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Frontiers in Neurology 2024Spatial orientation refers to the perception of relative location and self-motion in space. The accurate formation of spatial orientation is essential for animals to...
INTRODUCTION
Spatial orientation refers to the perception of relative location and self-motion in space. The accurate formation of spatial orientation is essential for animals to survive and interact safely with their environment. The formation of spatial orientation involves the integration of sensory inputs from the vestibular, visual, and proprioceptive systems. Vestibular organs function as specialized head motion sensors, providing information regarding angular velocity and linear acceleration via the semicircular canals and otoliths, respectively. However, because forces arising from the linear acceleration (translation) and inclination relative to the gravitational axis (tilt) are equivalent, they are indistinguishable by accelerometers, including otoliths. This is commonly referred to as the tilt - translation ambiguity, which can occasionally lead to the misinterpretation of translation as a tilt. The major theoretical frameworks addressing this issue have proposed that the interpretation of tilt versus translation may be contingent on an animal's previous experiences of motion. However, empirical confirmation of this hypothesis is lacking.
METHODS
In this study, we conducted a behavioral experiment using goldfish to investigate how an animal's motion experience influences its interpretation of tilt vs. translation. We examined a reflexive eye movement called the vestibulo-ocular reflex (VOR), which compensatory-rotates the eyes in response to head motion and is known to reflect an animal's three-dimensional head motion estimate.
RESULTS
We demonstrated that the VORs of naïve goldfish do not differentiate between translation and tilt at 0.5 Hz. However, following prolonged visual-translation training, which provided appropriate visual stimulation in conjunction with translational head motion, the VORs were capable of distinguishing between the two types of head motion within 3 h. These results were replicated using the Kalman filter model of spatial orientation, which incorporated the variable variance of process noise corresponding to the accumulated motion experience.
DISCUSSION
Based on these experimental and computational findings, we discuss the neural mechanism underlying the resolution of tilt-translation ambiguity within a context analogous to, yet distinct from, previous cross-axis VOR adaptations.
PubMed: 38774058
DOI: 10.3389/fneur.2024.1304496 -
BioRxiv : the Preprint Server For... May 2024Our understanding of how vision functions as primates actively navigate the real-world is remarkably sparse. As most data have been limited to chaired and typically...
Our understanding of how vision functions as primates actively navigate the real-world is remarkably sparse. As most data have been limited to chaired and typically head-restrained animals, the synergistic interactions of different motor actions/plans inherent to active sensing - e.g. eyes, head, posture, movement, etc. - on visual perception are largely unknown. To address this considerable gap in knowledge, we developed an innovative wireless head-mounted eye tracking system called for small mammals, such as marmoset monkeys. Our system performs hair-free ye-cording using ackpack mounted miccontrollers. Because eye illumination and environment lighting change continuously in natural contexts, we developed a segmentation artificial neural network to perform robust pupil tracking in these conditions. Leveraging this innovative system to investigate active vision, we demonstrate that although freely-moving marmosets exhibit frequent compensatory eye movements equivalent to other primates, including humans, the predictability of the visual system is enhanced when animals are freely-moving relative to when they are head-fixed. Moreover, despite increases in eye/head-motion during locomotion, gaze stabilization actually improved over periods when the monkeys were stationary. Rather than impair vision, the dynamics of gaze stabilization in freely-moving primates has been optimized over evolution to enable active sensing during natural exploration.
PubMed: 38766147
DOI: 10.1101/2024.05.11.593707 -
Brain Stimulation 2024Phase synchronization over long distances underlies inter-areal communication and importantly, modulates the flow of information processing to adjust to cognitive...
BACKGROUND
Phase synchronization over long distances underlies inter-areal communication and importantly, modulates the flow of information processing to adjust to cognitive demands.
OBJECTIVE
This study investigates the impact of single-session, cross-frequency (Alpha-Gamma) bifocal transcranial alternating current stimulation (cf-tACS) to the cortical visual motion network on inter-areal coupling between the primary visual cortex (V1) and the medio-temporal area (MT) and on motion direction discrimination.
