Glossary

Actin:

A family of proteins that form microfilaments in the cytoskeleton of the cell and also form fibrils in muscle cells. Actin polymerization is a critical process that is involved in cell movement.

Action potential:

A large electrical current, lasting one to two milliseconds, which propagates along the axon’s presynaptic terminal. At this terminal, electrical activity leads to the release of neurotransmitter onto the post-synaptic terminal of the target neuron.

Alzheimer’s disease:

A neurodegenerative disease that is progressive with age and is associated with dementia.

Aphasia:

A group of language disorders that result from lesions in specific regions of the brain that control language. Different types of aphasia include Wernicke’s aphasia or the ability to understand language and Broca’s aphasia, the ability to speak.

Astrocyte:

Star-shaped glial cells in the brain and spinal cord. They are the most plentiful cell type in the brain and play a critical supportive role in providing nutrients and other signals to the neurons.

Autism or autism spectrum disorder:

A group of neurodevelopmental disorders generally with onset in childhood that influence how the affected individual interacts with others, learns and communicates.

Axon:

The long extension that emanates from the cell body of the neuron and ends in presynaptic terminals, where it connects to other cells and sends signals.

Basal ganglia:

A region of the brain that controls movement and is involved in Parkinson’s disease. Neurons in the basal ganglia produce dopamine, the neurotransmitter that is deficient in Parkinson’s disease.

Brain:

A complex organ that mediates memory, emotion, movement, sensation and all behavior. It is made of different parts including the cerebrum, the cerebellum and the brain stem. The brain communicates to the body through the spinal cord.

Broca’s area:

A region of the brain in the left frontal cortex that is involved in spoken or written language.

Cell migration:

The process by which cells move during development and the formation of multicellular organisms. This can involve the directed movement of single cells, like immune cells, or groups of cells.

Cerebral cortex:

The outer region of the cerebral hemisphere, which is comprised of the frontal, parietal, temporal and occipital lobes.

Cerebral hemispheres:

The two hemispheres of the brain, connected by axons referred to as the corpus callosum, which coordinate the activities of these two hemispheres. Each cerebral hemisphere is composed of the cortex, the basal ganglia (controls movement), hippocampus (memory) and amygdala (emotions like fear).

Cognition:

The process of acquiring knowledge and understanding the senses, experience and thought. Cognitive psychology is focused on the study of mental processes. Cognitive neuroscience is the study of the brain.

Complement component:

A plasma or blood protein that is comprised of many distinct components. The proteins work with the immune system to combat infection and activate both the innate (phagocytes) and adaptive (T cells) parts of the immune system. Genetic changes in specific complement component abnormalities (C3, C1q) have been associated as a risk factor for Alzheimer’s disease and schizophrenia.

Cytoskeleton:

A network of microscopic filaments and tubules in the cytoplasm of cells that give the cell its shape and regulate the ability of individual cells to migrate.

Dendrite:

A branched extension that emanates from the cell body of a neuron and receives signals from other neurons through the synapse.

Dopamine:

A neurotransmitter that controls voluntary movement and cognition. Deficiency of dopamine is found in Parkinson’s disease. An excess of dopaminergic signaling has been implicated in schizophrenia.

Epilepsy:

A disorder of the brain characterized by seizures or involuntary movements, due to electrical dysfunction of the brain.

Filamin:

A group of large proteins that bind to the actin cytoskeleton and to adhesion receptors on the surface of cells. Filamins regulate cell adhesion and migration.

Fractalkine:

A small protein or chemokine that mediates inflammation.

Frontal lobe:

A lobe in the cerebral cortex that mediates executive functions like memory, speech and movement of the body.

Golgi stain:

A silver staining technique that is used to image neurons using light microscopy.

Interneuron:

A type of neuron that connects between neurons and regulates their activity. Some interneurons inhibit the activity of other neurons (inhibitory neurons).

Ketogenic diet:

A low-carbohydrate, high-fat diet that is used to treat people with seizure disorders.

Lateral geniculate nucleus (LGN):

A structure in the thalamus that is part of the mammalian visual pathway. It is in an area of thalamus that connects with the optic nerve.

Lysosome:

An organelle within all cells that gets rid of the waste within the cell, a type of garbage can. It degrades material that is taken up by phagocytes, including cellular debris or pathogens.

