The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning (23 page)

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Authors: Daniel Bor

BOOK: The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning
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Although in the real brain, the guys responsible for yellow or black would be represented by the amalgam of thousands or even millions of similar neurons, this analogy illustrates many aspects of how attention can be generated in the brain. One important feature is that as information flows through the cortex, it increasingly gets filtered and combined to reveal its hidden, richer meaning.
Initially, our senses are constantly performing the first stage of filtering. As soon as visual information enters our cortex, any data concerning edges are already preferentially filtered for us. Then each simple detail activates a set of neurons tuned to only one or two basic features, but these neurons pass on that relatively raw information to later, more sophisticated neurons that are designed to represent ideas not just about single features, but combinations, or—even later in the stream—actual objects.
All of these separate neuronal populations, each activated by the various sensory inputs received at that moment, are trying to broadcast their own information, and each group is competing to shout with the loudest voice. But if certain combinations of basic features are spotted in the world that correspond, say, to a well-learned danger, then these set off a chain of actions in the brain. Those neurons that have detected the threat are given priority over any others.
This winning signal now recruits all related areas. If you’ve experienced a fear of wasps, and one is buzzing around, anything remotely wasp-like suddenly is mistaken for a wasp—you initially think that horsefly over there is one too, and perhaps even, for a moment, mistake the fridge sound for a wasp’s noise. This is because all the neurons relevant to the details of a wasp are so active that these primed neurons are latching onto any tiny hint of it—and many false positive reports can occur. But if a true wasp is spotted, then all relevant neuronal regions will activate faster than usual and collaborate on recognizing the threat and then avoiding it. In the meantime, any neurons not currently coding for this danger will have their activity suppressed so as not to get in the way.
In other words, there is a constant competition occurring in the brain between different factions of neurons representing different chunks of information. Those groups that have the highest current biological relevance are given a leg up in activity, a head start, so that their influence rapidly spreads to more and more brain regions, until many areas of the brain will be dealing with this piece of information in their own way—and this amplification for this object or feature will be bouncing back and forth in the brain, constantly reinforced. At that point, the competition has effectively been won by this source of information, and any neurons representing some competing information will not only fail to broadcast their data widely, but have their activity inhibited by the neurons that
are
dealing with the relevant information. The winners in these battles are indeed oppressive victors, squashing any potential dissent, but in this way attention remains focused and we can respond efficiently to any danger, without being distracted.
This ideas-based, winner-takes-all system sounds simple, but emerging out of it is an amazingly flexible mechanism for much of the cortex in concert to shape itself according to some current purpose, whether it be a biological threat, such as a wasp sting, or a more complex task we’ve consciously set, such as composing a piece of writing. Large swaths of the cortex can recreate its own mountainous landscape of combinations of activated or inhibited neuronal coalitions in a highly pointed way, reflecting all sensory, memory, cognitive, and motor features of the goal of the moment.
ATTENTIONAL VICTORIES EMERGING INTO CONSCIOUSNESS
 
At what point does this attentional battle turn into consciousness? In line with Libet’s free-will experiments and Nikolov’s neuronal decision modeling data, at the first ramping up of decision activity, and the onset of the attentional war, there is no sign of awareness. Instead, neuronal activity probably becomes conscious when the battle is clearly won, when all features of a goal are significantly bound together in frenetic activity throughout the cortex, and all nonrelevant details are simultaneously shut down.
Consequently, when we spot that wasp, we don’t see lines of yellow independent from lines of black, both distinct from a couple of wings and all quite separate from a vague buzzing sound. Instead, the collaborative endpoint of the processing bursts through into awareness. We immediately know we are near a wasp, can hear and see it very much as a single yet compound object, orient our heads toward it, and already are thinking where to move away from it or what means we can use to push it out the window—and little else aside from that wasp at that moment occupies our consciousness.
The process of combining more primitive pieces of information to create something more meaningful is a crucial aspect both of learning and of consciousness and is one of the defining features of human experience. Once we have reached adulthood, we have decades of intensive learning behind us, where the discovery of thousands of useful combinations of features, as well as combinations of combinations and so on, has collectively generated an amazingly rich, hierarchical model of the world. Inside us is also written a multitude of mini strategies about how to direct our attention in order to maximize further learning. We can allow our attention to roam anywhere around us and glean interesting new clues about any facet of our local environment, to compare with and potentially add to our extensive internal model.
The example of our attentional system being driven by some biologically important external object may be the normal form of attention in the animal kingdom, where most species have a considerably simpler mental life than we do. But if you have far greater processing capacity and a more elaborate internal model of the world, then you also have far more choice about what to attend to, as so much more than the latest obvious threat or sign of food could potentially aid your biological goals, if analyzed carefully.
Without any obvious external threat forcing itself on our attentional system, how is the choice made to attend to any of the seemingly infinite options? On the one hand, consciousness and complex thought can constrain the process in a number of ways. We can logically interrogate the reasoning behind each major option and heavily favor one side in the neuronal battle to follow. We are certainly not limited to the small set of more instinctive attentional filtering systems. Instead, we can consciously create almost any kind of neuronal filter, strongly boosting attention for one feature of the inner or outer world and suppressing others. In this way, we can seemingly choose what to attend to—in other words, what to be aware of.
On the other hand, despite our impressive conscious ability to bias what we attend to, the basic competitive neuronal mechanism of attention is just the same in these seemingly voluntary, internal choices of attention as it is for the immediate external drivers of our attentional system. Out of the many fighting voices in our minds, conscious control is but one choice, commonly pitted against a set of various bullying unconscious desires, where only a single voice can win out, to ruthlessly recruit to its cause all conceptually related neurons throughout the cortex and suppress any dissenters.
Here, with these neuronal wars, we can return to the question of emergentism, where advanced ideas on one level emerge out of the interactions of simpler, lower-level objects, with a clear proposal for the mechanism of emergentism in relation to awareness: Multiple factions of neurons competitively interact, with two kinds of feedback—a positive form that can rapidly boost neuronal activity, and a negative form that can rapidly inhibit it. The complex interplay between these two opposing feedback loops at the level of local neurons can dynamically tune and activate much of the cortex, giving rise to highly flexible, global, synergistic information processing and consciousness.
18
OVERESTIMATING THE VALUE OF EMOTIONS
 
