz and colleagues showed in the early 1970s that if forced to guess about whether a stimulus is present in their blind field, some observers do better than chance.
[42][page needed] This ability to detect stimuli that the observer is not conscious of can extend to discrimination of the type of stimulus (for example, whether an 'X' or 'O' has been presented in the blind field).
[citation needed] Electrophysiological evidence from the late 1970s has shown that there is no direct retinal input from S-cones to the superior colliculus, implying that the perception of color information should be impaired.
[43][44][45] However, more recent evidence point to a pathway from S-cones to the superior colliculus, opposing previous research and supporting the idea that some chromatic processing mechanisms are intact in blindsight.
The movement of facial muscles used in smiling and frowning were measured and reacted in ways that matched the kind of emotion in the unseen image.
[53] Alexander and Cowey investigated how contrasting stimuli brightness affects blindsight patients' ability to discern movement.
Prior studies have already shown that blindsight patients are able to detect motion even though they claim they do not see any visual percepts in their blind fields.
[54] To test the effect of brightness on the subject's ability to determine motion they used a white background with a series of colored dots.
[55] To test the relationship between attention and awareness, they had the participant try to determine where a target was and whether it was oriented horizontally or vertically on a computer screen.
To the researchers' delight, he moved around every obstacle with ease, at one point even pressing himself up against the wall to squeeze past a trashcan placed in his way.
The girl's grandfather, Mr. J., had suffered a stroke that had left him completely blind apart from a tiny spot in the middle of his visual field.
To put it in a more complex way, recent physiological findings suggest that visual processing takes place along several independent, parallel pathways.
However, some of these people still experience the blindsight phenomenon,[26] though this too is controversial, with some studies showing a limited amount of consciousness without V1 or projections relating to it.
[34] The information leads to a qualitative assessment that included "scotoma stimulation, with the LGN intact had fMRI activation of ~20% of that under normal conditions".
[62] Other evidence suggests that "the LGN projections that survive V1 removal are relatively sparse in density, but are nevertheless widespread and probably encompass all extrastriate visual areas," including V2, V4, V5 and the inferotemporal cortex region.