The subiculum sensitizes retrosplenial cortex layer 2/3 pyramidal neurons

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Cognitive Neuroscience

Background:

• The retrosplenial cortex (RSC) is a key brain region connecting various areas and involved in cognitive functions.
• RSC neurons, particularly granular layer 2/3 pyramidal cells, show increased activity linked to hippocampal sharp wave-ripples.
• These neurons exhibit delayed spiking in response to current injection.

Purpose of the Study:

• To investigate a novel form of short-term intrinsic plasticity in mouse granular RSC layer 2/3 pyramidal cells.
• To determine the role of subicular afferents in modulating RSC neuronal activity.

Main Methods:

• In vitro and in vivo patch-clamp recordings in mouse models.
• Optogenetic stimulation of axonal afferents.
• Somatic current injection to assess neuronal responses.

Main Results:

• Granular RSC layer 2/3 pyramidal cells displayed delayed spikes upon current injection.
• A preceding depolarization (priming) significantly shortened spike latencies, a phenomenon termed facilitatory priming.
• This priming effect was replicated by activating subicular afferents, but not neocortical ones.
• The facilitatory priming lasted over 3 seconds, indicating a sustained increase in neuronal sensitivity.

Conclusions:

• Subicular inputs play a crucial role in modulating information processing within the RSC.
• Facilitatory priming represents a unique form of short-term plasticity in RSC circuits.
• This plasticity mechanism may enhance information integration in the RSC layer 2/3 circuits.