from CEREBRUM 2009
Imagine for a moment that we are looking back from 2050 to consider the major scientific breakthroughs of the early 21st century. What will we see? The human genome, of course. Dark matter in the cosmos, perhaps. Renewable and sustainable energy sources, one hopes. But one of the most profound breakthroughs is so fundamental that we may take it for granted. Four centuries after Descartes, we are finally resolving the split between mind and brain, recognizing, as did Emily Dickinson, that the brain is “wider than the sky,” wide and deep enough to contain the mind.
This has not been easy for us to accept. Just as the world looks flat, not round, the ineffable qualities of consciousness, imagination and memory all seem subjectively divorced from the three pounds of tissue in our heads. Yet Dickinson may have called it just right: “they will differ, if they do, / As syllable from sound.” In 2050 this may well appear to be the singular insight of our era.
Modern neuroscience has put the brain and the mind back together, with far-reaching implications. Suddenly a range of interesting psychological problems, from dreams to moral decision, becomes tractable via brain science. Rather than “reducing” psychology to biology, neuroscience research has consistently deepened and broadened psychological inquiry, helping us to understand aspects of mental experience that could not be discerned form subjective experience. Neurolinguistics, which maps the representations of grammar and distinct languages in the brain, is perhaps the most famous example of this phenomenon. Neuroimaging has not “reduced” our understanding of language; it has transformed it, revealing relationships neither intuitive nor accessible with psychological approaches. Cognitive neuroscience, social neuroscience, affective neuroscience and behavioral neuroscience have given us comparable insights, demonstrating that brain research is prone more to expanding frontiers than to reductionism.
But an even more profound implication of putting the brain and the mind back together is emerging in clinical research. For the first time, we can begin to address mental disorders as brain disorders. Although biological psychiatry has sought to do this for five decades, most of that effort has been mired in very simplistic models of brain function that considered for example, depression as a “chemical imbalance” or schizophrenia as a “dopamine disorder.” In the past decade, clinical neuroscientists have begun to study mental illnesses as disorders of brain circuits. This change may prove to be a fundamental transformation in how we study, diagnose and treat these very disabling illnesses. For instance, we may discover that the behavioral and cognitive manifestations of these illnesses are a late stage of a chronic brain process that could be detected years before psychosis or mood disturbance. Imagine the impact of predictive and preemptive medicine for schizophrenia or bipolar disorder. At the very least, we will need to begin training a new generation of mental health workers in cognitive and affective neuroscience so that the will be able to expand our understanding of mental disorders just as neuroscientists are expanding our understanding of mental life.
Cerebrum 2009 provides brilliant examples of how mental disorders can be addressed as brain disorders. David Speigel explains how split personality or dissociative identity disorder arises from trauma. As he notes, “the problem is not that they have more than one personality, but rather they have less than one—a fragmentation of self rather than a proliferation of selves.” Spiegel describes this fragmentation as a form of sever, chronic, early onset-post-traumatic stress disorder. Recent neuroimaging research suggests that the traumatic experience may be out of sight but not out of mind. Understanding how the brain isolates traumatic memories is providing insights into how unconscious processes can have profound effects on observable behavior, including the fragmentation of the sense of self.
Remarkably, clinical neuroscience is helping us understand psychological treatments as well as psychological experience As Elizabeth Norton Lasley reports in “A Road Paved by Reason, “ cognitive behavior therapy (CBT), first developed more than four decades by Aaron “Tim” Beck, has been shown repeatedly to be an effective treatment for mood and anxiety disorders. Lasley describes new research that looks at how CBT changes the brain as well as behavior. For its antidepressant effect, CBT appears to use different pathways than medication does, although there must be some final common targets for lifting depressed mood. By studying the neural effects o psychotherapy, we are getting our first glimpse of the pathways of recovery.
One common target for medication and CBT in the treatment of depression may be a little-known site deep in the brain’s prefrontal cortex, Area 25. While rarely studied by neuroanatomists or neurophysiologists, Area 25 has emerged as a critical player in neuroimaging studies of depressed patients who recover, following either psychotherapy or pharmacologic treatment. As Jamie Talan notes in “Deep Brain Stimulation Offers Hope in Depression, “ neurologist Helen Mayberg has borrowed a treatment from Parkinson’s disease to develop a new approach to treatment-refractory depression. For many, (but not all) patients, deep brain stimulation leads to a lasting reduction in depressive symptoms. Welcome to the new age of addressing mental illnesses as brain disorders—beginning with recognition of the circuitry, identifying a hub for this circuit, manipulating this hub surgically and finally resolving the symptoms.
Elsewhere, one f the most perplexing areas where psychiatric and neurological symptoms overlap is traumatic brain injury (TBI). Although post –traumatic stress disorder (PTSD) has been a tragic result of recent wars and natural disasters, TBI is considered a relatively new problem as modern protective equipment allows more soldiers to survive severe head and blast injuries. TBI has been associated with cognitive and behavioral problems, often as disabling as PTSD, but there has been no diagnostic test or evident brain lesion identified. Wayne Gordon describes the consequences of unidentified TBI and the promise of a screening approach that should increase detection and awareness of this troubling and mysterious syndrome.
This edition of Cerebrum also includes reports on other important clinical problems for which neuroscience is yielding new, sometimes surprising insights. Richard J. Bonnie, Donna T. Chen, and Charles P. O’Brien describe the ethical dilemma presented by an effective new treatment for heroin addition. Extended-release naltrexone may reduce relapse in addicts who have been incarcerated. Is it ethical to require parolees to take the drug? If this treatment is not a requirement, what is the most ethical means by which to implement it? Denise C. Park, addressing a different social concern, speaks to the challenge of maintaining neural health as we age. Does the adage “use it or lose it? Apply to our brains? Park describes a theory of scaffolding in the aging brain that requires continuous activation to maintain brain health. How do we know which mental exercises are strengthening this scaffolding in the aging brain that requires continuous activation to maintain brain health. How do we know which mental exercises are strengthening this scaffold and which efforts are wearing down an aging infrastructure? On a related topic, Guy McKhann and Brenda Patoine describe the common disabling problem of cognitive dysfunction following cardiac surgery. As they note, What is good for the heart is good for the brain.” With a longitudinal controlled study of patients undergoing cardiac surgery, McKhann and colleagues have demonstrated that some of the decline in cognitive function may be the result of neurovascular disease associated with coronary artery disease and not with the surgical procedure, as many believe.
While this edition of Cerebrum captures many of the frontiers where neuroscience is having an impact on human health, some of the most exciting areas of brain science are not yet ready for translation to the clinic. Note, for instance, Sebastian Seung’s introduction to the emerging discipline of “connectomics,” mapping the brain’s wiring diagram. To understand how the brain functions we will need to know much more about how it is wired. Can we map the connections between all 100 billion neurons in the human brain? Not yet. But, as Seung explains, we can develop tools for this project in simpler brains, leading to a human connectome project that may someday reveal a comprehensive wiring diagram of our brains just as the human genome project provided a registry of our genes.
As neuroscience puts the brain and the mind together, we are seeing exciting new opportunities to make a difference for people with brain disorders. The need is great. These disorders, especially depression and addictive disorders are the largest source of medical disability for young people in the developed world. With the aging of our population, dementia and stroke will become increasingly costly causes of medical morbidity and mortality. Brain science offers our best hope for reducing disability and ensuring a mentally healthy, lengthened life span. This edition of Cerebrum provides a superb introduction to the opportunities as well as the challenges that lie in translating neuroscience to the clinic. Enjoy.