Repeated Spiral Drawings in Essential Tremor: a Possible Limb-Based Measure of Motor Learning.

To investigate changes in tremor severity over repeated spiral drawings to assess whether learning deficits can be evaluated directly in a limb in essential tremor (ET). A motor learning deficit in ET, possibly mediated by cerebellar pathways, has been established in eye-blink conditioning studies, but not paradigms measuring from an affected, tremulous limb. Computerized spiral analysis captures multiple characteristics of Archimedean spirals and quantifies performance through calculated indices. Sequential spiral drawing has recently been suggested to demonstrate improvement across trials among ET subjects. One hundred and sixty-one ET and 80 age-matched control subjects drew 10 consecutive spirals on a digitizing tablet. Degree of severity (DoS), a weighted, computational score of spiral execution that takes into account spiral shape and line smoothness, previously validated against a clinical rating scale, was calculated in both groups. Tremor amplitude (Ampl), an independent index of tremor size, measured in centimeters, was also calculated. Changes in DoS and Ampl across trials were assessed using linear regression with slope evaluations. Both groups demonstrated improvement in DoS across trials, but with less improvement in the ET group compared to controls. Ampl demonstrated a tendency to worsen across trials in ET subjects. ET subjects demonstrated less improvement than controls when drawing sequential spirals, suggesting a possible motor learning deficit in ET, here captured in an affected limb. DoS improved independently of Ampl, showing that DoS and Ampl are separable motor physiologic components in ET that may be independently mediated.

Digitized spiral analysis may be a potential biomarker for brachial dystonia.

INTRODUCTION: Objective measures for detection and quantification of dystonic movements may guide both diagnosis and clinical monitoring. Digitized spiral analysis is a non-invasive method used to assess upper limb motor control in movement disorders and may have utility in dystonia. We aimed to determine if digitized spiral analysis can distinguish dystonia subjects from controls, and evaluated correlation with a validated clinical rating scale. METHODS: Kinematic, dynamic, and spatial attributes of Archimedean spirals drawn with an inking pen on a digitizing tablet were compared for participants with brachial dystonia and either Tor1A (DYT1) (n = 15) or THAP1 (DYT6) mutations (n = 12) and age and gender matched controls (n = 27) using Receiver Operator Characteristics (ROC) analysis. Spiral indices including an overall degree of severity (DoS) were also calculated and correlated with clinical severity ratings as measured by the Burke-Fahn-Marsden scale. RESULTS: Dystonia spirals had significantly higher severity scores as well as higher measures of spiral irregularity compared to controls. ROC analysis demonstrated that the DoS score had good discriminative ability to distinguish dystonia spirals from controls, with an Area Under the Curve (AUC) of 0.87. Measures of spiral irregularity correlated with validated clinical rates of dystonia severity in the analyzed arm, with one particular index, Residue of Theta vs R, showing the highest correlation (r = 0.55, p = 0.005). CONCLUSION: Digitized spiral analysis may be a promising non-invasive method to objectively quantify brachial dystonia. It may also be a useful way to monitor subtle changes in dystonia severity over time not captured with current clinical rating scales.

GABAergic inhibition gates excitatory LTP in perirhinal cortex.

The perirhinal cortex (PRh) is a key region downstream of auditory cortex (ACx) that processes familiarity linked mnemonic signaling. In gerbils, ACx-driven EPSPs recorded in PRh neurons are largely shunted by GABAergic inhibition (Kotak et al., 2015, Frontiers in Neural Circuits, 9). To determine whether inhibitory shunting prevents the induction of excitatory long-term potentiation (e-LTP), we stimulated ACx-recipient PRh in a brain slice preparation using theta burst stimulation (TBS). Under control conditions, without GABA blockers, the majority of PRh neurons exhibited long-term depression. A very low concentration of bicuculline increased EPSP amplitude, but under this condition TBS did not significantly increase e-LTP induction. Since PRh synaptic inhibition included a GABAB receptor-mediated component, we added a GABAB receptor antagonist. When both GABAA and GABAB receptors were blocked, TBS reliably induced e-LTP in a majority of PRh neurons. We conclude that GABAergic transmission is a vital mechanism regulating e-LTP induction in the PRh, and may be associated with auditory learning.

Sensory processing in Huntington's disease.

OBJECTIVE: An intriguing electrophysiological feature of patients with Huntington's disease (HD) is the delayed latency and decreased amplitude of somatosensory long-latency evoked potentials (LLeps). We investigated whether such dysfunction was associated with delayed conscious perception of the sensory stimulus. METHODS: Sixteen HD patients and 16 control subjects faced a computer screen showing the Libet's clock (Libet et al., 1983). In Rest trials, subjects had to memorize the position of the clock handle at perception of either electrical or thermal stimuli (AW). In React, additionally, they were asked to make a fist with their right hand, in a simple reaction time task (SRT). LLseps were recorded from Cz in both conditions. RESULTS: LLeps negative peak latency (N2) and SRT were abnormally delayed in patients in all conditions. AW was only abnormally prolonged in the React condition but the time difference between AW and the negative peak of the LLeps was not different in the two groups. There was a significant negative correlation between SRT and AW or LLeps amplitude in patients but not in healthy subjects. CONCLUSION: Our HD patients did not show abnormalities in conscious perception of sensory stimuli but their LLeps abnormalities were more marked when they had to react. This is compatible with failure to detect stimulus salience rather than with a cognitive defect. SIGNIFICANCE: HD patients at early stages of the disease have preserved subjective perception of sensation but faulty sensorimotor integration.

Osteoporosis and metabolic syndrome according to socio-economic status, contribution of PTH, vitamin D and body weight: The Canarian Osteoporosis Poverty Study (COPS).

BACKGROUND: Poverty is associated with a great number of diseases, but the prevalence of vitamin D deficiency, secondary hyperparathyroidism and the potential association of osteoporosis, osteoporotic fractures and metabolic syndrome in this situation are less well known. OBJECTIVE: To evaluate the associations between poverty, bone density, fragility fractures and metabolic syndrome in a population of southern European postmenopausal women. Also, to assess the potential role of vitamin D and parathyroid hormone (PTH) levels in these associations. METHOD: Cross-sectional study was carried out in 1 250 postmenopausal Caucasian Spanish women. The socio-economic status of the participants was determined after a personal interview, according to the criteria of the Spanish Institute of Statistics. Participants were divided into two socio-economic levels: low (poverty) and medium or high socioeconomic level. The study protocol included a health questionnaire, a complete physical examination, lateral radiograph of the dorsal and lumbar spine and measurement of bone mineral density (BMD) at the lumbar spine (L2-L4) and proximal femur. Fasting blood was obtained to measure 25-hydroxy-vitamin D (25-OHD), intact PTH and selected biochemical variables. RESULTS: Low socio-economic status was associated with 25-OHD insufficiency, higher values of PTH, higher body weight and body mass index (BMI), lower values of BMD at the lumbar spine and a higher prevalence of fragility fractures, both vertebral and nonvertebral. Poverty was also associated with higher prevalence of metabolic syndrome, but this association was driven mainly by the higher BMI and not by poverty itself. Both vitamin D insufficiency and elevated PTH were consistently related to poverty and osteoporotic fractures. CONCLUSIONS: Poor postmenopausal women in southern Europe have a high prevalence of metabolic syndrome and osteoporotic fractures. Poverty was associated with higher BMI and metabolic syndrome on the one hand and, on the other, with 25OHD insufficiency, higher PTH levels and osteoporosis. 25OHD insufficiency and/or secondary hyperparathyroidism do not have a significant influence on the presence of metabolic syndrome in this population.