As the BOLD effect depends on blood flow and alcohol is vasoactive, we determined if steady state alcohol infusion affected the olfactory sensory system response. For this we used a voxel-by-voxel factorial model as implemented in SPM5 to define the boundaries of functional ROIs for primary olfactory (piriform) cortex by examining the [NApO > odorless sniffing] olfactory main effect (height threshold p < 0.001, extent threshold k > 5 voxels). Mean activity from these functionally defined volumes was extracted and compared to mean activity under alcohol infusion in a 2(Condition) × 2(Group) mixed model. Neither left nor right piriform responses showed significant main effects or interactions (p’s ≥ 0.50). This suggests that the primary olfactory cortex BOLD response to odorants with little appetitive significance was unchanged by alcohol infusion. Voxel-wise testing in a factorial (Condition × Group) model similarly showed no significant differences (p > 0.05, uncorrected) in either piriform or orbitofrontal (associative olfactory) cortex (see Figure 4).
