Despite all the recent advances in the cognitive and neurosciences, there’s still much about the human brain that we do not know. Here are 8 of the most baffling problems currently facing science.
1. What is consciousness?
Without question, conscious awareness is the most astounding — and most perplexing — aspect of the human brain. It’s what makes us the unique, self-reflective creatures that we are. Consciousness allows us to experience and react to our environment in an apparently self-directed way. We’re not just zombies; we have our own private thoughts, feelings, opinions, and preferences — and these traits allow us to figure out the world and operate within it.
But we are still quite a ways off from understanding how the brain produces phenomenal experience, or qualia. Neuroscientists cannot explain how incoming sensations get routed around such that they can be translated into subjective impressions like taste, color, or pain. Or how we can conjure a mental image in our minds on demand.
Scientists think it has something to do with the way the sensory parts of the brain are linked to midbrain structures (like the thalamus). Consciousness may also arise from, in the words of Daniel Dennett, a "bundle of semi-independent agencies." Or what Marvin Minsky calls the “Society of Mind.” As Minsky notes, “Consciousness is a word that you use to not discuss the 40 or 50 different processes that are going on at various times...”
These theories runs in stark contrast to the Cartesian theater model which suggests that there’s a single and identifiable place in the brain where “it all comes together.” More controversially, some scientists have even proposed quantum effects. But ultimately, we haven’t really got a clue.
2. How much of our personality is determined by our brain?
This is the old nature versus nurture debate. And it’s a conundrum that’s difficult — if not impossible — to quantify. Some scientists, like Steven Pinker, argue that we’re all born with genetic predispositions that influence our psychologies. This is the denial of the “blank slate hypothesis,” which suggests that the mind has no innate traits, and that most, of not all, of our individual preferences are socially constructed.
Studying twins who have been separated at birth can help — but only somewhat. It’s difficult to tell where the effects of genes start and where they end, particularly as they’re either reinforced or suppressed by social experiences. Epigenetics, in which genetic expression is either paused or activated according to environmental circumstances, complicate the issue even further. But in a way, the nature versus nurture debate is moot; the brain is a constant work in progress, a sponge that’s perpetually feeding off the environment.
3. Why do we sleep and dream?
We spend about a third of our lives asleep, but we’re not entirely sure why we do it.
Virtually every animal sleeps, which is crazy if you think about it. Sleep must be incredibly important because evolution hasn’t devised a way around it. It’s a condition in which conscious awareness has been (for the most part) shut off, leaving us unaware of our surroundings and completely vulnerable. Deprived of enough sleep, we would eventually die.
So what’s the purpose behind it? It could be a way to recharge the brain and replenish the body’s energy stores. Or, it could help us consolidate and store important memories while throwing out the neural nonsense we don’t need. And indeed, there seems to be some credence to the idea that sleep helps us encode our long-term memories.
Or, as Giulio Tononi has argued, sleep may be a way to bring our brain cells back to a baseline state. He writes:
Our hypothesis is somewhat controversial among our fellow neuroscientists who study sleep's role in learning and memory because we suggest that the return to baseline results from a weakening of the links among the neurons that fire during sleep. Conventional wisdom holds, instead, that brain activity during sleep strengthens the neural connections involved in storing newly formed memories. Yet years of research with organisms ranging from flies to people lend support to our notions.
As for dreaming, scientists are equally baffled — though there are no shortage of explanations. It could be an accidental side-effect of random neural impulses, a way of simulating and coping with real world threats, or as way to process painful emotions.
4. How do we store and access memories?
Like a computer’s hard drive, memories are physically recorded in our brains. But we have no idea how our brains do this, nor do we know how this information gets oriented in the brain.
What’s more, there isn’t just one kind of memory. We have both short-term and long-term memory. There’s also declarative memories (names and facts), and non-declarative (like so-called muscle memory). And within our long-term memories we have “flashbulb” memories where we’re able to remember the precise details of what we were doing during momentous events. And to complicate things further, different parts of our brain perform different memory tasks; it’s a rather complex interplay between our synapses and neurons.
Neuroscientists think that memory storage depends on the connection between synapses and the strength of associations; memories aren’t so much encoded as discrete bits of information, but rather as relations between two or more things (e.g. touching a hot element causes pain). Relatedly, memories of an event may be stored in a matrix of interconnected neurons in our brains called an “engram”, or memory trace. And in fact, scientists recently implanted a false memory into a mouse working under this assumption.
That said, scientists still aren’t sure how memories form, why certain memories degrade and fade, why we sometimes develop false memories, and why we can’t always access information when we want. It’s likely a very fuzzy and imperfect process.
