What is consciousness?
The quest to understand consciousness is an ancient one - one that wanders into the realms of history, religion and philosophy, to name a few. Tristan Bekinschtein heads up Cambridge University’s consciousness and cognition lab, where he and the team look at what’s going on in the brain while people do a range of processes, consciously or otherwise, and he spoke to Katie Haylor. First up, Katie asked, what does consciousness actually mean?
Tristan - Consciousness is composed by three main factors: levels - when you're conscious or unconscious by being awake or asleep, or by being awake or sedated/anaesthetised, or when you're awake normal or in coma. Conscious access, whether you're aware of something that happened in your environment are you not aware; you did not see the car coming, or the content of your mind, where you think of what you're thinking.
Katie - Now I understand that it's not as simple as saying “ah, the conscious mind is in this particular part of the brain”, how does consciously physically manifest itself in the brain?
Tristan - Consciousness manifests like an umbrella aspect of how you process complex stimuli. If you're trying to remember stuff and you put effort in trying to remember a particular aspect of a scene, let's say a swimming competition and you are particularly interested in how they move their arms for you to get better at the stroke, you are making a conscious effort to look at that in a visual spatial task.
Katie - Okay. So it's going to be parts of the brain involved in processing images that are going to have to come into play here, right?
Tristan - And all of the other much more wider networks that are related to you consciously, effortfully doing something and it's stored in the memory, so in that case you have attention, memory, and visual/spatial processing. You are using consciousness-related brain networks to guide what you do with memory and attention and visual/spatial processing.
Katie - Would it be fair to say that consciousness integrates a whole load of circuits at varying levels across your brain?
Tristan - So the most common theme of discussion between conscious and unconscious processing is how much we can integrate of a particular event or a scene unconsciously. Because it seems that we do very little unconsciously in terms of complex integration of information and we really need to be conscious to integrate information in a flexible manner. So very common definitions from people who work in consciousness is conscious processing is the capacity that we have to integrate complex stimuli and be able to report that.
Katie - Because, of course, things may happen that we pick up on that we aren't necessarily consciously aware of?
Tristan - That will be a discussion in the field of cognitive neuroscience, but I think there's quite a fair agreement that most of what we perceive, where we get into our senses, does not reach consciousness as the flexible part, so we have a lot of unconscious processing happening all the time. Some of that is processed consciously, usually guided by attention.
Katie - One of the things that you work on is understanding the different levels of consciousness, can you tell me a bit about well firstly what they are?
Tristan - So one is now, we're talking, we're awake. Later at night we might get a bit drowsy while playing Candy Crush or whatever is the bad thing in terms of sleep hygiene that you do. And then we'll sometimes actually stop reading or stop playing Candy Crush for a moment and we are in the transition at that time.
Katie - You realise you've read a sentence five times in your book and it's not going in?
Tristan - Yes, clearly it’s a state that isn’t stable, that transition. Low alertness, but you’re still trying to do stuff. It’s like a fight. You constantly try to do something but there is pressure from a brain system to actually go into another state, which is asleep. And then you reach light sleep and you have your eyes closed. You might be still holding the book. If this carries on into the normal transition to deeper sleep then you are in deep sleep. As the night progresses you may find yourself in what is called REM sleep. You will oscillate between light sleep, deep sleep and REM through the night and then you will wake up in the morning. If everything is well.
Katie - These transitions between different states is something that you're quite interested in. How much do we know about what changes in the brain when you're awake compared to when you start getting drowsy, compared to when you start drifting into that light sleep? Can we track those changes?
Tristan - Yeah I mean these changes are tracked thousands of times in many hospitals in the world as they do polysomnography which is putting an EEG, putting in something to measure your airways so to see how you breathe, your heartbeat, your muscles of your face. Polysomnography - many things about sleep. That's what it means.
The person who's going to look at this - a sleep physiologist - and the technicians will say “oh this person is awake, look and they’re getting drowsy. Look at this brain activity and muscles and etc etc. Oh look he sleeps”. And they will characterize these things. So this has been done since the 1940s in you know the definition of brain related sleep things have been done. Now what do we know more from the research point of view, it's of course more than just identifying particular brain signals. We know a bit more because we know more about how to ask the brain networks how they're doing, rather than just finding little signatures in the brain activity.
We do have competing networks between what is called resting state brain network and active attention network. These are simplistic views of what the brain networks are doing but in the end there are two different networks in the brain that we can see with EEG and functional MRI and other techniques. We can image that and capture these two networks. The one that it's mainly about idling and mainly about paying attention, doing something related to the external world, so the attention one.
Katie - OK so using imaging techniques like magnetic resonance imaging or EEG you can lock into which bits of the brain are active in particular states of consciousness?
Tristan - Yeah, you can actually characterize the state by looking at those different networks and you can characterize the state also by their responsivity, because if you're asleep and I call your name, most likely I will need to call your name louder and many times until you actually respond. So sleeping in a way is also a threshold of responsiveness state right? It’s how much energy you have to give to the system to obtain or respond from it. Of course we can characterize the brain activity while I call you several times and you're asleep, and we can see that your brain activity as you respond to your name compared to other names in sleep still is different. You do have a brain signature for your name even if you don't wake up and say “hey what's up Jason?”.
Katie - Really?
Tristan - Yes. Many people disregard the experiment as trivial because they say “well if you have kids you know that with a little cry, very specific stimuli, you would wake up immediately”. But if there's a crash two blocks a way and is much louder, much more salient but not relevant to you then you do not necessarily wake up. So these aspects of relevance to your life, it's not a minor point. Being unconscious by sleep, that doesn't mean your cognition is shut down.
Katie - Devil's advocate question for someone who's an expert in consciousness - why study the thing in the first place?
Tristan - Do you want to know who you are? It seems to be that you asked the question “Who am I” or “who are humans, when we’re conscious?”, so can we actually understand how we think? Sure. That's cognitive neuroscience. Can we actually understand how we think in terms of conscious beings? Well then it'd be nice to know in research wise, not just philosophers in an armchair saying “well we are conscious and this is blah blah blah” and then you know ask cognitive scientist, we say “oh can we check that beautiful claim?”.
It’s just another aspect of cognition - memory, attention, language, other aspects of cognition and you have consciousness.