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Non-Hebbian synapses in rat visual cortex
A Kossel1, T Bonhoeffer, J Bolz
1Friedrich-Miescher-Labor Max-Planck-Gesellschaft, Tübingen, FRG.
Neuroreport
|October 1, 1990
Summary
Hebbian learning rules for synaptic plasticity in the brain are not strictly followed. Synaptic reinforcement spreads to neighboring neurons, suggesting a developmental mechanism for cortical organization.
Area of Science:
- Neuroscience
- Cellular Neuroscience
- Systems Neuroscience
Background:
- Long-term potentiation (LTP) in the mammalian central nervous system (CNS) is often explained by Hebbian principles, where correlated pre- and postsynaptic activity strengthens synaptic connections.
- The Hebbian rule posits that synaptic strengthening is limited to the directly activated postsynaptic neuron.
Purpose of the Study:
- To investigate the validity of the strict Hebbian rule in cortical synaptic plasticity.
- To explore the spatial extent and stimulus specificity of synaptic reinforcement.
Main Methods:
- Utilizing double intracellular recordings in the mammalian cortex.
- Employing paired-pulse stimulation protocols to induce and measure synaptic changes.
Main Results:
- Synaptic reinforcement was observed not only in the directly depolarized postsynaptic neuron but also in adjacent, non-coactivated neurons.
- The observed synaptic enhancement was stimulus-specific, occurring only for the stimulated afferent fibers.
- This spread of synaptic reinforcement suggests a mechanism beyond simple Hebbian correlation.
Conclusions:
- The strict Hebbian rule is not universally applicable in the mammalian cortex.
- Synaptic plasticity can extend to neighboring neurons, potentially influencing cortical development.
- This phenomenon may contribute to the functional clustering of neurons in the cortex during development.