Coming in handy: CeTI-Age - A comprehensive database of kinematic hand movements across the lifespan.

The Tactile Internet aims to advance human-human and human-machine interactions that also utilize hand movements in real, digitized, and remote environments. Attention to elderly generations is necessary to make the Tactile Internet age inclusive. We present the first age-representative kinematic database consisting of various hand gesturing and grasping movements at individualized paces, thus capturing naturalistic movements. We make this comprehensive database of kinematic hand movements across the adult lifespan (CeTI-Age-Kinematic-Hand) publicly available to facilitate a deeper understanding of intra-individual-focusing especially on age-related differences-and inter-individual variability in hand kinematics. The core of the database contains participants' hand kinematics recorded with wearable resistive bend sensors, individual static 3D hand models, and all instructional videos used during the data acquisition. Sixty-three participants ranging from age 20 to 80 years performed six repetitions of 40 different naturalistic hand movements at individual paces. This unique database with data recorded from an adult lifespan sample can be used to advance machine-learning approaches in hand kinematic modeling and movement prediction for age-inclusive applications.

Individual resting-state alpha peak frequency and within-trial changes in alpha peak frequency both predict visual dual-pulse segregation performance.

Although sensory input is continuous, information must be combined over time to guide action and cognition, leading to the proposal of temporal sampling windows. A number of studies have suggested that a 10-Hz sampling window might be involved in the "frame rate" of visual processing. To investigate this, we tested the ability of participants to localize and enumerate 1 or 2 visual flashes presented either at near-threshold or full-contrast intensities, while recording magnetoencephalography. The inter-stimulus interval (ISI) between the 2 flashes was varied across trials. Performance in distinguishing between 1 and 2 flashes was linked to the alpha frequency, both at the individual level and trial-by-trial. Participants with a higher resting-state alpha peak frequency showed the greatest improvement in performance as a function of ISI within a 100-ms time window, while those with slower alpha improved more when ISI exceeded 100 ms. On each trial, correct enumeration (1 vs. 2) performance was paired with faster pre-stimulus instantaneous alpha frequency. Our results suggest that visual sampling/processing speed, linked to peak alpha frequency, is both an individual trait and can vary in a state-dependent manner.

Perceptual Quality Assessment of Compressed Vibrotactile Signals Through Comparative Judgment.

In this article, we present a comprehensive scheme for the quality assessment of compressed vibrotactile signals with human assessors. Inspired by the multiple stimulus test with hidden reference and anchors (MUSHRA) from the audio domain, we designed a method in which each compressed signal is compared to its original signal and rated on a numerical scale. For each signal tested, the hidden reference and two anchor signals are used to validate the results and provide assessor screening criteria. Differing from previous approaches, our method is hierarchically structured and strictly timed in a sequential manner to avoid experimental confounds and provide precise psychophysical assessments. We validated our method in an experiment with 20 human participants in which we compared two state-of-the-art lossy codecs. The results show that, with our approach, the performance of different codecs can be compared effectively. Furthermore, the method also provides a measure of subjective quality at different data compression rates. The proposed procedure can be easily adapted to evaluate other vibrotactile codecs.

Temporal Integration Windows in Neural Processing and Perception Aligned to Saccadic Eye Movements.

When processing dynamic input, the brain balances the opposing needs of temporal integration and sensitivity to change. We hypothesized that the visual system might resolve this challenge by aligning integration windows to the onset of newly arriving sensory samples. In a series of experiments, human participants observed the same sequence of two displays separated by a brief blank delay when performing either an integration or segregation task. First, using magneto-encephalography (MEG), we found a shift in the stimulus-evoked time courses by a 150-ms time window between task signals. After stimulus onset, multivariate pattern analysis (MVPA) decoding of task in occipital-parietal sources remained above chance for almost 1 s, and the task-decoding pattern interacted with task outcome. In the pre-stimulus period, the oscillatory phase in the theta frequency band was informative about both task processing and behavioral outcome for each task separately, suggesting that the post-stimulus effects were caused by a theta-band phase shift. Second, when aligning stimulus presentation to the onset of eye fixations, there was a similar phase shift in behavioral performance according to task demands. In both MEG and behavioral measures, task processing was optimal first for segregation and then integration, with opposite phase in the theta frequency range (3-5 Hz). The best fit to neurophysiological and behavioral data was given by a dampened 3-Hz oscillation from stimulus or eye fixation onset. The alignment of temporal integration windows to input changes found here may serve to actively organize the temporal processing of continuous sensory input.