Modification of persistent responses in medial prefrontal cortex during learning in trace eyeblink conditioning

Area of Science:

• Neuroscience
• Cognitive Science
• Behavioral Psychology

Background:

• Persistent neural spiking is thought to reflect active memory maintenance for behavioral responses.
• This response pattern is observed in learning paradigms like trace eyeblink conditioning, which involve a delay between stimulus and response.
• It remains unclear if persistent spiking is learned or an inherent response type.

Purpose of the Study:

• To investigate whether persistent neural responses are acquired through learning or represent a pre-existing response category.
• To examine the role of the medial prefrontal cortex (mPFC) in the initial learning phase of trace eyeblink conditioning.

Main Methods:

• Single-unit activity was recorded from the medial prefrontal cortex (mPFC) of rabbits.
• Recordings were conducted during the early stages of trace eyeblink conditioning.
• Analysis focused on persistent spiking responses to a conditioned stimulus (tone).

Main Results:

• Persistent spiking responses to the tone stimulus were observed in the mPFC from the very first training sessions.
• Most cells exhibiting persistent responses showed this pattern even before paired training began.
• The magnitude of persistent responses decreased during the first training session, an effect not seen on subsequent days or after learning criterion was met.

Conclusions:

• Persistent spiking responses to discrete stimuli do not appear to be learned.
• Experience during training modifies the robustness of these persistent responses.
• Potential mechanisms for this modification include changes in cellular properties, network dynamics, neuromodulation, or synaptic efficacy.