Can anyone offer insight into Parkinson's disease and behavior changes?

The dementia most often associated with Parkinson's disease is PDD -- Parkinson's Disease Dementia. It is one of the Lewy Body Dementias. Both Parkinson's Disease itself and PDD involve protein deposits in the brain. A website that has many articles explaining aspects of the dementia is by the Lewy Body Dementia Association -- LBDA.org This can help you understand what to expect.