How to live with consciousness – Chapter 1: What is consciousness?

In this series of articles, I will try to elucidate the links between consciousness, goals and goal hierarchies, and the mode of being that is most adaptive thriving in life, given the fact that we are conscious. I will begin with consciousness.

When and why did consciousness evolve?

What is the adaptive value of consciousness? When did it evolve? To answer these questions, we need to take an evolutionary lens to the problem of consciousness. The Attention Schema Theory (AST) of consciousness does just that and can perhaps provide some answers. The theory suggests that consciousness arose as a solution to a problem faced by nervous systems: it is impossible to deeply process all of the incoming sensory information. Over millions of years, nervous systems, under environmental selection pressures, evolved to select between those signals that are important to the survival and reproduction of the organism and those that are not. Consciousness may thus be, if the theory is correct, a mechanism to select which information to fully process.

The journey to a full-fledged mechanism for selective attention began half a billion years ago, before the evolution of a central brain. The first noteworthy step in this lengthy process is the development of the most rudimentary form of signal selection. To understand when this feature emerged, we can compare animals. Specifically, we can compare animals which can selectively enhance signals to those that cannot and analyze their genomes to estimate the split between both species. Consider the genus hydra, which are small, fresh-water organisms. Their nervous system is extremely simple and consists of a nerve net. A nerve net is a web of neurons spread over a region, and in the case of the hydra all over its body. The nerve net allows the hydra to respond to stimuli originating in the environment but not to detect the source of the stimulus. Thus, if poked, these simple animals will typically produce the same response regardless of the point of contact. The split between hydras and other animals seems to have occurred 700 million years ago. The ability to select between competing signals must have evolved shortly (in evolutionary terms) after that.

Interestingly, the ability to selectively enhance certain signals does not require a central brain and each sense – sight, touch, sound – can select independently between competing stimuli. One of the functions of a central brain is therefore to coordinate between the senses and direct the selecting capabilities of all relevant sensory organs to the same object. Think of a cat turning its head towards the direction of an incoming sound. This coordinating function is executed in many animals by a brain region called the tectum. We can narrow down the period in which the tectum evolved because it seems to be absent in invertebrates while all vertebrates – fish, reptiles, birds and mammals – have one. Vertebrates evolved around 520 million years ago, during the Cambrian Explosion, therefore the tectum and thus the central control of attention must have evolved in this vicinity.

The way the tectum works is by constructing internal models. An internal model is a simulation that keeps track of the things that need to be controlled and allows for planning and prediction. Say a body needs to move forward in space. The tectum continually simulates the current state of the eyes, head, arms and legs and makes predictions about how these body parts will move next, and what the consequences of these movements are – for instance the uneven distribution of weight on the left side or right side of the body might warrant the tensing of the muscle on the opposite side to offset the uneven distribution. The tectum compares the predictions of its model with the actual sensory input and if both match, the movement is going as planned.

Around 350 to 300 million years ago a new brain structure – the dorsal cortex – began to emerge in reptiles. Birds and mammals evolved from reptiles and thus inherited their version of the dorsal cortex. In birds it is called the wulst and in mammals it is called the neocortex. The neocortex has radically expanded in humans and is like an upgraded tectum. Like the tectum, the cortex takes in sensory stimuli but can execute several functions depending on the context – looking away, making a sound, or storing the event in memory for future use.

Another important difference between the tectum and the cortex is the type of attention they control. Whereas the tectum directs overt attention – focusing the eyes, ears or nose towards something – the cortex seems to direct covert attention – directing the “spotlight” of attention towards something without directing the sensory organs towards that thing. For instance, your attention could focus on a conversation happening in another room because you heard one of the speakers say your name. This would be an example of covert attention. However, covert attention is not limited to external things: you can focus your covert attention on emotions, thoughts, and memories.

Where does awareness come from?

