Neuroscience - Cognitive Control

Towards the seat of consciousness

The question "what is consciousness?" represents one of the great frontiers of contemporary science. Thanks to studies of humans and animals, we now know that it is a subtly nuanced state whose nature and intensity varies according to the brain's intrinsic level of activity, its chemical microclimate and the information it receives from outside.

By exploiting the normal vicissitudes of waking, sleeping and dreaming states, we are now beginning to explore how consciousness is expressed and controlled. For example, I have been involved in studies comparing brain activation in REM sleep with that in lucid-dreaming states, in which we retain much executive brain function. They seem to confirm the central importance of one specific area of the frontal brain - the dorsolateral prefrontal cortex - in regulating many key aspects of consciousness, including attention, decision-making and voluntary action.

A combination of imaging techniques, judicious measures of subjective experience and detailed cellular and molecular-level studies will continue to deepen our understanding of our cognitive command centres in the coming years. With them we hope to crack the puzzle of consciousness, and perhaps correct the dysfunctional states of the brain we now call mental illness. Allan Hobson

Allan Hobson is emeritus professor of psychiatry at Harvard Medical School in Cambridge, Massachusetts

The connectome

Mental maps              

Understanding the routes by which populations of brain cells share information would be a major step towards understanding how our brains function. But although we can infer individual connections, we have no basic wiring diagram of the human brain.

This is hardly surprising. The brain contains approximately 100 billion neurons, and a single neuron may connect to 10,000 others. Yet emerging techniques mean we are now making headway in this daunting task.

Using electron microscopes, for example, we can probe animal brains neuron-by-neuron, connection-by-connection, in the hope of discovering characteristic circuits that repeat themselves throughout the brain. From a wider perspective, brain imaging technologies can map the brain's highways - large "cables" consisting of many thousands of connections between distinct brain regions.

The US National Institutes of Health has begun to fund a major effort, the Human Connectome Project, to generate a comprehensive map of large-scale brain connections in humans. Following its directions, we might arrive at a better understanding of how the brain's regions interact to produce behaviour. Tim Behrens

Tim Behrens is a neuroscientist at the University of Oxford

 

Mirror neurons

The key to how we learn and think - possibly

The saying "monkey see, monkey do" couldn't be more true. Thanks to "mirror" neurons that fire not only when we perform an action ourselves but also when we see others perform it, our primate brains subconsciously mimic every behaviour they ever witness.

That's the theory, at least. Mirror neurons were first discovered in macaques in the 1990s, and brain scans using functional MRI had hinted that they exist in humans too. But it wasn't until May this year that researchers measured the firing of mirror neurons in humans directly, using electrodes implanted in the brains of epileptic patients awaiting surgery (Current Biology, vol 20, p 750).

While proponents of the power of mirror neurons claim they explain everything from empathy and compassion to a penchant for porn, their exact significance remains controversial. The next few years will see us homing in on what exactly they can and cannot explain about human cognition.

 

Top-down processing

Our past determines our present           

The human eye is a camera that faithfully records everything in front of us, passing the information through the brain's visual processor before it pops out as a conscious experience.

This "bottom-up" process represents the textbook view. In truth, we are realizing that our experience is closer to a form of augmented reality, in which our brain redraws what it sees to best fit our expectations and memories.

The same goes for our other senses, and the growing suspicion is that kinks in this system of "top-down processing" might shed light on neurological disorders such as schizophrenia, autism and dyslexia. Whether or not that turns out to be the case, this idea is radically changing our view of how our past influences our here and now.

 

Neuronal recycling

Culture is a parasite           

The architecture of our brains far predates writing, religion and art. So how come we acquire these cultural traits and abilities with such ease?

The standard answer is that our big, plastic brains have a uniquely flexible and generalized learning capacity. But is that true? The human brain is not homogeneous, after all, but organized into specialised areas. Moreover, brain imaging reveals that abilities such as reading and mathematics have distinct "neuronal niches"; they too are confined to specific brain circuits.

That is compelling evidence for an idea known as neuronal recycling: that our cultural abilities invaded and parasitised brain circuits originally dedicated to evolutionarily older, but related functions. Reading, for example, seems to occupy circuits sensitive to complex shapes and with good connections to areas dealing with language (Reading in the Brain, Viking, 2009). If correct, it is our brains shape our culture, rather than our culture our brains. Human ingenuity is not unlimited, but fundamentally constrained by neural architecture.

 

Nootropics

Food for thought           

You've got a big report to file, and the clock is ticking. If only you could concentrate harder, recall facts and figures more effectively, or just shake off that feeling of fatigue after yesterday's late night.

Soon a brain boost might follow a visit to your local pharmacy. Psychostimulant drugs such as Ritalin and Adderall, prescribed to treat attention-deficit hyperactivity disorder, and Aricept, used as a treatment for Alzheimer's disease, have been shown to improve concentration and recall in healthy people, too.

Such drugs are not currently available without a prescription, but some researchers say they should be. Multiply that extra brain power by the 7 billion members of the human race, they say, and the benefits to society and the pursuit of knowledge would soon start to add up. But is a race of drugged-up super-brains what we really want to be? Food for thought indeed.