Attenuated Activity across Multiple Cell Types and Reduced Monosynaptic Connectivity in the Aged Perirhinal Cortex

Area of Science:

• Neuroscience
• Aging Research
• Cognitive Neuroscience

Background:

• The perirhinal cortex (PER) is crucial for memory and stimulus discrimination, acting as a cortical-hippocampal inhibitory gate.
• Aging is associated with PER-dependent behavioral deficits and reduced principal neuron activation.
• The role of PER interneurons in age-related circuit alterations remains uncharacterized.

Purpose of the Study:

• To investigate the role of perirhinal cortex (PER) interneurons in aged rats.
• To characterize age-related changes in PER circuit properties, including firing rates and synaptic connectivity.

Main Methods:

• Recorded PER neuronal activity in young and aged rats traversing a circular track with novel objects.
• Differentiated interneurons from principal cells using autocorrelogram, waveform, and firing rate.
• Assessed monosynaptic excitatory and inhibitory connections between PER neurons.

Main Results:

• Aged rats exhibited lower firing rates in PER interneurons compared to young rats.
• Running speed did not account for the observed differences in interneuron firing rates.
• Aged rats showed a significant reduction in detected excitatory and inhibitory monosynaptic connections in the PER.

Conclusions:

• Reduced interneuron firing and synaptic connectivity in the aged PER suggest impaired feedforward inhibition.
• This age-related circuit dysfunction may compromise information flow to the hippocampus, contributing to cognitive aging.
• Targeting PER circuit imbalances could be a therapeutic strategy for age-related cognitive decline.