Habituation and migraine.

The most reproducible and ubiquitous interictal abnormality of the migraineurs' brain is lack of habituation in neuronal information processing. The underlying mechanisms are uncertain. Increased neuronal excitability, decreased inhibition or decreased pre-activation levels have all been proposed as possible culprits. The present review summarizes the available data on habituation in migraine patients obtained with different methodological approaches. We will discuss the change of habituation level over the migraine cycle and we will show that these data congruently indicate that the sensory cortices of migraineurs react excessively to repetitive, but not to a small series of stimuli. Although the precise cellular and molecular mechanisms of this hyper-responsivity must still be determined, we will describe experimental data suggesting that a dysrhythmic thalamo-cortical activity due to inadequate monoaminergic control might be a plausible explanation.