Lecture 2/3

Conditioning and Responses

  • Concept of Stimulation

    • Two stimulations can produce responses, even without shock stimuli post-conditioning.

    • Responses include:

    • Activation of somatosensory cortex with just tone.

    • Generation of movement, freezing, and activation of the motor cortex without shock.

Historical Experiments in Fear Conditioning

  • John Watson and Little Albert Experiment (1920)

    • Conducted by John Watson and Rosalie Rayner.

    • Aimed to condition a baby boy, Little Albert, to fear white rats using classical conditioning principles.

    • Pre-conditioning Phase: Little Albert showed no fear of rats.

    • Conditioning Phase: Loud noise (striking a steel bar with a hammer) paired with a rat led to fear after six pairings.

    • Post-conditioning: Albert expressed fear towards white rats and similar stimuli (e.g., rabbits, dogs, furry objects, masks).

Development and Conditioning in Animals

  • Brain Development Observation

    • Memory develops as the brain matures.

    • Conditioning improves with age; younger animals (P15) learn tasks less efficiently compared to older ones (P21).

    • Experiment Setup: Shock stimuli paired during conditioning.

    • Behavior Measurement: Responses like freezing and heart rate were monitored.

    • Outcomes indicate older animals show improved memory and faster responses to safe spots during shock conditions.

Human Memory and Learning Processes

  • Memory Causation and Synaptic Changes

    • Learning involves synaptic changes from the cortex to hippocampus and vice versa.

    • Importance of Sleep: Plays a critical role in memory consolidation.

    • During sleep, synaptic pathways undergo reverberation which aids memory retrieval the next day.

Sleep Stages and Functions

  • Sleep Cycle Description

    • Sleep consists of various stages with cycles of brain activity.

    • Stages:

    • Stage 1: Light sleep

    • Stage 2: Deeper sleep (spindles and K complexes present)

    • Stage 3 and 4: Deep sleep (less frequency, higher amplitude)

    • REM sleep: Dreaming occurs, exhibits high brain activity similar to wakefulness.

    • Typically, individuals experience 4-5 cycles a night.

    • Lack of dream recollection is typically indicative of a good sleep experience.

Polysomnography in Sleep Studies

  • Polysomnography Overview

    • Measures physiological functions during sleep.

    • EEG, breath movements, airflow, snoring, and muscle activity monitored to diagnose sleep disorders.

    • Recordings reveal brain and bodily functions during various sleep phases.

Brain Activity and Neurochemistry During Sleep

  • Neurotransmitter Activities

    • Melatonin release regulated by light exposure; increases darkness.

    • Suprachiasmatic nucleus acts as a biological clock, inhibiting cortical activity during sleep.

Memory Consolidation during Sleep Stages

  • Memory Encoding and Sleep Phases

    • During wakefulness, hippocampus and prefrontal cortex are active.

    • Slow-wave sleep allows global synaptic weakening followed by relevant reactivation and Long-Term Potentiation (LTP) induction.

    • REM sleep enhances synaptic reconnections for memory consolidation.

    • Studies show rats display brain activation patterns similar to their learning experiences during sleep.

The Role of BDNF in Memory and Learning

  • Brain-Derived Neurotrophic Factor (BDNF) Overview

    • Crucial for neuron survival, growth, and learning enhancement.

    • Levels of BDNF can be measured in the bloodstream, indicating brain health.

    • BDNF promotes neurogenesis in the hippocampus crucial for adaptive learning.

Neurogenesis Stages and Environmental Influences

  • Stages of Neurogenesis

    • Proliferation: Birth of neural stem cells.

    • Differentiation: Cells mature into neurons.

    • Migration: New neurons reach the hippocampus.

    • Survival: Only essential neurons remain.

    • Integration: Neurons connect within the existing brain network.

    • Environmental factors like physical activity and cognitive stimulation influence neurogenesis.

Factors for Boosting BDNF Levels

  • Core Pillars for Brain Health

    • Physical Activity: Immediate BDNF boost from exercise.

    • Cognitive Stimulation: Long-term increase from engaging activities.

    • Mindfulness: Protects existing BDNF levels by lowering stress.

Neuro Sustainability Concept

  • Designing Environments for Brain Health

    • Environments can be tailored to support neurogenesis and cognitive health through:

    • Reducing stress through nature access (biophilic design).

    • Encouraging physical activity with walkable communities.

    • Fostering cognitive engagement through novel and complex surroundings.

Neurotrophic Factors and Their Functions

  • Neurotrophic Factors Overview

    • Types: NGF, Neurotrophin 3, 4, and others impacting synaptic responses and growth.

    • Tyrosine kinase receptors mediate their effects on neurons, critical for signaling pathways promoting neuron survival and differentiation.

Interaction of Neurotrophic Factors and Synaptic Efficacy

  • Neural Communication Mechanisms

    • Neurotrophic factors like BDNF increase synaptic strength and promote learning through various signaling pathways.

Genetic Influences on Memory and Neurogenesis

  • Genetic Factors Affecting Brain Function

    • Variations in neurotrophic factor genes can affect individual cognitive abilities and susceptibility to disorders.

    • Understanding genetic backgrounds can help explain differences in memory performance and resilience against neurological conditions.

Final Reflection on Neuroplasticity

  • The Dynamic Nature of the Brain

    • Continuous interplay of experiences affects neural pathways.

    • Memory is not fixed; it's an ongoing process shaped by environment, experience, and individual actions.