20.STP

Neurophysiology XX: Short-term Plasticity

1. Short-term Synaptic Plasticity

• Plasticity: The ability of synapses to change strength based on activity levels.

• Modulation: Temporary changes in synaptic strength, usually due to neurochemical stimuli.

2. Facilitation and Depression

• Presynaptic Stimulation: Two closely spaced stimuli can cause varied response amplitudes.

• Facilitation: The second response (S2) exceeds the first (S1).

• Synaptic Depression: High-frequency stimulation can lead to reduced transmission.

• Causes of Strength Changes: Factors include spike width, Ca2+ channel types, release sites, and more.

3. Time Scales of Plasticity

• Short-term Depression: PSP amplitude decreases with successive spikes; returns to baseline in 5-10 seconds.

• Short-term Potentiation: Increased second response due to short interval stimuli; exhibits exponential time course.

• Post-tetanic Potentiation (PTP): Enhanced response following high-frequency stimulation; lasts for about a minute.

4. Key Mechanisms

• Residual Ca2+ Hypothesis: Accumulation of Ca2+ enhances neurotransmitter release following spikes.

• Ca2+ Binding Proteins: Facilitate vesicle mobilization and fusion with varying kinetics.

• Postsynaptic Regulation: Presynaptic behavior varies with different postsynaptic properties.

5. Functional Implications

• Facilitating Synapses: Optimize information transfer during bursts of spikes.

• Depressing Synapses: More efficient for conveying single spikes.