A person in the final stages of Parkinson Disease has slow and troubled thinking, coupled with interferences in memory concentrations. Patients have delusional thinking that cause paranoia, irritability and anxiety, explains the Alzheimer's Association.
Late stages of Parkinson Disease cause dementia, which interferes with the short and long term memory. Damage to brain cells interrupt normal cell communication; this interferes with the thinking capacity of the patient, who gets constant memory lapses. The patient's thinking is not objective, since they cannot make sound judgments. They have trouble interpreting instructions and visual information, due to brain changes that affect thinking functions, explains the Alzheimer's Association.
Patients exhibit delusional thinking where they become paranoid of normal events and people around them. As stated by WebMd.com, late stages of the disease are characterised by hallucinations and thoughts of fear. Although there are no physical fears to warrant the paranoia, patient's ability to reason is heavily impaired at this stage. Medicines used to treat late Parkinson Disease also cause mental disturbances that make patients delusional of realities around them.
Cognitive impairment in the brain causes a distorted and disorganized thinking where patients have difficulties carrying simple tasks like feeding and walking. It makes it hard for them to focus on activities like conversations coherently. According to the Alzheimer's Association, changes in the thinking causes the muffled speech and irritability.