METHODS
Based on the well-established phase-amplitude coupling (PAC) mechanism driving information processing in the visual system, we designed a novel directionally tuned cf-tACS protocol. Directionality of information flow was inferred from the area receiving low-frequency tACS (e.g., V1) projecting onto the area receiving high-frequency tACS (e.g., MT), in this case, promoting bottom-up information flow (Forward-tACS). The control condition promoted the opposite top-down connection (from MT to V1, called Backward-tACS), both compared to a Sham-tACS condition. Task performance and EEG activity were recorded from 45 young healthy subjects. An additional cohort of 16 stroke patients with occipital lesions and impairing visual processing was measured to assess the influence of a V1 lesion on the modulation of V1-MT coupling.
RESULTS
The results indicate that Forward cf-tACS successfully modulated bottom-up PAC (V1 α-MT ɣ) in both cohorts, while producing opposite effects on the reverse MT-to-V1 connection. Backward-tACS did not change V1-MT PAC in either direction in healthy participants but induced a slight decrease in bottom-up PAC in stroke patients. However, these changes in inter-areal coupling did not translate into cf-tACS-specific behavioural improvements.
CONCLUSIONS
Single session cf-tACS can alter inter-areal coupling in intact and lesioned brains but is probably not enough to induce longer-lasting behavioural effects in these cohorts. This might suggest that a longer daily visual training protocol paired with tACS is needed to unveil the relationship between externally applied oscillatory activity and behaviourally relevant brain processing.
Topics: Humans; Male; Female; Stroke; Adult; Transcranial Direct Current Stimulation; Motion Perception; Young Adult; Middle Aged; Electroencephalography; Visual Cortex; Primary Visual Cortex; Aged
PubMed: 38763414
DOI: 10.1016/j.brs.2024.05.007 -
Acta Psychologica Jul 2024Depression affects a significant portion of the global adult population, with chronic pain patients being particularly susceptible to severe depression. Pain and mental...
BACKGROUND
Depression affects a significant portion of the global adult population, with chronic pain patients being particularly susceptible to severe depression. Pain and mental illness contribute to an imbalance in the autonomic nervous system, affecting heart function. Myofascial release promises to improve mental and physical health by addressing fascial dysfunctions.
OBJECTIVE
This study aims to investigate the influence of myofascial release on emotional states and autonomic nervous system functioning in individuals with chronic neck pain and depression. Additionally, it seeks to evaluate the myofascial release effect on fascial properties, pain intensity and sensitivity, and cervical spine range of motion.
METHOD
Experimental Study.
RESULT
The study revealed significant enhancements in the myofascial release group, such as a substantial reduction in pain perception and stiffness, increased range of motion of the cervical spine, heart rate variability, positive affect, and pressure pain threshold. The effect sizes of these improvements ranged from small to large. No significant differences were observed in elasticity and tone.
CONCLUSION
The findings suggest that myofascial release has a positive impact on individuals with chronic neck pain and depression, particularly in reducing pain intensity. Integrating myofascial release into treatment approaches may be beneficial. However, further research is needed to confirm and expand upon these findings, explore long-term effects, and better understand the clinical significance of certain outcomes.
TRIAL REGISTRATION
http://www.osf.io, doi.org/10.17605/OSF.IO/6F5RS.
Topics: Humans; Neck Pain; Chronic Pain; Male; Female; Adult; Middle Aged; Depression; Range of Motion, Articular
PubMed: 38759583
DOI: 10.1016/j.actpsy.2024.104325 -
Neuroscience of Consciousness 2024Attributing a visual motion signal to its correct source-be that external object motion, self-motion, or some combination of both-seems effortless, and yet often...
