The brain controls everything that we perform. Possible things like picking up the pen, solving a jigsaw puzzle, talking to someone, fondly recalling  memory; every task that we perform every day in our life is monitored and controlled by the brain.

If the brain starts degenerating, it may gently lead to delay in cognition which can further lead to Dementia or Alzheimer’s in extreme cases. Most people experience cognitive degeneration with mild symptoms like forgetfulness, unclear speech, processing things at a slowly, difficulty in recalling simple or basic words. Cognitive degeneration is common to happen in old age, but there can other reasons for delayed cognition at a younger age because of a poor diet,  concussion, addiction to substances like alcohol, drugs, etc.