Study Guide · NEURO 1000 Superheroes & the Brain

1. What is Neuroscience? 2. Neuroanatomy 3. Brain Function & the Nervous System 4. Vision & Hearing 5. Touch & Pain 6. Muscle Control 7. Fear, Bravery & Mind Control 8. Altering Perception & Memory 9. Zombies 10. Morality & Consciousness 11. Brain–Computer Interfaces 12. Brain Evolution & Superhero Anatomy

Week 1 · May 26

1 · What is Neuroscience?

Reading: pp 6–13 · 📑 Lecture 1 notes

Neuroscience is the study of the nervous system — how billions of neurons generate sensation, movement, emotion, thought, and behavior. It spans levels: molecules → cells → circuits → systems → behavior → cognition. Modern tools let us watch and even control the living brain, which is exactly why yesterday's science fiction is becoming plausible.

📖 Reading recap (pp 6–13):

Neuroscience studies the nervous system across levels — molecules → cells → circuits → systems → behavior.
The brain was the last organ understood; for centuries we could only study damaged brains (e.g., Phineas Gage) to guess what regions did.
Scanning changed everything: MRI shows structure, fMRI shows activity (blood flow), EEG/MEG show fast electrical timing, CT/PET add other views.
No scanner is best at everything — researchers combine methods (MRI detail + fMRI/EEG speed) to see both where and when.
Consciousness doesn't feel physical, which is why linking mind to brain took so long.

Neuron — the brain's signaling cell; sends electrical & chemical messages.

Neuron doctrine — the brain is built from discrete cells, not one continuous web.

fMRI — images blood-flow changes to show which regions are active.

EEG — records electrical brain waves through the scalp (fast timing).

Lesion study — infer a region's job from what's lost when it's damaged.

Optogenetics — use light to switch specific neurons on/off in animals.

Hero hook: Every "impossible" power is a hypothesis about a brain mechanism. Neuroscience gives us the rulebook for judging whether a character's ability could exist.

Verified depth: The brain runs ~86 billion neurons (modern isotropic-fractionator count; older texts — including this book — round to "100 billion"). Neuroscience works across levels: molecules → synapses → cells → circuits → systems → behavior. Sources: Azevedo et al. 2009; von Bartheld et al. 2016 (PMC5063692).

Week 1 · May 28

2 · Neuroanatomy

Reading: pp 15–35, 50–69

The CNS (brain + spinal cord) integrates information; the PNS (all other nerves) carries it in and out. A neuron has dendrites (receive), a soma (cell body), an axon (transmits), and axon terminals (release transmitter). Myelin from glial cells insulates axons for speed. Know the big regions and what they do.

📖 Reading recap (pp 15–35, 50–69):

The brain splits into forebrain (cerebrum + thalamus/hypothalamus), midbrain, and hindbrain (pons, cerebellum, medulla).
The cerebrum is ~¾ of the brain, in two hemispheres joined by the corpus callosum; its surface folds into gyri (bumps) and sulci (grooves) to pack in area.
Four lobes: frontal (planning/movement), parietal (touch/space), temporal (hearing/memory), occipital (vision).
Deep structures: thalamus (sensory relay), hypothalamus (hormones/drives), basal ganglia (movement), limbic system (emotion + memory), cerebellum (~10% of volume, coordination).
Gray matter = cell bodies; white matter = myelinated axon highways.

Cerebral cortex — wrinkled outer layer; thought, perception, voluntary action. Lobes: frontal, parietal, temporal, occipital.

Cerebellum — "little brain"; coordination, balance, timing of movement.

Brainstem — midbrain/pons/medulla; breathing, heart rate, arousal, life support.

Thalamus — relay station routing most senses to the cortex.

Hypothalamus — master controller of hormones, hunger, temperature, drives.

Limbic system — amygdala, hippocampus & co.; emotion and memory.

Glia — support cells (e.g., oligodendrocytes/Schwann make myelin; astrocytes maintain the environment).

Gray vs white matter — gray = cell bodies/processing; white = myelinated axons/wiring.

Hero hook: Professor X's telepathy lives in an overgrown cortex; a creature's super-coordination would need a monster cerebellum. Map a power to a region first.

Verified depth: Myelin is made by oligodendrocytes in the CNS and Schwann cells in the PNS; it lets the signal jump node-to-node (saltatory conduction) for speed. The cortex is folded to pack more surface area into the skull — that surface is where most conscious thinking happens. Source: The Human Brain Book pp 68–73 (cerebral cortex, brain cells, myelin).