Attributing a visual motion signal to its correct source-be that external object motion, self-motion, or some combination of both-seems effortless, and yet often involves disentangling a complex web of motion signals. Existing literature focuses on either translational motion (heading) or eye movements, leaving much to be learnt about the influence of a wider range of self-motions, such as active head rotations, on visual motion perception. This study investigated how active head rotations affect visual motion detection thresholds, comparing conditions where visual motion and head-turn direction were either congruent or incongruent. Participants judged the direction of a visual motion stimulus while rotating their head or remaining stationary, using a fixation-locked Virtual Reality display with integrated head-movement recordings. Thresholds to perceive visual motion were higher in both active-head rotation conditions compared to stationary, though no differences were found between congruent or incongruent conditions. Participants also showed a significant bias to report seeing visual motion travelling in the same direction as the head rotation. Together, these results demonstrate active head rotations increase visual motion perceptual thresholds, particularly in cases of incongruent visual and active vestibular stimulation.
PubMed: 38757119
DOI: 10.1093/nc/niae019 -
American Journal of Ophthalmology Case... Jun 2024To present a case of molecularly confirmed oculocutaneous albinism (OCA) and retinitis pigmentosa (RP).
PURPOSE
To present a case of molecularly confirmed oculocutaneous albinism (OCA) and retinitis pigmentosa (RP).
OBSERVATIONS
A 46-year-old male with a lifelong established diagnosis of OCA and baseline best corrected visual acuity (BCVA) of 20/200, presented for worsening visual acuity over the last few years. BCVA was light perception and hand motion at face for the right and left eye, respectively. Fundus exam showed hypopigmented fundi with visible choroidal vessels and blunted foveal reflexes in both eyes. Optical coherence tomography showed foveal hypoplasia and outer retinal degenerative changes not typical of OCA. Fundus autofluorescence (FAF) imaging showed focal areas of decreased signal at the fovea, similar to areas of atrophy in an age matched patient with -RP. Genetic testing identified a homozygous disease-causing variant in c.1467dup, p. (Ala490Cysfs*20) causing OCA, and a homozygous pathogenic variant c.304C > A, p. (Arg102Ser) in causing autosomal recessive RP.
CONCLUSIONS AND IMPORTANCE
This is the first report of a patient with OCA and RP. The lack of pigmentary changes can make the diagnosis of RP challenging in patients with albinism. FAF can show features suggestive of RP and genetic testing can establish the diagnosis. The findings described herein may help physicians diagnose an extremely rare phenotype.
PubMed: 38745847
DOI: 10.1016/j.ajoc.2024.102068 -
Frontiers in Behavioral Neuroscience 2024The physicality of the world in which the animal acts-its anatomical structure, physiology, perception, emotional states, and cognitive capabilities-determines the...
The physicality of the world in which the animal acts-its anatomical structure, physiology, perception, emotional states, and cognitive capabilities-determines the boundaries of the behavioral space within which the animal can operate. Behavior, therefore, can be considered as the subspace that remains after secluding all actions that are not available to the animal due to constraints. The very signature of being a certain creature is reflected in these limitations that shape its behavior. A major goal of ethology is to expose those constraints that carve the intricate structure of animal behavior and reveal both uniqueness and commonalities between animals within and across taxa. Exploratory behavior in an empty arena seems to be stochastic; nevertheless, it does not mean that the moving animal is a random walker. In this study, we present how, by adding constraints to the animal's locomotion, one can gradually retain the 'mousiness' that characterizes the behaving mouse. We then introduce a novel phenomenon of high mirror symmetry along the locomotion of mice, which highlights another constraint that further compresses the complex nature of exploratory behavior in these animals. We link these findings to a known neural mechanism that could explain this phenomenon. Finally, we suggest our novel finding and derived methods to be used in the search for commonalities in the motion trajectories of various organisms across taxa.
PubMed: 38741684
DOI: 10.3389/fnbeh.2024.1381852 -
Brain Stimulation 2024Virtually everyone is exposed to power-frequency MF (50/60 Hz), inducing in our body electric fields and currents, potentially modulating brain function. MF-induced...
