Transcranial direct current stimulation preconditioning modulates the effect of high-frequency repetitive transcranial magnetic stimulation in the human motor cortex

Experimental studies emphasize the importance of homeostatic plasticity as a mean of stabilizing the properties of neural circuits. In the present work we combined two techniques able to produce short-term (5-Hz repetitive transcranial magnetic stimulation, rTMS) and long-term (transcranial direct current stimulation, tDCS) effects on corticospinal excitability to evaluate whether and how the effects of 5-Hz rTMS can be tuned by tDCS preconditioning. Twelve healthy subjects participated in the study. Brief trains of 5-Hz rTMS were applied to the primary motor cortex at an intensity of 120% of the resting motor threshold, with recording of the electromyograph traces evoked by each stimulus of the train from the contralateral abductor pollicis brevis muscle. This interventional protocol was preconditioned by 15 min of anodal or cathodal tDCS delivered at 1.5 mA intensity. Our results showed that motor-evoked potentials (MEPs) increased significantly in size during trains of 5-Hz rTMS in the absence of tDCS preconditioning. After facilitatory preconditioning with anodal tDCS, 5-Hz rTMS failed to produce progressive MEP facilitation. Conversely, when 5-Hz rTMS was preceded by inhibitory cathodal tDCS, MEP facilitation was not abolished. These findings may give insight into the mechanisms of homeostatic plasticity in the human cerebral cortex, suggesting also more suitable applications of tDCS in a clinical setting.     

Sleep quality in caregivers of patients with Alzheimer's disease and Parkinson's disease and its relationship to quality of life

ABSTRACT Background: Knowledge about sleep complaints of caregivers of patients with Alzheimer's disease (AD) and Parkinson's disease (PD) is limited, and we lack information about the relationship between caregivers' sleep problems and their quality of life (QoL). Methods: We evaluated subjective sleep quality and its relationship to QoL in a group of 80 caregivers of patients with AD (ADCG, n = 40) and PD (PDCG, n = 40), and in 150 controls. Information about night-time complaints was collected using the Pittsburgh Sleep Quality Index (PSQI). QoL was measured using the McGill QoL Questionnaire. Results: Eighteen ADCG (45%), 22 PDCG (55%), and 45 (30%) controls reported poor sleep quality. Mean global PSQI score of PDCG (6.25 ± 3.9) was not significantly different from that of ADCG (5.8 ± 3.5; p = 0.67). However, both PDCG and ADCG scored significantly higher than control group (4.3 ± 3.1; p < 0.01). ADCG frequently reported difficulties falling asleep (72.5%) and disturbed sleep (100%). PDCG reported reduced subjective sleep quality (80%) and increased sleep disturbances (100%). Poor sleep quality was associated with depressive symptoms and correlated with QoL in caregivers of both groups, particularly the psychological symptoms domain. Conclusions: Among caregivers of patients with AD and PD, poor sleep quality is frequent and significantly linked to QoL and depressive symptoms. Identifying the nature of sleep disturbances not only in patients but also in their caregivers is important as appropriate treatment may lead to a better management of the needs of families coping with these patients.     

Bone mineral density in adult patients treated with various antiepileptic drugs

There is considerable evidence suggesting, that older antiepileptic drugs (AEDs) and some of the newer ones decrease bone mineral density (BMD). However, there is only limited and conflicting data concerning the effect of levetiracetam on BMD. In this cross-sectional study we analysed data from 168 adult consecutive outpatients treated with AEDs for more than 2 years, and who underwent measurement of the BMD. We compared the incidence of decreased BMD among the patients treated with 6 different AEDs: carbamazepine (CBZ), oxcarbazepine (OXC), valproic acid (VPA), lamotrigine (LTG), topiramate (TPM) and levetiracetam (LEV). Among the patients on monotherapy, reduced BMD was present significantly most often in patients treated with LEV and those treated with OXC. In the group of patients on polytherapy there was no significant difference in the incidence of low BMD among patients treated with various AEDs. Our data suggest that patients on long-term treatment with LEV have a higher risk for affection of bone density.     

A novel autosomal dominant GDAP1 mutation in an Italian CMT2 family

We report the clinical, electrophysiological, and skin biopsy findings of an Italian Charcot-Marie-Tooth disease type 2 (CMT2) family with a novel heterozygous GDAP1 mutation. We observed a marked intra-familial phenotypic variability, in age at onset and disease severity which ranged from a typical CMT phenotype to an asymptomatic status. Electrophysiological study, consistent with an axonal sensory-motor neuropathy, confirmed a different degree of severity and disclosed minimal electrophysiological abnormalities also in the asymptomatic subjects. Skin biopsy findings showed a variable loss of large and small somatic nerve fibers. Molecular analysis identified a novel heterozygous missense mutation (Arg120Gly) in the GDAP1 gene which co-segregated with the disease within the pedigree. In conclusion, our findings confirm that the GDAP1 autosomal dominant mutations underlie a pronounced phenotypic variability, mimicking the effects of reduced penetrance. Notably, electrophysiological study in this family allowed to reveal hidden positive family history and assess a dominant inheritance pattern, revealing subclinical neuropathy in asymptomatic mutation carriers.     

Eye movements modulate the spatiotemporal dynamics of word processing

Active reading requires coordination between frequent eye movements (saccades) and short fixations in text. Yet, the impact of saccades on word processing remains unknown, as neuroimaging studies typically employ constant eye fixation. Here we investigate eye-movement effects on word recognition processes in healthy human subjects using anatomically constrained magnetoencephalography, psychophysical measurements, and saccade detection in real time. Word recognition was slower and brain responses were reduced to words presented early versus late after saccades, suggesting an overall transient impairment of word processing after eye movements. Response reductions occurred early in visual cortices and later in language regions, where they colocalized with repetition priming effects. Qualitatively similar effects occurred when words appeared early versus late after background movement that mimicked saccades, suggesting that retinal motion contributes to postsaccadic inhibition. Further, differences in postsaccadic and background-movement effects suggest that central mechanisms also contribute to postsaccadic modulation. Together, these results suggest a complex interplay between visual and central saccadic mechanisms during reading.