Cognition

Adult hippocampal neurogenesis (AHN) is the process by which new neurons arise from neural stem and progenitor cells in the subgranular zone of the hippocampal dentate gyrus (DG)…

Amyloid-β (Aβ) is a family of peptides of 36–43 amino acids cleaved from the amyloid precursor protein (APP) by β- and γ-secretase; the 42-residue form (Aβ42) is especially prone…

Amyloid precursor protein is a type I transmembrane glycoprotein encoded on chromosome 21 and expressed widely in the central nervous system. In the non-amyloidogenic pathway…

BDNF is a growth-factor protein that supports neuronal survival, synapse formation, and — at least in animal models — adult hippocampal neurogenesis (its extent in adult humans…

The blood-brain barrier (BBB) is a highly selective neurovascular interface formed by specialised endothelial cells lining cerebral capillaries, reinforced by tight-junction…

Cerebral blood flow (CBF) is the volume of blood delivered per unit time, expressed in mL per 100 g per minute, regulated via autoregulation, arterial CO₂ sensitivity, and…

Cerebral small vessel disease (CSVD) encompasses a spectrum of pathological changes affecting the perforating arteries, arterioles, capillaries and venules of the brain,…

Cognitive reserve, developed and formalised by Yaakov Stern building on earlier brain-reserve work (Katzman and colleagues, late 1980s), refers to the brain's functional…

Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease are proteins measured in lumbar puncture samples that reflect core brain pathologies: Aβ42 (and the Aβ42/40 ratio)…

The default mode network (DMN) is a set of anatomically connected cortical and subcortical regions — including the medial prefrontal cortex, posterior cingulate cortex, precuneus…

Flow, described by psychologist Mihaly Csikszentmihalyi, is a state of deep absorption in a challenging activity matched to one's skill, accompanied by reduced self-awareness and…

Fluid vs crystallized intelligence is a distinction within the Cattell-Horn-Carroll (CHC) framework between two broad cognitive factors with divergent lifespan trajectories.…

Gait speed — typically assessed over a 4- or 6-metre walk at comfortable pace — is one of the most robust and inexpensive functional biomarkers of systemic aging, integrating…

Hippocampal volume measures the size of the brain region central to memory consolidation and spatial navigation. Atrophy rates vary by cohort and method: meta-analyses report…

Ikigai is a Japanese concept loosely translated as a sense of purpose or reason for being, encompassing everyday sources of meaning — relationships, routines, small pleasures —…

Lewy bodies are eosinophilic intraneuronal inclusions composed predominantly of aggregated α-synuclein protein, first described by Friedrich Lewy in 1912 and identified as the…

Loneliness, the subjective feeling of social disconnection, is now recognised as an independent risk factor for cardiovascular disease, dementia, and early mortality.…

Microglia are the brain's resident innate immune cells, derived from yolk-sac progenitors that colonise the CNS during early embryogenesis and are maintained independently of…

Defined by Petersen's diagnostic criteria (objective cognitive decline on testing, preserved daily functioning, not meeting dementia threshold), mild cognitive impairment exceeds…

Mindfulness is the trained practice of bringing non-judgmental attention to present-moment experience, typically through meditation. Randomised trials show modest but consistent…

The Mini-Mental State Examination (MMSE), introduced by Folstein, Folstein and McHugh in 1975, is a 30-point structured clinical interview assessing orientation, registration,…

The Montreal Cognitive Assessment (MoCA), developed by Ziad Nasreddine and published in 2005, is a 30-point, 10-minute bedside screening tool covering visuospatial/executive…

Neuroinflammation is activation of the brain's innate immune system — principally microglia and astrocytes — by protein aggregates, injury, or sterile aging signals, producing…

Neuroplasticity is the brain's lifelong capacity to reorganise its structure and synaptic connections in response to learning, experience, and injury. It underpins memory…

Polyvagal theory, proposed by Stephen Porges in 1995, posits that distinct vagal branches — a phylogenetically newer ventral-vagal complex and an older dorsal vagal pathway —…

The prefrontal cortex (PFC), comprising Brodmann areas 9, 10, 11, 46, and 47 and related regions, is the cortical seat of executive function, working memory, cognitive…

Presenilin 1 (PSEN1) and presenilin 2 (PSEN2) are nine-transmembrane proteins that form the catalytic core of the gamma-secretase complex together with nicastrin, APH-1 and…

Synaptic plasticity is the activity-dependent change in synaptic strength considered the cellular substrate of learning and memory. The cardinal form is long-term potentiation…

Tau is a microtubule-associated protein that under normal conditions stabilises the axonal cytoskeleton by binding to tubulin; in Alzheimer's disease and other tauopathies it…

TREM2 (triggering receptor expressed on myeloid cells 2) is a single-pass transmembrane receptor expressed almost exclusively by microglia in the brain. It senses anionic lipids,…

Vascular dementia is cognitive impairment severe enough to disrupt daily function that is attributable to cerebrovascular disease, and is the second most common dementia subtype…

White matter hyperintensities (WMH) are regions of abnormally high signal intensity on T2-weighted and FLAIR MRI sequences within the cerebral white matter, reflecting focal…