One of the most important concepts of the disabilities movement is that people with disabilities should be at the "speaking center" of the conversation. In other words, it is crucial that people with disabilities speak for themselves and take the primary role in defining the conversations and various agendas that will affect them.
Unfortunately, this can be quite difficult for people with disabilities related to cognition and neurodevelopment. Access to first-person narratives from such people can be harder to come by. Below are two videos. One features Sondra Williams, whom I heard speak at a Joni and Friends event last year. Sondra is autistic. The second features a woman with Down Syndrome named Karen.
If you want to know more about these and other conditions that can create serious challenges for the people who live with them, the best way to do so is to listen to those people.