The Tell-Tale Brain

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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.

SUPERIOR TEMPORAL SULCUS (STS) The topmost of two horizontal furrows, or sulci, in the temporal lobes. The STS has cells that respond to changing facial expressions, biological movements such as gait, and other biologically salient inputs. The STS sends its output to the amygdala.

SUPRAMARGINAL GYRUS An evolutionarily recent gyrus that split off from the inferior parietal lobule. The supramarginal gyrus is involved in the contemplation and execution of skilled or semiskilled movements. It is unique to humans, and damage to it leads to apraxia.

SYMPATHETIC NERVOUS SYSTEM A branch of the autonomic nervous system, responsible for mobilizing the body’s energy and resources during times of stress and arousal. It does this by regulating temperature as well as increasing blood pressure, heart rate, and sweating in anticipation of exertion.

SYNAPSE A gap between two neurons that functions as the site of information transfer from one neuron to another.

SYNESTHESIA A condition in which a person literally perceives something in a sense besides the sense being stimulated, such as tasting shapes or seeing colors in sounds or numbers. Synesthesia is not just a way of describing experiences as a writer might use metaphors; some synesthetes actually experience the sensations.

SYNTAX Word order that enables compact representation of complex meaning for communicative intent; loosely synonymous with grammar. In the sentence “The man who hit John went to the car,” we recognize instantly that “the man” went to the car, not John. Without syntax we could not arrive at this conclusion.

TEMPORAL LOBE One of the four major subdivisions (the others being frontal, parietal, and occipital lobes) of each cerebral hemisphere. The temporal lobe functions in perception of sounds, comprehension of language, visual perception of faces and objects, acquisition of new memories, and emotional feelings and behavior.

TEMPORAL LOBE EPILEPSY (TLE) Seizures confined mainly to the temporal lobes and sometimes the anterior cingulate. TLE may produce a heightened sense of self and has been linked to religious or spiritual experiences. The person may undergo striking personality changes and/or become obsessed with abstract thoughts. People with TLE have a tendency to ascribe deep significance to everything around them, including themselves. One explanation is that repeated seizures may strengthen the connections between two areas of the brain: the temporal cortex and the amygdala. Interestingly, people with TLE tend to be humorless, a characteristic also seen in seizure-free religious people.

THALAMUS A structure consisting of two egg-shaped masses of nerve tissue, each about the size of a walnut, deep within the brain. The thalamus is the key “relay station” for sensory information, transmitting and amplifying only information of particular importance from the mass of signals entering the brain.

THEORY OF MIND The idea that humans and some higher primates can construct a model in their brains of the thoughts and intentions of other people. The more accurate the model, the more accurately and rapidly the person can predict the other person’s thoughts, beliefs, and actions. The idea is that there are specialized brain circuits in human (and some apes’) brains that allow for theory of mind. Uta Frith and Simon Baron-Cohen have suggested that autistic children may have a deficient theory of mind, which complements our view that a dysfunction of mirror neurons or their targets may underlie autism.