Cognitive Health — Terms Explained

Acetylcholine is a neurotransmitter essential for attention, memory formation, and learning. Its deficiency in the hippocampus and cortex is a hallmark of Alzheimer's disease.

Alzheimer's disease is a progressive neurodegenerative disorder characterized by accumulation of amyloid plaques and tau tangles in the brain, leading to memory loss, cognitive decline, and loss of daily function.

Amyloid beta is a protein fragment that accumulates abnormally in the brains of people with Alzheimer's disease, forming plaques that are central to the disease's pathology.

APOE4 is the most significant genetic risk factor for late-onset Alzheimer's disease, carried by approximately 25% of the population and increasing lifetime Alzheimer's risk two-to-fourfold depending on how many copies are inherited.

BDNF is a protein that promotes the survival, growth, and function of neurons. It is elevated by exercise, depleted by chronic stress, and plays a central role in memory, learning, and cognitive reserve.

The blood-brain barrier is a highly selective membrane that separates the brain's blood supply from the central nervous system, protecting the brain from toxins and pathogens while allowing essential nutrients to pass.

Brain atrophy is the progressive loss of brain tissue — neurons and their connections — that occurs with aging and is accelerated by neurodegenerative diseases such as Alzheimer's.

Cerebrovascular health refers to the condition of the blood vessels supplying the brain. Poor cerebrovascular health is a leading cause of cognitive impairment and strongly modifiable through cardiovascular risk management.

Circadian rhythms are internal biological clocks that regulate physiological processes on a roughly 24-hour cycle, including cognitive performance, which peaks and troughs predictably across the day.

The Clock Drawing Test is a neuropsychological assessment in which a person draws a clock face from memory to a specific time, measuring visuospatial ability, executive function, and working memory simultaneously.

A cognitive baseline is a documented record of an individual's cognitive performance at a specific point in time, used as a reference point to detect meaningful change in the future.

Cognitive reserve is the brain's resilience to neurological damage — the accumulated mental resources that allow some people to tolerate more pathology before showing symptoms of cognitive decline.

Confounding variables are factors that influence cognitive test performance independently of the underlying cognitive ability being measured — including sleep, mood, illness, time of day, and medication effects.

Cortisol is the primary stress hormone, essential for the acute stress response. Chronically elevated cortisol damages hippocampal neurons, impairs working memory, and is associated with accelerated cognitive aging.

The default mode network is a set of interconnected brain regions that are most active when the mind is at rest and not focused on external tasks — associated with self-referential thinking, mind-wandering, and autobiographical memory.

Dementia is an umbrella term for a group of conditions characterized by progressive decline in cognitive function severe enough to interfere with daily life.

Dopamine is a neurotransmitter central to reward, motivation, movement, and working memory. Its disruption underlies Parkinson's disease and plays a significant role in cognitive aging and depression.

Episodic memory is the ability to recall specific personal experiences and events in their context of time and place — the memory system most severely and selectively impaired in the earliest stages of Alzheimer's disease.

Frontotemporal dementia is a group of brain disorders caused by progressive damage to the frontal and temporal lobes, typically presenting with personality changes, behavioral disinhibition, or language difficulties rather than memory loss.

The glymphatic system is the brain's waste clearance network, discovered in 2012, that uses cerebrospinal fluid flow along blood vessels to flush out metabolic byproducts — including amyloid-beta — primarily during deep sleep.

The hippocampus is a brain structure essential for forming new memories and spatial navigation. It is among the first regions damaged in Alzheimer's disease.

Insulin resistance — reduced cellular responsiveness to insulin — impairs the brain's energy metabolism and is associated with increased Alzheimer's risk, leading some researchers to call Alzheimer's 'Type 3 diabetes.'

Lewy body dementia is caused by abnormal deposits of alpha-synuclein protein in the brain, producing a combination of cognitive fluctuations, visual hallucinations, movement symptoms, and sleep disturbances.

Longitudinal cognitive tracking is the practice of measuring cognitive performance repeatedly over time to identify meaningful trends, distinguish real change from normal variation, and detect early decline.

Mild cognitive impairment is a condition involving measurable decline in one or more cognitive domains that goes beyond normal aging but does not significantly interfere with daily life.

The Mini-Cog is a brief three-minute cognitive screening test combining a three-word recall task and a clock drawing test, designed for rapid use in primary care settings.

The Mini-Mental State Examination is a 30-point cognitive screening tool developed in 1975 that assesses orientation, memory, attention, language, and visuospatial ability in approximately 10 minutes.

The Montreal Cognitive Assessment (MoCA) is a brief 10-minute screening tool for mild cognitive impairment, widely used in clinical settings and validated across multiple languages and populations.

Neuroinflammation is the activation of the brain's immune response, involving microglia and astrocytes, which plays a complex role in both protecting the brain and contributing to neurodegenerative disease when chronically activated.

Neuroplasticity is the brain's ability to change its structure and function in response to experience, learning, injury, or disease — throughout the lifespan.

Neurotransmitters are chemical messengers that transmit signals between neurons across synaptic gaps, enabling all brain communication from movement and sensation to memory and emotion.

Oxidative stress occurs when free radical production overwhelms the brain's antioxidant defenses, causing cellular damage that contributes to neurodegeneration and cognitive aging.

The practice effect is the improvement in cognitive test performance that occurs with repeated exposure to the same test, independent of any real change in underlying cognitive ability.

The prefrontal cortex is the front portion of the frontal lobe responsible for executive functions: planning, decision-making, working memory, impulse control, and social behavior.

Processing speed — the rate at which the brain takes in, processes, and responds to information — is one of the earliest and most sensitive cognitive domains to show age-related decline.

REM (Rapid Eye Movement) sleep is the stage associated with vivid dreaming and plays a critical role in emotional memory processing, cognitive integration, and creative thinking.

The Self-Administered Gerocognitive Examination (SAGE) is a paper-based cognitive screening test that people can complete at home and bring to a physician, designed to detect early cognitive impairment.

Sleep architecture refers to the structure of sleep — the pattern and proportion of different sleep stages (NREM stages 1, 2, 3, and REM) that cycle through the night and each serve distinct cognitive and physiological functions.

Slow-wave sleep is the deepest stage of non-REM sleep, characterized by large, slow brain waves. It is the stage most critical for physical restoration, memory consolidation, and glymphatic clearance of brain waste including amyloid-beta.

Tau is a protein that stabilizes the internal skeleton of neurons. In Alzheimer's and other neurodegenerative diseases, abnormally modified tau forms tangles that disrupt neuronal function and spread through the brain.

Vascular dementia is cognitive decline caused by reduced blood flow to the brain, typically due to strokes or damage to the brain's small blood vessels.

White matter lesions are areas of damage in the brain's white matter — the fiber tracts connecting brain regions — commonly caused by small vessel disease and associated with processing speed slowing and increased dementia risk.

Working memory is the cognitive system that temporarily holds and manipulates information in conscious awareness. Its capacity — typically 4 plus or minus 1 'chunks' — is a fundamental constraint on complex cognition and declines with age and disease.