Basic Concepts

The table below lists 173+ terms frequently used in neuroscience and nootropic literature. Contains. This dictionary extends from neurotransmitter systems to brain regions, from mitochondrial pathways to memory mechanisms, from epigenetics to longevity research; It can be used as a reference source when reading article profiles and blog articles.

Term Definition
NGF (Nerve Growth Factor) A protein that supports the growth, survival and repair of neurons. Ingredients such as Lion's Mane support neuroplasticity by increasing NGF production.
BDNF (Brain Derived Neurotrophic Factor) Growth factor that plays a key role in learning and memory and promotes the formation of new neurons and synapses (neurogenesis). Exercise increases Lion's Mane and PQQ BDNF; chronic stress and sleep deprivation pressures.
acetylcholine Neurotransmitter closely associated with learning, memory, attention and muscle control. Alpha-GPC and CDP-Choline provide precursors for acetylcholine synthesis; Huperzine A slows down its degradation.
GABA The brain's primary inhibitory (sedative) neurotransmitter. Provides calmness and relaxation by reducing nervous activity; It is associated with anxiety, sleep and seizure threshold. It acts in the body through GABA-A and GABA-B receptors.
adaptogen Herbal substances that restore the body's capacity to adapt to physical and mental stress (homeostasis). Ashwagandha, Rhodiola, Tongkat Ali and Panax ginseng are typical examples; They regulate the HPA axis and cortisol release.
neuroplasticity The brain's ability to rewire itself by making new connections in response to experience, learning, or damage. LTP involves neurogenesis and dendritic remodeling.
racetam Family of synthetic nootropics starting with Piracetam. It supports the acetylcholine system by positively modulating AMPA receptors. Piracetam, aniracetam, oxiracetam and pramiracetam are members of this family.
choline Essential nutrient required for acetylcholine synthesis and cell membrane (phosphatidylcholine) construction. It is produced in limited amounts in the body; It is rich in eggs, liver and fish. Nootropic choline sources: Alpha-GPC, CDP-Choline, DMAE.
neurotransmitter Chemical messengers that carry signals across the synapse gap between neurons. Dopamine, serotonin, GABA, glutamate and acetylcholine are prime examples. Release is regulated by reuptake and enzyme degradation.
synapse The junction between two neurons where signals are transmitted via neurotransmitters. This gap, which converts the electrical impulse into a chemical signal, is approximately 20 nm wide.
Bioavailability The ratio that expresses how much of an ingested substance can reach the bloodstream unchanged and have an effect. First pass metabolism, solubility and carrier proteins are decisive for oral intake. Piperine and liposome formulations may increase low bioavailability.
Half life The time it takes for the concentration of a substance in the body to be halved. It is the critical parameter in determining dosing frequency: substances with short half-lives (L-Tyrosine ~1 hour) require multiple doses per day, substances with long half-lives (modafinil 12–15 hours) require a single dose.
HPA Axis Hypothalamic-Pituitary-Adrenal axis: the main hormonal system that regulates the body's stress response and cortisol release. When chronically activated, it causes neurotoxicity, immunosuppression and sleep disturbance. Adaptogens help balance the HPA axis.
cortisol The main stress hormone produced by the adrenal glands. Adaptive in the short term; however, chronically high cortisol can shrink the hippocampus, suppress neurogenesis, and impair sleep quality. Ashwagandha and Tongkat Ali lower cortisol.
NMDA Receptor Glutamate receptor, which plays a central role in learning, memory and synaptic plasticity (LTP). It requires both glutamate and voltage (depolarization) to function normally. Magnesium L-Threonate optimizes the function of this receptor by increasing brain magnesium levels.
dopamine Neurotransmitter that plays a role in motivation, reward, focus, decision-making and motor control. L-Tyrosine and Mucuna pruriens support dopamine synthesis; Dopamine deficiency can lead to anhedonia, loss of motivation and difficulty concentrating.
serotonin Neurotransmitter associated with mood, sleep, appetite, social bonding and emotional balance. 5-HTP is a direct precursor of serotonin; tryptophan is its more distant precursor. 95% of it is produced in the intestine.
glutamate The brain's main excitatory neurotransmitter; It acts through AMPA, NMDA and kainate receptors. It is necessary for learning and plasticity; However, excessive amounts cause excitotoxicity (neuron death).
AMPA Receptor Glutamate receptor responsible for rapid excitatory synaptic transmission. The number of AMPA receptors increases during LTP. Racetams (piracetam, aniracetam) promote learning by positively allosterically modulating the AMPA receptor.
Acetylcholinesterase (AChE) Enzyme that breaks down acetylcholine in synapses. Huperzine A and DMAE inhibit this enzyme, prolonging the duration of action of acetylcholine. It is the target of Alzheimer's drugs (donepezil, etc.).
Blood-Brain Barrier (BBB) Selectively permeable structure consisting of special endothelial cells surrounding brain capillaries. Protects the brain against pathogens and toxins; For a nootropic to have a neurotropic effect, it must be able to overcome this barrier. Small, lipophilic and non-ionized molecules pass through more easily.