Week 2 · Jun 1

3 · Brain Function & the Nervous System

Reading: pp 36–49, 70–73

Neurons talk using the action potential — an all-or-none electrical spike that races down the axon when the membrane passes threshold. At the synapse, the spike triggers release of neurotransmitters that excite or inhibit the next cell. The autonomic nervous system runs automatic functions: sympathetic = "fight or flight," parasympathetic = "rest and digest."

📖 Reading recap (pp 36–49, 70–73):

~86 billion neurons + about 10× as many glial support cells.
Neuron parts: dendrites (receive) → soma (cell body) → axon (sends) → synapse; myelin insulates the axon for speed.
Three neuron shapes: unipolar, bipolar (e.g., retina), and multipolar (most brain neurons).
The nerve impulse = an action potential: from rest (~−70 mV), Na⁺ rushes in (depolarize) then K⁺ flows out (repolarize); all-or-none, and faster jumping node-to-node along myelin.
At the synapse: spike → Ca²⁺ entry → neurotransmitter release → receptors → an EPSP (excite) or IPSP (inhibit) on the next cell.
The autonomic system runs automatically: sympathetic = fight-or-flight, parasympathetic = rest-and-digest; a reflex arc can act through the spinal cord alone.

Action potential — all-or-none Na⁺/K⁺ spike; the neuron's signal.

Resting potential — the charged, ready state (~−70 mV) before firing.

Synapse — tiny gap where one neuron chemically signals the next.

Glutamate / GABA — main excitatory / inhibitory transmitters.

Dopamine — reward, motivation, movement (Parkinson's = too little).

Serotonin / acetylcholine — mood & sleep / muscle activation & attention.

Reflex arc — sensory→spinal cord→motor, fast response without the brain.

Sympathetic vs parasympathetic — arousal (adrenaline) vs calming.

Hero hook: A hero's burst of strength under threat is the sympathetic system + adrenaline. "Speedsters" would need impossibly fast action potentials — a great place to test the science.

Verified depth: At rest the inside sits near −70 mV (textbook value; in vivo records sometimes show −60 to −68 mV). Past threshold, voltage-gated Na⁺ channels open and Na⁺ floods in (positive-feedback Hodgkin cycle) → the spike peaks around +30 to +40 mV; voltage-gated K⁺ channels then open to repolarize. The ionic mechanism was nailed down by Hodgkin & Huxley (1952, squid giant axon), who shared the 1963 Nobel with Eccles. Chemical transmission itself was first proven by Otto Loewi's 1921 frog-heart “Vagusstoff” experiment (later identified as acetylcholine; 1936 Nobel with Henry Dale). At the synapse, presynaptic depolarization opens voltage-gated Ca²⁺ channels → Ca²⁺ triggers vesicle fusion via the SNARE complex (synaptobrevin/VAMP, syntaxin, SNAP-25 — the protein Botox cleaves). Postsynaptic receptors come in two flavors: ionotropic (AMPA, NMDA, GABA-A — fast direct ion flow) and metabotropic (G-protein coupled — slower, longer-lasting). EPSPs (Na⁺ in) and IPSPs (Cl⁻ in / K⁺ out) sum spatially & temporally at the axon hillock to decide whether the cell fires. “All-or-none” describes only the propagated axon spike — graded dendritic potentials are not — and stimulus strength is coded by firing frequency. Sources: Hodgkin & Huxley 1952 J Physiol; Nobel Foundation 1936 & 1963 speedreads; Borges & Garcia 2021 (PMID 34046754) Loewi centennial; StatPearls NBK538143.

Week 2 · Jun 3

4 · Senses — Vision & Hearing

Reading: pp 78–92, 100–108

Light enters the eye and hits the retina, where rods (dim light, motion) and cones (color, detail) convert it to signals that travel the optic nerve → thalamus → primary visual cortex (V1) in the occipital lobe. Sound vibrates the eardrum → cochlea, where hair cells turn frequencies into signals → auditory cortex in the temporal lobe.

📖 Reading recap (pp 78–92, 100–108):

Senses work by transduction — turning a physical stimulus (light, sound) into neural signals.
Vision: light → retina; rods see dim light/motion, cones see color/detail (densest at the fovea).
Visual pathway: retina → optic nerve → optic chiasm → LGN (thalamus) → V1 (occipital lobe); then a dorsal "where" and ventral "what" stream.
Hearing: sound → eardrum → ossicle bones → cochlea; hair cells transduce it, mapped by frequency (tonotopy).
Auditory signals → auditory cortex (temporal lobe); two ears let you localize sound.

Retina — light-sensing sheet at the back of the eye.

Rods vs cones — night/peripheral vision vs color & sharp detail.

Optic nerve / V1 — carries vision to the occipital cortex for processing.

Cochlea — fluid-filled inner-ear spiral that decodes sound frequency.

Hair cells — convert sound vibrations into neural signals.

