Glossary of Terms

This section provides definitions for some of the key terms related to the brain and early childhood development. To find the definition of a particular word, use the alphabet key (below) to navigate to that section of the alphabet.

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

— A —
Adrenaline –
non-technical term for hormone epinephrine (see definition for epinephrine)
Adverse Childhood Experiences (ACEs) –
experiences including things like physical and emotional abuse, neglect, caregiver mental illness, and household violence. The more ACEs a child experiences, the more likely he or she is to suffer from things like heart disease and diabetes, poor academic achievement, and substance abuse later in life.
Alpha-linolenic acid (ALA) –
part of limbic system in the brain; responsible for receiving and integrating emotions and emotional information
Amygdala –
part of limbic system in the brain; responsible for receiving and integrating emotions and emotional information
Arachidonic acid (ARA)–
fatty acid, or lipid substance, found in breast milk and in brain tissue
Astrocytes (Astroglia) –
star-shaped glial cells that provide physical and nutritional support for neurons by cleaning up brain debris, transporting nutrients to neurons, holding neurons in place, digesting parts of dead neurons, and regulating contents of extracellular space.
Atrophy –
wasting away or failure of a body part to develop
Attachment –
the formation of a close emotional bond between infants and the adults who regularly care for them
Axon –
the neuron’s long fiber that carries impulses away from the cell to other neurons

— B —
Basal ganglia –
a group of nuclei located under the cerebral cortex; involved in initiating and inhibiting voluntary movement and cognitive functioning
Brain –
the organ that controls all of our bodily processes, including basic functions such as breathing and digestion, automatic processes such as reflexes, and conscious processes such as thinking, language, memory, movements and coordination
Brain stem –
one of the four major parts of the brain, it monitors basic, vital functions such as heartbeat, body temperature, and digestion. The brain stem is the first part of the brain to develop.
Broca’s area –
structure located in the frontal lobe of the brain that controls the production of spoken and written language

— C —
Cell body (soma) –
the command center of the neuron that makes decisions about whether or not to send electrical impulses to other neurons
Cerebellum –
one of four major parts of the brain, it is responsible for initiating and timing movements and is important for balance, posture, and coordinating how muscles work together. The cerebellum begins developing after the brain stem, but before the parts of the brain responsible for conscious thought and action.
Cerebral cortex –
one of four major parts of the brain, it controls most of our conscious, voluntary actions. The cerebral cortex is the last part of the brain to finish developing, and development is not complete until the mid 20s.
Connection –
linkage of one nerve cell to other nerve cells across a microscopic space in which chemicals act to move impulses or messages among nerve cells
Consistency –
creating a positive environment for a young child that is predictable, orderly, and has routines for necessary activities like meals and sleep, yet is flexible
Corpus callosum –
the band of fibers that connects the two hemispheres, allowing communication between the right and left sides of the brain
Cortisol –
a stress hormone that is released to help our bodies deal with threats

— D —
Dendrites –
the extensions of a neuron that receive impulses from nearby neurons
Docosahexaenoic acid (DHA) –
long-chain fatty acid found in breast milk and also in tissue in eye and brain

— E —
Electroencephalogram (EEG) –
specially-designed cap lined with sponges that allows researchers to measure brain waves in different parts of the brain through the skull. The EEG is an effective technique to study the brains of infants and young children.
Essential fatty acids (EFAs) –
key dietary components that contribute to the growth and development of the brain. They are “essential” because the body cannot make them, and they must be consumed through diet or purified supplements.
Enzymes –
protein-based substance that acts as a catalyst to initiate or speed up specific chemical reactions in the body
Event-related optical signal (EROS) –
Technology that allows researchers to measure changes in optical properties of the brain through optical fibers as the patient is exposed to certain stimuli. The EROS is an effective technique to study the brains of infants and young children.
Executive function –
a set of skills that underlie the capacity to plan ahead and meet goals, display self-control, follow multiple-step directions even when interrupted, and stay focused despite distractions, among others.
Expressive aphasia –
when a person is able to comprehend language, but cannot translate their thoughts into spoken, written, or sign language; occurs after damage to Broca’s area

— F —
Fragile X syndrome –
genetic disease that causes severe cognitive delays, especially in boys
Frontal lobe –
the part of the brain located behind the forehead that is involved in critical thinking, problem-solving, planning, reasoning, and decision making
Functional magnetic resonance imaging (fMRI) –
Method of measuring brain activity by tracking changes while the patient completes simple tasks, such as reciting words out loud or looking at pictures on a screen. The fMRI is not effective in measuring the brain activity of infants and young children because it requires the patient to lie still for long periods of time.