Mitochondria The power plant of the cell; organelle that produces ATP through oxidative phosphorylation. Since brain cells are the body's most energy-dense tissue, mitochondrial health is directly related to cognitive performance. Creatine, NMN, CoQ10 and PQQ support mitochondrial function.
ATP Adenosine triphosphate: the universal energy unit of the cell. While the brain accounts for 2% of body weight, it consumes 20% of total ATP consumption. Disruption of ATP production leads to brain fog and fatigue.
neurogenesis Formation of new neurons. In the adult brain, it occurs mainly in the DG (dentate gyrus) region of the hippocampus. BDNF, exercise, Lion's Mane, and some adaptogens support neurogenesis; chronic stress and alcohol pressures.
LTP (Long Term Potentiation) Permanent strengthening of the synaptic connection between neurons firing together; The molecular basis of Hebb plasticity. NMDA receptor activation occurs through AMPA receptor depletion and dendritic protein synthesis. It is the cellular basis of learning and memory.
LTD (Long Term Weight Loss) Weakening of less used synaptic connections as a result of low-frequency stimulation. It clarifies brain signals and increases learning efficiency by pruning unnecessary connections; It establishes balance with LTP.
hippocampus Brain region that plays a central role in creating new episodic memories, spatial learning and navigation. It is extremely sensitive to chronic cortisol and oxidative stress; It is dependent on BDNF and neurogenesis.
Prefrontal Cortex Brain region responsible for planning, decision-making, impulse control, attention and working memory. It is sensitive to dopaminergic and cholinergic support; Chronic stress and sleep deprivation impair function.
myelin Lipid-rich insulating sheath wrapped around axons by oligodendrocytes. It increases nerve conduction speed up to 100 times. Omega-3 fatty acids, B12 and uridine support myelin health.
dendrite Branched extensions of the neuron that receive signals from other cells. Dendritic density and number of spines increase with learning; This structural change is the apparent basis of neuroplasticity.
axon The long extension of the neuron through which it transmits electrical signals to distant target cells. In axons covered with myelin sheath, the signal flows much faster by saltatory conduction.
Glial Cells Brain cells that support, nourish, protect and clean neurons. There are three main groups: astrocytes, oligodendrocytes and microglia; They make up more than half of the brain cells.
Neurotrophic Factor A family of proteins that regulate the growth, survival, and differentiation of neurons. BDNF (hippocampus/cortex), NGF (cholinergic neurons), and GDNF (dopaminergic neurons) are prime examples.
NAD+ Critical coenzyme in cellular energy metabolism, DNA repair and sirtuin activation. It decreases dramatically with age; It can be renewed with NMN and NR (nicotinamide riboside). Low NAD+ is associated with mitochondrial degradation and accelerated aging.
Circadian Rhythm Approximately 24-hour internal biological clock governed by the SCN (suprachiasmatic nucleus). It cyclically regulates sleep-wake, hormone release, metabolism and cognitive performance. Blue light and irregular sleep hours disrupt the rhythm.
melatonin Hormone secreted from the pineal gland with darkness, regulating sleep onset and circadian rhythm. Blue light exposure at night suppresses melatonin release. Low dose (0.5–1 mg) is effective in jet-lag and sleep-phase disorder.
Norepinephrine (Noradrenaline) Neurotransmitter/hormone that plays a role in alertness, attention, working memory, and stress response. It is synthesized by the Tyrosine → L-DOPA → Dopamine → Norepinephrine chain; It is released from the locus coeruleus in the brainstem.
Monoamine Oxidase (MAO) A family of enzymes that break down monoamines such as dopamine, serotonin and norepinephrine in synapses via the oxidative pathway. MAO-A plays a role predominantly in the serotonoergic system, while MAO-B plays a role in the dopaminergic system. MAO inhibitors increase the levels of these substances.
SSRI Selective serotonin reuptake inhibitor: a class of antidepressants that increase the level of serotonin in the synaptic cleft. Concomitant use with 5-HTP or St. John's wort increases the risk of serotonin syndrome.
nootropic Low-toxicity substance that safely supports cognitive functions. Corneliu Giurgea coined the term in 1972; According to Giurgea criteria, the nootropic substance should increase memory, protect brain function, have low side effects and be non-toxic.
stack Use of multiple nootropics together for synergistic effect. In a well-designed stack, items complement each other through different mechanisms; For example, the combination of choline source + racetam is a classic synergistic stack.
Cyclic Usage (Cycling) A strategy of using a substance at regular intervals and taking breaks to prevent the development of tolerance and maintain receptor sensitivity. 5 days on / 2 days off or 8 weeks on / 4 weeks off are typical protocols.
Tolerance Decreasing effect over time at the same dose; gradually increasing dose requirement for equal effect. It develops due to receptor down-regulation, desensitization or enzyme induction.
Standardization Bringing the active ingredient to a constant ratio in herbal extracts (e.g. 50% bacocide, 0.3% hypericin). It ensures consistency and predictable effect between doses.