Transduction — converting a physical stimulus into a neural signal.

Hero hook: Superman's vision would need extra cone types or a different retina; Daredevil's "radar sense" leans on hyper-tuned hearing & auditory cortex remapping.

Verified depth: Full visual pathway: retina → optic nerve → optic chiasm (≈53% of fibers, from the nasal retina, cross) → optic tract → LGN of the thalamus → optic radiations → V1 (primary visual cortex = Brodmann area 17, on the calcarine sulcus of the occipital lobe). Net result: each hemisphere processes the opposite half of the visual field. Sources: StatPearls NBK553189; The Human Brain Book p 62.

Week 2 · Jun 5

5 · Senses — Touch & Pain

Reading: pp 78–92, 100–108

Skin mechanoreceptors sense pressure, vibration and texture; nociceptors sense damage and signal pain. These map onto the somatosensory cortex in the parietal lobe as the homunculus — body parts with more sensitivity (lips, fingertips) get more cortex. Gate control explains why rubbing a bump eases pain: non-pain signals can dampen pain signals in the spinal cord.

📖 Reading recap (pp 104–110):

Skin mechanoreceptors each detect something different: Pacinian (vibration), Meissner (light touch), Merkel (pressure/edges), Ruffini (stretch).
A stimulus makes a graded receptor potential; if big enough it triggers an action potential up the sensory nerve.
Touch maps onto the somatosensory cortex (postcentral gyrus) as the homunculus — sensitive parts (lips, fingertips) get more cortex.
Two routes up: the dorsal column (fine touch/position) and the anterolateral/spinothalamic (pain + temperature).
Pain: nociceptors on free nerve endings; A-delta = sharp/fast "first pain," C fibers = dull/slow "second pain."
The "sixth sense" is proprioception (body position); gate control + descending brakes and endorphins dampen pain.

Somatosensory cortex — parietal map of body touch & position.

Homunculus — distorted body map; sensitive parts = bigger area.

Nociceptor — receptor that detects tissue-damaging stimuli (pain).

Mechanoreceptor — detects touch, pressure, vibration.

Gate control theory — non-painful input can "close the gate" on pain.

Referred pain — pain felt at a site different from its source.

Hero hook: A character who feels no pain has knocked out nociception (real condition: congenital insensitivity to pain) — powerful but dangerous, since pain is protective.

Verified depth: Touch is sensed by four classic mechanoreceptors that share the same molecular core — the PIEZO2 ion channel (Coste & Patapoutian; 2021 Nobel Prize): Pacinian corpuscles (deep, rapid-adapting, vibration ~200–300 Hz), Meissner corpuscles (superficial, rapid-adapting, light touch & motion 40–60 Hz), Merkel disks (slow-adapting, edges and points), and Ruffini endings (slow-adapting, skin stretch). Two pathways carry the signal up: the dorsal column–medial lemniscus (fine touch, vibration, proprioception — ascends ipsilateral, decussates in the medulla, → VPL thalamus → postcentral gyrus = primary somatosensory cortex / homunculus) and the anterolateral / spinothalamic (pain & temperature — crosses in the spinal cord and projects to VPL plus insula, anterior cingulate, and amygdala — that's why pain has both a sensory and an emotional component). Nociceptors come in two fiber types: A-delta (lightly myelinated, fast, ~5–30 m/s, sharp "first pain") and C fibers (unmyelinated, slow, dull "second pain"); both express TRPV1 (the capsaicin/heat receptor, Julius 2021 Nobel) and the sodium channel Nav1.7 / SCN9A. Beyond the spinal "gate," descending pain control from the periaqueductal gray (PAG) → raphe magnus and locus coeruleus releases endogenous opioids (endorphins, enkephalins, dynorphins) onto μ/δ/κ receptors. Congenital insensitivity to pain has multiple causes — the classical CIPA form is NTRK1 loss-of-function (no NGF signaling so nociceptors never develop, with anhidrosis), while a separate form is SCN9A loss-of-function (no Nav1.7 = no propagated nociceptor signal; Cox et al. 2006 Nature). Sources: Coste et al. 2010 Science (PIEZO2); Cox et al. 2006 Nature (SCN9A CIP); UTHealth Neuroscience Online Ch.4 & Ch.8; Nobel Foundation 2021 advanced; The Human Brain Book pp 104–110.

Week 3 · Jun 8

6 · Muscle Control

Reading: pp 110–122

Voluntary movement starts in the primary motor cortex, travels the corticospinal tract to the spinal cord, then out to muscle at the neuromuscular junction, where acetylcholine triggers contraction. The basal ganglia select and smooth actions; the cerebellum fine-tunes timing and balance. A motor unit is one motor neuron + the fibers it controls.

