Long-term depression at thalamocortical synapses in developing rat somatosensory cortex

Area of Science:

• Neuroscience
• Developmental Neuroscience
• Synaptic Plasticity

Background:

• Sensory experience during critical periods shapes brain development.
• Thalamocortical circuit development is thought to involve synaptic plasticity like LTP and LTD.
• The role of LTD in vivo during development remains less understood.

Purpose of the Study:

• To investigate the expression and developmental timing of long-term depression (LTD) at thalamocortical synapses.
• To determine the properties and mechanisms underlying thalamocortical LTD.
• To compare LTD with previously studied LTP in the barrel cortex.

Main Methods:

• Electrophysiological recordings in rat barrel cortex.
• Induction of LTD at thalamocortical synapses.
• Pharmacological manipulation using NMDA receptor antagonists.
• Age-dependent experiments to assess developmental timing.
• Minimal stimulation to evaluate synaptic transmission properties.

Main Results:

• Thalamocortical synapses in the rat barrel cortex express LTD.
• LTD is most readily induced during a specific developmental critical period.
• Thalamocortical LTD is homosynaptic and requires N-methyl-D-aspartate (NMDA) receptor activation.
• The decline of LTD with age is not linked to changes in inhibition or NMDA receptor voltage dependence.
• LTD induction does not significantly alter synaptic failure rate, unlike LTP.

Conclusions:

• LTD is a functional form of plasticity at thalamocortical synapses during development.
• The developmental time course of LTD aligns with critical periods for plasticity.
• Both LTD and LTP likely contribute to the refinement of thalamocortical inputs during sensory development.