Extract Solvent-condensed form of the active ingredients of a plant. More potent and standardizable compared to raw plant powder; Ratios such as 10:1, 100:1 show how many times it is concentrated compared to the raw plant.
lipophilic Fat soluble substance. Lipophilic nootropics (sulbutiamine, aniracetam, vitamin D) more easily cross the blood-brain barrier; Their bioavailability increases when taken with a fatty meal.
hydrophilic Substance dissolved in water. It can also be absorbed on an empty stomach; They may need carrier proteins or special transport mechanisms to cross the blood-brain barrier.
agonist Substance that mimics the action of a natural stimulant (ligand) by activating a receptor. Full agonist produces maximum response, partial agonist produces limited response.
Antagonist A substance that inhibits natural signaling by binding to and blocking a receptor. Caffeine is an antagonist of adenosine receptors; In this way, it temporarily hides sleep pressure.
Allosteric Modulator A substance that alters the receptor response at a point other than the primary binding site of the receptor (allosteric site). Racetams are positive allosteric modulators of the AMPA receptor; Benzodiazepines are positive modulators of GABA-A.
placebo A fake treatment that does not contain active ingredients and is used for control purposes. The placebo effect, which can lead to real physiological changes through psychological mechanisms such as expectation, learning and stress reduction, should be taken into account in research.
Double-Blind Study Gold standard study design in which neither the participant nor the researcher knows who is taking the actual substance, minimizing the placebo effect and investigator bias.
Meta-analysis A method that statistically combines data from multiple independent studies on the same subject and obtains stronger and generalizable results. It is one of the highest levels of the evidence hierarchy.
antioxidant Substance that neutralizes cellular damage (oxidative stress) caused by free radicals. Glutathione, vitamin C, vitamin E are endogenous/dietary antioxidants; curcumin, resveratrol and NAC are supplementary antioxidants.
Oxidative Stress Imbalance between reactive oxygen species (ROS) production and antioxidant defense capacity. Neuronal aging is directly related to mitochondrial dysfunction and neurodegenerative diseases.
neuroinflammation Inflammatory response in brain tissue by activation of microglia and astrocytes. It is protective in the acute state, and contributes to neuronal damage and cognitive decline through the release of cytokines in the chronic state. Omega-3, curcumin and NAC suppresses.
Cholinergic System Network of neurons using acetylcholine. Critical for learning, memory and attention; basal forebrain cholinergic neurons target the hippocampus and cortex. In Alzheimer's, this system is damaged early and severely.
Dopaminergic System Network of neurons using dopamine. The mesolimbic pathway manages reward and motivation, the mesocortical pathway manages executive functions, and the nigrostriatal pathway manages motor control.
Serotonergic System A network of serotonin neurons originating from the raphe nucleus and spreading throughout the brain. It plays a role in mood, sleep, appetite, social behavior and pain modulation.
GABAergic System Inhibitory neuron network using GABA. Prevents excessive brain activity; Most anxiety, epilepsy and sleep medications (benzodiazepines, barbiturates, phenibut) target this system.
Working Memory The capacity to hold and process information in the mental scene for a short time; foundation of problem solving and reasoning. It depends on the prefrontal cortex, dopamine D1 receptor activity, and acetylcholine.
neuromodulator A signaling molecule that regulates a wider neuronal network diffusely, not in a single synaptic gap. Dopamine, serotonin, and acetylcholine can function as both neurotransmitters and neuromodulators.
phospholipid Amphiphilic molecules consisting of glycerol, fatty acids and phosphate group; The basic building block of cell membranes. Phosphatidylserine and phosphatidylcholine are critical for neural membrane health, signal transduction, and neuroplasticity.
Ginsenoside Dammarein and oleanlic triterpene glycoside components of Panax ginseng root. It is primarily responsible for adaptogenic, energy-boosting, neuroprotective and immunomodulatory effects.
bacocide Active dammarane-type saponin components of Bacopa monnieri. It strengthens memory by supporting synaptic transmission and dendritic branching; It acts on the serotonin and cholinergic system.
Withanolide Steroid components in the lactone structure of Ashwagandha (Withania somnifera) root. It reduces cortisol by balancing the HPA axis, has an anxiolytic effect through GABA-A modulation, and supports testosterone synthesis.
flavonoid Subclass of polyphenols found in plants with antioxidant and anti-inflammatory effects. Apigenin, quercetin, luteolin, and epigallocatechin gallate (EGCG) are associated with brain health; apigenin has an anxiolytic effect through GABA-A modulation.
polyphenol A class of powerful antioxidant compounds of plant origin, carrying more than one phenolic group. Curcumin, resveratrol, green tea catechins and rosmarinic acid are the best-studied neuroactive polyphenols.
alkaloid Nitrogen-containing compounds found in plants that often have strong effects on the nervous system. Huperzine A (AChE inhibitor), berberine (AMPK activator) and vinpocetine (PDE1 inhibitor) are nootropics of alkaloid origin.
triterpenoid Active ingredient class of Centella asiatica (asiaticoside, madecasozide). Supports collagen synthesis, BDNF production and neural repair; It is of interest in neuroplasticity research.
saponin Vegetable foaming glycosides; It takes its name from the Latin sapo, meaning soap. Ginsenoside and bacoside are triterpene saponins; It also has side effects that can facilitate the absorption of other ingredients by increasing intestinal permeability.
