Clock-Feedthrough Compensation in MOS Sample-and-Hold Circuits

All MOS sample-and-hold circuits suffer to a greater or lesser extent from clock-feedthrough (CLFT), also called charge-injection. During the transition from sample to hold mode, charge is transferred from an MOS transistor switch onto the hold capacitor, thus the name charge-injection. This error can lead to considerable voltage change across the capacitor, and predicting the extent of the induced error potentials is important to circuit designers. Previous studies have shown a considerable dependency of CLFT on signal voltage, circuit impedances, clock amplitude and clock fall-time. The focus of this work was on the signal dependency of the CLFT error and on the CLFT induced signal distortion in open-loop sample-and-hold circuits. CLFT was found to have a strongly non-linear, signal dependent, component, which may cause considerable distortion of the sampled signal. The parameters influencing this distortion were established. It was discovered that distortion could be reduced by more than 20dB through careful adjustment of the clock fall-rate. Several circuit solutions that can help reduce the level of distortion arising from CLFT are presented. These circuits can also reduce the absolute level of CLFT. Simulations showed their effectiveness, which was also proven in silicon. The CLFT reduction methods used in these circuits are easily transferable to other switched-capacitor circuits and are suitable for applications where space is at a premium (as, for example, in analogue neural networks). A new saturation mode contribution to CLFT was found. It is shown to give rise to increased CLFT under high injection conditions

Psychological factors associated with phantom limb pain:A review of recent findings

Phantom limb pain (PLP) is a common phenomenon occurring after the amputation of a limb and can be accompanied by serious suffering. Psychological factors have been shown to play an important role in other types of chronic pain, where they are pivotal in the acquisition and maintenance of pain symptoms. For PLP, however, the interaction between pain and psychological variables is less well documented. In this review, we summarize research on the role of emotional, motivational, cognitive, and perceptual factors in PLP. The reported findings indicate that emotional factors modulate PLP but might be less important compared to other types of chronic pain. Additional factors such as the amount of disability and adjustment to the amputation appear to also play a role. Bidirectional relationships between stress and PLP have been shown quite consistently, and the potential of stress and tension reduction in PLP treatment could be further exploited. Little is known about the role of cognitive variables such as attention or expectation. Catastrophizing seems to aggravate PLP and could be targeted in treatment. Body perception is altered in PLP and poses a potential target for novel mechanistic treatments. More research on psychological factors and their interactions in PLP is needed

The rubber hand universe:On the impact of methodological differences in the rubber hand illusion

The rubber hand illusion (RHI) is a widely applied paradigm to investigate changes in body representations. Extensive scientific interest has produced a great variability in the observed results and many contradictory findings have been reported. Taking into account the numerous variations in the experimental implementation of the RHI, many of these contradictive findings can be reconciled, but to date a thorough analysis of the methodological differences between RHI studies is lacking. Here we summarize and analyse methodological differences between RHI studies. In distinction from other reviews focusing on the integration of findings from various studies, the present paper is devoted to the differences in (i) the experimental setup, (ii) the method used to induce the RHI, (iii) the quantification of its effects, and (iv) aspects of the experimental design and data analysis. This approach will provide a reference frame for the interpretation of previous studies as well as for the design of future studies

What does “moderate pain” mean? Subgroups holding different conceptions of rating scales evaluate experimental pain differently

