No negative BOLD Responses observed in the SC of visual pathways in Sprague-Dawley Rat

Motivation: Neurovascular coupling variations across rat strains may result in different BOLD responses to the same visual stimuli. Goal(s): To investigate whether high-frequency visual stimulation induces negative BOLD signals in the superior colliculus (SC) of Sprague-Dawley (SD) rats, which has seen in Long-Evans (LE) rats. Approach: We conducted fMRI on 13 SD rats using an 11.7T animal scanner with EPI, applying classical visual stimulation to investigate continuity illusion effect. Results: Both low- and high-frequency stimulation induced positive BOLD responses (PBRs) in the LGN and SC, while V1 showed negative BOLD responses (NBRs) only at frequencies above 8 Hz. Impact: We observed similar BOLD responses in LGN and V1 of SD and LE rats. However, unlike LE rats exhibited negative BOLD responses in SC at high frequencies, SD rats exhibited positive BOLD responses in SC, suggesting strain-dependent neurovascular coupling differences.