Vagus Nerve 10th cranial nerve; The longest autonomic nerve that carries bidirectional signals between the brain and the intestine. 80% of the signal goes from the gut to the brain. It transmits microbiome-derived serotonin, GABA and neurotransmitter precursors to the brain.
microbiome A community of trillions of microorganisms living in the intestine. Produces 95% of serotonin, GABA and short-chain fatty acids; It affects brain function and mood through the vagus nerve and immune system.
Enteric Nervous System The nerve network in the intestinal wall works partially independently, without being dependent on the brain; It contains approximately 500 million neurons. It has been referred to as the 'second brain' and functions in digestion, immunity and mood regulation.
Short Chain Fatty Acids (SCFA) Butyrate, acetate and propionate produced by intestinal bacteria through dietary fiber fermentation. Protects the intestinal wall, reduces neuroinflammation and regulates microglia maturation; Its effects on brain health are the subject of active research.
psychobiotic Probiotic strains that may have a positive effect on mood, anxiety or cognitive function. Lactobacillus rhamnosus and Bifidobacterium longum 1714 have been associated with anxiety reduction in clinical studies.
adenosine Metabolite accumulated in brain cells during wakefulness; It creates sleep pressure and fatigue by binding to A1 and A2a receptors. Caffeine blocks adenosine receptors, providing temporary wakefulness; Sleep clears this accumulation.
Nitric Oxide (NO) Short-lived signaling molecule that relaxes vascular smooth muscles, leading to vasodilation and increased blood flow. Some nootropics increase cerebral blood flow via NO; Vinpocetine and Ginkgo biloba use this mechanism.
Phosphodiesterase (PDE) A family of enzymes that degrade the secondary messengers cAMP and cGMP. PDE inhibition increases the level of these messengers, increasing the cellular energy signal. Vinpocetine inhibits PDE1 and caffeine inhibits PDE1–5.
catecholamine Class of neurotransmitters/hormones that include dopamine, norepinephrine, and epinephrine synthesized from tyrosine. They are key regulators of attention, alertness, and the stress response; L-Tyrosine supports the catecholamine pool.
L-DOPA Direct amino acid precursor of dopamine; It crosses the blood-brain barrier by active transport. Mucuna pruriens is a natural source of L-DOPA. It is also known as levodopa, the main drug in the treatment of Parkinson's.
monoamine Neurotransmitters carrying a single amino group (dopamine, serotonin, norepinephrine, histamine). It is destroyed by oxidative deamination by the MAO enzyme.
Reuptake Reabsorption of the released neurotransmitter from the synaptic gap by the presynaptic neuron via transporter proteins. Reuptake inhibitors (SSRI, NDRI, etc.) strengthen the neurotransmitter effect by prolonging the signal.
synaptogenesis Formation of new synapses; Although it is especially intense during the developmental period, it also continues in the adult brain. Uridine, omega-3 and choline provide the biochemical building blocks of this process.
Dendritic Spine Small mushroom-shaped projections on dendrites that house a single excitatory synapse. Their intensity increases with learning; atrophy is associated with cognitive decline. Magnesium L-Threonate can increase dendritic spine density.
Amygdala The brain area where fear, anger, anxiety and emotional memory are processed. Overactivation can lead to chronic anxiety; Adaptogens and GABAergic substances may reduce amygdala excitability.
microglia Immune cells of the brain; It clears damaged neurons and pathogen residues by phagocytosis. Their chronic activation contributes to neuronal damage and cognitive decline by releasing pro-inflammatory cytokines.
Cytokine Cellular communication proteins produced by immune and glial cells. Pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6 can cross the blood-brain barrier and lead to brain fog, depression, and cognitive impairment.
Cognitive Reserve The brain's capacity to protect cognitive function against damage or aging. It is strengthened by education level, learning habits, exercise and a rich social environment; Higher reserve ensures late onset of symptoms in Alzheimer's disease.
Brain Fog Fuzzy thinking, difficulty finding words, and a feeling of mental fatigue. Neuroinflammation may be related to lack of sleep, choline/tyrosine deficiency, thyroid disorder, or blood sugar fluctuation.
Anxiolytic Substance or effect that reduces anxiety. GABA-A positive modulators (benzodiazepine, phenibut, valerian), 5-HT1a agonists and adaptogens have anxiolytic effects; Their mechanisms and addiction potentials are very different from each other.
psychostimulant Substance that increases alertness, attention and energy. Caffeine (adenosine antagonist), modafinil (DAT inhibitor), and phenylpiracetam are examples of this class; addictive potential and cardiovascular effects are variable.
Methylation Common biochemical process involving the addition of a methyl group (-CH₃) to molecules. It plays critical roles in neurotransmitter synthesis, gene expression (epigenetics), DNA repair and detoxification. B12, folate and SAMe are methylation donors.
AMPK (AMP-Activated Protein Kinase) Cellular energy sensor; It is activated when the ATP/AMP ratio decreases, increasing glucose uptake, fat oxidation and mitochondrial biogenesis, and suppressing anabolic processes. Berberine and exercise are potent AMPK activators.