Background Pain ratings are almost ubiquitous in pain assessment, but their variability is high. Low correlations of continuous/numerical rating scales with categorical scales suggest that individuals associate different sensations with the same number on a scale, jeopardizing the interpretation of statistical results. We analysed individual conceptions of rating scales and whether these conceptions can be utilized in the analysis of ratings of experimental stimuli in pain‐free healthy individuals and people with reoccurring/persistent pain. Methods Using a free positioning task, healthy participants (N = 57) and people with reoccurring/persistent pain (N = 57) ad libitum positioned pain descriptors on lines representing intensity and un‐/pleasantness scales. Furthermore, participants rated experimental thermal stimuli on visual analogue scales with the same end anchors. A latent class regression approach was used to detect subgroups with different response patterns in the free positioning task, indicating different conceptions of pain labels, and tested whether these subgroups differed in their ratings of experimental stimuli. Results Subgroups representing different conceptions of pain labels could be described for the intensity and the un‐/pleasantness scale with in part opposing response patterns in the free positioning task. Response patterns did not differ between people with and without pain, but in people with pain subgroups showed differential ratings of high intensity experimental stimuli. Conclusions Individuals\u27 conceptions of pain labels differ. These conceptions can be quantified and utilized to improve the analysis of ratings of experimental stimuli. Identifying subgroups with different conceptions of pain descriptions could be used to improve predictions of responses to pain in clinical contexts. Significance The present results provide a novel approach to incorporate individual conceptualizations of pain descriptors, which can induce large distortions in the analysis of pain ratings, in pain assessment. The approach can be used to achieve better pain estimates, representing individual conceptions of pain and achieving a better comparability between individuals but also between pain‐free persons and patients with chronic pain. Particularly, in clinical settings this could improve quantification of perceived pain and the patient‐clinician communication

Brain-behaviour correlates of habitual motivation in chronic back pain

Nees F, Ruttorf M, Fuchs X, Rance M, Beyer N. Brain-behaviour correlates of habitual motivation in chronic back pain. Scientific Reports. 2020;10(1): 11090

Psychological Factors Associated with Phantom Limb Pain. A Review of Recent Findings

Fuchs X, Flor H, Bekrater-Bodmann R. Psychological Factors Associated with Phantom Limb Pain. A Review of Recent Findings. Pain Research and Management. 2018;2018(Special Issue): 5080123.Phantom limb pain (PLP) is a common phenomenon occurring after the amputation of a limb and can be accompanied by serious suffering. Psychological factors have been shown to play an important role in other types of chronic pain, where they are pivotal in the acquisition and maintenance of pain symptoms. For PLP, however, the interaction between pain and psychological variables is less well documented. In this review, we summarize research on the role of emotional, motivational, cognitive, and perceptual factors in PLP. The reported findings indicate that emotional factors modulate PLP but might be less important compared to other types of chronic pain. Additional factors such as the amount of disability and adjustment to the amputation appear to also play a role. Bidirectional relationships between stress and PLP have been shown quite consistently, and the potential of stress and tension reduction in PLP treatment could be further exploited. Little is known about the role of cognitive variables such as attention or expectation. Catastrophizing seems to aggravate PLP and could be targeted in treatment. Body perception is altered in PLP and poses a potential target for novel mechanistic treatments. More research on psychological factors and their interactions in PLP is needed

The rubber hand illusion induced by visual-thermal stimulation

Trojan J, Fuchs X, Speth S-L, Diers M. The rubber hand illusion induced by visual-thermal stimulation. Scientific Reports. 2018;8(1): 12417.In the rubber hand illusion (RHI), synchronous touch of a real hand and an artificial hand leads to the feeling of the artificial hand belonging to one’s own body. This study examined whether the RHI can be induced using visual–thermal instead of visual–tactile stimulus patterns and to which extent the congruency between temperature and colour of the visual stimulus influences the RHI. In a within-subject design, we presented cold vs. warm thermal stimuli to the participants’ hidden hand combined with red vs. blue visual stimuli presented synchronously vs. asynchronously at a fake hand. The RHI could be induced using visual–thermal stimuli, yielding RHI vividness ratings comparable to the visual-tactile variant. Congruent (warm–red, cold–blue) synchronous stimulus patterns led to higher RHI vividness than incongruent (warm–blue, cold–red) synchronous combinations; in the asynchronous conditions, an inverse effect was present. Temperature ratings mainly depended on the actual stimulus temperature and were higher with synchronous vs. asynchronous patterns; they were also slightly higher with red vs. blue light, but there were no interactions with temperature or synchrony. In conclusion, we demonstrated that the RHI can be induced via visual-thermal stimuli, opening new perspectives in research on multi-sensory integration and body representations

Perceptual drifts of real and artificial limbs in the rubber hand illusion

Fuchs X, Riemer M, Diers M, Flor H, Trojan J. Perceptual drifts of real and artificial limbs in the rubber hand illusion. Scientific Reports. 2016;6(1): 24362