So far in this chapter, I’ve been describing how attention is a key component of consciousness. Attention is a filtering and boosting mechanism, taking the entirety of the sensory input we receive, including much that is irrelevant to us, and converting this into a far more finite, refined output containing only those items that are most germane to our current goals. It is this output that we are conscious of and that I will explore in more detail for the remainder of this chapter. But first, I turn to two particular forms of conscious content: emotions and self-consciousness.
It would be churlish to underestimate the role that emotions play in our conscious lives. Emotions continuously, profoundly shape our thoughts and behavior, and many would say it is the panoply of so many vivid sentiments that give true color and meaning to life. I don’t deny any of this. But some theorists have put emotions as both the core evolutionary driving force of consciousness and its main contents. There are good reasons to reject such a position.
For instance, there are many moments in our lives when we’re not conscious of any particular emotion, even though we’re nevertheless very much aware of something.
But what would happen if we lived our entire lives in such a grey state? Would we still be conscious? In the book
Descartes’ Error
, Antonio Damasio discussed a patient, known as Elliot, who in many ways is a modern version of Phineas Gage. Elliot, also following damage to his orbitofrontal cortex, also underwent a radically shifted mental world. His life is now almost devoid of any emotions whatsoever. He goes through life continuously in a neutral emotional gear. But his level of consciousness seems hardly dented, even if his social decisions are abnormal, just as Gage’s were. In total contrast, a severe attentional deficit following brain damage, as I’ll describe in the next chapter, crushes awareness.
At the same time, intense emotions can seem to shrink consciousness in unhealthy ways. For instance, some people become sufficiently nervous when speaking in public that they stumble over words, or momentarily forget what they meant to say. Their minds go blank, and it almost feels as if their awareness of everything except the object of their nerves has disappeared. Ramp this up many notches, and terror, an emotion designed to save our lives, regularly kills because it profoundly diminishes consciousness and therefore intelligent control. For instance, it is tragically common in plane crashes for passengers to be trapped in their seats because they repeatedly press the safety belt as if it had a car’s release button instead of the plane’s metal lever. The most minuscule conscious analysis of the situation is unavailable to them because they are paralyzed by fear.
LAYERS OF AWARENESS
 
A closely related topic is self-awareness. Some theorists claim that we are only truly conscious when we are self-aware, and that our sense of self is the most critical component of any conscious experience. Again it is suggested that evolutionary pressures for a more sophisticated model of oneself were responsible for generating consciousness in the first place.
Self-awareness is actually a rather confusing term. It has at least three different meanings. The first, less grandiose definition of self-awareness is simply the state in which an animal is aware of itself as distinct from all the animate and inanimate objects around it, and it thinks and acts in accord with this basic assumption. In a sense, all creatures need to make this conceptual distinction, irrespective of consciousness, so any creature that also happens to be conscious will automatically have this version of self-awareness. This may seem a trivial point, but it emphasizes how embedded within our biological makeup this heavy distinction between us and the rest of the universe is. Self-awareness based on this definition may not be a necessary component of consciousness, but instead just an accidental consequence of something being a conscious animal with an evolutionary heritage.
Indeed, the case of the conjoined twins Tatiana and Krista, who appear to have conscious experiences that are not their own, provide tentative evidence that this accidental combination need not always occur. Occasionally, under special circumstances like this, we might be able to have experiences, but not be the owner of those experiences.
Various psychiatric populations also hint at a possible separation between consciousness and the self. For instance, in certain cases of multiple personality disorder, patients may attribute many of their experiences to other personalities within them. One patient reported “Joy is happy and playful, so sometimes when I’m down she becomes me. Sometimes it cheers me up, but sometimes it is only Joy who is happy and I’m still upset.” Here, seemingly as a strategy to improve her mood, this patient lets an alternative identity take over her experiences.
Although multiple personality disorder is a controversial diagnosis (it has been suggested that all such patients fabricate these extra personalities in a desperate attempt to protect them from some past trauma), less controversial is an analogous situation in schizophrenia. One of the hallmarks of schizophrenia is a genuine belief that the voices within your own mind are not your own. In other words, many schizophrenics are convinced that some part of their own experiences at least partially belongs to someone else.
Although rather circumstantial, all these pieces of evidence point to a potential loosening of the glue between experience and a sense of self, reaffirming the possibility that their apparent inseparability might be accidental.

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