SIRT1 (Sirtuin-1) NAD+-dependent histone deacetylase; It regulates aging processes through mitochondrial biogenesis (PGC-1α activation), DNA repair and inflammation control. Resveratrol activates SIRT1 directly and NMN activates SIRT1 through NAD+ increase.
Glutathione (GSH) The body's most powerful endogenous antioxidant; glycine, cysteine ​​and glutamate tripeptide. It neutralizes reactive oxygen species, detoxifies heavy metals and supports immune function. NAC increases glutathione synthesis by providing cysteine.
Reactive Oxygen Species (ROS) Unstable, highly reactive oxygen compounds (O₂⁻, H₂O₂, OH•) formed as a result of mitochondrial electron leakage, inflammation, or environmental toxins. It functions in cell signaling in controlled amounts; Excessive amounts cause oxidative stress and neuron damage.
NF-κB (Nuclear Factor Kappa B) Transcription factor that activates pro-inflammatory genes (TNF-α, IL-6, IL-1β, COX-2). Chronic activation is a key driver of systemic and neural inflammation. Curcumin, omega-3 and resveratrol have anti-inflammatory effects through NF-κB inhibition.
PGC-1α (Peroxisome Proliferator Activating Receptor Gamma Coactivator 1-alpha) Master transcription coactivator regulating mitochondrial biogenesis. Exercise, cold and some nootropics (PQQ, resveratrol) increase the production of new mitochondria through PGC-1α activation.
mitophagy Clearing of damaged or dysfunctional mitochondria by cells through the selective autophagic pathway. Mitochondria maintain healthy cellular function as a quality control system; Its deficiency is associated with neurodegeneration.
autophagy The cell's self-renewal mechanism in which damaged proteins and organelles are broken down by lysozymes. This process, which won the Nobel Prize (2016, Yoshinori Ohsumi), is closely related to aging and neurodegenerative diseases.
GABA-A Receptor Ionotropic GABA receptor that opens a chloride (Cl⁻) channel; creates a fast inhibitory post-synaptic potential. Benzodiazepine, barbiturate and alcohol are positive allosteric modulators of GABA-A. Apigenin and valerian (valerenic acid) also modulate GABA-A.
GABA-B Receptor G-protein coupled metabotropic GABA receptor; It produces a slower but longer-lasting inhibitory effect. Phenibut is a direct agonist of this receptor; This mechanism creates a strong anxiolytic effect and high addiction potential.
GABA Transaminase (GABA-T) Enzyme that breaks down GABA by converting it to succinate semialdehyde. Rosmarinic acid, a component of lemon balm, increases synaptic GABA concentration by inhibiting GABA-T; this mechanism creates a different, milder anxiolytic profile from benzodiazepine receptor activation.
Orexin / Hypocretins Neuropeptides secreted from the lateral hypothalamus and controlling the wakefulness-sleep transition. Orexin deficiency leads to narcolepsy; modafinil maintains wakefulness by indirectly activating orexin neurons.
VDR (Vitamin D Receptor) Nuclear receptor found in many brain cells, including neurons, oligodendrocytes, and microglia. Active vitamin D (calcitriol) binds to the VDR and regulates the expression of critical genes such as dopamine synthesis, neurotrophin production and neuroinflammation.
SHBG (Sex Hormone Binding Globulin) Plasma protein that binds most of testosterone and estrogen. High SHBG reduces the level of bioavailable (free) testosterone. Tongkat Ali increases free testosterone by inhibiting SHBG.
Cerebral Blood Flow The amount of blood reaching the brain tissue per minute. The brain consumes 15–20% of total cardiac output; Insufficient cerebral blood flow negatively affects cognitive performance, attention and reaction speed. Vinpocetine and Ginkgo biloba increase this flow.
Serotonin Syndrome Potentially dangerous condition that develops as a result of excessive increase in serotoninergic activity. It may include agitation, tremors, tachycardia, hyperthermia, and in severe cases, seizures. It can be triggered by combinations of SSRI + MAOI, SSRI + 5-HTP or SSRI + St. John's wort.
Excitotoxicity Damage or death of neurons due to excessive activation of NMDA receptors due to excessive glutamate release and subsequent calcium influx. Ischemia is the main damage mechanism in trauma and neurodegenerative diseases. NAC and taurine show protective effects against excitotoxicity.
Eugeroic (Alertness Enhancer) A class of substances that promote physiological alertness without producing sedation or amphetamine-like side effects. Modafinil and adrafinil are the best known of this class; Its effects arise not from adenosine antagonism, but from orexin and dopaminergic mechanisms.
CYP450 (Cytochrome P450) A superfamily of enzymes that metabolize drugs and foreign chemicals in the liver. Subtypes such as CYP3A4, CYP2D6 are the primary metabolism pathway of many drugs; Herbs such as St. John's wort (CYP3A4 inducer) can alter the effectiveness of many medications.
piperine Active component of black pepper; It increases the bioavailability of concomitant substances through inhibition of CYP3A4 and P-glycoprotein. It has been shown to increase the bioavailability of curcumin by up to 2000%; It is also synergistic with resveratrol.
liposome Nanoscale vesicle that encapsulates the drug or nutrient within the lipid bilayer. It is used to increase the absorption of substances with low bioavailability (glutathione, vitamin C, resveratrol); It releases the contents directly into the cell by fusion with cell membranes.
