Ongoing in vivo experience triggers synaptic metaplasticity in the neocortex.

Area of Science:

• Neuroscience
• Synaptic Plasticity
• Sensory Processing

Background:

• In vivo experience can impair long-term potentiation (LTP) and enhance long-term depression (LTD).
• This suggests continued experience might degrade neural representations, contradicting learning principles.

Purpose of the Study:

• To investigate how ongoing whisker stimulation affects synaptic strengthening in the mouse barrel cortex.
• To elucidate the molecular mechanisms underlying experience-dependent synaptic plasticity.

Main Methods:

• Electrophysiological recordings in vivo and in vitro in mouse barrel cortex.
• Examined synaptic responses at layer 4-2/3 synapses during ongoing sensory stimulation.
• Investigated the roles of N-methyl-d-aspartate (NMDA) and metabotropic glutamate receptors (mGluRs).

Main Results:

• NMDA receptor activation was necessary for initial synaptic strengthening but later suppressed further potentiation.
• Continued sensory activity induced further synaptic strengthening.
• This later strengthening required metabotropic glutamate receptor activation, not NMDA receptors.

Conclusions:

• Synaptic plasticity exhibits a switch in mechanism during sustained sensory input.
• Metabotropic glutamate receptors mediate experience-dependent synaptic strengthening after initial NMDA receptor-dependent potentiation.
• This provides a mechanism for how continued experience enhances neural representations over time.