Consciousness and the Social Brain

though only the witch were present. For example, a neuron that codes for green, if it is in a consciousness area of the brain, should be active only when the wicked witch with her green skin rises into consciousness. In contrast, a visual brain area that does not participate in consciousness, that merely processes whatever comes in through the eyes, should be active in the same, unchanging pattern, regardless of whether Dorothy or the witch has risen into consciousness, because the actual visual stimulation to the eyes is constant.
    If anyone hoped to find a specific visual-consciousness network using this method, the hope was disappointed. The answer seemed to be smeared out over the entire visual system. 1 , 3 , 4 No specific network of brain areas stood out as the site of visual consciousness. Some evidence of an effect of binocular rivalry was found almost everywhere, with more of an effect in areas that were higher up the processing hierarchy.
    In the end, the lessons about consciousness from binocular rivalry are ambiguous. A major part of the ambiguity comes from the correlational nature of the experiment. Even if a particular brain area responds in a manner correlated with visual consciousness, do those neurons necessarily cause consciousness? Perhaps they pipe information to some other part of the brain that constructs consciousness. Or perhaps the critical information flows back to those visual neurons. Perhaps some other relationship exists between consciousness and the responses of those particular neurons. The experiment is correlational, with all the interpretational difficulties of that type of study. Correlation does not imply causation.
    At least one clear pattern emerges from the binocular rivalry literature. When one visual stimulus rises into consciousness, its signals throughout the visual cortex grow stronger and more consistent. 1 , 3 – 5 This finding probably fits with most theories of consciousness. It is certainly consistent with the attention schema theory. In the attention schema theory, visual information encoded in visual cortex will join reportable consciousness only when it is strong enough, or consistent enough, or in some other way boosted enough, to robustly impact other brain systems and in that way become linkable to the attention schema.
    I do not mean to suggest that the attention schema theory provides a detailed mechanistic explanation of the results from binocular rivalry. The experiments, because of their correlational nature, are open to multiple interpretations. But the results from that body of work are at least consistent with the attention schema theory. Perhaps I should say the results from binocular rivalry are at least not
inconsistent
with the attention schema theory.
Blindsight

    One of the best-studied syndromes related to consciousness is blindsight. 6 , 7 The cerebral cortex contains an area at the back of the brain called the primary visual cortex. Most visual information that gets into the cortex reaches the primary visual cortex first and then is sent on to other cortical regions. When the primary visual cortex is damaged, such as from a stroke, people report that they are blind in the affected part of visual space. Since the primary visual cortex contains a map of visual space, damage to one part of the map will affect visual processing for only one specific region of the visual world. For example, a patient might be blind in the upper right quadrant. The patient reports a total lack of visual conscious experience in the blind region.
    If you seat a patient of this type in front of a screen and present visual images in the blind region, the patient denies seeing anything. The patient may even remind you, “I’m blind there. Why even bother asking?” But if pressed to guess, many patients can indicate exactly when the image appears. They can point accurately to the stimulus and can sometimes report about its motion and brightness, all the while insisting that nothing is present and that the answers are random guesses. Clearly visual processing is present, visual information is present, and the ability for that information to guide movement is present. But visual consciousness is not present. The brain processes the information, but the information does not reach awareness. Primary visual cortex seems to be necessary for visual awareness. In blindsight, whatever regions of the brain are still receiving visual input, processing it, and responding to it,