REM Sleep The stage of sleep in which rapid eye movements are observed, intense dreaming occurs, and the consolidation of memories occurs. 4–6 cycles occur during the night; REM duration increases with each cycle. REM deficiency has serious negative effects on emotional regulation and learning.
NREM Sleep (Deep Sleep) Stage 3 sleep, where slow brain waves (delta) dominate; Physical repair, growth hormone release, and declarative memory consolidation occur during this phase. It decreases with age; magnesium and valerian may support NREM.
Sleep Pressure (Homeostatic Sleep Drive) It is the increased need for sleep due to adenosine and other 'sleep factors' accumulated during wakefulness. Adenosine reuptake is cleared during sleep; Accumulation of sleep debt linearly increases cognitive impairment.
Brain Waves Frequency bands of the collective electrical activity of neurons measured by EEG. Gamma (>30 Hz) predominates in intense cognitive effort, beta (13–30 Hz) in active thought, alpha (8–13 Hz) in calm wakefulness, theta (4–8 Hz) in deep meditation and memory encoding, and delta (<4 Hz) in deep sleep.
Alpha Waves Brain waves with a frequency of 8–13 Hz; It is dominant in a relaxed and calm state of wakefulness, with the eyes closed. It is associated with the state of 'calm focus'. L-Theanine is the most researched substance that increases alpha waves.
Theta Waves Brain waves with a frequency of 4–8 Hz; It becomes evident during deep meditation, hypnagogic state and memory encoding in the hippocampus. It is associated with creativity and intuitive thinking; Regular meditation increases theta power.
epigenetics A set of hereditary modifications that regulate gene expression without changing the DNA sequence. DNA methylation and histone modifications are the main mechanisms. Lifestyle, diet, stress and some nootropics (resveratrol, curcumin) can change the epigenetic profile.
telomere Protective caps consisting of repetitive nucleotide sequences at the ends of chromosomes; It shortens with each cell division. Their length is considered one of the indicators of biological aging. Chronic stress and oxidative damage rapidly erode telomeres.
Cellular Senescence Senescent cells that have lost the capacity to divide but have not died and continue to secrete inflammatory factors (SASP). It accumulates in tissue, causing inflammation, loss of tissue function and signs of aging; senolytic probes target these cells.
Longevity It is a field of research and practice that aims to extend not only life span but also healthy functioning life span (healthspan). NAD+ supplementation (NMN, NR), resveratrol, berberine, fasting and exercise were the main interventions examined.
COMT (Catechol-O-Methyltransferase) Enzyme that inactivates catecholamines such as dopamine, norepinephrine and epinephrine. Val158Met polymorphism affects COMT activity: low-activity Met/Met individuals have higher dopamine levels in the prefrontal cortex and are more sensitive to stress.
Loading Dose A high initial dose of a substance taken initially to rapidly reach the effective concentration in the blood; then continue with a lower maintenance dose. It is commonly applied in creatine protocols (20 g/day × 5 days, followed by 3–5 g/day).
Maintenance Dose Dosage administered to maintain constant blood/tissue levels after the loading phase or during long-term use. Must exceed the minimum effective dose; however, tolerance must balance cost and risks of side effects.
synergism When two or more substances are used together, the effective doses decrease or the effect exceeds the arithmetic sum. Caffeine + L-Theanine, racetam + choline source and PQQ + CoQ10 are classic synergistic combinations.
Receptor Down-Regulation A decrease in the intensity or sensitivity of a receptor or transporter in response to chronic stimulation. It is the primary mechanism of tolerance development; cyclic use may reverse this regulation.
neurohormesis Exposure to low doses of stress activates protective neuronal responses and makes neurons more resilient in the long term. Cold showers, fasting and low-dose physical exercise trigger this mechanism; Some herbal compounds use the same pathway via mild oxidative stress.
Psychoneuroimmunology Interdisciplinary field that studies bidirectional interactions between psychological factors, the nervous system, and the immune system. The main findings of this field are that chronic stress suppresses immunity and increases neuroinflammation.
Pineal Gland Small brain gland, also known as the pineal gland; It regulates the circadian rhythm by synthesizing melatonin with darkness. A dark environment at night is critical for calibration; It undergoes calcification with age and melatonin production decreases.
tryptophan Essential amino acid that is the distant precursor of serotonin and melatonin synthesis. Its passage into the brain depends on competition with large neutral amino acid transporters; Carbohydrate-loaded meals reduce this competition through insulin release, preferentially transporting tryptophan to the brain.
Glymphatic System The brain's 'lymphatic' cleansing network, which is activated during sleep. Cerebrospinal fluid (CSF) is pumped through aquaporin-4 channels of astrocytes; beta-amyloid, tau and metabolic waste are removed overnight. Lack of sleep inhibits this clearance, increasing neurodegenerative risk.
