Affiliations: Department of Neuroscience and Imaging, University G.
d'Annunzio of Chieti-Pescara, Chieti, Italy | Aging Research Center, "G. d'Annunzio" University
Foundation, Chieti, Italy | Institute for Ageing and Health,
Wolfson Research Centre, Campus for Ageing and Vitality, Newcastle University, Newcastle Upon Tyne,
UK | Università del Sacre Cuore, Istituto di
Radiologia, Rome, Italy
Note: [] Corresponding author: Prof. Marco Onofrj, Chair of the
Department of Neurology, Aging Research Center, Ce.S.I. "Gabriele d'Annunzio"
University Foundation Chieti-Pescara, Via dei Vestini, 66100, Chieti, Italy.
Tel./Fax: +39 0871 562019; E-mail: onofrj@unich.it
Abstract: Visual Hallucinations (VH) are a common non-motor symptom of
Parkinson's Disease (PD) and the Lewy body dementias (LBD) of Parkinson's
disease with dementia (PDD) and Dementia with Lewy Bodies (DLB). The origin of
VH in PD and LBD is debated: earlier studies considered a number of different
possible mechanisms underlying VH including visual disorders, Rapid Eye
Movement (REM) Sleep Intrusions, dysfunctions of top down or bottom up visual
pathways, and neurotransmitter imbalance. More recently newer hypotheses
introduce, among the possible mechanisms of VH, the role of attention networks
(ventral and dorsal) and of the Default Mode Network (DMN) a network that is
inhibited during attentional tasks and becomes active during rest and self
referential imagery. Persistent DMN activity during active tasks with
dysfunctional imbalance of dorsal and ventral attentional networks represents a
new hypothesis on the mechanism of VH. We review the different methods used to
classify VH and discuss reports supporting or challenging the different
hypothetical mechanisms of VH.
