Various brain regions are activated during a migraine attack

Several lines of evidence suggest activation of different regions of the brain at different stages of a migraine attack.

• During the premonitory phase, positron emission tomography (PET) studies have shown activation of the hypothalamus in individuals with nitroglycerin-triggered migraine attacks.^{[Maniyar et al., 2014]}
• During aura, magnetic resonance imaging (MRI) studies have shown activation of the visual cortex in individuals who experience migraine attacks during the aura stage.^{[Hadjikhani et al., 2001]} Furthermore, the slow and contiguously progressive nature of blood oxygenation level-dependent (BOLD) signal activation has been linked to the cortical spreading depression phenomenon.^{[Hadjikhani et al., 2001]}
• During the headache phase of the migraine attack, PET studies have shown increased blood flow in some cerebral regions of the brain as well as in the brainstem.^{[Weiller et al., 1995]}

References:
Hadjikhani N, Sanchez Del Rio M, Wu O, et al. Mechanisms of migraine aura revealed by functional MRI in human visual cortex. Proc Natl Acad Sci USA 2001; 98 (8): 4687–4692.

Maniyar FH, Sprenger T, Monteith T, et al. Brain activations in the premonitory phase of nitroglycerin-triggered migraine attacks. Brain 2014; 137 (Pt 1): 232–241.

Weiller C, May A, Limmroth V, et al. Brain stem activation in spontaneous human migraine attacks. Nat Med 1995; 1 (7): 658–660.