Astrocyte The most common cell of the brain; provides metabolic support to neurons, ion homeostasis, neurotransmitter recycling and blood-brain barrier maintenance. Monitors neuronal activity and adjusts glutamate and GABA levels; It is the main actor of the glymphatic system.
hypothalamus Center of hormonal and autonomic nervous system control; It regulates hunger, thirst, body temperature, circadian rhythm, stress response (CRH release) and reproductive functions. The hypothalamus, the control tower of the HPA axis, is one of the indirect targets of nootropic effects.
thalamus Central relay station that directs sensory information (pain, touch, vision, hearing) to relevant cortical regions. It also acts as a sleep-wake switch; Suppression of thalamic activity during anesthesia and sleep extinguishes consciousness.
Cerebellum Hindbrain structure where motor coordination, balance and motor learning are managed. Recent research shows that the cerebellum also plays a role in cognitive function, attention, and emotion regulation. Consolidation of motor skills occurs here, requiring repeated practice per session.
Basal Ganglia A collection of deep brain nuclei densely connected to the cortex, thalamus, and brainstem. It plays a key role in habit formation, procedural learning, action selection, and coordination of motivational behaviors. It is highly dependent on dopaminergic support; It is damaged early in Parkinson's.
Mesolimbic Pathway (Reward Pathway) The pathway through which dopamine neurons originating from the ventral tegmental area (VTA) extend to the nucleus accumbens; The neural infrastructure of reward expectation, motivation, addiction, and pleasure experience. The vast majority of addictive substances hijack this pathway.
Locus Coeruleus Small but powerful nucleus in the brainstem; primary source of norepinephrine release to the entire brain. It plays a central role in stress, arousal, attention focus, and the fight-or-flight response. It is one of the structures affected early in Alzheimer's and stress-induced cognitive impairment.
Rafe Nucleus A collection of nuclei in the brainstem that send broad serotonin projections to the brain and spinal cord. Regulates mood, sleep, appetite and pain modulation; It is the source of the serotoninergic network targeted by antidepressants (SSRIs).
Cerebral Cortex The outermost layer of the brain; 2–4 mm thick folded structure responsible for sensory processing, motor control, language, thought, memory and consciousness. It is divided into four main lobes: frontal, parietal, temporal and occipital lobe.
Entorhinal Cortex Critical transition zone between the hippocampus and neocortex where memory and spatial information are filtered. It controls the pathway to long-term memory storage; It is one of the areas where destruction first begins in Alzheimer's.
Executive Functions Higher-level cognitive abilities such as planning, decision-making, abstract thinking, working memory updating, mental flexibility and inhibitory control. It is dependent on the prefrontal cortex; Insufficient sleep, chronic stress and dopamine deficiency negatively affect these functions.
Cognitive Flexibility The ability to update thought and behavior strategy in response to changing conditions or rules. It is governed by the prefrontal cortex and basal ganglia; Low cognitive flexibility is associated with rigid thought patterns, decreased performance under stress, and learning disabilities.
Episodic Memory Memory system that stores personal events and experiences with the context of time and place. It is the type of memory that is most dependent on the hippocampus; It is the system that deteriorates earliest in Alzheimer's. BDNF and sleep quality directly support episodic memory.
Memory Consolidation The process of converting newly learned information into permanent long-term memory. It occurs in two stages: synaptic consolidation (first hours) and system consolidation (during sleep, over weeks). Lack of sleep blocks the second stage.
Memory (Engram) The neuronal cell populations in which a particular memory is encoded and the pattern of synaptic connections between them. Specific engrams can be deleted or recreated with optogenetic tools; These studies are shaping the future of treatments for memory disorders.
D1/D2 Receptor Major dopamine receptor subtypes. Class D1 (D1, D5) supports working memory and attention function in the prefrontal cortex by activating adenylyl cyclase. D2 class (D2, D3, D4) is involved in reward and emotion processing in the mesolimbic pathway and is the target of antipsychotics.
5-HT1A Receptor Serotonin receptor, which is densely found in the prefrontal cortex and hippocampus; When activated, it reduces anxiety, regulates mood and supports neurogenesis. Buspirone (anxiolytic) and some herbal compounds act via 5-HT1A agonism.
Endocannabinoid System Endogenous lipid signaling system that works through CB1 receptors in the brain and CB2 receptors in peripheral tissues. It regulates pain, appetite, mood, memory and neuroprotection. Anandamide and 2-AG are the major endogenous cannabinoids; It is the basic mechanism of retrograde synaptic inhibition.
SAMe (S-Adenosylmethionine) The body's universal methyl donor; It plays a critical role in neurotransmitter synthesis (dopamine, serotonin, norepinephrine methylation), DNA methylation, myelin maintenance and glutathione production. In B12 and folate deficiency, the SAMe cycle is disrupted. It is prescribed as an antidepressant in some countries.
homocysteine Intermediate product of methionine metabolism; high serum levels increase the risk of cardiovascular disease and cognitive decline. It lowers B12, B6 and folate (B9) homocysteine; Deficiency of these vitamins leads to homocysteine ​​accumulation and vascular neural damage.
