Olfactory Information Storage Engages Subcortical and Cortical Brain Regions That Support Valence Determination

Area of Science:

• Neuroscience
• Olfactory System Research
• Brain Plasticity

Background:

• The olfactory bulb (OB) transmits sensory data to the piriform cortex (PC).
• Long-term potentiation (LTP) in the anterior PC (aPC) is primarily driven by prefrontal cortex inputs, suggesting extra-olfactory regions contribute to olfactory memory.

Purpose of the Study:

• To investigate the effects of different olfactory bulb stimulation frequencies on brain activity.
• To explore the neural mechanisms underlying olfactory information processing and storage, particularly the role of the prefrontal cortex.

Main Methods:

• Functional magnetic resonance imaging (fMRI) BOLD responses were measured during 20 Hz and 100 Hz OB stimulation.
• Nuclear immediate early gene expression was assessed in key brain regions.
• Long-term potentiation (LTP) in the anterior piriform cortex (aPC) was induced and measured.

Main Results:

• BOLD signal increases were observed in the anterior olfactory nucleus (AON), PC, entorhinal cortex, nucleus accumbens, dorsal striatum, ventral diagonal band of Broca, prelimbic-infralimbic cortex (PrL-IL), dorsal medial prefrontal cortex, and basolateral amygdala.
• 100 Hz OB stimulation elicited significantly stronger BOLD responses in the PrL-IL, PC, and AON compared to 20 Hz stimulation.
• 100 Hz stimulation induced LTP in the aPC and increased immediate early gene expression in the aPC, AON, and PrL-IL.

Conclusions:

• Olfactory bulb stimulation, particularly at higher frequencies, activates a network including the prefrontal cortex, supporting olfactory information processing and storage.
• The prelimbic-infralimbic cortex (PrL-IL) plays a role in modulating behavioral responses to odors.
• Olfactory information storage in the anterior piriform cortex (aPC) is integrated within a broader neural network involved in evaluating odor valence.