Cognitive and Tactile Factors Affecting Human Haptic Performance in Later Life

Background: Vision and haptics are the key modalities by which humans perceive objects and interact with their environment in a target-oriented manner. Both modalities share higher-order neural resources and the mechanisms required for object exploration. Compared to vision, the understanding of haptic information processing is still rudimentary. Although it is known that haptic performance, similar to many other skills, decreases in old age, the underlying mechanisms are not clear. It is yet to be determined to what extent this decrease is related to the age-related loss of tactile acuity or cognitive capacity. Methodology/Principal Findings: We investigated the haptic performance of 81 older adults by means of a cross-modal object recognition test. Additionally, we assessed the subjects ’ tactile acuity with an apparatus-based two-point discrimination paradigm, and their cognitive performance by means of the non-verbal Raven-Standard-Progressive matrices test. As expected, there was a significant age-related decline in performance on all 3 tests. With the exception of tactile acuity, this decline was found to be more distinct in female subjects. Correlation analyses revealed a strong relationship between haptic and cognitive performance for all subjects. Tactile performance, on the contrary, was only significantly correlated with male subjects ’ haptic performance. Conclusions: Haptic object recognition is a demanding task in old age, especially when it comes to the exploration o

Genetic regulation of Nrnx1 expression: an integrative cross-species analysis of schizophrenia candidate genes

Neurexin 1 (NRXN1) is a large presynaptic transmembrane protein that has complex and variable patterns of expression in the brain. Sequence variants in NRXN1 are associated with differences in cognition, and with schizophrenia and autism. The murine Nrxn1 gene is also highly polymorphic and is associated with significant variation in expression that is under strong genetic control. Here, we use co-expression analysis, high coverage genomic sequence, and expression quantitative trait locus (eQTL) mapping to study the regulation of this gene in the brain. We profiled a family of 72 isogenic progeny strains of a cross between C57BL/6J and DBA/2J (the BXD family) using exon arrays and massively parallel RNA sequencing. Expression of most Nrxn1 exons have high genetic correlation (r>0.6) because of the segregation of a common trans eQTL on chromosome (Chr) 8 and a common cis eQTL on Chr 17. These two loci are also linked to murine phenotypes relevant to schizophrenia and to a novel human schizophrenia candidate gene with high neuronal expression (Pleckstrin and Sec7 domain containing 3). In both human and mice, NRXN1 is co-expressed with numerous synaptic and cell signaling genes, and known schizophrenia candidates. Cross-species co-expression and protein interaction network analyses identified glycogen synthase kinase 3 beta (GSK3B) as one of the most consistent and conserved covariates of NRXN1. By using the Molecular Genetics of Schizophrenia data set, we were able to test and confirm that markers in NRXN1 and GSK3B have epistatic interactions in human populations that can jointly modulate risk of schizophrenia

To stimulate or not to stimulate? A rapid systematic review of repetitive sensory stimulation for the upper-limb following stroke

Abstract: Background: Repetitive sensory stimulation (RSS) is a therapeutic approach which involves repeated electrical stimulation of the skin’s surface to improve function. This rapid systematic review aimed to describe the current evidence for repetitive sensory stimulation (RSS) in rehabilitation of the upper-limb for people who have had a stroke. Main text: Methods: Relevant studies were identified in a systematic search of electronic databases and hand-searching in February 2020. The findings of included studies were synthesized to describe: the safety of RSS, in whom and when after stroke it has been used, the doses used and its effectiveness. Results: Eight studies were included. No serious adverse events were reported. The majority of studies used RSS in participants with mild or moderate impairments and in the chronic stage after stroke. Four studies used RSS in a single treatment session, reporting significant improvements in strength and hand function. Findings from longitudinal studies showed few significant differences between control and experimental groups. Meta-analysis was not possible due to the heterogeneity of included studies. Conclusions: This review suggests that there is insufficient evidence to support the use of RSS for the upper-limb after stroke in clinical practice. However, this review highlights several clear research priorities including establishing the mechanism and in whom RSS may work, its safety and optimal treatment parameters to improve function of the upper-limb after stroke

Age-related changes in the joint position sense of the human hand

Tobias Kalisch,1,2,* Jan-Christoph Kattenstroth,2,* Rebecca Kowalewski,2 Martin Tegenthoff,1 Hubert R Dinse21Department of Neurology, BG-Kliniken Bergmannsheil, Ruhr-University Bochum, Bochum, Germany; 2Neural Plasticity Lab, Institute for Neuroinformatics, Ruhr-University Bochum, Bochum, Germany*These authors contributed equally to this workAbstract: Age-related changes in lower limb joint position sense and their contributions to postural stability are well documented. In contrast, only a few studies have investigated the effect of age on proprioceptive hand function. Here, we introduce a novel test for measuring joint position sense in the fingers of the human hand. In a concurrent matching task, subjects had to detect volume differences between polystyrene balls grasped with their dominant (seven test stimuli: 126–505 cm3) and their nondominant hand (three reference stimuli: 210, 294, and 505 cm3). A total of 21 comparisons were performed to assess the number of errors, the weight of errors (ie, the volume difference between test and reference stimuli), and the direction of errors (ie, over- or underestimation of test stimulus). The test was applied to 45 healthy subjects aged 21 to 79 years. Our results revealed that all variables changed significantly with age, with the number of errors showing the strongest increase. We also assessed tactile acuity (two-point discrimination thresholds) and sensorimotor performance (pegboard performance) in a subset of subjects, but these scores did not correlate with joint position sense performance, indicating that the test reveals specific information about joint position sense that is not captured with pure sensory or motor tests. The average test–retest reliability assessed on 3 consecutive days was 0.8 (Cronbach's alpha). Our results demonstrate that this novel test reveals age-related decline in joint position sense acuity that is independent from sensorimotor performance.Keywords: aging, hand functions, joint position sens