It’s a humbling experience to look up at the night sky and realise just how much we don’t know about the universe. It’s even more humbling to ponder our inner universe and realise just how much more we don’t know about that, either.
When it comes to human consciousness, despite centuries of introspection and more recent investigations using sophisticated instruments, we really know very little for sure. Even the existence or otherwise of what some call the ‘Cartesian Theatre’ inside our heads is hotly debated. What it is, how it works or why is frankly anybody’s guess.
One of the first problems to tackle, when it comes to discussing consciousness, is just what do we mean by ‘consciousness’, anyway? This is not so straightforward as most people seem to think. Just being aware of one’s surroundings and reacting to them is something even a flatworm is capable of. Insects are capable of acting apparently with intention, even with pinprick brains.
Human-level consciousness, though, seems another thing entirely.
Conscious perception is the ability of human beings to become aware of the stimuli received by their senses. It is a different state from simply being awake, where sensations are processed automatically and unreflectively. Rather, conscious perception requires a detailed and voluntary analysis of external stimuli. For example, we can breathe automatically, but we can also be aware of our breathing and modify its rhythm. Likewise, when listening to a song, we can pay attention to and differentiate the instruments that compose it.
Even more importantly, music feels like something. This is what philosophers call ‘qualia’. Beethoven’s Moonlight Sonata, a relatively simple piece, feels like something, where an AI-programmed imitation Beethoven piece does not. Even a simple, two-chord Ramones song can make us feel something. Similarly, the sight and smell of a rose feels like something that no amount of descriptions from botany and chemistry can.
Recently, neurologists have set out to find the part of the brain where this change in perception occurs. Researchers had traditionally suspected that such a function must be controlled by the cerebral cortex, because it is where advanced brain processing occurs.
New research, though, suggests that it occurs literally much deeper in the brain.
The thalamus is an egg-shaped structure buried deep inside the brain, just above the brain stem itself. It’s an ancient structure, first appearing in vertebrates as early as 560 million years ago. The human thalamus begins to develop in the foetus from five to six weeks after conception.
The new research claims to show that the thalamus is activated when a person begins to pay close attention to external stimuli.
The thalamus has never been ruled out from being involved in conscious perception, however it has typically been assigned a minor role as a filter that prepares sensory information to the cortex. A new study recently published in Science redefines that view, positioning the thalamus as an active participant in conscious perception […]
To see whether a patient’s brain region “lights up” with activity when paying conscious attention to something, it’s necessary for that patient to be aware of stimuli – that is, be conscious – while simultaneously having their brain surveyed with invasive sensors.
But in this new research, a team from Beijing Normal University in China turned to a group of people who already had thin electrodes inserted into their brains as part of an experimental headache therapy, bypassing the ethical question of whether this sort of research justifies an invasive operation.
With the patients wired up, the researchers administered a visual perception test. A blinking object was displayed on a screen, periodically disappearing. Doing so meant that patients had to pay close attention to the object rather than just passively observing. The researchers reasoned that this necessitated conscious perception.
The researchers say that this is one of the first simultaneous recordings of conscious perception, and the information they recorded, they say, offers strong evidence for the hypothesis that the thalamus region acts a kind of gateway to conscious perception. “The findings indicate that the intralaminar and medial thalamic nuclei regulate conscious perception. This conclusion represents a significant advance in our understanding of the network that forms the basis of visual consciousness in humans,” the authors write.
It’s important, though, to clarify just what the experiment possibly does and doesn’t do. It appears to show a region of the brain that “lights up” when we’re engaged in conscious perception of external stimuli.
All well and good: but what it doesn’t do, any more than the overhyped fMRI experiments, is show ‘thoughts in action’. It shows neural activity correlated with certain types of thoughts. It certainly doesn’t show a neural correlation with introspection: thinking about thinking.
Still, every step deeper into the workings of the brain is a potential step forward in understanding the mind. At least in part.
