As I mentioned in the Prologue, fMRI, or functional magnetic resonance imaging, is a twist on the ordinary MRI machine your doctor uses. The nineteenth-century scientists had concluded correctly that the key to identifying what part of the brain is at work at any given time is that when nerve cells are active, circulation increases, because the cells increase their consumption of oxygen. With fMRI, scientists can map oxygen consumption from outside the skull, through the quantum electromagnetic interactions of atoms within the brain. Thus fMRI allows the noninvasive three-dimensional exploration of the normal human brain in operation. It not only provides a map of the structures in the brain but indicates which among them are active at any given moment, and allows scientists to follow how the areas that are active change over time. In that way, mental processes can now be associated with specific neural pathways and brain structures.
On many occasions in the past pages I’ve said that an experimental subject’s brain had been imaged, or remarked that a particular part of the brain was or was not active in some circumstance. For example, I said that patient TN’s occipital lobe was not functioning, explained that it is the orbitofrontal cortex that is associated with the experience of pleasure, and reported that brain-imaging studies show the existence of two centers of physical pain. All these statements were made possible by the technology of fMRI. There have been other new and exciting technologies developed in recent years, but the advent of fMRI changed the way scientists study the mind, and this advance continues to play a role of unparalleled importance in basic research.
Were we sitting in front of a computer housing your fMRI data, scientists would be able to make a slice of any section of your brain, and in any orientation, and view it almost as if they had dissected the brain itself. The image above, for example, displays a slice along the brain’s central plane, as the subject engages in daydreaming. The shaded areas on the left and right indicate activity in the medial prefrontal cortex and the posterior cingulate cortex, respectively.
Neuroscientists today commonly divide the brain into three crude regions, based on their function, physiology, and evolutionary development.35 In that categorization, the most primitive region is the “reptilian brain,” responsible for basic survival functions such as eating, breathing, and heart rate, and also for primitive versions of the emotions of fear and aggression that drive our fight-or-flight instincts. All vertebrate creatures—birds, reptiles, amphibians, fish, and mammals—have the reptilian brain structures.
The second region, the limbic system, is more sophisticated, the source of our unconscious social perception. It is a complex system whose definition can vary a bit from researcher to researcher, because although the original designation was anatomical, the limbic system has come to be defined instead by its function as the system in the brain instrumental in the formation of social emotions. In humans, the limbic system is often defined as a ring of structures, some of which we have already run into, including the ventromedial prefrontal cortex, dorsal anterior cingulate cortex, amygdala, hippocampus, hypothalamus, components of the basal ganglia, and, sometimes, the orbitofrontal cortex.36 The limbic system augments the reflexive reptilian emotions and is important in the genesis of social behaviors.37 Many of the structures in this second region are sometimes grouped together into what is called the “old mammalian brain,” which all mammals have, as opposed to the third region—the neocortex, or “new” mammalian brain—whose structures the more primitive mammals generally lack.
The neocortex lies above most of the limbic system.38 You may recall from Chapter 2 that it is divided into lobes and is oversized in humans. It is this gray matter that people usually think of when they talk about the brain. In Chapter 2, I talked about the occipital lobe, which is located at the back of your head and contains your visual primary processing centers. In this chapter, I’ve talked about the frontal lobe, which is, as the name indicates, located at the front.
The genus
The frontal lobe contains regions governing the selection and execution of fine motor movements—especially of the fingers, hands, toes, feet, and tongue—that are clearly important for survival in the wild. It is interesting to note that control of the motor movements of the face is based in the frontal lobe, too. As we’ll see in Chapter 5, the fine nuances of facial expression are also crucial to survival because of the role they play in social communication. In addition to regions associated with motor movements, as I mentioned earlier, the frontal lobe contains a structure called the prefrontal cortex. “Prefrontal” means, literally, “in front of the front,” and that’s where the prefrontal cortex sits, just behind the forehead. It is in this structure that we most clearly see our humanity. The prefrontal cortex is responsible for planning and orchestrating our thoughts and actions in accordance with our goals, and integrating conscious thought, perception, and emotion; it is thought to be the seat of our consciousness.39 The ventromedial prefrontal cortex and the orbitofrontal cortex, parts of the limbic system, are subsystems within the prefrontal cortex.
Though this anatomical division of the brain into reptilian; limbic, or old mammalian; and neocortex, or new mammalian, is useful—and I’ll occasionally refer to it—it’s important to realize that it is a simplified picture. The full story is more complex. For example, the neat evolutionary steps it implies are not quite the way things happened; some so-called primitive creatures have neocortical-like tissue.40 As a result, the behavior of those animals may not be as completely instinct-driven as once thought. Also, the three discrete areas are described as almost independent, but in reality they are integrated and work in concert, with numerous neural interconnections among them. The complexity of the brain is reflected by the fact that the hippocampus alone, a tiny structure deep in the brain, is the subject of a textbook several inches thick. Another recent work, an academic article that described research on a single type of nerve cell in the hypothalamus, was over one hundred pages long and cited seven hundred intricate experiments. That’s why, despite all the research, the human mind, both conscious and unconscious, still holds enormous mystery, and why tens of thousands of scientists worldwide are still working to elucidate the function of these regions, on the molecular, cellular, neural, and psychological levels, providing ever deeper insights into how the pathways interact to produce our thoughts, feelings, and behavior.
With the advent of fMRI and the growing ability of scientists to study how different brain structures contribute to thoughts, feelings, and behavior, the two movements that followed behaviorism began to join forces. Social psychologists realized they could untangle and validate their theories of psychological processes by connecting them to their sources in the brain. Cognitive psychologists realized they could trace the origins of mental states. Also, the neuroscientists who focused on the physical brain realized they could better understand its functioning if they learned about the mental states and psychological processes the different structures produce. And so the new field of social cognitive neuroscience, or, simply, social neuroscience, emerged. It is a menage a trois, a “household of three”: social psychology, cognitive psychology, and neuroscience. I said earlier that the first ever social neuroscience meeting took place in April 2001. To get an idea of how fast the field exploded, consider this: The first ever academic publication employing fMRI came in 1991.41 In 1992, there were only four such publications in the entire year. Even as late as 2001, an Internet search using the words “social cognitive neuroscience” yielded just 53 hits. But an identical search performed in 2007 yielded more than 30,000.42 By then, neuroscientists were turning out fMRI studies every three hours.
Today, with researchers’ new ability to watch the brain at work and to understand the origins and depth of the unconscious, the dreams of Wundt, James, and the others in the New Psychology who wanted to make that field into a rigorous experimental science are finally being realized. And though Freud’s concept of the unconscious was flawed, his stress on the importance of unconscious thought is appearing ever more valid. Vague concepts like the id and the ego have now given way to maps of brain structure, connectivity, and function. What we’ve learned is that much of our social perception—like our vision, hearing, and memory—appears to proceed along pathways that are not associated with awareness, intention, or conscious effort. How this subliminal programming affects our lives, the way we present ourselves, the way we communicate with and judge people, the way we react to social situations, and the way we think of ourselves, is the territory we are about to explore.
