Brain Health

Dopamine

A neurotransmitter that drives motivation, focus, pleasure, and mood. The nucleus accumbens is the primary dopamine reward center. Constant high-stimulation inputs (porn, cocaine, social media, gambling) flood dopamine so repeatedly that receptors downregulate — you need more stimulation to feel anything. This is the neurological engine behind addiction and the reason 'brain rot' from social media is neurologically real.

Nucleus Accumbens

The brain's reward and motivation center. Repeated dopamine spikes from pornography, social media scrolling, or cocaine cause it to 'deaden' — receptors reduce in number and sensitivity. This makes everyday pleasures feel flat and drives compulsive seeking behavior to recover the signal. The same mechanism makes early exposure especially dangerous for developing brains.

Prefrontal Cortex (PFC)

The front third of the brain responsible for judgment, impulse control, planning, self-regulation, and emotional modulation. Not fully developed until age 25. Alcohol, marijuana, poor sleep, and chronic stress all directly suppress PFC activity — which is why bad decisions cluster around those states. Conscientious people (those who reliably follow through on commitments) show better frontal lobe function and live measurably longer.

Hippocampus

A seahorse-shaped structure deep in the temporal lobes critical for memory formation, spatial orientation, and mood. Generates ~700 new stem cells per day through neurogenesis. The first region to shrink in Alzheimer's disease — explaining why short-term memory is the first symptom. Alcohol, marijuana, chronic stress, and insulin resistance all suppress hippocampal neurogenesis. Exercise, omega-3s, saffron, and sleep all promote it.

Amyloid-Beta & Plaques

Amyloid-beta is a protein fragment that lives inside neurons. When it accumulates in excess, it clumps into sticky plaques between brain cells — a primary hallmark of Alzheimer's pathology. One single night of sleep deprivation raises amyloid-beta by ~4%. The brain's glymphatic system clears it mainly during deep slow-wave sleep. Insulin resistance impairs both clearance and the signaling that prevents aggregation — the basis for calling Alzheimer's 'Type 3 Diabetes.'

Tau Tangles (Neurofibrillary Tangles)

Twisted fibers of tau protein accumulating inside neurons. Normally tau stabilizes structural 'tracks' inside cells. When it becomes hyperphosphorylated (driven by insulin resistance and inflammation), it detaches and clumps, blocking nutrient transport and killing neurons. Tau tangles correlate more closely with cognitive decline than amyloid plaques do.

Glymphatic System

The brain's waste-clearance network. Cerebrospinal fluid is pumped through channels surrounding blood vessels to flush metabolic waste — including amyloid-beta and tau — from brain tissue. It operates almost exclusively during deep slow-wave sleep (60% more active than when awake). This is the mechanistic reason chronic sleep deprivation is a direct Alzheimer's risk factor: you are literally not cleaning your brain.

SPECT Scan (Brain Imaging)

Single Photon Emission Computed Tomography. Dr. Amen uses SPECT to measure blood flow and metabolic activity in living brain tissue — showing function, not just anatomy. It reveals overactivity, underactivity, and damage patterns linked to psychiatric and neurological conditions. How Amen identified the 'scalloping' appearance of alcoholic brains, patterns associated with trauma and PTSD, and documented damage in 80% of NFL players scanned.

ANTs (Automatic Negative Thoughts)

Thoughts that arise automatically and distort reality toward worst-case interpretations: catastrophizing, mind-reading, fortune-telling, emotional reasoning. ANTs decrease prefrontal cortex activity and increase amygdala firing. Large-scale studies show negativity bias measurably reduces PFC function — impairing motivation, focus, and mood. CBT-derived techniques to challenge ANTs are head-to-head as effective as antidepressants for mild-moderate depression.

Blood-Brain Barrier / 'Leaky Brain'

A selective barrier of tightly-joined endothelial cells lining brain capillaries — acting like a bouncer deciding what enters the brain. High blood pressure kills the one-cell-thick capillaries feeding the BBB, causing it to degrade. A leaky BBB allows passive diffusion of inflammatory molecules, toxins, and pathogens into neural tissue — accelerating neurodegeneration. Alcohol, processed foods, insulin resistance, and chronic hypertension all degrade it.

Neuroinflammation

Inflammatory processes within the brain — involving microglia (the brain's immune cells), cytokines, and oxidative stress. A key driver in Alzheimer's, depression, bipolar disorder, and TBI recovery. COVID-19 causes neuroinflammation, explaining post-COVID anxiety and cognitive symptoms — which respond to anti-inflammatory protocols, not SSRIs. Exercise-released IL-6 acts as an anti-inflammatory myokine in the brain (opposite to its role in disease contexts).

Insulin Resistance in the Brain (Type 3 Diabetes)

Brain neurons require glucose for fuel, and insulin receptors exist throughout the brain. When neurons become insulin-resistant, they are starved of energy — accelerating amyloid plaque formation and tau tangles. A 2019 study showed people on high simple-carb diets had a 400% increased Alzheimer's risk. Some researchers now call Alzheimer's 'Type 3 Diabetes' to reflect this metabolic root cause.

