The third-stimulus temporal discrimination threshold: focusing on the temporal processing of sensory input within primary somatosensory cortex.

The somatosensory temporal discrimination threshold (STDT) has been used in recent years to investigate time processing of sensory information, but little is known about the physiological correlates of somatosensory temporal discrimination. The objective of this study was to investigate whether the time interval required to discriminate between two stimuli varies according to the number of stimuli in the task. We used the third-stimulus temporal discrimination threshold (ThirdDT), defined as the shortest time interval at which an individual distinguishes a third stimulus following a pair of stimuli delivered at the STDT. The STDT and ThirdDT were assessed in 31 healthy subjects. In a subgroup of 10 subjects, we evaluated the effects of the stimuli intensity on the ThirdDT. In a subgroup of 16 subjects, we evaluated the effects of S1 continuous theta-burst stimulation (S1-cTBS) on the STDT and ThirdDT. Results show that ThirdDT is shorter than STDT. We found a positive correlation between STDT and ThirdDT values. As long as the stimulus intensity was within the perceivable and painless range, it did not affect ThirdDT values. S1-cTBS significantly affected both STDT and ThirdDT, although the latter was affected to a greater extent and for a longer period of time. We conclude that the interval needed to discriminate between time-separated tactile stimuli is related to the number of stimuli used in the task. STDT and ThirdDT are encoded in S1, probably by a shared tactile temporal encoding mechanism whose performance rapidly changes during the perception process. ThirdDT is a new method to measure somatosensory temporal discrimination.NEW & NOTEWORTHY To investigate whether the time interval required to discriminate between stimuli varies according to changes in the stimulation pattern, we used the third-stimulus temporal discrimination threshold (ThirdDT). We found that the somatosensory temporal discrimination acuity varies according to the number of stimuli in the task. The ThirdDT is a new method to measure somatosensory temporal discrimination and a possible index of inhibitory activity at the S1 level.

Neuroimaging correlates of blinking abnormalities in patients with progressive supranuclear palsy.

OBJECTIVE: We aimed to identify the possible relationship between blinking abnormalities and neuroimaging changes in patients with progressive supranuclear palsy. METHODS: We studied 18 patients with progressive supranuclear palsy and 13 healthy subjects. Voluntary and spontaneous blinking were recorded using kinematic techniques. Changes in brain structures were detected by T1-weighted magnetic resonance imaging and voxel-based morphometry. We then sought possible correlations between blinking and neuroimaging abnormalities in patients. RESULTS: Kinematic analysis indicated several abnormalities during voluntary blinking and a markedly reduced spontaneous blink rate in patients compared with healthy subjects. Neuroimaging showed gray matter loss in cortical and subcortical structures and lower white matter volume in the brainstem. Gray matter loss in subcortical structures correlated with the prolonged pause duration between the closing and opening phases, during voluntary blinking. CONCLUSIONS: This study provides a more specific insight into the pathophysiological mechanisms underlying blinking abnormalities in progressive supranuclear palsy.

Salivary alpha-synuclein in the diagnosis of Parkinson's disease and Progressive Supranuclear Palsy.

INTRODUCTION: Alpha-synuclein (α-syn) aggregation is the pathological hallmark of Parkinson's Disease (PD). In this study, we measured α-syn total (α-syntotal), oligomeric α-syn (α-synolig) and α-synolig/α-syntotal ratio in the saliva of patients affected by PD and in age and sex-matched healthy subjects. We also compared salivary α-syntotal measured in PD with those detected in Progressive Supranuclear Palsy (PSP), in order to assess whether salivary α-syn can be used as a biomarker for PD and for the differential diagnosis between PD and PSP. METHODS: We studied 100 PD patients, 20 patients affected by PSP and 80 age- and sex-matched healthy subjects. ELISA analysis was performed using two commercial ELISA platforms and a specific ELISA assay for α-syn aggregates. RESULTS: We detected lower α-syntotal and higher α-synolig in PD than in healthy subjects. Conversely in PSP salivary α-syntotal concentration was comparable to that measured in healthy subjects. Receiver Operating Characteristic analyses revealed specific cut-off values able to differentiate PD patients from healthy subjects and PSP patients with high sensitivity and specificity. However, there was no significant correlation between clinical and molecular data. CONCLUSION: Salivary α-syn detection could be a promising and easily accessible biomarker for PD and for the differential diagnosis between PD and PSP.

Re-emergent tremor in Parkinson's disease.

