With respect to the Brain and its functions – it is underused and the reasons being that since Man has been on Earth there have been major shifts in how it has been utilized.
Since Man lived in primitive conditions to now there has been much change and the Brain has had to adapt to these changes. We are talking about the rise and fall of civilizations and Spirituality played a major part. Therefore, of course that part of the Brain to do with linking with Higher Dimensions came into use until the demise of that particular civilization. Then it lay dormant.
Just to note, that every major civilization has been linked in some way, to a greater or lesser degree to Spirituality.