Head Direction Research Articles

A dynamic simulation-based methodology for systematic assessment of workability on floating wind turbines

Abstract Floating offshore wind technology experiences significant motion responses when exposed to environmental wave and wind loads, possibly interfering with technicians conducting maintenance work. Industrial interest is rising in the assessment of workability, as impairments will decrease the availability of the asset and possibly affect the business case for the wind farm project. Quantification of impairments are formed from three workability indicators: Nordforsk Seakeeping Criteria, ISO 2631-1, and ISO 6897. The present work shows a likely workability decrease, quantified to 2.4% for the Nordforsk Seakeeping Criteria, for the UMaine VolturnUS-S reference platform and the IEA 15MW reference wind turbine. Peak wave period and wave heading direction are found to affect the results and indicate the importance of conducting the study in site-representative conditions. In addition, varying results for different indicators and methodological approaches indicate the need for common rules and standards in the floating wind industry to enable transparency during project development.

Grade III Direct Head of Rectus Femoris Myotendinous Tear in a Recreational Athlete, a Case Report

The rectus femoris is a principal muscle in the quadriceps muscle group. It plays a major role in flexion of the hip and extension of the knee joint and works as an important dynamic stabilizer for both joints. This case report details the presentation, diagnosis, and treatment of a high-grade rectus femoris tear in a young physically active patient. Furthermore, we detail the mechanism of injury, clinical signs, and symptoms, in addition to images and findings used to confirm the diagnosis. Different treatment approaches are highlighted. The outcomes of conservative management in comparison with surgical intervention is explored in the literature. The aim of this case study was to contribute more to the understanding of rectus femoris tears and to shed light on various aspects associated with this rare injury.

Continuous integration of heading and goal directions guides steering.

Navigating animals must integrate a diverse array of sensory cues into a single locomotor decision. Insects perform intricate navigational feats using a brain region termed the central complex in which an animal's heading direction is transformed through several layers of circuitry to elicit goal-directed locomotion. These transformations occur mostly in the fan-shaped body (FB), a major locus of multi-sensory integration in the central complex. Key aspects of these sensorimotor computations have been extensively characterized by functional studies, leveraging the genetic tools available in the fruit fly. However, our understanding of how neuronal activity in the FB dictates locomotor behaviors during navigation remains enigmatic. Here, we manipulate the activity of two key neuronal populations that input into the FB-the PFN a and PFN d neurons-used to encode the direction of two complex navigational cues: wind plumes and optic flow, respectively. We find that flies presented with unidirectional optic flow steer along curved walking trajectories, but silencing PFN d neurons abolishes this curvature. We next use optogenetic activation to introduce a fictive heading signal in the PFNs to establish the causal relationship between their activity and steering behavior. Our studies reveal that the central complex guides locomotion by summing the PFN-borne directional signals and shifting movement trajectories left or right accordingly. Based on these results, we propose a model of central complex-mediated locomotion wherein the fly achieves fine-grained control of sensory-guided steering by continuously integrating its heading and goal directions over time.

Pott's Puffy Tumor in Young Age: A Systematic Review and Our Experience.

Background: Pott's Puffy Tumor (PPT) in young-age patients is a rare clinical entity characterized by osteomyelitis of the frontal bone with a subperiosteal abscess collection. Previous reviews primarily consist of small, retrospective case series and anecdotal reports. This study aims to present the largest, most up-to-date systematic review of essential clinical findings, diagnostic modalities, microbiologic considerations, and treatment approaches for managing PPT in pediatric and adolescent populations. Methods: PubMed, Scopus, and Web of Science databases were systematically screened until 3 January 2024. The protocol of this investigation was registered on PROSPERO in January 2024, and the systematic review was performed according to the PRISMA statement. The study included 184 patients from 109 articles and an additional case from the authors' institution. Results: PPT commonly stems from untreated rhinosinusitis, respectively, acute pansinusitis, frontal acute rhinosinusitis and chronic rhinosinusitis, and direct head trauma. Infections typically involve a polymicrobial anaerobe-predominant microbiome. Computed tomography and magnetic resonance imaging are routinely used for presurgical assessment and posttreatment surveillance. Intracranial complications were significantly associated with the type of surgical treatment (p value < 0.0001). Conclusions: PPT is a significant and relatively morbid disease often under-recognized and misdiagnosed due to its variable clinical presentation. Management includes both antimicrobial therapy and surgical intervention, emphasizing the importance of an interdisciplinary approach.

Drosophila require both green and UV wavelengths for sun orientation but lack a time-compensated sun compass.

Celestial orientation and navigation are performed by many organisms in contexts as diverse as migration, nest finding and straight-line orientation. The vinegar fly, Drosophila melanogaster, performs menotaxis in response to celestial cues during tethered flight and can disperse more than 10 km under field conditions. However, we still do not understand how spectral components of celestial cues and pauses in flight impact heading direction in flies. To assess individual heading, we began by testing flies in a rotating tether arena using a single green LED as a stimulus. We found that flies robustly perform menotaxis and fly straight for at least 20 min. Flies maintain their preferred heading directions after experiencing a period of darkness or stopping flight, even up to 2 h, but reset their heading when the LED changes position, suggesting that flies do not treat this stimulus as the sun. Next, we assessed the flies' responses to a UV spot alone or a paired UV-green stimulus - two dots situated 180deg apart to simulate the solar and antisolar hemispheres. We found that flies respond to UV much as they do to green light; however, when the stimuli are paired, flies adjust for sudden 90deg movements, performing sun orientation. Lastly, we found no evidence of a time-compensated sun compass when we moved the paired stimuli at 15degh-1 for 6 h. This study demonstrates that wavelength influences how flies respond to visual cues during flight, shaping the interpretation of visual information to execute an appropriate behavioral response.