BACKGROUND
Virtually everyone is exposed to power-frequency MF (50/60 Hz), inducing in our body electric fields and currents, potentially modulating brain function. MF-induced electric fields within the central nervous system can generate flickering visual perceptions (magnetophosphenes), which form the basis of international MF exposure guidelines and recommendations protecting workers and the general public. However, magnetophosphene perception thresholds were estimated 40 years ago in a small, unreplicated study with significant uncertainties and leaving open the question of the involved interaction site.
METHODS
We used a stimulation modality termed transcranial alternating magnetic stimulation (tAMS), delivering in situ sinusoidal electric fields comparable to transcranial alternating current stimulation (tACS). Magnetophosphene perception was quantified in 81 volunteers exposed to MF (eye or occipital exposure) between 0 and 50 mT at frequencies of 20, 50, 60 and 100 Hz.
RESULTS
Reliable magnetophosphene perception was induced with tAMS without any scalp sensation, a major advantage as compared to tACS. Frequency-dependent thresholds were quantified using binary logistic regressions hence allowing to establish condition dependent probabilities of perception. Results support an interaction between induced current density and retinal rod cells.
CONCLUSION
Beyond fundamental and immediate implications for international safety guidelines, and for identifying the interaction site underlying phosphene perception (ubiquitous in tACS experiments), our results support exploring the potential of tAMS for the differential diagnosis of retinal disorders and neuromodulation therapy.
Topics: Humans; Male; Adult; Female; Phosphenes; Transcranial Magnetic Stimulation; Visual Perception; Young Adult; Sensory Thresholds; Magnetic Fields; Middle Aged
PubMed: 38740182
DOI: 10.1016/j.brs.2024.05.004 -
Biology Open Jun 2024The common sunfish (Lepomis gibbosus) likely relies on vision for many vital behaviors that require the perception of small objects such as detection of prey items or...
The common sunfish (Lepomis gibbosus) likely relies on vision for many vital behaviors that require the perception of small objects such as detection of prey items or body marks of conspecifics. A previous study documented the single target acuity (STA) for stationary targets. Under many, if not most, circumstances, however, objects of interest are moving, which is why the current study tested the effect of the ecologically relevant parameter motion on sunfish STA. The STA was determined in two sunfish for targets moving randomly at a velocity of 3.4 deg/s. The STA for moving targets (0.144±0.002 deg) was equal to the STA for stationary targets obtained from the same fish individuals under the experimental conditions of this/the previous study. Our results contribute to a comprehensive understanding of fish vision, extending the large data set available on grating acuity.
Topics: Animals; Fishes; Vision, Ocular; Perciformes; Visual Acuity
PubMed: 38738649
DOI: 10.1242/bio.060455 -
Nature Communications May 2024Accurate perception and behavior rely on distinguishing sensory signals arising from unexpected events from those originating from our own voluntary actions. In the...
Accurate perception and behavior rely on distinguishing sensory signals arising from unexpected events from those originating from our own voluntary actions. In the vestibular system, sensory input that is the consequence of active self-motion is canceled early at the first central stage of processing to ensure postural and perceptual stability. However, the source of the required cancellation signal was unknown. Here, we show that the cerebellum combines sensory and motor-related information to predict the sensory consequences of active self-motion. Recordings during attempted but unrealized head movements in two male rhesus monkeys, revealed that the motor-related signals encoded by anterior vermis Purkinje cells explain their altered sensitivity to active versus passive self-motion. Further, a model combining responses from ~40 Purkinje cells accounted for the cancellation observed in early vestibular pathways. These findings establish how cerebellar Purkinje cells predict sensory outcomes of self-movements, resolving a long-standing issue of sensory signal suppression during self-motion.
Topics: Animals; Purkinje Cells; Male; Macaca mulatta; Head Movements; Cerebellum; Vestibule, Labyrinth; Motion Perception
PubMed: 38734715
DOI: 10.1038/s41467-024-48376-0