Eventually, the researchers may even understand how the brain creates visual consciousness itself — and why V1 is so crucial. One idea is that consciousness relies on communication to and from many areas of the brain — and maybe V1 is working as a hub that helps orchestrate that broadcast.
People with blindsight cannot see what's in front of them, yet they can somehow "feel" the contents of a scene Credit: iStock. Picking apart the experience may also reveal further clues about the power of unconscious mind. To understand how, imagine that you are part of a strange puppet show. You have been blindfolded, and your limbs are tied to invisible strings.
Every so often, they are tugged here or there by a hidden puppet master, leading you through a complicated dance. That puppet show is essentially what happens when someone with blindsight navigates their way past obstacles — with the non-conscious mind acting as the puppet master.
This, in turn, begins to cast doubt on some long-held assumptions about the very nature, and purpose, of consciousness. After all, it is by no means certain that other animals have a rich inner life like us, so it must have emerged for some reason. In this way, our heightened awareness helps highlight the most important parts of a scene, giving us the chance to respond. By exploring their unconscious, blindsight patients have opened new paths for the study of the human mind Credit: iStock.
Except Robert Kentridge at the University of Durham has evidence to suggest this too may be wrong. His insight came when he was talking to a blindsight subject in between some of the basic visual tests, in which he flashed different images at different parts of the blind spot.
The subject had said that he thought he would do better if we were told where, in the blind spot, the image would appear. Even so, he was happy to play along and design a separate experiment where he could give the subject a clue about where the image might appear. The results were a kind of paradox : even though the participant was still not able to actually see anything, his subconscious discrimination seemed to be quicker.
For this reason, Kentridge thinks we need to rethink our ideas about consciousness and attention. Rather than it acting as a spotlight to boost perception, he instead suspects that consciousness may have evolved to boost memory, drawing together all the different pieces of information into a cohesive picture that is easier to remember.
These are just the first of many clues that may eventually solve the riddles of human consciousness. Sadly, Daniel will not be taking part in those further experiments.
By gently reaching into his darkness, however, he has shown the way for others to follow, guiding us through some of the biggest mysteries of the human mind. In Depth Neuroscience. Blindsight: the strangest form of consciousness. Share using Email. The method of testing for visual capacity is usually deeply different in humans and in other animals. Humans are typically asked to give descriptions or to comment on visual appearances and differences, whereas animals are trained to make alternative choices for which they are usually rewarded, devoid of any commentary.
Even when a human subject is asked to make a discrimination between, say, two wavelengths, he is usually explicitly instructed verbally as to what colour attribute he should be responding, and more importantly there is an important implicit assumption that he will be aware of that attribute, or will tell us if he is not. But what would obtain if the human subject is tested in a manner that is closer to animal methodology, being asked simply to make a forced-choice "guess" or choice between the visual stimuli whether or not he cannot "see" them, e.
The result of using this methodology was that DB could succeed in a variety of discriminations by "guesswork" in his blind field, even though he said he did not "see" them. He could, for example, tell whether a grating was oriented in one or another direction, whether a stimulus was moving or stationary. His visual acuity could be measured by varying the spacing of a grating, with forced-choice guesses about whether there were "lines" or "no lines. In fact, his ability matched reasonably well that of monkeys without primary visual cortex.
The most remarkable feature undoubtedly was the high level of visual proficiency in making discriminations in the absence of acknowledged awareness by him. He was astonished when shown his results, as were Weiskrantz and Warrington when conducting the tests that demonstrated his impressive performance without awareness.
DB remained convinced that he was simply guessing and was at chance. These first results, by Weiskrantz and coworkers, were published in Brain in It was the first account of a hemianopic subject's performance over a wide range of visual tasks combined with his parallel "commentaries" about them.
In later research the pattern was formalized by the addition of "commentary response keys" as well as "discrimination response keys. The oxymoron "blindsight" was generated as a result of Weiskrantz having to respond urgently to produce a title for a seminar he was invited to give to Oxford neurologists, and under this pressure he spontaneously came up with "Blindsight and Hindsight" - "blindsight" to describe the striking behavioural results and "hindsight" to suggest an implication of the midbrain visual pathways for its mediation.
The term first appeared in print in a short article in Lancet in Sanders et al. The term stuck - so much so that it eventually appeared in standard dictionaries. DB continued to be the subject of sustained study over ten years by Weiskrantz in collaboration with Warrington, resulting in a book "Blindsight" in , with a second edition in , in which DB's capacity to detect, to discriminate orientation, movement, form, under a variety of conditions was studied and their possible implications considered..
It early became apparent, also, that rapid transient events, e. This was dubbed Blindsight Type 2 in contrast to the situation in which there was absolutely no reported experience, Type 1. DB later returned as a focus of interest and a number of follow-up studies appeared well into Weiskrantz et al. The basic phenomenon of "unconscious" visual capacity remains, although his sensitivity has improved markedly.
Other subjects, e. More recently it has become clear that the phenomenon is not rare. Sahraie et al. Types of visual attributes that can be discriminated by blindsight subjects in the absence of their experience of the stimuli include colour, different orientation of lines or gratings, simple shapes, motion, onset and termination of visual events. Interestingly, the emotional expression of unseen faces in the blind field can be "guessed" at better than chance levels.
There are, however, changes in relation to normal vision. Motion perception is retained for simple displacement of a bar or a spot, but more complex motion patterns "third order motion" seem to be seriously affected.
Good colour discrimination remains again, in the absence of any experience of colour per se, but there is a shift towards a relative increase in sensitivity of long wave-lengths red and a decrease of middle wave-lengths green.
From that, we may be able to work out what the evolutionary function of consciousness is, which is something that we are still relatively in the dark about. On the other hand, if we could prove that people with blindsight are conscious of what is in front of them, this raises no less interesting and exciting questions about the limits of consciousness.
What is their consciousness actually like? How does it differ from more familiar kinds of consciousness? And precisely where in the brain does consciousness begin and end? If they are conscious, despite damage to their visual cortex, what does that tell us about the role of this brain area in generating consciousness?
In my research, I am interested in the way that blindsight reveals the fuzzy boundaries at the edges of vision and consciousness. My goal is to develop more nuanced views of perception and consciousness that can help us understand their distinctly fuzzy edges.
To ultimately understand these cases, we will need to employ careful philosophical reflection on the concepts we use and the assumptions we make, just as much as we will need a thorough scientific investigation of the mechanics of the mind. Decarbonising Transport: How do we work together to make an impact? Sport for a new generation — Birmingham, Birmingham. Eyewitness identification from a different angle — Birmingham, Birmingham. Edition: Available editions United Kingdom. Become an author Sign up as a reader Sign in.
Brain scan of a boy with fever and alteration of consciousness. Suttha Burawonk. Henry Taylor , University of Birmingham.
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