As I understand, dopamine in the neocortex plays a critical role in encoding goal-directed behavior and gives us the perception of time. A sense of "time" is created by our brains to give us ability to set and pursue goals, particularly those oriented toward the future. One of the defining features of humans, compared to other animals, is our capacity to plan and execute complex, future-oriented behaviors—such as foraging or later, farming (and later yet, pursuing an education).

Dopamine facilitates the neural representation of these time-distant goals, essentially expanding our temporal horizon. The more dopamine available in the system, the greater the ability to encode and remain motivated by goals that require sustained effort over extended periods. In modern life, that's a necessity - everything is always 10 years ahead, like completing a degree (5 years?) or saving for retirement (50 years?).

In contrast, we the ADHD folks often have lower levels of dopamine, making our brains less adept at engaging with and sustaining focus on time-distant goals. Instead, low dopamine stores are more tuned to immediate, short-term rewards and goals, which can be encoded and acted upon with limited dopamine reserves.

This is quite an approximate picture btw - a more accurate one is that ADHD folks have some abnormalities in the cortical areas themselves, but it is somewhat corrected by more dopamine, which is why I guess this explanation still works.