Therapy Dog Presence During Chemotherapy in a Day Chemotherapy Unit: A Prospective Pilot Comparative Pre-Post Study.

Although Parkinson's disease (PD) is traditionally defined as a movement disorder, PD affects numerous non-motor circuits leading to a variety of non-motor symptoms. Hallucinations are one such frequent non-motor symptom, with 30–50% of PD patient experiencing them regularly. The prevalence of hallucinations has been found to increase >50% in advanced stages of PD and often includes structured visual hallucinations (VH). VH almost invariably consist of humans or animals that are perceived centrally, often in dim light and are usually not frightening. VH are among the most clinically relevant and debilitating non-motor symptoms and are associated with a more severe form of the disease characterized by a more rapid cognitive decline and dementia, earlier home placement, and a higher risk of mortality. VH in PD have been linked with dopaminergic treatment as well as visual dysfunction (for review see). Neurally, VH and visual deficits have been associated with altered structures in the visual pathways and retinal pathology. Neuroimaging studies also described impairments in posterior visual-perceptual brain networks and attention networks, as well as altered integration of bottom-up visual signals with top-down cognitive processes (i.e., dysfunctional integration between fronto-parietal and visual brain networks). Structured VH in PD almost always involve animate-social objects, that is humans or animals (>80%), whereas VH of inanimate objects are more rarely reported (<20%). However, current theories fail to account for the prominent social component of VH in PD. Even if impairments in higher visual perception have been observed, to date no selective disturbance in the perception of social visual stimuli (versus control visual stimuli) has been reported. Humans are highly reliant on social interaction and its absence has been argued to induce significant physical and psychological distress and social hypervigilance. Moreover, hallucinations in general and in patients with psychosis and with Alzheimer's disease have been linked to social traits of perceived social isolation. However, social isolation has not been investigated in PD patients with VH nor in relation to social perception. Finally, PD patients have impairments in social cognition, such as inferring person's intentions, emotions and mental states (theory of mind), and these latter functions have been related to the trait of anthropomorphism, which is the tendency to ascribe human-like characteristics to non-human stimuli. It has recently been argued that anthropomorphism is associated with specific hallucinations; however, this has not been tested in patients with PD.