Serotonin

A neurotransmitter involved in mood, appetite, sleep, and social behavior. ~95% is produced in the gut. SSRIs increase serotonin availability by blocking reuptake. However, the 'chemical imbalance' theory of depression has been substantially challenged — a 2022 landmark meta-analysis (Moncrieff et al.) found no consistent difference in serotonin between depressed and non-depressed people. SSRIs may work for some people, but not through the mechanism that was marketed.

Anterior Cingulate Gyrus

Dr. Amen calls this the 'brain's gear shifter' — it lets you shift attention between thoughts, be cognitively flexible, and go with the flow. When overactive (seen with trauma, OCD, and childhood adversity), people get stuck on thoughts and have trouble letting go. The past stays 'in front of them.' Amen uses timeline orientation as a clinical indicator of trauma: people who visualize the past in front of rather than behind them tend to show this overactivation.

BDNF (Brain-Derived Neurotrophic Factor)

Called 'fertilizer for the brain.' BDNF promotes neuronal growth, survival, and formation of new synaptic connections — essential for learning, memory, and mood. Exercise is the most potent natural trigger: aerobic training releases it abundantly, and resistance training releases it via the myokine irisin. Low BDNF is consistently associated with depression and Alzheimer's risk. Chronic stress, processed food, and alcohol suppress it.

Cognitive Reserve

The brain's resilience against damage — its ability to maintain function despite accumulating pathology. Like VO2 max for the brain: higher reserve = larger buffer against Alzheimer's plaques, strokes, and other insults. Two people can have identical amyloid loads — one retains full cognition (high reserve), the other has lost it (low reserve). Built over decades through exercise, novelty, learning, and social engagement.

Myokines

Signaling proteins secreted by contracting muscle fibers during exercise — acting like hormones that travel to the brain, liver, bones, and fat. Key brain-health myokines: irisin (signals BDNF expression in the hippocampus), IL-6 from exercise context (anti-inflammatory — opposite to its disease-context role), and lactate (Zone 3–5 fuel AND signaling molecule). Pharmaceuticals are spending billions trying to replicate them.

Irisin (FNDC5)

A myokine released by muscle during heavy resistance training. Irisin crosses the blood-brain barrier and signals BDNF to express itself in the hippocampus — directly stimulating new neuron growth. It's a core molecular link between lifting heavy and building a bigger, healthier brain. Named after Iris, the Greek goddess of the rainbow (a bridge between worlds).

APOE E4 Gene

The strongest known genetic risk factor for late-onset Alzheimer's. APOE comes in three variants: E2 (protective), E3 (neutral — most common), E4 (risk). One copy of E4 raises risk ~3× for men and ~6× for women. Two copies: ~10× for men and ~15× for women. Chris Hemsworth carries two copies. APOE4 is not a death sentence — lifestyle interventions (especially exercise) substantially offset the elevated risk. Test with a simple blood test.

Mild Cognitive Impairment (MCI)

The pre-dementia state — measurable cognitive decline beyond normal aging, but not severe enough to fully impair daily life. It represents early neuronal loss, primarily in the hippocampus. MCI is the critical intervention window: you can slow or partially reverse its progression through exercise, sleep, and metabolic control. Once MCI progresses to Alzheimer's, there is no reversal. ~10–15% of MCI cases progress to dementia per year.

VO2 Max

The maximum rate your body can consume oxygen during intense exercise — the gold standard of cardiovascular fitness and the single strongest predictor of all-cause mortality. Begins declining around age 35. The Norwegian 4×4 protocol (4 min at 90–95% max HR, 4 min rest, × 4) is the gold standard for improving it. Higher VO2 max correlates directly with preserved cognitive function and lower Alzheimer's risk.

Creatine Monohydrate

One of the most researched supplements. For muscles: replenishes ATP faster during high-intensity efforts. For the brain: the brain uses creatine as an energy buffer. During sleep deprivation, concussion, stroke, or metabolic stress, supplemental creatine protects cognitive function by keeping neurons fueled. An Alzheimer's study found creatine patients preserved cognitive function AND had more energy to exercise. Dose: 3–5g/day of monohydrate.

Gray Matter vs. White Matter

Gray matter = outer cortex containing neuron cell bodies — responsible for processing and computation. White matter = deeper brain tissue containing myelinated axons (the 'highways' connecting regions). With age and disease, gray matter thins (atrophy) and white matter develops lesions. Resistance training slows gray matter atrophy. Hypertension and poor sleep are the primary drivers of white matter lesions.

Left Ventricular Hypertrophy

Age-related thickening and stiffening of the heart's main pumping chamber. As the wall thickens, the cavity shrinks and less blood is pumped per beat — reducing delivery to the brain. Driven by chronic hypertension and sedentary aging. Ben Lavine's study showed that Zone 5 HIIT can reverse this and remodel a 50-year-old heart to function like a 30-year-old's — but only if started before age 65.