📖 Reading recap (pp 110–122):

Regulation: the hypothalamus + brainstem (reticular formation/RAS) keep homeostasis — breathing, heart rate, temperature — mostly automatically.
Neuroendocrine: the hypothalamus–pituitary unit releases hormones via feedback loops.
Voluntary movement: the primary motor cortex (precentral gyrus) sends the "go" → corticospinal tract → spinal motor neurons → neuromuscular junction (acetylcholine) → muscle.
Two systems: pyramidal (direct cortex→cord) and extrapyramidal (basal ganglia + cerebellum select, smooth, and time movement).
Feedback sensors: muscle spindles (length) and Golgi tendon organs (tension); a motor unit = one motor neuron + its fibers.
Mirror neurons fire both when you act and when you watch someone else act — a basis for imitation/empathy.

Primary motor cortex — frontal strip that commands voluntary movement.

Corticospinal tract — main highway from cortex to spinal motor neurons.

Neuromuscular junction — synapse between motor neuron and muscle.

Acetylcholine (ACh) — transmitter that makes muscle contract.

Basal ganglia — initiate & smooth movement (Parkinson's/Huntington's).

Cerebellum — coordination, timing, error-correction of movement.

Hero hook: Super-strength isn't just bigger muscles — it needs more motor units firing together, tougher tendons/bone, and a brain that can command them without tearing the body apart.

Hero hook — Elastigirl vs Mr. Incredible: Two different proprioceptors explain two different powers. Elastigirl stretches, so her muscle spindles (which fire when a muscle lengthens and normally trigger a protective stretch reflex) must be recalibrated by her gamma motor neurons to tolerate enormous length changes without snapping her back — her spindles "reset" to each new length. Mr. Incredible lifts impossible loads, so his Golgi tendon organs (which sense muscle tension and normally inhibit contraction to protect the tendon — the "autogenic inhibition" safety brake) must have a far higher threshold, letting him generate force that would tear a normal tendon. Spindles talk during her every stretch; GTOs talk during his every maximal pull.

Verified depth: The primary motor cortex sits in the precentral gyrus (Brodmann area 4), somatotopically arranged as the motor homunculus. Output runs through two systems: the pyramidal system (corticospinal & corticobulbar tracts), whose upper-motor-neuron axons descend through the internal capsule and mostly cross at the medullary pyramids — so left cortex drives the right side of the body — with giant Betz cells as its largest layer-V outputs; and the extrapyramidal system (basal ganglia + cerebellum), which selects, smooths, and times movement off the main highway. A motor unit (Sherrington) = one alpha-motor-neuron + the fibers it innervates; small precise units run the eye and finger, huge units run the quads. Sensors close the loop: muscle spindles report muscle length (stretch reflex), Golgi tendon organs report muscle tension (protective inhibition). The neuromuscular junction releases acetylcholine onto nicotinic receptors; this synapse is the target of α-bungarotoxin (nAChR antagonist), curare, and botulinum toxin (blocks ACh release via SNAP-25). Cerebellar damage produces ataxia & decomposition of movement; basal-ganglia damage at the substantia nigra pars compacta kills dopamine neurons → Parkinson's disease (treated with L-DOPA or deep-brain stimulation of the subthalamic nucleus). “Hysterical” superhuman strength isn't magic — voluntary muscle output is normally capped near 60–70% of true max by spinal & cortical inhibitory circuits to protect tendon & bone; extreme stress (adrenaline + reduced central inhibition) partially releases that cap. Myostatin (GDF8) is the genetic negative regulator of muscle growth — myostatin loss-of-function produces hyper-muscled mice, Belgian Blue cattle, and at least one documented human child with double the normal muscle mass. Sources: Purves Neuroscience (NBK10962); Schuelke et al. 2004 NEJM (human myostatin mutation); Škarabot et al. 2021 J Physiol on neural enhancement of MVC; The Human Brain Book pp 112–122.

Week 3 · Jun 10

7 · Fear, Bravery & Mind Control

Reading: pp 126–141

The amygdala is the brain's threat detector; it drives fear and learns danger through fear conditioning. It triggers the HPA axis, releasing cortisol (the stress hormone). The prefrontal cortex regulates and can override fear — the basis of bravery. "Mind control" means hijacking these circuits or their chemistry.

📖 Reading recap (pp 126–141):

Emotions are body + brain responses that bias thought and behavior — hard to measure because they're subjective.
The amygdala is the threat detector; it learns danger through fear conditioning and triggers the HPA axis → cortisol + a sympathetic surge.
Two routes to the amygdala (LeDoux): a fast crude "low road" (thalamus→amygdala) and a slower accurate "high road" (thalamus→cortex→amygdala).
Desire & reward run on dopamine and the nucleus accumbens.
Bravery isn't the absence of fear — it's an actively driven circuit; the prefrontal cortex regulates and can override fear.

