Incidental visual processing of spatiotemporal cues in communicative interactions: An fMRI investigation

The interpretation of social interactions between people is important in many daily situations. The coordination of the relative body movements between them may provide visual cues that observers use without attention to discriminate such social interactions from the actions of people acting independently of each other. Previous studies highlighted brain regions involved in the visual processing of interacting versus independently acting people, including posterior superior temporal sulcus, and areas of lateral occipitotemporal and parietal cortices. Unlike these previous studies, we focused on the incidental visual processing of social interactions; that is, the processing of the body movements outside the observers’ focus of attention. In the current study, we used functional imaging to measure brain activation while participants were presented with point-light dyads portraying communicative interactions or individual actions. However, their task was to discriminate the brightness of two crosses also on the screen. To investigate brain regions that may process the spatial and temporal relationships between the point-light displays, we either reversed the facingdirection of one agent or spatially scrambled the local motion of the points. Incidental processing of communicative interactions elicited activation in right anterior STS only when the two agents were facing each other. Controlling for differences in local motion by subtracting brain activation to scrambled versions of the point-light displays revealedsignificant activation in parietal cortex for communicative interactions, as well as left amygdala and brain stem/cerebellum. Our results complement previous studies and suggest that additional brain regions may be recruited to incidentally process the spatial and temporal contingencies that distinguish people acting together from people acting individually

Evoked compound action potential (ECAP)-controlled closed-loop spinal cord stimulation in an experimental model of neuropathic pain in rats

\ua9 2023, The Author(s).Background: Preclinical models of spinal cord stimulation (SCS) are lacking objective measurements to inform translationally applicable SCS parameters. The evoked compound action potential (ECAP) represents a measure of dorsal column fiber activation. This measure approximates the onset of SCS-induced sensations in humans and provides effective analgesia when used with ECAP-controlled closed-loop (CL)-SCS systems. Therefore, ECAPs may provide an objective surrogate for SCS dose in preclinical models that may support better understanding of SCS mechanisms and further translations to the clinics. This study assessed, for the first time, the feasibility of recording ECAPs and applying ECAP-controlled CL-SCS in freely behaving rats subjected to an experimental model of neuropathic pain. Methods: Adult male Sprague–Dawley rats (200–300 g) were subjected to spared nerve injury (SNI). A custom-made six-contact lead was implanted epidurally covering T11-L3, as confirmed by computed tomography or X-ray. A specially designed multi-channel system was used to record ECAPs and to apply ECAP-controlled CL-SCS for 30 min at 50 Hz 200 \ub5s. The responses of dorsal column fibers to SCS were characterized and sensitivity towards mechanical and cold stimuli were assessed to determine analgesic effects from ECAP-controlled CL-SCS. Comparisons between SNI rats and their controls as well as between stimulation parameters were made using omnibus analysis of variance (ANOVA) tests and t-tests. Results: The recorded ECAPs showed the characteristic triphasic morphology and the ECAP amplitude (mV) increased as higher currents (mA) were applied in both SNI animals and controls (SNI SCS-ON and sham SCS-ON). Importantly, the use of ECAP-based SCS dose, implemented in ECAP-controlled CL-SCS, significantly reduced mechanical and cold hypersensitivity in SNI SCS-ON animals through the constant and controlled activation of dorsal column fibers. An analysis of conduction velocities of the evoked signals confirmed the involvement of large, myelinated fibers. Conclusions: The use of ECAP-based SCS dose implemented in ECAP-controlled CL-SCS produced analgesia in animals subjected to an experimental model of neuropathic pain. This approach may offer a better method for translating SCS parameters between species that will improve understanding of the mechanisms of SCS action to further advance future clinical applications

A Complete Pipeline for Heart Rate Extraction from Infant ECGs

\ua9 2024 by the authors.Infant electrocardiograms (ECGs) and heart rates (HRs) are very useful biosignals for psychological research and clinical work, but can be hard to analyse properly, particularly longform (≥5 min) recordings taken in naturalistic environments. Infant HRs are typically much faster than adult HRs, and so some of the underlying frequency assumptions made about adult ECGs may not hold for infants. However, the bulk of publicly available ECG approaches focus on adult data. Here, existing open source ECG approaches are tested on infant datasets. The best-performing open source method is then modified to maximise its performance on infant data (e.g., including a 15 Hz high-pass filter, adding local peak correction). The HR signal is then subsequently analysed, developing an approach for cleaning data with separate sets of parameters for the analysis of cleaner and noisier HRs. A Signal Quality Index (SQI) for HR is also developed, providing insights into where a signal is recoverable and where it is not, allowing for more confidence in the analysis performed on naturalistic recordings. The tools developed and reported in this paper provide a base for the future analysis of infant ECGs and related biophysical characteristics. Of particular importance, the proposed solutions outlined here can be efficiently applied to real-world, large datasets

Insect Brains Use Image Interpolation Mechanisms to Recognise Rotated Objects

Recognising complex three-dimensional objects presents significant challenges to visual systems when these objects are rotated in depth. The image processing requirements for reliable individual recognition under these circumstances are computationally intensive since local features and their spatial relationships may significantly change as an object is rotated in the horizontal plane. Visual experience is known to be important in primate brains learning to recognise rotated objects, but currently it is unknown how animals with comparatively simple brains deal with the problem of reliably recognising objects when seen from different viewpoints. We show that the miniature brain of honeybees initially demonstrate a low tolerance for novel views of complex shapes (e.g. human faces), but can learn to recognise novel views of stimuli by interpolating between or ‘averaging’ views they have experienced. The finding that visual experience is also important for bees has important implications for understanding how three dimensional biologically relevant objects like flowers are recognised in complex environments, and for how machine vision might be taught to solve related visual problems

The integration of occlusion and disparity information for judging depth in autism spectrum disorder

In autism spectrum disorder (ASD), atypical integration of visual depth cues may be due to flattened perceptual priors or selective fusion. The current study attempts to disentangle these explanations by psychophysically assessing within-modality integration of ordinal (occlusion) and metric (disparity) depth cues while accounting for sensitivity to stereoscopic information. Participants included 22 individuals with ASD and 23 typically developing matched controls. Although adults with ASD were found to have significantly poorer stereoacuity, they were still able to automatically integrate conflicting depth cues, lending support to the idea that priors are intact in ASD. However, dissimilarities in response speed variability between the ASD and TD groups suggests that there may be differences in the perceptual decision-making aspect of the task

A stereo advantage in generalizing over changes in viewpoint on object recognition tasks

Four experiments examined whether generalization to unfamiliar views was better under stereo viewing as opposed to nonstereo viewing across different tasks and stimuli. The first three experiments used a sequential matching task in which observers matched the identity of shaded tube-like objects. Across Experiments 1-3, we manipulated the presentation method of the nonstereo stimuli (eye-patch versus showing the same screen image) and the magnitude of the viewpoint change (30° versus 38°). In Experiment 4, observers identified “easy” and “hard” rotating wireframe objects at the individual level under stereo and nonstereo viewing conditions. We found a stereo advantage for generalizing to unfamiliar views in all experiments. However, in these experiments, performance remained view-dependent even under stereo viewing. These results strongly argue against strictly 2D image-based models of object recognition, at least for the stimuli and recognition tasks used, and they suggest that observers used representations that contained view-specific local depth information