We now understand where attention comes from, and what its purpose is. It is the “spotlight”, which allows certain stimuli to be fully processed at the expense of others. It allows for a parsimonious allocation of resources to those things that are most important to process, indeed it would be too costly to process all incoming stimuli. A burning question remains: how come we are aware of our attention? Indeed, all of these processes could, in principle, be occurring without us being aware of them occurring.

Before continuing it would be useful to understand the difference between attention and awareness. Attention is the differential selection and processing of certain signals over others. Awareness is the subjective experience of those signals. To be aware of X is to say that X is an object of subjective awareness. Most of the time these are closely linked: you are aware of what you are attentive to. But it is possible to separate the two. For instance, in an experiment, participants were presented with a Gabor – a circle filled with black and white lines. The Gabor was dimmed such as to be barely visible and most of the time participants would not notice it. However, when a visual cue was presented later, participants would realize that the Gabor was there are along. Another example would be the following. Imagine you and your partner are intently reading in your study. On the wall of your study there is a large grandfather clock. Suddenly your partner looks up at the grandfather clock. You hear it ring and you realize that the ring you are hearing is in fact the 4th. It had rung 3 times before and you only now became aware of it.

Now recall that in order to control the body the tectum must construct an internal model of it. Similarly, in order to control attention, the cortex must construct a model of attention. Like the internal model of the body, the internal model of attention simulates the “spotlight” and this is what provides us with awareness. This is done to understand and make predictions about our environment and to remember and respond– at least according to AST.

After constructing a model of our own attention, the theory suggests we began constructing models of others attention. If I understand that I have a spotlight, maybe he or she also has a spotlight. For example, we may follow their gaze and understand that we are being watched. Humans aren’t the only species with this capability, in fact many birds such as crows and blue jays return alone to hideaways where they have stored food in the presence of others, to move the food and hide it elsewhere. Humans simply seem to have an extreme version of awareness.

The purpose of awareness

Figure 1: This image shows main regions of the default mode network (yellow) and connectivity between the regions color-coded by structural traversing direction (xyz → rgb)

Credit: Andreashorn

Good. We are now aware of ourselves and others. But what is the purpose of awareness? Why spend precious resources simulating attention? Awareness necessarily entails some notion of an “I”. There must be someone, or something that is aware. In other words, being aware necessitates some degree of “self”.

Researchers seem to have located the self in the default-mode network (DMN) of the brain. The DMN is a large-scale brain network primarily composed of the medial prefrontal cortex, the posterior cingulate cortex/precuneus and the angular gyrus. There are many pieces of evidence which suggest that the DMN is the seat of the self, but one especially convincing piece is found in the work of Carhart-Harris involving psychedelics. Specifically, Carhart-Harris has found an inhibition of the DMN when participants are under the influence of large doses of psychedelics. From an experimental perspective he finds that participants are in the middle of an “ego-death”, which means that participants no longer feel a separation between themselves and the environment. There is no longer an “I” experiencing something. Researchers have found similar findings with deep meditation.

The DMN is active when a person is unfocused, such as when a person is daydreaming or mind-wandering. Its functions include three main areas: (1) the self, (2) thinking about others and (3) remembering the past and thinking about the future.

The purpose of conscious awareness may then be the following. We construct models of ourselves to understand who we are. We construct models of others, to understand if they are good or bad, to understand what they are thinking and feeling, to understand our place within a group. And we construct models about the past and the future to understand what has been, but also to set goals for the future. We then compare our models to the actual input and if both are close enough, we continue on, concluding that our models of the phenomenon are good enough. Consider for example the following three questions:

  1. How many animals of each kind did Moses bring on the Ark?
  2. In the Biblical story, what was Joshua swallowed by?
  3. What is the nationality of Thomas Edison, inventor of the telephone?

Notice anything strange? Read them one more time. Is your model of the sentence close enough to the actual sentence?

In the next chapter of this essay, we will focus on the future planning capacities of the self. We will explore motivation, goals, how different goals fit together and how to plan effectively for the future.

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Tyler Kleinbauer
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