Amygdala — fear/threat hub; fast emotional responses.

Fear conditioning — learning to fear a cue paired with danger.

HPA axis — hypothalamus→pituitary→adrenal stress-hormone cascade.

Cortisol — main stress hormone; mobilizes the body.

Prefrontal cortex — judgment, control, regulating emotion (bravery).

Mind control (real) — drugs, stimulation, or suggestion altering these circuits.

Hero hook: Scarecrow's fear toxin = overdriving the amygdala. A true "mind controller" would need to bias another brain's transmitters or stimulate specific circuits.

Verified depth: Inside the amygdala, the lateral / basolateral nuclei are the INPUT and the central nucleus (CeA) is the OUTPUT — CeA drives the lateral hypothalamus (sympathetic surge) and the PAG (freezing). Auditory fear learning depends on LTP at thalamus→lateral-amygdala synapses (LeDoux; Rogan & LeDoux 1997). Courage isn't the absence of fear — it's a separate, actively driven circuit. Salay et al. Nature 2018 (Huberman lab, Stanford) found two adjacent clusters in the ventral midline thalamus: the xiphoid nucleus (Xi) → basolateral amygdala drives passive defense (freezing/hiding); the nucleus reuniens (Re) → medial prefrontal cortex drives active defense (confronting/tail-rattling) — and that Re→mPFC pathway is itself rewarding (mice will work to activate it), so courage is an actively reinforced circuit, not just the absence of fear. Bodily state can cause emotional state: Hsueh et al. Nature 2023 optogenetically paced mouse hearts to 900 bpm and produced anxiety-like behavior — but only in risky contexts (fast heart alone wasn't aversive); silencing the posterior insula abolished it, a modern causal validation of the James–Lange “body first” theory. Dolensek et al. Science 2020 used machine vision to identify six emotion states in mouse facial expressions (pleasure, disgust, pain, malaise, plus active and passive fear — mirroring the Xi/Re split), each linked to specific posterior-insula activity. Patient SM (Urbach-Wiethe disease, bilateral amygdala calcification from ECM1 mutations) doesn't fear snakes, spiders, or haunted houses — but does panic when inhaling CO₂, showing that interoceptive panic is an amygdala-independent pathway (Feinstein et al. 2013 Nature Neuroscience). So “fearless” isn't total — it depends on the route in. Sources: Salay et al. 2018 Nature 557:183; Hsueh et al. 2023 Nature 615:292; Dolensek et al. 2020 Science 368:89; Feinstein et al. 2013 Nat Neurosci; Izquierdo et al. 2016 Physiol Rev.

Week 3 · Jun 12

8 · Altering Perception & Memory

Reading: pp 154–164, 172–174

Perception is not passive recording — it's the brain actively constructing reality, heavily shaped by top-down processing (your expectations and memories bias what you sense). Attention is a limited spotlight: you can attend overtly (eyes on target) or covertly (eyes one place, focus another), and what you don't attend to can vanish (inattentional blindness). On the memory side, the hippocampus forms new episodic memories and helps move them to long-term storage (consolidation). Memory splits into declarative (facts/events you can state) and non-declarative /procedural (skills you just do). At the cellular level, repeated use strengthens synapses — long-term potentiation (LTP), the leading cellular mechanism of learning.

📖 Reading recap (pp 154–164, 172–174):

Perception is the brain actively building reality, shaped by top-down expectation — not passive recording.
Attention is a limited spotlight; you miss what you don't attend to (inattentional blindness). Illusions expose these limits.
Memory is reconstruction, not replay — recall re-fires the original neurons and is selective and unreliable.
Types: short-term/working vs long-term; declarative (facts/events) vs non-declarative/procedural (skills). Serial position = first + last items recalled best.
Flow: encode → consolidate (sleep helps) → retrieve; the hippocampus binds new episodic memories (Patient H.M.).
Reading/writing aren't innate: visual cortex → visual word-form area → linked to sound (Broca/auditory) → meaning (temporal lobe).

Perception — active construction of reality, not passive recording.

Top-down processing — expectations/memory bias incoming sensory data.

Attention — limited "spotlight"; overt (eyes) vs covert (focus only).

Inattentional blindness — missing the obvious when attention is elsewhere.

Hippocampus — builds new memories; damage = can't form new ones.

LTP — lasting strengthening of synapses with use ("fire together, wire together").

Declarative vs non-declarative — facts/events you state vs skills you perform.

Anterograde amnesia — can't form NEW memories (Patient H.M.).

