Neuroscience of Learning and Memory

Early formation and aggregation of communication in brain development leads to the emergence of specific cell types.
Stem cell research explores the potential to address deficits in the brain.
- Example: Inserting stem cells into regions of the brain affected by conditions such as Parkinson's Disease.
- Loss of specific neurons, namely dopamine-revergent neurons, is associated with Parkinson's, observable through lighter pigmentation in affected areas.

In the insertion of stem cells, the necessity of developing functional memory connections within neurons is critical.
Research focuses on gap junction communications that facilitate differentiation of stem cells into dopamine-revergent neurons.
This differentiation needs to be followed by the establishment of functional connections among surrounding neurons, characterized by axons and dendrites.

Popular early theory: The brain functions as a blank slate (tabula rasa), devoid of built-in knowledge or content.
- All knowledge is derived from direct environmental experiences.
The role of genes in brain development is acknowledged alongside experiential factors.
Roger Sperry's research in the 1940s explored the validity of the tabula rasa theory using tadpoles for experimental purposes.
- Focused on the orientation of the eye and its connections to the brain.

Experiment involved rotating the eye of tadpoles 180 degrees, allowing connections to reform.
- Hypothesis: If connections are experience-driven, rotating the eye would produce upside-down vision.
- Alternatively, if a guided pathway exists, visual processing should still correlate with the physical orientation of the eye post-rotation.
Findings: Mature frogs exhibited behaviors consistent with an upside-down world post-manipulation.
- Conclusion: Predetermined chemical pathways influence neuronal connection placement, termed chemoaffinity.

Neurotrophic factors are molecules supporting the survival and formation of synaptic connections among neurons.
- Key neurotrophic factor: Nerve Growth Factor (NGF), the first neurotrophin identified.
- Other neurotrophins include Brain-Derived Neurotrophic Factor (BDNF) and Insulin-like Growth Factor (IGF).
- Criteria to identify neurotrophic factors include presence in target areas, responses to receptors in neurons, and correlation with cellular functions in connection development.

Brain plasticity allows for synapse rearrangement based on activity.
Overproduction of synapses in young brains supports greater plasticity, producing approximately 50% more synapses than required.
Structural changes due to experience lead to variability in synaptic density and arrangement over lifespan.

The prefrontal cortex correlates with cognitive function, integrating functions such as working memory, planning, and impulse control.
Age-related cognitive changes may be linked to reduced hippocampal volume.

Hebb’s Rule: Neuronal connections strengthen when activated simultaneously; weaken when not.
Learning types at the neuronal level are classified into physiological (i.e. synaptic efficiency) and structural changes (i.e. dendritic remodeling).

Sensitization: Increased response following a prominent stimulus (e.g., loud sound).
Habituation: Decreased response after repeated stimulus exposure.

Gill Siphon Withdrawal Reflex (GSWR): Simple neural connections mediating sensory-motor responses.

Environmental enrichment alters neuronal structures, evidenced in musicians’ brains with differences in gray matter distribution.

NMDA receptors are ionotropic glutamate receptors: they allow ions to pass only under specific depolarization conditions.
Important for synaptic plasticity and long-term potentiation (LTP).

Involves significant calcium influx at NMDA receptors, activating intracellular processes that modify AMPA receptors, improving sodium and potassium ion conductance.

Distinctions in memory functions were explored through cases and neuropsychological studies.
HM's Case: Provided a basis for understanding memory forms (declarative vs. non-declarative).
- Declarative: Facts and knowledge we can verbally express.
- Non-declarative: Skills and habits shown through performance.

Memory is not confined to the hippocampus but involves a network encompassing parahippocampal regions and other areas for encoding and retrieval.
- Damage to any part of this network affects memory capabilities.

Patient N.A. experienced amnesia due to dorsomedial thalamus damage but retained short-term memory.
Korsakoff’s Syndrome: Caused by thiamine deficiency from chronic alcoholism, impacting memory and brain areas associated with memory.
K.C. Case Study: Demonstrated distinction between declarative and procedural memories following widespread brain damage.

Links memory loss to neurodegenerative changes in the brain, including amyloid plaques and tangles.

The diverse forms of memory reveal complexity in brain structures and functions, highlighting the contribution of various regions to different memory types, including spatial learning and procedural skills.