Neurophysiological basis of learning and memory.
Learning is the process of acquiring new information or behaviors as a result of experience, leading to a relatively permanent change in behavior. This involves modifications in the connections and communication patterns within neural networks, a concept known as synaptic plasticity. Memory is the ability to encode, store, and retrieve this learned information for future use.
Types of Memory:
- Short-term memory: Has limited capacity, requires repetition for maintenance, and is easily disrupted. Short-term memory includes sensory memory, which stores specific patterns of sensory activity, and working memory, which integrates short-term memory with long-term memory access for complex cognitive tasks.
- Long-term memory: Characterized by vast capacity and enduring storage. Long-term memory can be further classified into:
- Declarative (explicit) memory: Consciously recalled "what" memories, encompassing facts (semantic) and personal experiences (episodic). Declarative memory formation involves the hippocampus, thalamus, and frontal lobes. Structures involved are -Hippocampus, thalamus, frontal lobes.
- Non-declarative (implicit) memory: Unconsciously retrieved "how-to" memories, including skills, habits, and conditioned responses. Non-declarative memory relies on structures like the motor cortex, cerebellum, and basal ganglia. Structures involved are - Motor cortex, cerebellum, basal ganglia.
Key Processes in Memory:
- 1. Encoding: The initial processing and transformation of information into a neural representation suitable for storage.
- 2. Storage: The retention of encoded information over time, involving changes in synaptic strength and the formation of new neural connections.
- 3. Retrieval (Remembering): Accessing and bringing stored information back into conscious awareness or using it to guide behavior.
Mechanisms of Information Storage:
- Short-Term Memory:
- Specific patterns of neuronal activity that outlast the initiating stimulus.
- Reverberating circuits that maintain information for several hours.
- Functional modifications in synaptic transmission, such as altered neurotransmitter release.
- Long-Term Memory:
- Structural changes in neurons, including the formation of new synapses (synaptogenesis), the growth of dendrites, and alterations in the number of receptors.
- Changes in protein synthesis essential for long-lasting modifications in synaptic structure and function.
Types of Learning:
- Non-associative Learning: Changes in behavior due to repeated exposure to a single stimulus. Examples include habituation (decreased response to a repeated, non-threatening stimulus. Decreased ↓neurotransmitter release leads to less sensitivity,) and sensitization (is produced by painful stimuli, increased ↑neurotransmitter release leads to the painful/nauseous feeling.
The increase is due to presynaptic interneuron adding neurotransmitters to the synaptic terminal).