The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

REDUCTIONISM One of the most successful methods used by scientists to understand the world. It only makes the innocuous claim that the whole can be explained in terms of lawful interactions between (not simply the sum of) the component parts. For example, heredity was “reduced” to the genetic code and complementarity of DNA strands. Reducing a complex phenomenon to its component parts does not negate the existence of the complex phenomenon. For ease of human comprehension, complex phenomena can also be described in terms of lawful interactions between causes and effects that are at the “same level” of description as the phenomenon (such as when your doctor tells you, “Your illness is caused by a reduction in vitality”), but this rarely gets us very far. Many psychologists and even some biologists resent reductionism, claiming, for example, that you cannot explain sperm if you know only its molecular constituents but not about sex. Conversely, many neuroscientists are mesmerized by reductionism for its own sake, quite independent of whether it helps explain higher-level phenomena.

REUPTAKE A process by which released neurotransmitters are absorbed at the synapse for subsequent reuse.

SEIZURES A brief paroxysmal discharge of a small group of hyperexcitable brain cells that results in a loss of consciousness (grand mal seizure) or disturbances in consciousness, emotions, and behavior without loss of consciousness (temporal lobe epilepsy). Petit mal seizures are seen in children as a brief “absence.” Such seizures are completely benign and the child almost always outgrows them. Grand mal is often familial and begins in the late teens.

SELF-OTHER DISTINCTION The ability to experience yourself as a self-conscious being whose inner world is separate from the inner worlds of others. Such separateness does not imply selfishness or lack of empathy for others, although it may confer a propensity in that direction. Disturbances of self-other distinctions, as we have argued in Chapter 9, may underlie many strange types of neuropsychiatric illness.

SEMANTIC MEMORY Memory for the meaning of an object, event, or concept. Semantic memory for a pig’s appearance would include a cluster of associations: ham, bacon, oink oink, mud, obesity, Porky the Pig cartoons, and so on. The cluster is bound together by the name “pig.” But our research on patients with anomia and Wernicke’s aphasia suggests that the name is not merely another association; it is a key that opens a treasury of meanings and a handle that can be used for juggling the object or concept around in accordance with certain rules, such as those required for thinking. I have noticed that if an intelligent person with anomia or Wernicke’s aphasia, who can recognize objects but names them incorrectly, initially misnames an object (such as calling a paintbrush a comb), she often proceeds to use it as a comb. She is forced to head up the wrong semantic path by the mere act of mislabeling the object. Language, visual recognition, and thought are more closely interlinked than we realize.

SEROTONIN A monoamine neurotransmitter believed to play many roles including, but not limited to, temperature regulation, sensory perception, and inducing the onset of sleep. Neurons using serotonin as a transmitter are found in the brain and in the gut. A number of antidepressant drugs are used to target serotonin systems in the brain.

“SO WHAT” STREAM Not well defined or anatomically delineated, this pathway involves parts of the temporal lobes concerned with the biological significance of what you are looking at. Includes connections with the superior temporal sulcus, the amygdala, and the insula. Also called pathway 3.

STIMULUS A highly specific environmental event capable of being detected by sensory receptors.

STROKE An impeded blood supply to the brain, caused by a blood clot forming in a blood vessel, the rupture of a blood vessel wall, or an obstruction of flow caused by a clot or fat globule released from injury elsewhere. Deprived of oxygen (which is carried by the blood), nerve cells in the affected area cannot function and thus die, leaving the part of the body controlled by these cells also unable to function. A major cause of death in the West, stroke can result in loss of consciousness and brain function, and in death. During the last decade, studies have shown that feedback from a mirror can accelerate recovery of sensory and motor function in the arm in some stroke patients.

SUPERIOR PARIETAL LOBULE (SPL) A brain region that lies near the top of the parietal lobe. The right SPL is partially concerned with creating one’s body image using inputs from vision and area S2 (joint and muscle sense). The inferior parietal lobule is also involved in this function.