Characterizing and imaging gross and real finger contacts under dynamic loading

We describe an instrument intended to study finger contacts under tangential dynamic loading. This type of loading is relevant to the natural conditions when touch is used to discriminate and identify the properties of the surfaces of objects — it is also crucial during object manipulation. The system comprises a high performance tribometer able to accurately record in vivo the components of the interfacial forces when a finger interacts with arbitrary surfaces which is combined with a high-speed, high-definition imaging apparatus. Broadband skin excitation reproducing the dynamic contact loads previously identified can be effected while imaging the contact through a transparent window, thus closely approximating the condition when the skin interacts with a non-transparent surface during sliding. As a preliminary example of the type of phenomenon that can be identified with this apparatus, we show that traction in the range from 10 to 1000 Hz tends to decrease faster with excitation frequency for dry fingers than for moist fingers

Touch uses frictional cues to discriminate flat materials

In a forced-choice task, we asked human participants to discriminate by touch alone glass plates from transparent polymethyl methacrylate (PMMA) plastic plates. While the surfaces were flat and did not exhibit geometric features beyond a few tens of nanometres, the materials differed by their molecular structures. They produced similar coefficients of friction and thermal effects were controlled. Most participants performed well above chance and participants with dry fingers discriminated the materials especially well. Current models of tactile surface perception appeal to surface topography and cannot explain our results. A correlation analysis between detailed measurements of the interfacial forces and discrimination performance suggested that the perceptual task depended on the transitory contact phase leading to full slip. This result demonstrates that differences in interfacial mechanics between the finger and a material can be sensed by touch and that the evanescent mechanics that take place before the onset of steady slip have perceptual value

Handgrip fatiguing exercise can provide objective assessment of cancer-related fatigue: a pilot study

International audiencePurpose As a subjective symptom, cancer-related fatigue is assessed via patient-reported outcomes. Due to the inherent bias of such evaluation, screening and treatment for cancer-related fatigue remains suboptimal. The purpose is to evaluate whether objective cancer patients' hand muscle mechanical parameters (maximal force, critical force, force variability) extracted from a fatiguing handgrip exercise may be correlated to the different dimensions (physical, emotional, and cognitive) of cancer-related fatigue. Methods Fourteen women with advanced breast cancer, still under or having previously received chemotherapy within the preceding 3 months, and 11 healthy women participated to the present study. Cancer-related fatigue was first assessed through the EORTC QLQ-30 and its fatigue module. Fatigability was then measured during 60 maximal repeated handgrip contractions. The maximum force, critical force (asymptote of the force-time evolution), and force variability (root mean square of the successive differences) were extracted. Multiple regression models were performed to investigate the influence of the force parameters on cancer-related fatigue's dimensions. Results The multiple linear regression analysis evidenced that physical fatigue was best explained by maximum force and critical force (r = 0.81; p = 0.029). The emotional fatigue was best explained by maximum force, critical force, and force variability (r = 0.83; p = 0.008). The cognitive fatigue was best explained by critical force and force variability (r = 0.62; p = 0.035). Conclusion The handgrip maximal force, critical force, and force variability may offer objective measures of the different dimensions of cancer-related fatigue and could provide a complementary approach to the patient reported outcomes

The Vibrotactile Experience of the HOME Button on Smartphones

The vibration of the virtual HOME button is very important for smartphone users. To understand the user experience of different vibration modes of the HOME button, we designed 2 experiments to study this issue. Study 1 compared 4 different HOME buttons that were experienced either in or out of visual sight. The results showed that the perceived intensity was the key factor related to the tactile experience of the HOME button regardless of the particular vibration mode. Study 2 explored the influence of vibration intensity on users&rsquo; tactile experiences. The results showed that the frequency and amplitude of the vibration had a significant positive relationship with the overall evaluation of the tactile experience. More importantly, this effect was mediated by the perceived intensity. These results have implications for designing vibration modes that satisfy the needs of smartphone users. &copy; 2019, Springer Nature Switzerland AG.</p

Harmonious textures: The perceptual dimensions of synthetic sinusoidal gratings

International audienceNatural gratings explored by a finger generate vibratory patterns. These vibrations contain a wide range of frequencies, which include the fundamental spatial frequency of the grating and other (higher) harmonics. In this study, it was proposed to investigate how the fundamental and harmonic frequencies contribute to the perception of a virtual grating presented in the form of spatial pattern of friction force. Using multidimensional scaling methods, we established that the first overtone was the main characteristic used by the participants to identify gratings. When asked to rate the pleasantness to the touch, participants' preferences were for gratings with low spatial frequencies and low amplitudes. These results suggest new ways of creating meaningful, pleasant human-computer interactions in the context of surface-haptic displays

Antidepressive effects of targeting ELK-1 signal transduction

International audienceDepression, a devastating psychiatric disorder, is a leadingcause of disability worldwide. Current antidepressants addressspecific symptoms of the disease, but there is vast roomfor improvement1. In this respect, new compounds that actbeyond classical antidepressants to target signal transductionpathways governing synaptic plasticity and cellular resilienceare highly warranted2–4. The extracellular signal–regulatedkinase (ERK) pathway is implicated in mood regulation5–7, butits pleiotropic functions and lack of target specificity prohibitoptimal drug development. Here, we identified the transcriptionfactor ELK-1, an ERK downstream partner8, as a specificsignaling module in the pathophysiology and treatment ofdepression that can be targeted independently of ERK. ELK1mRNA was upregulated in postmortem hippocampal tissuesfrom depressed suicides; in blood samples from depressedindividuals, failure to reduce ELK1 expression was associatedwith resistance to treatment. In mice, hippocampal ELK-1 overexpressionper se produced depressive behaviors; conversely,the selective inhibition of ELK-1 activation prevented depression-like molecular, plasticity and behavioral states inducedby stress. Our work stresses the importance of target selectivityfor a successful approach for signal-transduction-basedantidepressants, singles out ELK-1 as a depression-relevanttransducer downstream of ERK and brings proof-of-conceptevidence for the druggability of ELK-1