Functional properties of corticothalamic circuits targeting paraventricular thalamic neurons

Area of Science:

• Neuroscience
• Neurobiology
• Systems Neuroscience

Background:

• Corticothalamic projections typically exhibit modest firing rates, modulating thalamic relay neurons.
• The role of high-order corticothalamic pathways in regulating thalamic nucleus activity remains less understood.

Purpose of the Study:

• To investigate the firing properties of prelimbic cortex (PL) projections to the anterior paraventricular thalamic nucleus (aPVT).
• To determine how PL-aPVT pathway activity influences aPVT neuron firing and regulates motivated behaviors.

Main Methods:

• Electrophysiological recordings in rats to assess neuronal activity.
• High-frequency stimulation of PL-aPVT projections.
• Analysis of action potential amplitudes and firing rates in aPVT neurons.
• Investigation of inhibitory inputs from the anteroventral thalamic reticular nucleus (avTRN).

Main Results:

• PL-aPVT projections exhibit high-frequency activity, unlike other corticothalamic pathways.
• High-frequency stimulation induced a depolarization block (DB) in a significant fraction of aPVT neurons, limiting firing rates.
• The anteroventral thalamic reticular nucleus (avTRN) differentially modulated aPVT firing based on spike fidelity and DB presence.

Conclusions:

• High-frequency PL-aPVT inputs can regulate aPVT neuron excitability via depolarization block, influencing motivated behaviors in a frequency-dependent manner.
• avTRN inputs play a crucial role in modulating the impact of PL inputs on aPVT activity, thereby controlling motivated behaviors.