Hero hook — mind manipulators, illusion or real?: Jean Grey, Scarlet Witch, and Professor X raise the key question: do they rewrite your mind, or just your perception? Because perception is top-down and attention is a narrow spotlight, the "cheaper" explanation is illusion — biasing the senses, hijacking attention, or injecting false perceptual input — which only needs the visual/auditory cortex and attentional networks. True memory implantation/erasure (Scarlet Witch's "WandaVision," a Men-in-Black neuralyzer) is harder: it would have to write to or disrupt the hippocampus and consolidation. Optical illusions are the everyday proof that your brain can be reliably fooled — a perception-manipulator is just an illusionist with a bigger toolkit.

Hero hook — heroes with memory disorders: Wolverine's healing factor constantly rewrites his brain → fragmented memory (a consolidation/storage failure); Moon Knight (Marc Spector) has dissociative identity disorder, with separate identities holding separate memories; Rogue absorbs others' memories and then can't tell which are hers — a source-monitoring problem.

Verified depth: Perception is constructive: classic inattentional blindness (Simons & Chabris 1999, the "invisible gorilla") and dichotic-listening studies (Cherry 1953) show attention is a hard bottleneck — unattended stimuli often never reach awareness. Memory is not one thing: Patient H.M. (Henry Molaison) had his bilateral medial temporal lobes (incl. hippocampus) removed in 1953; he developed dense anterograde amnesia (no new declarative memories) yet kept working memory and could still learn the mirror-tracing skill while never remembering having done it — proving declarative and non-declarative/procedural memory are separate systems (Scoville & Milner 1957). Patient K.C. lost episodic memory (personal events) after a motorcycle injury while keeping semantic knowledge. LTP — lasting strengthening of co-active synapses — is the leading cellular mechanism of learning, with consolidation (aided by sleep) shifting memories toward cortical storage. Sources: Scoville & Milner 1957 J Neurol Neurosurg Psychiatry (H.M.); Simons & Chabris 1999 Perception; Rosenbaum et al. 2005 (K.C.); The Human Brain Book pp 158–164.

Week 4 · Jun 15

9 · Zombies — "no minds, maybe muscles"

Reading: none assigned — apply prior weeks

A "zombie" is a thought experiment: movement and drives without higher cognition or consciousness. That would mean an intact brainstem and basal ganglia (driving walking, biting, aggression) but a knocked-out cortex (no planning, language, or awareness). Real parallels: rabies (aggression, drive to bite), Toxoplasma and Cordyceps fungus (parasites that hijack host behavior).

📖 Reading recap (apply earlier weeks — no new reading):

Combine what you know. A "zombie" = movement without a cortex.
Intact: brainstem (arousal/breathing) + basal ganglia (walking, biting) → it can move.
Offline: the cortex → no planning, language, or awareness.
Appetite would point to a broken hypothalamus (satiety circuit); energy is the real dealbreaker — no digestion/circulation = no ATP.
Real-world parallels: rabies (aggression + biting), Toxoplasma (alters rodent fear), Cordyceps (hijacks insect muscles).

Brainstem-driven behavior — basic movement/arousal without thought.

Cortex offline — no consciousness, planning, or language.

Rabies — virus causing aggression and a drive to bite (transmission).

Toxoplasma gondii — parasite that alters rodent (and maybe human) behavior.

Cordyceps — fungus that hijacks insect motor control ("zombie ants").

Persistent vegetative state — real "wakeful unawareness" (brainstem without cortex).

Hero hook: A believable zombie keeps the life-support + movement machinery but loses the cortex — which is exactly why it can walk and bite but can't plan or speak.

Hero hook — "are zombies real?": Walk through the requirements. Navigation without a cortex would lean on the superior colliculus + brainstem (reflexive orienting to motion/sound), not conscious vision. The insatiable appetite points to a broken hypothalamus — the lateral hypothalamus drives hunger, the ventromedial signals "full"; destroy the satiety circuit and feeding never stops (real in VMH-lesion animals). But energy is the dealbreaker: a body with no digestion or circulation can't make ATP, so a truly dead zombie violates basic bioenergetics. Consciousness: a cortex-less zombie that still acts is essentially the philosopher's "p-zombie" — and the fact that brainstem/basal-ganglia circuits can drive behavior without awareness is exactly why consciousness is thought to need the cortex/frontoparietal network, not just movement machinery.

Verified depth — and where the analogy breaks: Rabies (a Lyssavirus) inflames limbic/brain-stem circuits → agitation, aggression, hydrophobia, and is spread by biting. Toxoplasma gondii blunts the rodent amygdala's fear of cat odor (steering the host toward the cat it must infect next); claimed human effects are debated. Ophiocordyceps hijacks an ant's muscles — an insect, not a mammal — so a human "zombie fungus" is analogy, not mechanism. Sources: mBio 2019 (10.1128/mbio.02164-19); Toxoplasma review PMC4512725.