Blood Sugar and the Brain The brain uses glucose as its primary energy source; Hypoglycemia (low blood sugar) causes difficulty concentrating, irritability and impaired judgment, and chronic hyperglycemia causes neuronal damage through oxidative stress and inflammation. Brain fog and post-meal cognitive decline are often related to blood sugar fluctuations.
Insulin Resistance and the Brain Insufficient use of insulin by brain cells; impairs neuronal glucose uptake, decreases BDNF, and increases neuroinflammation. Alzheimer's disease is sometimes referred to as 'type 3 diabetes'. Berberine, exercise, and a low-glycemic diet improve insulin sensitivity.
mTOR (Mammalian Target of Rapamycin) Central kinase that regulates protein synthesis, cell growth, autophagy and neuroplasticity. While its excessive activation is associated with aging and cancer, its controlled activation contributes to neuroplasticity and synaptic strengthening. Rapamycin is an mTOR inhibitor; It is at the center of attention of some longevity researchers.
Beta-Amyloid (Aβ) Peptide formed by the proteolytic degradation of amyloid precursor protein (APP); It forms plaques, which are the most well-known marker of Alzheimer's pathology. The glymphatic system clears beta-amyloid from the brain during healthy sleep; It accelerates the accumulation of chronic sleep debt.
Tau Protein Neuronal protein that stabilizes axon microtubules; When hyperphosphorylated, it separates from microtubules and turns into tangles (neurofibrillary tangles). It is the primary pathological marker in Alzheimer's and other tauopathies.
neurodegeneration Pathological process in which neurons gradually lose their function and lead to their death. Oxidative stress, neuroinflammation, protein aggregation, and mitochondrial dysfunction are common mechanisms. Alzheimer's, Parkinson's and ALS are major neurodegenerative diseases.
neuroprotection Effect that activates or strengthens the mechanisms that protect neurons against damage, toxic substances, oxidative stress or excitotoxicity. Lion's Mane, NAC, omega-3, curcumin and Ginkgo biloba are nootropics that show neuroprotective properties.
Beta Waves Brain waves with a frequency of 13–30 Hz; It is dominant during active thinking, focusing and problem solving. High beta may be associated with anxiety and overthinking; low beta supports cognitive performance. Caffeine and L-Tyrosine increase beta power.
Gamma Waves Brain waves above 30 Hz, usually around 40 Hz; associated with high levels of information integration, cross-modal perception, and mental integration. It becomes evident in situations of intense meditation and deep focus. 40 Hz gamma entrainment is actively studied in Alzheimer's research.
neuropeptide Small protein molecules released by neurons and regulating signal transmission; orexin, substance P, neuropeptide Y, beta-endorphin and oxytocin are examples of this class. Unlike neurotransmitters, they generally act slower and more diffusely.
cAMP (Cyclic AMP) Secondary messenger molecule that transmits hormone and neurotransmitter signals into the cell. PDE inhibition increases cAMP, increasing neuronal excitability and plasticity signaling. Caffeine and vinpocetine partially affect cAMP levels through PDE inhibition.
Neurotrophic Factor Class of proteins that support the health, growth and differentiation of neural cells; BDNF, NGF and GDNF (for dopaminergic neurons) belong to this class. Exercise, quality sleep and some nootropics increase the expression of these factors.
phytoestrogen Herbal compounds that bind to estrogen receptors with low affinity; The main sources are isoflavones (soy), lignan seeds and red clover. Positive effects on perimenopausal symptoms have been suggested; however, its safety profile remains controversial, especially for hormone-sensitive conditions.
Seratonin-Dopamine Balance Serotonin and dopamine systems can function as antagonist pathways that balance each other. High serotonin can sometimes reduce dopaminergic motivation; This balance explains the sometimes observed trade-off between mood, motivation, and cognitive energy.
Cognitive Load Limit on the amount of information that working memory can hold at one time. Information overload divides attention resources and reduces learning efficiency. Focused single-task work and organizing the flow of information optimize cognitive load.
Sleep Debt Insufficient amount of sleep accumulated; In the short term, it impairs reaction speed, working memory, and emotional regulation. Long-term chronic sleep debt has been associated with neurodegenerative risk and metabolic disruption. Catching up on sleep over a single weekend isn't enough to close the long-term cognitive deficit.
Neurohormonal Regulation Bidirectional interactions between the brain and the endocrine system; Hormones control brain activity, and the brain controls hormone release. Cortisol, thyroid, estrogen, testosterone and insulin are the hormones that primarily affect cognitive performance.
Adaptive Immunity and the Brain Components of adaptive immunity, such as T cells and antibodies, have the capacity to regulate neuroplasticity and cognitive functions. Memory T cells are immune cells located in the meningeal lymphatic system and can produce BDNF-like neurotrophic factors.
Mitochondrial Biogenesis Production of new mitochondria from existing mitochondria; It is initiated by PGC-1α activation. Exercise, cold exposure, fasting and PQQ are the main stimuli that trigger mitochondrial biogenesis. It is one of the most effective ways to increase cognitive energy capacity in the long term.
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