Functional dissection of ipsilateral and contralateral neural activity propagation using voltage-sensitive dye imaging in mouse prefrontal cortex.

The prefrontal cortex (PFC) intrahemispheric activity and the interhemispheric connection significantly impacts neuropsychiatric disorder pathology This study aimed to generate a functional map of the PFC intra- and interhemispheric connections. Functional dissection of mouse PFCs was performed using the voltage-sensitive dye (VSD) imaging method with high speed (1 ms/frame), high resolution (256 × 256 pixels), and a large field of view (ca. 10 mm). Acute serial 350-µm slices were prepared from the bregma covering the PFC and numbered 1-5 based on their distance from the bregma (i.e., 1.70, 1.34, 0.98, 0.62, and 0.26 mm) with reference to the Mouse Brain Atlas. The neural response to electrical stimulation was measured at nine sites and then averaged; a functional map of the propagation patterns was created. Intracortical propagation was observed in slices 3-5, encompassing the anterior cingulate cortex (ACC) and corpus callosum (CC). The activity reached area 33 of the ACC. Direct white matter stimulation activated area 33 in both hemispheres. Similar findings were obtained via Di-I staining of the CC. Imaging analysis revealed directional biases in neural signals traveling within the ACC, whereby the signal transmission speed and probability varied based on the signal direction. Specifically, the spread of neural signals from cg2 to cg1 was stronger than that from cg1 to cg2, which has implications for interhemispheric functional connections. These findings highlight the importance of understanding the PFC functional anatomy in evaluating neuromodulators like serotonin and dopamine, as well as other factors related to neuropsychiatric diseases. Significance Statement This study utilized wide-field, high-speed, and high-resolution voltage-sensitive dye imaging (VSDI) to create a real-time functional map of intra- and interhemispheric connections in the prefrontal cortex (PFC) of mice. The PFC and anterior cingulate cortex (ACC) have critical roles in neuropsychiatric disorders, and the study found that neural signals within the ACC exhibit directional biases, which could affect interhemispheric functional connections. This finding could pave the way for more effective neuropsychiatric disorder treatments. The functional map created with VSDI is a potent tool for exploring functional connections in the brain and could provide valuable insights into how the brain processes information.