5. Are all aspects of cognition computational?
Computer scientist Alan Turing got the ball rolling on this one by arguing that any real-world computation — including cognition — can be translated into an equivalent computation involving a Turing machine. This has given rise to the functionalist model of human cognition; organic minds, goes the theory, are basically classical information-processors.
But some scientists, like Miguel Nicolelis, argues that the brain is not computable and no engineering can reproduce it. He says that human consciousness can’t be replicated in silicon because most of its important features are the result of unpredictable, nonlinear interactions among billions of cells.
Image: Star Trek: TNG
Indeed, our minds may be driven by certain functions that are purely analogue in nature — processes that require a physical basis. Or perhaps cognition and consciousness arise from an alternative form of computation that we have yet to discover. As Ray Kurzweil wrote in The Singularity is Near,
Computers do not have to use only zero and one.... The nature of computing is not limited to manipulating logical symbols. Something is going on in the human brain, and there is nothing that prevents these biological processes from being reverse engineered and replicated in nonbiological entities.
But what exactly are these processes? It seems clear — at least to me — that certain parts of human cognition have to be computational in nature (e.g. our innate ability to determine the trigonometry of moving objects). But which ones? And which ones aren’t?
6. How does perception work?
A primary function of the brain is to convert our senses into experiences. Our ability to perceive allows us to organize, identify, and interpret sensory information in way that helps us construct and understand our world. But how, exactly, does our brain transfer this incoming sensory information into such vivid qualitative experiences? And how is perception organized in the brain?
Image: The Matrix.
This is an issue that’s somewhat related to the hard problem of consciousness and the onset of qualia — that subjective feeling each one of us has after seeing the color red or tasting a piece of dark chocolate.
Neuroscientists point to the nervous system — the locus point of all human perception. Our various organs take in incoming stimulation, like light or molecules from an odor, and we somehow convert it into this thing we call ‘perception.’ We can often shape the texture of these experiences through learning, memory, and expectation, but many of them happen outside of conscious awareness. Perception is also controlled by different modules in the brain, which are in turn part of a broader cognitive web.
One theory is that perception is tied to active and pre-conscious attempts to make sense of the input. In other words, perception may be an active process of hypothesis testing. Work on optical illusions — in which we are presented with incorrect hypotheses — would seem to reinforce this suggestion. Perception may also work in tandem with attention (another challenging area of study).
7. Do we have free will?
Philosophers have debated this for millennia, and scientists are finally starting to wade into the discussion — and they’re not necessarily liking what they see.
Image: Matrix: Reloaded.
The debate over free will has given rise to cosmological determinism (everything proceeds over the course of time in a predictable way), indeterminism (the idea that the universe and our actions within it are random), and cosmological libertarianism/compatibilism (free will is logically compatible with deterministic views of the universe).
Less philosophically, experiments show that the unconscious mind initiates seemingly voluntary acts, some as much as 0.35 seconds earlier than conscious awareness. Back in the 1980s, Benjamin Libet concluded that we have no free will as far as the initiation of our movements are concerned, but that we had a kind of cognitive "veto" to prevent the movement at the last moment; we can't start it, but we can stop it. More recently, fMRI studies have shown that this delay, called the readiness potential, occurs as much as an entire second before awareness.
Skeptics argue that these experiments don’t prove anything, and/or that there are distortions in the data. Others dismiss it out of hand because of its disturbing ramifications.
8. How can we move and react so well?
We do an incredible job moving our bodies through space and time. But how we move so controllably remains a mystery.
Image: Pacific Rim.
Think of the dexterity required to thread a needle. Or to play a piano concerto. These accomplishments are all the more incredible when considering how slow, haphazard and unpredictable our motor nerve impulses actually are. Clearly, there’s something very sophisticated going on between our motor cortex and the cerebral cortex that allows for such smooth, efficient actions.
But there’s also the timing to consider. We all have internal clocks (yet another mystery in neuroscience), that do a remarkable job of relaying our environment to us in real time — even though there’s a cognitive delay.
It takes one-tenth of a second for our brains to process what it sees. Now, that might seem like a really short amount of time, but if an object is coming towards us at 120 mph, like a ball from a tennis serve, it will have travelled 15 feet before our brain is aware of it. According to a recent study, our brains “push” forward moving objects such that we perceive them as being further ahead in time and space than they really are. This means our brains are not in sync with the real world. And as noted earlier, we even initiate our movements before we’re consciously aware of them.