T1-weighted signal is known to be correlated with age and myelin content. T1-weighted images with optimized intracortical contrast were taken in subjects aged 17-45. The half cortical depth signal was mapped in 67 healthy controls and 43 individuals diagnosed with bipolar disorder type-1. We investigated the trajectory of the signal with age in each group and it was found that healthy signal trajectory follows a quadratic form with age, while no correlation with age was found in bipolar disorder. We have shown that it is possible to map signal trajectory changes in clinical populations across the cortex.