— G —
Gene –
unit on chromosomes by which hereditary characteristics are transmitted and determined
Glial cells –
supporting cells that enable neurons to function effectively in the brain, central nervous system, and peripheral nervous system. There are five different types of glial cells.
Gustatory cortex –
controls taste, located in the frontal lobe

— H —
Hemispheres –
the two halves into which the brain is divided (left and right)
Hippocampus –
part of the limbic system that processes emotions and memories
Hormone –
a substance produced by one tissue and conveyed by the bloodstream to another to effect physiological activity, such as growth

— I —
Immune factors –
Components found in breast milk that promote brain development by providing protection from infections
Insecure attachment –
a bond formed between infant and adult that is lacking in consistency, responsiveness and full trust and may cause the infant to feel angry, anxious, distressed or conflicted
Infant-directed speech –
way in which adults instinctively help infants learn language that includes a higher pitch, elongated vowel sounds, and exaggerated rhythms, but not nonsense words

— L —
Left hemisphere –
the left half of the brain that controls the right side of the body, processes specific details of a situation, and relies mainly on logic
Limbic system –
the structures of the brain that register and store emotional information
Lobe –
one of four sections or areas of the brain; each of the four lobes performs specific functions

— M —
Magnetoencephalography(MEG) –
new technology that provides the most accurate resolution for viewing the timing of nerve cell activity, down to the millisecond; it records brain activity by measuring very faint magnetic fields that emanate from the head as a result of brain activity
Microglia –
Glial cells that support neurons by digesting parts of dead neurons
Migration –
movement of neurons to pre-determined locations in the brain
Motor cortex –
band of fibers at the front of the parietal lobe that controls function of muscles that move the body
Myelin –
a fatty substance that surrounds and insulates a neuron’s axon
Myelination –
the process of forming a coating or sheath of fatty substances known as myelin on the axon of a neuron

— N —
Neural pathway –
a series of synapses that form a network in the brain
Neuron –
the basic cell making up the brain and nervous system, which receives electrical impulses from other neurons and sends out those impulses through networks of connections
Neurogenesis –
the process of forming neurons
Neuroscience –
the study of the nervous system and the brain
Neurotransmitter –
a chemical that carries information in the brain and affects communication between neurons

— O —
Occipital Lobe –
part of the brain, located at the rear of the cerebrum, where vision is processed
Ogliodendroglia (ogliodendrocytes) –
Glial cells that support neurons by providing myelin to neurons in the central nervous system
Olfactory blubs –
located against the underside of the frontal lobe; involved in the sense of smell
Omega-3 –
one of the two groups of essential fatty acids that is found largely in cold-water fish and seaweed

— P —
Parietal lobe –
part of the brain located on the crown of the head that processes sensory information for smell, taste and touch. An area at the front of the parietal lobe called the motor cortex is responsible for motor coordination.
Peripheral nervous system –
the networks of nerves outside the brain and spinal cord
Plasticity –
the brain’s ability to adapt to new experiences
Positive stress –
short-term, everyday stress that is a normal part of life and helps the brain learn how to manage everyday stressors
Positron Emission Tomography (PET) scan –
a brain imaging technology that generates a computerized image of the brain’s structure and of the activity levels in various parts of the brain
Prenatal period –
the period from conception to childbirth
the selective elimination or “weeding out” of non-essential synapses based on a child’s specific experiences

— R —
Resiliency –
the ability to survive and thrive in the face of traumatic life experiences
Right hemisphere –
the right half of the brain that controls the left side of the body, provides an overall impression of situations, relies more on symbols and imagery, and processes information in a more holistic manner

— S —
Satellite cells –
Glial cells that support neurons by providing physical support to neurons in the peripheral nervous system
Schwann cells –
Glial cells that support neurons by providing myelin to neurons in the peripheral nervous system
Secure attachment –
a strong, positive bond between infant and adult
Sensitive period –
an optimal period for the development and pruning of connections in a particular part of the brain
Separation anxiety –
distress shown by securely attached infants when a parent leaves them
Serotonin –
a neurotransmitter, derived from tryptophan, that is involved in sleep, depression, memory, and other neurological processes
Serve and return interactions –
sustained patterns of back-and-forth interactions that help build complex pathways of synaptic connections in the brain
Shaken baby syndrome –
forceful shaking of an infant or young child, before protective brain coatings and structure have developed, that causes serious and permanent damage to brain cells or even death
Soma –
see ‘cell body’
Stress –
any external stimulus that threatens the balance of the normal equilibrium in the body
Stress response –
the heightened state of arousal that our body goes through when it perceives a threat
Stressor –
an event or experience that causes stress
Synapse –
the microscopic gap between the axon of one neuron and the dendrite of another
Synapse formation –
the process of creating synapses, or connections, between neurons
Synaptic overproduction –
rapid formation in the first few years of more synapses or connections than are actually needed
Synaptogenesis –
the process of creating synapses, or connections, between neurons

— T —
Temporal lobe –
part of the brain located above the ears that is responsible for hearing, speech, and some learning and memory
Terminals –
connect to the dendrites of other neurons, creating networks by which the electrical impulses travel
Tolerable stress –
longer-term stressors (e.g., moving to a new home, changing child care providers) that becomes manageable because the child has a positive support system to help deal with the stress in a healthy way
Toxic stress –
overexposure to extreme or damaging stress, without the mitigating effects of a positive support system
Toxin –
any of various poisonous compounds that may occur in air, soil, water, food, or materials, and cause certain diseases when they enter or come in contact with the body
Trauma –
a wound or shock produced by sudden physical or psychological injury (e.g., violence or accident)

— V —
Visual cortex –
the portion of the cerebral cortex of the brain that receives and processes impulses from the optic nerves

— W —
Wernicke’s area –
area located in the temporal lobe that plays a critical role in the ability to understand meaningful speech