INTRODUCTION: Re-emergent tremor (RET) is a postural tremor that appears after a variable delay in patients with Parkinson's disease (PD). The aim of the present study was to evaluate the occurrence and the clinical characteristics of RET in a population of patients with PD. METHODS: We consecutively assessed 210 patients with PD. We collected the patients' demographic and clinical data. RET was clinically characterized in terms of latency, severity and body side affected. We also investigated a possible relationship with motor and non-motor symptoms and differences in the clinical features in patients with and without RET. RESULTS: RET was present in 42/210 patients. The mean latency of RET was 9.20 ± 6.8 seconds. Mean severity was 2.4 ± 1.9. RET was unilateral in 21 patients. Patients with RET had less severe speech, posture and gait disorders and upper limb and global bradykinesia than patients without RET. Similar findings were observed when we compared patients with RET with patients with tremor at rest associated with action tremor, patients with isolated action tremor and patients with no tremor. By contrast, patients with RET tremor did not clinically differ from those with isolated tremor at rest. CONCLUSION: Our results suggest that patients with RET and patients with isolated tremor at rest represent the same clinical subtype, whereas patients with action tremor (whether isolated or associated with tremor at rest) might belong to a distinct subtype that is clinically worse. Patients with RET represents a benign subtype of PD, even within the tremor-dominant phenotype.

Plasma Screening for Progranulin Mutations in Patients with Progressive Supranuclear Palsy and Corticobasal Syndromes.

Progranulin gene (GRN) mutations are characterized by heterogeneous presentations. Corticobasal syndrome (CBS) is often associated with GRN mutations, whereas association with progressive supranuclear palsy syndrome (PSPS) is rare. Plasma progranulin levels were evaluated in 34 patients, including 19 with PSPS, 12 with CBS, and 3 with mixed signs, with the purpose to screen for the presence of causal mutations, associated with low levels. We found undetectable levels in a patient with CBS. Sequencing confirmed the presence of the Thr272fs deletion. Progranulin mutation screening is suggested in cases of CBS, even in the absence of positive family history for dementia and/or movement disorders.

MRI gray and white matter measures in progressive supranuclear palsy and corticobasal syndrome.

We evaluated MRI measures of gray and white matter damages in 19 patients with progressive supranuclear palsy (PSP), 11 with corticobasal syndrome (CBS), and 14 healthy subjects (HS) to differentiate patients with PSP from those with CBS. We calculated surface-based maps of the cortical volume, cortical thickness, surface area, and voxel level maps of sub-cortical volume, and diffusion tensor imaging parameters using automated scripts implemented in FreeSurfer and FSL toolboxes. No significant differences in cortical volume loss were observed between PSP and CBS. When cortical volume was divided into cortical thickness and surface area, cortical thickness in peri-rolandic brain regions was significantly smaller in CBS than in PSP patients, whereas surface area was significantly smaller in PSP than HS. We also found widespread volume loss in sub-cortical structures in patients with PSP and CBS in comparison to HS. Both patient groups displayed diffusion tensor imaging abnormalities: compared to HS, widespread fractional anisotropy and radial diffusivity changes were observed in PSP, whereas axial and radial diffusivity changes were prominent in CBS. Mini-mental state examination positively correlated with diffusion changes in patients with PSP. In conclusion, cortical thickness, surface area, and diffusion tensor imaging parameters may be sensitive enough to help differentiate patients with PSP from those with CBS.

Correlation of protection against Japanese encephalitis virus and JE vaccine (IXIARO(®)) induced neutralizing antibody titers.

Immune sera from volunteers vaccinated in a blinded Phase 3 clinical trial with JE-VAX(®) and a new Japanese encephalitis virus (JEV) vaccine (IC51 or IXIARO), were tested for the ability to protect mice against lethal JEV challenge. Sera from IXIARO vaccinated subjects were pooled into four batches based on neutralizing antibody measured by plaque reduction neutralization test (PRNT(50) titer): high (∼200), medium (∼40-50), low (∼20) and negative (<10). Pooled sera from JE-VAX(®) vaccinated subjects (PRNT(50) titer∼55) and pooled JEV antibody negative pre-vaccination sera were used as controls. Groups of ten 6- to 7-week-old female ICR mice were injected intraperitoneally with 0.5 ml of each serum pool diluted 1:2 or 1:10, challenged approximately 18 h later with a lethal dose of either JEV strain SA14 (genotype III) or strain KE-093 (genotype I) and observed for 21 days. All mice in the non-immune serum groups developed clinical signs consistent with JEV infection or died, whereas high titer sera from both IXIARO and JE-VAX(®) sera protected 90-100% of the animals. Statistical tests showed similar protection against both JEV strains SA14 and KE-093 and protection correlated with the anti-JEV antibody titer of IXIARO sera as measured by PRNT(50). Ex vivo neutralizing antibody titers showed that almost all mice with a titer of 10 or greater were fully protected. In a separate study, analysis of geometric mean titers (GMTs) of the groups of mice vaccinated with different doses of IXIARO and challenged with JEV SA14 provided additional evidence that titers≥10 were protective.