Can Parkinson's affect perception?

According to the The National Institute of Neurological Disorders, Parkinson's disease is a chronic and progressive a motor system disorder which is thought to be a cause of a loss of dopamine-producing brain cells. It slows down a person's motor skills and as it progresses it gets worse. Symptoms of Parkinson's disease include tremors,stuttering, problems talking and walking,difficulty chewing and swallowing, sleep problems, and difficulty remembering things. Some people with Parkinson's can barely hold their own tooth brush or get dressed in the morning, tasks most people take for granted. As it progresses patients also seem to have mood disorders such as depression and anxiety. Most people with Parkinson's also eventually develop dementia. Some patients even experience ringing in the ears and hallucinations.

It has been about twelve years since my grandfather has been diagnosed with Parkinson's disease. Although some medications help, there is no cure and he seems to get worse as time passes. As he enters the later stages of the disease he seems to have developed rare symptoms that seem to affect his memory, sight, hearing, and his sense of touch. He has heard people talking in the house when there is no one there. He felt like he was holding a dish towel when there was nothing in his hand. He also has hallucinations, such as seeing objects in the road or in a room when there was nothing there. Could it be the way his brain is affecting his nervous system? Like most illnesses, it is difficult to determine if Parkinson's is the main reason for these issues or if there are other factors involved, such as medication, etc. Although rare and usually seen toward the end stages of the disease, these symptoms are not uncommon. Parkinson's used to be mainly thought of as a motor skills disease, but according to the National Parkinson's foundation, current research is looking more into the "non-motor" symptoms and how Parkinson's effects the brain.