Attentional processes in Parkinson’s disease: a systematic review

Parkinson’s disease (PD) is typically known as a neurodegenerative disorder affecting motor skills. It is characterized by the loss of dopamine-producing neurons in the substantia nigra and subsequent accumulation of Lewy bodies in the residual neurons. Although cognitive impairments are a significant aspect of PD, there has been limited investigation and analysis of these changes. This is despite the fact that they represent a highly disabling aspect for patients who experience them daily. In particular, attentional deficits and vigilance deficits appear to be significant determinants of the patient’s quality of life. Therefore, the present systematic review aims to examine studies that have assessed the difference in these aspects, using several attentional tests, between subjects with PD and healthy controls (HC). The systematic review was conducted in accordance with the PRISMA Statement method and 25 studies were included. The results indicate that individuals with Parkinson’s disease (PD) exhibit mainly deficits in sustained attention, inhibitory control of distractors, identified as top-down deficits, and a general slowdown in reaction times. It has not been possible to identify the role played by dopaminergic therapy on attentional performance due to a paucity of studies comparing medicalized and non-medicalized patients. However, it is believed that an attention disorder may depend on alterations in dopaminergic circuits. In light of these data, further studies should be conducted in order to gather more evidence on attentional functioning in Parkinson’s and to better understand any influence of dopaminergic therapy.