Week 4 · Jun 17

10 · Neural Basis of Morality & Consciousness

Reading: pp 138–141, 176–192

Moral judgment leans on the ventromedial prefrontal cortex (vmPFC) (weighing harm & emotion) and theory of mind (modeling others' minds). Damage shifts moral choices (e.g., the trolley problem). Consciousness — subjective awareness — is still debated: the hard problem asks why physical processes feel like anything. Theories include the global workspace (broadcasting info brain-wide).

📖 Reading recap (pp 138–141, 176–192):

Consciousness = awareness of yourself, your thoughts, and time — broad and hard to measure objectively.
At rest the default mode network handles introspection/mind-wandering; conscious level tracks the frontoparietal network (it shuts down under anesthesia, deep sleep, vegetative states).
Attention gates what reaches awareness; consciousness can be altered by sleep/dreams and drugs.
Free will? Brain activity can predict a simple choice seconds before you feel you decided.
Moral brain: the vmPFC adds emotion to judgments and theory of mind models other people (the trolley problem probes this).

vmPFC — ventromedial PFC; integrates emotion into moral decisions.

Theory of mind — inferring others' beliefs, intentions, feelings.

Trolley problem — classic dilemma probing harm vs outcome.

Consciousness — subjective, first-person awareness.

Hard problem — why/how physical brains produce experience.

Global workspace — theory: consciousness = brain-wide broadcast of info.

Hero hook: Could a droid be conscious or moral? You'd need the function (a global workspace + a model of others) — and then face the hard problem of whether it truly feels.

Verified depth: Morality: people with vmPFC damage rate attempted-but-failed harm (even attempted murder) as MORE acceptable — and accidental harm as less blameworthy — because the vmPFC normally adds the emotional weight of bad intent (judgment then defaults to outcomes). The resting brain: when you're not doing a task, the default mode network (medial PFC, posterior cingulate, posterior parietal, medial temporal) lights up — it's the substrate of introspection, mind-wandering, and self-referential thought (Alves et al. 2019 Comm Biol). Conscious states track the frontoparietal network: it deactivates across anesthesia, deep sleep, and vegetative states. Free will? Libet (1983) and Soon et al. (2008 Nat Neurosci) found prefrontal/parietal activity predicts a simple choice up to several seconds before people report deciding — raising the question of whether conscious "will" causes the act or just narrates it. Consciousness theory: a 2025 preregistered adversarial collaboration (Cogitate Consortium, Nature) pitted Global-Workspace vs Integrated-Information theory and substantially challenged key predictions of both — neither was confirmed. Sources: Young et al. 2010 Neuron; Soon et al. 2008 Nat Neurosci; Alves et al. 2019 Comm Biol; Cogitate Consortium 2025 Nature.

Week 4 · Jun 19

11 · Futuristic Brain–Computer Interfaces

Reading: pp 203, 216–219

A brain–computer interface (BCI) reads neural signals and/or writes to the brain. Electrodes record spikes; algorithms decode intended movement to drive a cursor, robotic arm, or prosthetic. Going the other way, stimulation can restore sensation or treat disease (e.g., deep brain stimulation for Parkinson's). This is the real science behind cyborgs.

📖 Reading recap (pp 203, 216–219):

Brain monitoring & stimulation: EEG and implanted electrodes can read activity; deep brain stimulation can write to a circuit (e.g., Parkinson's).
A BCI records neural signals → decodes intent → drives a cursor, robotic arm, or prosthetic.
Neuroprosthetics can replace lost functions (limb, cochlear implant, retinal implant).
Plasticity lets the brain learn the device until it feels like part of the body.
The future: enhancement and repair raise real ethical questions — consent, identity, neural-data privacy, fair access.

BCI — system linking brain activity to a computer/device.

Neural decoding — translating recorded activity into intended action.

Microelectrode array — chip that records many neurons at once.

Neuroprosthetic — device replacing a lost function (limb, vision, hearing).

Deep brain stimulation — implanted electrodes that modulate a circuit.

Plasticity — the brain rewiring to use new inputs/devices.

Hero hook: Cyborg's tech arm, the Winter Soldier's prosthetic — all plausible BCIs: decode motor intent, drive the limb, and feed sensation back. Plasticity is what makes it feel like "yours."

