Brain Damage, Identity & Neuropsychology

Visual Pathways, Emotion, and "Impostor" Experiences

• Head injury case: patient can label objects/people but sometimes believes close relations (or self in mirror) are impostors.
• Neurological explanation
‑ Visual cortex normally projects to two parallel targets:
• "What/where" recognition regions (ventral & dorsal streams).
• Limbic/emotional structures (especially pathway toward the medial temporal lobe & amygdala).
‑ Trauma near medial temporal lobes severed the visual–emotion link but spared ventral stream object recognition.
‑ Result: cognitive recognition without the unconscious affective “familiarity signal.”
• Leads to interpretation “looks like Mom, but feels wrong ⇒ must be an impostor.” (Capgras-like delusion)
• Modality-specific:
‑ Auditory pathway to emotion remained intact → telephone conversations with mother feel normal.
• Intermittency puzzle:
‑ Sometimes apartment/faces feel familiar, sometimes not → unclear why pathway occasionally re-engages.
‑ Highlights limited understanding of dynamic limbic gating, context-dependent arousal, and memory cueing.

Broader Principle: Change the Brain → Change the Mind

• Capgras example demonstrates that subtle wiring changes alter core identity judgments.
• General theme: neurological insult (injury, infection, tumor, degeneration) reshapes beliefs, perception, emotion, morality.

Other Clinical Vignettes of Brain-Based Mind Change

• Orbital/temporal tumor in Italian pediatrician
‑ Tumor compressed critical impulse-control & sexual-behavior circuits → emergent pedophilic actions.
‑ Removal of tumor abolished urges; used as mitigating evidence in court (neuroscience & legal ethics).
• Viral encephalitis
‑ Clive Wearing: bilateral hippocampal destruction → profound anterograde & retrograde amnesia, ≈30\,\text{s} memory span.
• “Disembodied Woman” (Oliver Sacks)
‑ Acute sensory-neuronitis destroyed proprioceptive feedback → loss of body ownership; lids “float into space” when eyes closed.
• Neurodegenerative diseases
‑ Alzheimer’s, Parkinson’s, Huntington’s, Chronic Traumatic Encephalopathy (CTE) produce cascading cognitive, mood, & identity alterations over time.

Four Classic Oliver Sacks Case Chapters (Required Knowledge)

• The Disembodied Lady → Proprioceptive loss.
• The President’s Speech → Pure Wernicke’s aphasia (comprehension deficit, fluent jargon).
• Cupid’s Disease → Neurosyphilis & its psychiatric sequelae.
• A Matter of Identity → Korsakoff’s syndrome from chronic alcoholism (anterograde amnesia + confabulation).
• Found in: “The Man Who Mistook His Wife for a Hat” (title case: patient mistook wife’s head for his hat—visual agnosia).
• Sacks himself had prosopagnosia (face blindness) and produced extensive public talks on hallucinations & music (“Musicophilia,” “An Anthropologist on Mars”).

Brain–Machine Interfaces (BMI) & Neuro-Prosthetics

• Monkey cursor-control video: cortex electrodes decode intended movement → robotic arm moves in real time.
• Human application: quadriplegic individual uses neural implant to control detached robotic limb by thought alone.
‑ Development cost quoted \approx120\,000,000 (research phase).
• Elon Musk’s Neuralink: pig implants & first human volunteers; goal = high-bandwidth bidirectional BMI.
• Consumer-grade EEG toy “Mindflex”
‑ Headband extracts crude attentional signals; players levitate foam ball by concentration (honors-thesis experiment example).
• Implications
‑ Rehabilitation: restore mobility, speech, sensation after stroke/ amputation.
‑ Enhancement: potential future of brain-to-cloud cognition; raises ethical, identity, and privacy debates.

Psychological Identity Reconstruction After Acquired Brain Injury (ABI)

• First post-injury year = critical for renegotiating “Who am I?”
• ABI disrupts pre-injury roles, memories, personality traits → patients must integrate deficits & new abilities.
• Research sparse; calls for interdisciplinary focus (clinical psych + neurology + social support).
• Upcoming Unit 4: pharmacological modulation (antidepressants, hallucinogens) as another route to altering brain processing and thus self-concept.

Ethical, Philosophical, and Practical Takeaways

• Legal responsibility: To what extent is a crime committed “by a tumor” or “by a person”?
• Free will debate: Motor-intention studies & prosthetics challenge intuition of volitional control.
• Privacy & autonomy: BMI data streams could expose thoughts; consent frameworks needed.
• Emotional salience: Much of “familiarity” operates unconsciously; stripping it away destabilizes identity.

Key Terms & Concepts

• Capgras Delusion – belief familiar individuals are impostors (here vision-specific).
• Prosopagnosia – facial recognition deficit (Sacks).
• Amygdala – limbic nucleus generating affective tags for stimuli.
• Medial Temporal Lobe – memory & emotion integration hub.
• Anterograde Amnesia – inability to form new long-term memories (Clive Wearing).
• Wernicke’s Aphasia – fluent but nonsensical speech + poor comprehension.
• Korsakoff Syndrome – thiamine-deficiency brain damage from alcoholism.
• BMI – interface translating neural activity into machine control (and vice versa).
• ABI – any non-congenital brain insult (trauma, stroke, infection) acquired after normal development.