Magnetic resonance imaging (MRI):

A non-invasive imaging method that uses a magnet to image structures in the brain. Functional MRI is a method that uses MRI to detect changes in blood flow and oxygen consumption in the brain, to detect regions of the brain that are more or less active.

Memory:

The encoding of data or information.

Microglial cell:

A specialized type of phagocyte that is found in the brain and removes damaged cells and neurons and helps to control infection.

Motor neuron:

A type of neuron that controls muscle and movement. Motor neurons make synapses with muscle cells sending information from the central nervous system (CNS) to control movement.

Nerve:

A nerve is comprised of a bundle of axons that transmit information from neurons.

Neural circuit:

A network that forms between a group of neurons that are interconnected and influence each other’s activity.

Neurology:

The area of medicine focused on the brain and how it goes awry in disease. Neurologists focus on the care of patients with diseases of the nervous system, including seizure disorders, stroke, Alzheimer’s disease and Parkinson’s disease.

Neuron:

The primary cell of the nervous system. There are approximately 100 billion neurons in the human brain. Each neuron makes around 1,000 synapses, resulting in a complex network of connections. Neurons can extend long distances from the brain to the periphery with the cell body, often a meter or more away from some of the synapses that an individual neuron makes.

Neurotransmitter:

A chemical released by an activated neuron that activates an adjacent cell (typically another neuron). It is a chemical that is released by one neuron through its synapse and binds to the receptor on another neuron, altering the flow of current in the receiving neuron.

Parkinson’s disease:

A neurological disorder associated with deficiency in brain cells in the basal ganglia that make dopamine. Parkinson’s symptoms often develop gradually over years and include progressive movement disorders such as tremor, loss of balance and a shuffling gait as well as non-motor symptoms such as depression, anxiety, sleep disorders and various cognitive impairments.

Periventricular heterotopia:

A rare neurological disease that commonly presents with seizures, and is associated with a defect in neuronal cell migration early in development.

Phagocyte:

A type of innate immune cell in the body that can engulf and remove cellular debris and pathogens. The two primary cells of the innate immune system are neutrophils and macrophages. Microglial cells are a type of macrophage.

Plasticity:

The ability of neurons and their connections (synapses) to change based on experience and activity.

Positron-emission tomography (PET):

PET is a type of imaging method that reports brain function through the use of radioactive molecules to probe specific brain activities. This can be used to read out the metabolism or blood flow in the brain. More recent methods are used to quantify synapses in different regions of the brain (using the SV2A synapse marker).

Protein:

A biomolecule made up of amino acids. Thousands of different proteins in any cell are enzymes that catalyze the chemical reactions of life, while other proteins can serve structural roles.

Reflex:

An involuntary unlearned response to an external stimulus, like the knee jerk test, commonly done by neurologists. In the case of the spinal reflex like the knee jerk reflex, it is mediated by neurons in the spinal cord and does not require signals from the brain.

Rapid eye movement (REM):

At night you fluctuate between two types of sleep, REM sleep and non-REM sleep. REM sleep is associated with rapid movement of eyes and increased brain activity during sleep. REM sleep is associated with dreaming and the consolidation of memories.

Rett syndrome:

A rare genetic disorder that affects brain development in girls. It is a type of neurodevelopmental autism spectrum disorder.

Reye’s syndrome:

A rare, serious brain condition linked with aspirin use during viral infections in children, and associated with liver and brain damage.

Schizophrenia:

A serious mental illness that affects how a person thinks, acts and feels.

Sensory neuron:

One of the three major types of neurons. Sensory neurons detect sensation in the periphery like touch.

Synapse:

The point of contact between two neurons through which signals and information are transmitted. The synaptic cleft is the gap between two neurons through which chemical signals are propagated.

Synaptogenesis:

The developmental process of the formation of synapses, maintenance of synapses and activity-dependent elimination of synapses.

Systemic lupus erythematosus (lupus):

A systemic autoimmune disease in which the immune system attacks its own tissues and leads to inflammation in multiple organs, including the joints, skin, brain and kidney.

Tuberous sclerosis:

A rare genetic condition that causes benign tumors in different tissues, including the brain.

Visual system:

A sensory circuit that travels from the retina of the eye to the cortex. This is the circuit that Hubel and Wiesel dissected to understand how vision works.

Wernicke’s area:

The region of the left parietal lobe that handles language comprehension.