Mind Over (Brain) Matter

            Human nature has been a favorite focus of deep thinking since the earliest philosophers.  The words, “Know thyself,” inscribed at the entrance of the Temple of Apollo at Delphi, which dates back to 4^th century B.C., are early evidence of the uniquely human fascination with ourselves.  Over the centuries questions of human nature have increasingly overlapped with questions of the human brain.  We are all familiar with the 17^th century philosopher Rene Descartes’ “I think, therefore I am.”  Descartes believed the capacity to think was the only reliable proof of existence.  Perception via the senses is subjective and different for different people and thus an insufficient tool to go about answering the question of whether or not you and I are real.  So it is impossible to think of ways to prove our existence, but even the simplest thought is proof enough.  And since the brain is the seat of thought, it follows logically that the brain is key to our existence and to understanding ourselves.

            Or does it?

            Descartes himself probably wouldn’t have bought this.  His dualism philosophy posits a mind-body dichotomy such that the mind interacts with but exists separate from the body, separate from the brain.  This was a powerful idea.  The idea that the mind and the brain are two separate entities is prevalent in our society today (I once had a conversation with a neuroscience graduate student on this topic and she asked, “But what about the intangibles, like love?”).  I suspect that the power of Descartes’ dualism, however brilliant he was, lies not in the spread of one man’s idea, but in the ability of that man to identify and package an idea that was already instinctive to humans throughout history.  However, many of today’s cognitive neuroscientists are fighting that instinct in favor of a mechanistic approach.  The days of Cartesian dualism may be numbered.

            One example is a recent study in the journal Science that investigated the influence of genes on cognitive abilities. Ten sets of siblings, each consisting of a pair of male identical twins and a non-twin brother had their brains scanned using functional magnetic resonance imaging (fMRI) while they performed a memory task.  The siblings were asked to memorize a short span of digits, then they were then given a “distraction” task to disrupt that memory: either a simple arithmetic problem (2 + 4 = 7, yes or no?) or instructions to categorize a picture of an object.  They were then shown a number and asked if it was among the numbers in the memory task.  The team, led by Jan Willem Koten Jr. of RWTH Aachen University in Germany, found that the men used two different strategies to retain the digits in their memory.  Some used brain areas associated with language while others used the visual-spatial memory system, something like counting on fingers.  They found that the memory task took longer when the language pathways were employed.  And this is where the influence of genes was seen.  The pairs of twins, who share 100% genetic identity, used the same strategy more often than their non-twin brothers, who share 50% of their genes.  Says Koten, “There are qualitative differences in how individuals think, and these differences have a substantial genetic component.”

            Normally, during fMRI studies, the data on brain activation is averaged over groups.  The Koten study suggests that averaging subjects can miss individual differences in how their brains accomplish a task.  Not only might this be problematic for interpreting the data, but by not appreciating the variability between individuals, we might be missing an opportunity to learn about the relationship between genes and brain activity.  Richard Haier of the University of California, Irvine, School of Medicine states, “This combination of neuroimaging and genetic analysis marks the beginning of new efforts to explain, rather than explain away, individual differences in cognitive intelligence.”

            Other neuroscientists are sounding more and more anti-Cartesian.  Eric Kandel, Columbia University neuroscientist and Nobel laureate, wrote (one of my all-time favorite quotes): “What we commonly call the mind is just a set of operations performed by the brain.”   He elaborates this point in his book, In Search of Memory: The Emergence of a New Science of Mind, where he argues that we should reconsider the word “mind” not as a noun but as a verb.  The brain does something.  To mind is the job of the brain.  To refer to the mind—as virtually all of us do—is to imply that there exists something separate from the brain that allows us to remember numbers or, if we’re lucky enough, to fall in love.

            Understandably, many people are uncomfortable with the idea that genes determine in part how our brains function; that is, how smart, violent, ambitious, shy, benevolent, republican we are.  But such concerns shouldn’t prevent us from studying whether or not—or how—they do.  Even if we do discover that human nature can be read from DNA sequences that are not created equally, human society can make the choice to treat them as such.  Hmmm, sounds like a job for a philosopher.