Mormonism teaches that we take with us to heaven all the intelligence we gain in this life. If that intelligence is somewhat lacking, do we need to be concerned if, in the perfect body we are resurrected with, we will have use of 100% of the capacity of our brain, whereas now we only use a small percentage?
There is progression beyond the grave in mental, spiritual, and physical respects. When we are resurrected, we are brought forth as we are laid down. The infant who dies will be resurrected as an infant, and the old man as an old man. Both will grow toward their ideal form and stature.
We will continue to learn and progress. I would imagine that the memories of our pre-earth life will be restored, but apart from that we will have to learn line upon line and precept upon precept the truths of eternity that we do not now know.
Spiritually we will yet be responsible before God for our actions. We may yet repent of wrongdoing and increase in faith, love, and charity, as we continue to perfect ourselves. As a matter of fact, the word perfection is a relative term. We will never cease to learn and to progress within the sphere to which we will be assigned as a result of the degree of righteousness and obedience to God that we will have achieved during mortality. B. H. Roberts had this to say on the subject in his Outlines of Ecclesiastical History, p.417:
In the revelation from which we have summarized what has been written here, in respect to the different degrees of glory, it is said that those of the terrestrial glory will be ministered unto by those of the Celestial; and those of the telestial will be ministered unto by those of the terrestrial–that is, those of the higher glory minister to those of a lesser order of glory. We can conceive of no reason for all this administration of the higher to the lower, unless it be for the purpose of advancing our Father’s children along the lines of eternal progression.