Prefrontal cortex neurons encode ambient light intensity differentially across regions and layers.

Area of Science:

• Neuroscience
• Neurobiology

Background:

• The medial prefrontal cortex (mPFC) is known to be influenced by light, affecting emotional and cognitive functions.
• However, direct evidence of light encoding within the mPFC has been lacking.

Purpose of the Study:

• To investigate the presence and characteristics of light-encoding neurons in the medial prefrontal cortex (mPFC).
• To explore the functional implications of mPFC photosensitivity in relation to light intensity and specific brain pathways.

Main Methods:

• Extracellular recordings were performed in awake mice to identify photosensitive neurons in the mPFC.
• The study inhibited intrinsically photosensitive retinal ganglion cells (ipRGCs) and the perihabenular nucleus (PHb) to assess their role in mPFC photosensitivity.
• Neuronal firing rates were analyzed in response to varying light intensities and gradients.

Main Results:

• Over half of the recorded mPFC neurons exhibited photosensitivity.
• This photosensitivity was reduced upon inhibition of ipRGCs or the PHb.
• A subset of mPFC neurons (15%) encoded light intensity through monotonic changes in firing rate, categorized into enhancing and suppressing types.
• Similar light-encoding neuron types were found in the PHb with faster responses and higher sensitivity.
• Light differentially affected prelimbic (suppression) and infralimbic (enhancement) activity, aligning with their known roles in behavior.

Conclusions:

• The medial prefrontal cortex (mPFC) possesses photosensitive neurons, indicating a direct substrate for light's influence on its functions.
• Prefrontal photosensitivity, modulated by ipRGCs and the PHb, may play a role in regulating emotional and cognitive processes.
• These findings suggest that mPFC light sensitivity could be a novel therapeutic target for psychiatric and addiction disorders.