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

ANGULAR GYRUS A brain area situated in the lower part of the parietal lobe near its junction with the occipital and temporal lobes. It is involved in high-level abstraction and abilities such as reading, writing, arithmetic, left-right discrimination, word representation, the representation of fingers, and possibly also comprehension of metaphor and proverbs. The angular gyrus is possibly unique to humans. It is also probably rich in mirror neurons that allow you to see the world from another’s point of view spatially and (perhaps) metaphorically—a key ingredient in morality.

ANOSOGNOSIA A syndrome in which a person who suffers a disability seems unaware of, or denies the existence of, the disability. (Anosognosia is Greek for “denial of illness.”)

ANTERIOR CINGULATE A C-shaped ring of cortical tissue abutting and partially encircling the front part of the large bundle of nerve fibers, called the corpus callosum, that link the left and right hemispheres of the brain. The anterior cingulate “lights up” in many—almost too many—brain-imaging studies. This structure is thought to be involved in free will, vigilance, and attention.

APHASIA A disturbance in language comprehension or production, often as a result of a stroke. There are three main kinds of aphasia: anomia (difficulty finding words), Broca’s aphasia (difficulty with grammar, more specifically the deep structure of language), and Wernicke’s aphasia (difficulty with comprehension and expression of meaning).

APOTEMNOPHILIA A neurological disorder in which an otherwise mentally competent person desires to have a healthy limb amputated in order to “feel whole.” The old Freudian explanation was that the patient wants a large amputation stump resembling a penis. Also called body integrity identity disorder.

APRAXIA A neurological condition characterized by an inability to carry out learned purposeful movements despite knowing what is expected and having the physical ability and desire to do so.

ASPERGER SYNDROME A type of autism in which people have normal language skills and cognitive development but have significant problems with social interaction.

ASSOCIATIVE LEARNING A form of learning in which the mere exposure to two phenomena that always occur together (such as Cinderella and her carriage) leads subsequently to one of the two things spontaneously evoking the memory of the other. Often invoked, incorrectly, as an explanation of synesthesia.

AUTISM One of a group of serious developmental problems called autism spectrum disorders that appear early in life, usually before age three. While symptoms and severity vary, autistic children have problems communicating and interacting with others. The disorder may be related to defects in the mirror-neuron system or the circuits it projects to, although this has yet to be clearly established.

AUTONOMIC NERVOUS SYSTEM A part of the peripheral nervous system responsible for regulating the activity of internal organs. It includes the sympathetic and parasympathetic nervous systems. These originate in the hypothalamus; the sympathetic component also involves the insula.

AXON The fiber-like extension of a neuron by which the cell sends information to target cells.

BASAL GANGLIA Clusters of neurons that include the caudate nucleus, the putamen, the globus pallidus, and the substantia nigra. Located deep in the brain, the basal ganglia play an important role in movement, especially control of posture and equilibrium and unconscious adjustments of certain muscles for execution of more voluntary movements regulated by the motor cortex (see frontal lobe). The finger and wrist movements for screwing a bolt are mediated by the motor cortex, but adjusting the elbow and shoulder to carry this out requires the basal ganglia. Cell death in the substantia nigra contributes to signs of Parkinson’s disease, including a stiff gait and the absence of postural adjustments.

BIPOLAR DISORDER A psychiatric disorder characterized by wild mood swings. Individuals experience manic periods of high energy and creativity and depressed periods of low energy and sadness. Also called manic depressive disorder.

BLACK BOX Before the advent of modern imaging technologies in the 1980s and 1990s, there was no way to peer inside the brain, hence it was likened to a black box. (The phrase is borrowed from electrical engineering.) The black-box approach is also one favored by cognitive psychologists and perceptual psychologists, who draw flow diagrams, or charts that indicate purported stages of information processing in the brain without being burdened by knowledge of brain anatomy.