🔑 Key Definitions
Enriched Environment: Living conditions with enhanced sensory, social, and motor stimulation that promote brain development
Dendritic Sprouting: Growth of new dendritic branches in response to environmental stimulation and learning
Hypoxia: Oxygen deprivation that causes irreversible brain damage, particularly in developing nervous system
Sensory Deprivation: Lack of normal sensory input during critical periods leading to permanent functional deficits
Dendritic Sprouting: Growth of new dendritic branches in response to environmental stimulation and learning
Hypoxia: Oxygen deprivation that causes irreversible brain damage, particularly in developing nervous system
Sensory Deprivation: Lack of normal sensory input during critical periods leading to permanent functional deficits
👤 Important Figures
- David Hubel & Torsten Wiesel - Dark room kitten experiments demonstrated irreversible effects of visual deprivation during critical period
- Mark Rosenzweig - Pioneer of enriched environment research; showed structural brain changes from environmental complexity
- William Greenough - Documented dendritic sprouting and synaptic changes resulting from environmental enrichment
🧠 Classic Experiments & Findings
- Hubel & Wiesel Dark Room Kittens: Kittens raised in darkness developed blind despite normal eyes; demonstrated critical period for visual system
- Rosenzweig Enriched Environment: Rats in complex cages showed increased cortical thickness, more dendritic branching, greater synaptic density
- Greenough's Dendritic Sprouting: Quantified structural changes - enriched rats had 25% more dendritic branches in visual cortex
⚠️ Harmful Effects on Development
- Hypoxia: Permanent neuronal death; developing brain highly vulnerable; effects include cognitive impairment, motor deficits
- Teratogenic Drugs: Thalidomide (limb deformities), alcohol (FAS), cocaine (growth restriction), all cause irreversible damage
- Sensory Deprivation: Lack of visual, auditory, or tactile input during critical periods leads to permanent perceptual deficits
📈 Environmental Effects Summary
- Enrichment Benefits: Increased dendritic branching, more synapses, thicker cortex, enhanced cognitive abilities
- Deprivation Consequences: Reduced connections, thinner cortex, permanent functional impairments
- Timing Critical: Effects strongest during sensitive periods; limited recovery possible after
💡 Exam Tips
- Connect all three researchers: Hubel/Wiesel (deprivation bad) + Rosenzweig/Greenough (enrichment good)
- Enriched environment effects are STRUCTURAL - you can measure dendritic changes
- Remember: Dark room kittens were anatomically normal but functionally blind
- Hypoxia = oxygen deprivation = irreversible = permanent damage
- Thalidomide is classic example of teratogenic drug - use for exam answers
- Key principle: Experience shapes brain structure, especially during critical periods