Transcranial magnetic stimulation improves cognition over time in Parkinson's disease

 Parkinson's disease (PD) is the second most frequent neurodegenerative disease. Cardinal symptoms of PD consist of motor deficits caused by the loss of dopaminergic neurons in the substantia nigra pars compacta. It is now known that patients with PD have cognitive deficits, even in the early phase of the disease and mild cognitive impairment (MCI) in patients with PD has been shown to increase the incidence of dementia.

MCI can affect one or more cognitive domains. Previous studies reported an association between MCI and functional alterations in the dorsolateral prefrontal cortex (DLPFC) and in the caudate nucleus [3,4]. Indeed, during execution of a cognitive task, Monchi et al. (2012) showed reduced activation in the cognitive part of the cortico-striatal loop, which involves the DLPFC and the caudate nucleus, in patients with PD compared to healthy controls [5]. This decreased activation has also been reported to be stronger in PD patients with MCI (PD-MCI) compared to those with normal cognition at the same stage of the disease [6]. While dopaminergic medication may help stabilize motor symptoms in Parkinson's disease, very few therapies are currently available to improve cognitive deficits or stop their decline.

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