Nucleus basalis involvement in conditioned neuronal responses in the rat frontal cortex

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Cholinergic System Research

Background:

• Rat frontal cortex neurons show altered firing patterns after a tone cue and rewarding medial forebrain bundle stimulation.
• The nucleus basalis provides significant cholinergic innervation to the cortex and is linked to cognitive functions.
• Acetylcholine (ACh) plays a role in cognitive processes.

Purpose of the Study:

• To investigate the role of the nucleus basalis cholinergic system in generating conditioned neuronal responses in the rat frontal cortex.
• To test the hypothesis that nucleus basalis cholinergic neurons are essential for these learned responses.

Main Methods:

• Local microinjection of atropine (cholinergic antagonist) into the frontal cortex.
• Unilateral kainic acid lesioning of the nucleus basalis.
• Monitoring firing rates of nucleus basalis neurons during cue-MFB stimulation.

Main Results:

• Atropine suppressed conditioned responses in 22 of 25 cortical units.
• Nucleus basalis lesions reduced the proportion of responding cortical units from 70% to 25% ipsilaterally.
• 28 of 38 nucleus basalis unit recordings showed significant firing rate changes during the paradigm.

Conclusions:

• The nucleus basalis cholinergic neurons are integral to the generation of conditioned neuronal responses in the rat frontal cortex.
• Cholinergic signaling from the nucleus basalis is necessary for learned neural plasticity in response to reward-predicting cues.