Hero hook — pick a character: Professor X + Cerebro is the most on-the-nose BCI: Cerebro is a read/write interface that amplifies his telepathic signal to reach other brains — in real terms, a whole-brain recorder/stimulator. Iron Man's suit responds to Tony's intent like a motor-decoding BCI; Cyborg and Brainiac fuse nervous system to machine. Ethics: real BCIs raise consent, privacy of neural data ("brain hacking"), identity/agency (who acted — you or the decoder?), and unequal access. If you could ethically build one, the highest-leverage target is the primary motor cortex / precentral gyrus (to restore movement in paralysis) or the hippocampus (to restore memory) — both are where current research actually lives.

Verified depth: Implanted microelectrode arrays now decode intended speech and movement in people with paralysis — a 2023 Nature study restored near-conversational speech (~62–78 words/min) straight from cortical activity. The brain's plasticity lets users learn to drive cursors and robotic limbs until the device starts to feel like their own. Source: Willett et al., Nature 2023 (s41586-023-06377-x).

Week 4 · Jun 22

12 · Brain Evolution & Superhero Anatomy

Reading: pp 48–49

Like every other organ, brains evolved — and you can read that history in the shape of the brain. Fish run on a tiny cerebrum + big cerebellum; amphibians add a thin layer of forebrain tissue; reptiles expand the basal forebrain (the so-called "reptilian brain"); birds beef up the cerebellum for flight; mammals layer on a six-layered neocortex + a limbic system + the corpus callosum; humans stretch the frontal lobe and fold the cortex hard to pack more surface area into a fixed skull. This is the lens for asking, "what would have to change in a brain for X superpower to work?"

📖 Reading recap (pp 48–49):

Nervous systems evolved from simple nerve nets → nerve clusters (ganglia) → the centralized vertebrate brain.
Gross trend: fish (big cerebellum) → amphibians (big olfactory bulb) → reptiles (bigger forebrain) → birds (flight cerebellum) → mammals → humans.
Mammals added the six-layered neocortex, the limbic system (emotion/memory), and the corpus callosum.
Humans stand out for a huge frontal lobe and heavy cortical folding (gyrification), packing more surface into the skull.
Size isn't everything — Neanderthals had bigger brains; wiring matters more (and the popular "triune brain" model is now mostly refuted).

Encephalization quotient (EQ) — brain-to-body size ratio; rough cognitive proxy.

Gyrification — folding the cortex to pack more surface into the skull.

Neocortex — the six-layered mammalian outer cortex; not present in reptiles.

Limbic system — mammalian innovation for emotion + memory.

Corpus callosum — placental-mammal-only fiber bridge between hemispheres.

Triune brain — MacLean's 1960s reptile/paleo/neo model — popular but mostly refuted.

Hero hook — Reptil: Humberto Lopez's reptile transformations are a thought experiment in comparative neuroanatomy. Cortex should smooth out (fewer folds = less abstract reasoning); olfactory bulb and optic tectum should enlarge (smell-tracking + fast visual reflexes); brainstem & basal nuclei should dominate (snap-reaction over emotion). Reverse on the way back to human form.

Hero hook — Venom: Unlike Reptil, the body isn't re-evolving — an alien symbiote is integrating with the existing human brain. Predict hijacking, not replacement: prefrontal control overridden (impulse and aggression unfiltered), amygdala & reward circuitry amped up (the famous craving for phenethylamine — a real trace amine in chocolate that humans normally clear in seconds via MAO-B), and the "we" speech as a sign that two agents are sharing the language network.

Verified depth: The vertebrate brain's major innovation is the six-layered neocortex, present only in mammals; reptiles have a different "dorsal cortex" that's structurally not the same, which is why MacLean's popular triune brain model ("reptilian brain inside us") is now largely refuted — comparative neuroanatomy 2020s argues the supposed homologies don't hold and that the avian pallium does sophisticated work without any cortex (Güntürkün & Bugnyar 2016; Striedter 2005). Cortical expansion in primates is driven less by adding cells and more by gyrification, which packs more surface area into a skull-constrained volume; human cortex is ~2,500 cm² folded into ~1,400 cm³ of skull. Human EQ sits around 7× expected for a mammal of our body size; absolute size isn't the only signal (Neanderthals had larger brains than modern humans but were outcompeted). Mammals also gain a true corpus callosum connecting the hemispheres — birds and reptiles don't have one — and a limbic system (hippocampus, amygdala, cingulate, fornix) that lets emotion and memory shape behavior beyond reflex. So "what would a Kryptonian / symbiote / reptile brain change?" maps onto real evolutionary axes: cortex layers, fold count, limbic complexity, hemisphere bridging, and the relative size of olfactory vs visual processing. Sources: Güntürkün & Bugnyar 2016 Trends Cogn Sci; Striedter 2005 Principles of Brain Evolution; Herculano-Houzel 2009 Front Hum Neurosci (cortical neuron counts); Carter, The Human Brain Book pp 48–49.