the parietal lobe
The key functions of the brains Parietal lobe affected by dementia present as follows:
Language usage is affected and frequently manifests itself as the inability to recall words and their meanings. In an individual I am aquainted with this condition persists as a frustrating struggle to find words that were previously a common part of the individuals' vocabulary and until recently, in regular use.
Lack of spatial awareness and an inability to judge distances correctly is common and is another result of atrophy or damage to the parietal lobe. This can manifest itself when reaching out to pick up nearby objects, like pills on a plate, or a knife and fork.
Descending stairs can be dangerous, in particular if the individual can't see the end of each step (many of us don't even bother to look down).
Opening doors can present difficulty as their exact location in relation to the individual may be confusing.
Eventually, the ability to recognise friends and acquaintances can become problematic and long term relationships can be severely affected as people fail to realise that they are dealing with the disease and not the person.
As dementia progresses many individuals fail to recognize their own spouses and offspring.