This is the paper I wrote in Leiden for the Consciousness course.

Introduction

Will Stephen Hawking be conscious still if he loses control over his last healthy muscle? Most people who are acquainted with his thoughts would definitely agree that he will still be conscious, but locked in as if guarded by the multi-headed dog Cerberus in Greek mythology who makes sure nothing escapes the underworld. In Hawking’s case, nothing would escape his mind, no one else but he would know its content. Just like having the experience of knowing who Stephen Hawking is made you expect he would be conscious, so do our brain’s expectations shape what we become conscious of. These expectations are the Cerberus of consciousness that our brains have learned through experiencing our environments. These expectations are like perception filters that consider unexpected events as non-relevant, and thus keep them from awareness.

From experience to awareness

Blakemore and Cooper (1970) demonstrated that kittens deprived from horizontal lines in early development did not respond to horizontal stimuli later, even when they had learned to navigate their new environment after the early deprivation stage. In addition, their cortical cells did not respond to the deprived orientation. What this means is that kittens who had seen only vertical lines their entire life could not see horizontal lines at least consciously to respond to them. After the deprivation stage they had learned to navigate their environment and after a while were able to orientate in space without issues (Blakemore & Cooper, 1970). However, that would mean they must have been able to perceive corners in some way, and that their eyes were not blind. Similarly, people with blindsight have fully functioning eyes, but the cortical cells do not respond, and yet they navigate corridors full of obstacles without help (Weiskrantz, Warrington, Sanders, & Marshall, 1974). So even if the kittens did not respond to horizontal lines explicitly, there is reason to believe that the information of the horizontal stimuli was still processed in the brain somewhere. Lack of awareness does not mean lack of processing. I am taking the plunge here to predict that there occurred processing that deemed the stimulus irrelevant and that is why they ended up ignoring it. The quality of output depended on the quality of the environment. Hence, what this study shows is that experiences acquired in relation to the environment shaped the awareness of the kittens.

Bridging the gap

What was the process that made the kittens unaware of the stimuli they subconsciously still perceived? The link between experiences and awareness becomes clearer in the following study. Laak, Vasser, Uibopuu & Aru (2017) came up with an unexpected experiment. The participants were wearing a Virtual Reality (VR) headset that showed a grid of dots in one color. Participants had to look at a marked midpoint and move their own hand in front of their face as if it covered a part of one hemifield. Since they were wearing a VR headset, they could not see their hand. They had to indicate any change in the dots’ color. Results? Exiting. The hand’s position inhibited participants from seeing a spot change color in the VR at the place the hand was. Their reaction time was significantly longer than in the control tests when the spot changed color in a place where the hand was not (Laak, Vasser, Uibopuu, & Aru, 2017). This indicates that because their brains had learned throughout life that one cannot see behind one’s own hand, their brains expected not to see anything in the hemifield which without the VR would be covered by the hand. Their brains knew where the body parts were, but did not know that with VR the position of own limbs would not matter. Their experiences with their own bodies shaped their brain’s expectation, so an unexpected event was kept from awareness.

It is the expectations that we build with the interactions between our body and environment through our senses that define whether we become aware of a stimulus or not. A person who has not heard about Stephen Hawking would think he is not conscious if he would see him after his last healthy muscle stops functioning. In assessing this we must pay attention to that lack of output does not mean lack of consciousness; lack of conscious awareness does not mean lack of processing.

Limitations

There is a possibility that Blakemore and Cooper (1970) claimed wrongly that the kittens navigated their environment well after the deprivation stage. This would mean that my case to make the conclusion that the kittens’ brains still processed the deprived stimuli somewhere like in the case of blindsight (Weiskrantz, Warrington, Sanders, & Marshall, 1974) is weakened. If this were the case, the similarities that remain would only be the fact that in both cases eyes functioned well, but cortical cells did not respond (Blakemore & Cooper, 1970; Weiskrantz, Warrington, Sanders, & Marshall, 1974). I am not confident if these facts alone would be enough to make the conclusion that the kittens’ brains still processed the info subconsciously. Similarly, if cats in general only behave in reaction to stimuli and are never conscious as I expect them to be, the case for it to support my argument about experiences shaping awareness would be weakened. Only the kittens would know. However, as the kittens have no way to communicate to us about whether they are conscious or not, so will Stephen Hawking once he loses motoric control over his last functioning muscle. Lack of output does not mean lack of awareness, and I remain firm to believe the kittens experienced awareness of the stimuli they responded to.

Conclusion

What we can be aware of depends on how we have interacted with the environment. We are unaware of a new stimulus that is unrelated to anything we formerly have experienced, because the former experiences have defined what should be considered relevant to attend to, relevant to be aware of. Our brain’s expectations are like a gatekeeper, the Cerberus that says: “It does not match my data about the environment, this must be flawed, there seems to be no reason to attend to it!” and thus the kittens did not respond to horizontal lines and people missed the spot change color in VR.

References:

Blakemore, C., & Cooper, G. F. (1970). Development of the brain depends on the visual environment. Nature; 228 (5270), 477-478; DOI: 10.1038/228477a0.

Laak, K.-J., Vasser, M., Uibopuu, O. J., & Aru, J. (2017). Attention is withdrawn from the area of the visual field where the own hand is currently moving. Neuroscience of Consciousness; 3 (1), 1-7; DOI: 10.1093/nc/niw025.

Weiskrantz, L., Warrington, E. K., Sanders, M., & Marshall, J. (1974). Visual capacity in the hemianopic field following a restricted occipital ablation. Brain; 97 (DEC), 709-728; DOI: 10.1093/brain/97.1.709.