Neuroscience and Sleep: Limbic System, Brain Structures, and Sleep Disorders

Limbic System

neural system located mostly in the forebrain — below the cerebral hemispheres associated with emotions and drives (includes the amygdala, hypothalamus, hippocampus, thalamus, and pituitary gland)

Hypothalamus

a limbic system neural structure lying below (hypo) the thalamus; it directs several maintenance activities (eating, drinking, body temperature), helps govern the endocrine system, and is linked to emotion and reward.

Pituitary Gland

the 'master control gland;' controls other glands and makes the hormones that trigger growth.

Amygdala

two lima-bean-sized neural clusters in the limbic system; linked to emotion.

Hippocampus

a neural center located in the limbic system; helps process explicit (conscious) memories — of facts and events — for storage.

Occipital Lobes

the portion of the cerebral cortex lying at the back of the head; it includes areas that receive information from the visual fields.

Temporal Lobe

the portion of the cerebral cortex lying roughly above the ears; it includes the auditory areas, each of which receives information primarily from the opposite ear. They also enable language processing.

Parietal Lobes

the portion of the cerebral cortex lying at the top of the head and toward the rear; it receives sensory input for touch and body position.

Association Areas

areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather, they are involved in higher mental functions such as learning, remembering, thinking, and speaking.

Somatosensory Cortex

a cerebral cortex area at the front of the parietal lobes that registers and processes body touch and movement sensations.

Frontal Lobes

the portion of the cerebral cortex lying just behind the forehead. They enable linguistic processing, muscle movements, higher-order thinking, and executive functioning (such as making plans and judgments).

Prefrontal Cortex

functions in attention, planning, working memory, and the expression of emotions and appropriate social behaviors.

Motor Cortex

a cerebral cortex area at the rear of the frontal lobes that controls voluntary movements.

Split Brain

a condition resulting from surgery that isolates the brain's two hemispheres by cutting the fibers (mainly those of the corpus callosum) connecting them.

Corpus Callosum

the large band of neural fibers connecting the two brain hemispheres and carrying messages between them.

Broca's Area

a frontal lobe brain area, usually in the left hemisphere, that helps control language expression by directing the muscle movements involved in speech.

Wernicke's Area

a brain area, usually in the left temporal lobe, involved in language comprehension and expression.

Aphasia

impairment of language, usually caused by left hemisphere damage either to Broca's area (impairing speaking) or to Wernicke's area (impairing understanding).

Contralateral Hemispheric Organization

the cerebral hemisphere that is controlling an organ or part on the opposite side of the body.

Neuroplasticity

the brain's ability to change, especially during childhood, by reorganizing after damage or by building new pathways based on experience.

Lesion

tissue destruction. Brain lesions may occur naturally (from disease or trauma), during surgery, or experimentally (using electrodes to destroy brain cells).

Electroencephalogram (EEG)

an amplified recording of the waves of electrical activity sweeping across the brain's surface. These waves are measured by electrodes placed on the scalp.

fMRI (functional MRI)

a technique for revealing blood flow and, therefore, brain activity by comparing successive MRI scans. fMRI scans show brain function as well as structure.

Hormones

chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues.

Adrenaline

hormone that prepares the body for a "fight-or-flight-or-freeze" response to stress by increasing the heart rate and the blood flow to muscles.

Leptin

a hormone secreted by fat cells that regulate food intake by inhibiting hunger.

Ghrelin

hormone secreted by the stomach that stimulates appetite.

Melatonin

produced in the pineal gland that regulates sleep-wake cycles.

Oxytocin

produced in the hypothalamus and released by the pituitary gland that plays a role in childbirth, social bonding, and sexual reproduction.

Agonist

a molecule that increases a neurotransmitter's action.

Antagonist

a molecule that inhibits or blocks a neurotransmitter's action.

Reuptake Inhibitors

a substance that interferes with the reabsorption of neurotransmitters by the presynaptic neurons that released them.

Stimulants

drugs that excite neural activity and speed up body functions.

Depressants

drugs that reduce neural activity and slow body functions.

Hallucinogens

psychedelic ("mind-manifesting") drugs that distort perceptions and evoke sensory images in the absence of sensory input.

Opioids

opium and its derivatives; they depress neural activity, temporarily lessening pain and anxiety.

Tolerance

the diminishing effect with regular use of the same dose of a drug, requiring the user to take larger and larger doses before experiencing the drug's effect.

Addiction

an everyday term for compulsive substance use (and sometimes for dysfunctional behavior patterns, such as out-of-control gambling) that continue despite harmful consequences.

Withdrawal

the discomfort and distress that follow discontinuing an addictive drug or behavior.

Consciousness

our subjective awareness of ourselves and our environment.

Circadian Rhythm

the biological clock; regular bodily rhythms (for example, of temperature and wakefulness) that occur on a 24-hour cycle.

Hypnagogic Sensations

bizarre experiences, such as jerking or a feeling of falling or floating weightlessly, while transitioning to sleep.

REM Sleep (Paradoxical)

rapid eye movement sleep; a recurring sleep stage during which vivid dreams commonly occur. (Also known as paradoxical sleep, because the muscles are relaxed.)

REM Rebound

the tendency for REM sleep to increase following REM sleep deprivation (created by repeated awakenings during REM sleep).

Activation-Synthesis Hypothesis

explains dreams as a product of cerebral cortex interpretation of random neural activity rising from the brainstem.

Consolidation Dream Theory

hypothesis that dream content is influenced by memory consolidation.

Insomnia

recurring problems in falling or staying asleep.

Narcolepsy

a sleep disorder characterized by uncontrollable sleep attacks. The suffered may lapse directly into REM sleep, often at inopportune times.

REM Sleep Behavior Disorder

a sleep disorder in which normal REM paralysis does not occur; instead, twitching, talking, or even kicking or punching may occur, often acting out one's dream.

Sleep Apnea

a sleep disorder characterized by temporary cessations of breathing during sleep and repeated momentary awakenings.

Somnambulism

a sleep disorder of episodes typically occurring during the first hours of sleep and involve getting out of bed and walking, (although the individual may also perform more complicated tasks, such as eating, talking, or operating machinery).