Neural oscillations can be modulated by non-invasive brain stimulation techniques, including transcranial alternating current stimulation (tACS). However, direct evidence of tACS effects at the cortical level in humans is still limited. In a tACS-electroencephalography co-registration setup, we investigated the ability of tACS to modulate cortical somatosensory information processing as assessed by somatosensory-evoked potentials (SEPs). To better elucidate the neural substrates of possible tACS effects we also recorded peripheral and spinal SEPs components, high-frequency oscillations (HFOs), and long-latency reflexes (LLRs). Finally, we studied whether changes were limited to the stimulation period or persisted thereafter. SEPs, HFOs, and LLRs were recorded during tACS applied at individual mu and beta frequencies and at the theta frequency over the primary somatosensory cortex (S1). Sham-tACS was used as a control condition. In a separate experiment, we assessed the time course of mu-tACS effects by recording SEPs before (T0), during (T1), and 1 min (T2) and 10 min (T3) after stimulation. Mu-tACS increased the amplitude of the N20 component of SEPs compared to both sham and theta-tACS. No differences were found between sham, beta-, and theta-tACS conditions. Also, peripheral and spinal SEPs, P25, HFOs, and LLRs did not change during tACS. Finally, mu-tACS-induced modulation of N20 amplitude specifically occurred during stimulation (T1) and vanished afterwards (i.e., at T2 and T3). Our findings suggest that TACS applied at the individual mu frequency is able to modulate early somatosensory information processing at the S1 level and the effect is limited to the stimulation period.

Non-motor symptoms (NMSs) of Parkinson’s disease (PD) were recognized by James Parkinson himself about 200 years ago and are now considered to be an integral part of PD, significantly contributing to the deterioration of patients’ quality of life. Although awareness of NMSs is growing, and several scientific societies now have dedicated non-motor study groups, the NMS burden is still the hidden face of PD and in most cases, clinicians’ views are focused on the motor symptoms alone. The literature was reviewed using several databases and scientific journals; this review provides a comprehensive description of the most common NMSs in PD, their clinical phenotype, social impact, diagnosis, and therapeutic management. Early recognition of these features may lead to more prompt and effective treatment and may help to better understand patients’ needs.

Background: Patients with frontotemporal degeneration (FTD) often manifest parkinsonism, which likely results from cortical and subcortical degeneration of brain structures involved in motor control. We used a multimodal magnetic resonance imaging (MRI) approach to investigate possible structural and/or functional alterations in FTD patients with and without parkinsonism (Park+ and Park−). Methods: Thirty FTD patients (12 Park+, 18 Park−) and 30 healthy controls were enrolled and underwent 3T MRI scanning. MRI analyses included: (1) surface-based morphometry; (2) basal ganglia and thalamic volumetry; (3) diffusion-based probabilistic tractography of fiber tracts connecting the supplementary motor area (SMA) and primary motor cortex (M1) to the putamen, globus pallidus, and thalamus; and (4) resting-state functional connectivity (RSFC) between the aforementioned regions. Results: Patients in Park+ and Park− groups showed comparable patterns of cortical thinning in frontotemporal regions and reduced thalamic volume with respect to controls. Only Park+ patients showed reduced putaminal volume and reduced fractional anisotropy of the fibers connecting the SMA to the globus pallidus, putamen, and thalamus, with respect to controls. Park+ patients also showed decreased RSFC between the SMA and putamen with respect to both Park− patients and controls. Conclusions: The present findings support the hypothesis that FTD patients with parkinsonism are characterized by neurodegenerative processes in specific corticobasal ganglia-thalamocortical motor loops.

Non-motor symptoms (NMS) of Parkinson's disease (PD) were recognized by James Parkinson himself about 200 years ago and are now considered to be an integral part of PD, significantly contributing to the worse of patients’ quality of life. Although awareness of NMS is growing, and several scientific societies have now dedicated non-motor study groups, the NMS burden is still the hidden face of PD and in most cases the clinicians’ views are focused on the motor symptoms alone. Literature research has been performed using several databases and scientific journals; this review provides a comprehensive description of the most common NMS in PD, their clinical phenotype, social impact, diagnosis, and therapeutic management. Early recognition of these features may lead to more prompt and effective treatment and may help to better understand patients’ needs.