Working memory is our brain’s ‘post-it note’. We make mental scribbles of bits of information we need to remember and also work with that information. For example, if you were baking a cake that fed only two people, but you had four people coming to dinner, you need working memory to remember the ingredients and to multiply them in your head so that everyone gets a slice. Without it we would be lost literally, we wouldn’t be able to juggle directions in our head to get to that important meeting at a new location and would forget important phone numbers and contacts. Working memory is just as critical for a variety of activities at school, from complex tasks like reading comprehension and mental math, to simple activities such as navigating around the school and taking the right books for homework.Anecdotally, I've heard that this is the reason why high functioning autistic individuals have difficulty with driving.
It appears there's a correlation between Developmental Coordination Disorder (DCD) (a term often used interchangeably with dyspraxia) and poor working memory. See, e.g.: Working Memory and Learning in Children with Developmental Coordination Disorder and Specific Language Impairment. It appears that there is also a correlation between DCD and specific language impairment. See, e.g.: Comparing Language Profiles: Children with Specific Language Impairment and Developmental Coordination Disorder. For more information, see Dyspraxia and Working Memory.
My sense is that, with Brad, his motor coordination issues are connected to his cognitive issues. Perhaps the link is working memory. Perhaps it's not. Just another piece of the puzzle to consider.