Distinct codes for environment structure and symmetry in postrhinal and retrosplenial cortices

Complex sensory information arrives in the brain from an animal’s first-person (‘egocentric’) perspective. However, animals can efficiently navigate as if referencing map-like (‘allocentric’) representations. The postrhinal (POR) and retrosplenial (RSC) cortices are thought to mediate between sensory input and internal maps, combining egocentric representations of physical cues with allocentric head direction (HD) information. Here we show that neurons in the POR and RSC of female Long-Evans rats are tuned to distinct but complementary aspects of local space. Egocentric bearing (EB) cells recorded in square and L-shaped environments reveal that RSC cells encode local geometric features, while POR cells encode a more global account of boundary geometry. Additionally, POR HD cells can incorporate egocentric information to fire in two opposite directions with two oppositely placed identical visual landmarks, while only a subset of RSC HD cells possess this property. Entorhinal grid and HD cells exhibit consistently allocentric spatial firing properties. These results reveal significant regional differences in the neural encoding of spatial reference frames.

Presubicular VIP expressing interneurons receive facilitating excitation from anterior thalamus

The presubiculum is part of the parahippocampal cortex and plays a fundamental role for orientation in space. Many principal neurons of the presubiculum signal head direction, and show persistent firing when the head of an animal is oriented in a specific preferred direction. GABAergic neurons of the presubiculum control the timing, sensitivity and selectivity of head directional signals from the anterior thalamic nuclei. However, the role of vasoactive intestinal peptide (VIP) expressing interneurons in the presubicular microcircuit has not yet been addressed. Here, we examined the intrinsic properties of VIP interneurons as well as their input connectivity following photostimulation of anterior thalamic axons. We show that presubicular VIP interneurons are more densely distributed in superficial than in deep layers. They are highly excitable. Three groups emerged from the unsupervised cluster analysis of their electrophysiological properties. We demonstrate a frequency dependent recruitment of VIP cells by thalamic afferences and facilitating synaptic input dynamics. Our data provide initial insight into the contribution of VIP interneurons for the integration of thalamic head direction information in the presubiculum.

A behavioral analysis system MCFBM enables objective inference of songbirds’ attention during social interactions

Understanding animal behavior is crucial in behavioral neuroscience, aiming to unravel the mechanisms driving these behaviors. A significant milestone in this field is the analysis of behavioral reactions during social interactions. Despite their importance in social learning, the behavioral aspects of these interaction are not well understood in detail due to the lack of appropriate tools. We introduce a high-precision, marker-based motion-capture system for analyzing behavior in songbirds, accurately tracking body location and head direction in multiple freely moving finches during social interaction. Focusing on zebra finches, our analysis revealed variations in eye use based on individuals presented. We also observed behavioral changes during virtual and live presentations and a conditioned-learning paradigm. Additionally, the system effectively analyzed social interactions among mice. This system provides an efficient tool for advanced behavioral analysis in small animals and offers an objective method to infer their focus of attention.

Indirect Shear Wave Excitation for Brain Magnetic Resonance Elastography with Minimal Cerebral Blood Flow Alteration.

This work demonstrates the initial prototype of the indirect excitation method, which can generate shear waves in the brain with minimal changes in CBF. A simple system was designed to produce stable vibrations underneath the neck. Instead of directly stimulating the skull, shear waves were indirectly transmitted to the brain through the spine and brainstem. Phantom results showed that the proposed actuator did not interfere with the routine imaging sequence and successfully generated multifrequency shear waves. When compared with the conventional direct head stimulation method, brain MRE results from the proposed actuator showed no significant differences in terms of intraclass correlation coefficients (ICC) and coefficients of variation (CV). Moreover, the octahedral shear strain (OSS) generated by the indirect excitation in the frontal and parietal lobes decreased by 25.96% and 16.73% respectively. Evaluation of CBF in healthy volunteers revealed no significant changes for the indirect excitation method, whereas significant decreases in CBF were observed in four subregions when employing direct excitation. The proposed actuator offers a more accurate and comfortable approach to MRE measurements while causing minimal CBF alterations. This work presents the first demonstration of an indirect excitation brain MRE system that minimizes CBF changes, thus holding potential for future applications of brain MRE.

Intrinsic Bipolar Head-Direction Cells in the Medial Entorhinal Cortex.

Head-direction (HD) cells are a fundamental component in the hippocampal-entorhinal circuit for spatial navigation and help maintain an internal sense of direction to anchor the orientation in space. A classical HD cell robustly increases its firing rate when the head is oriented toward a specific direction, with each cell tuned to only one direction. Although unidirectional HD cells are reported broadly across multiple brain regions, computation modelling has predicted the existence of multiple equilibrium states of HD network, which has yet to be proven. In this study, a novel HD variant of bipolar HD cells in the medial entorhinal cortex (MEC) are identified that exhibit stable double-peaked directional tuning properties. The bipolar patterns remain stable in the darkness and across environments of distinct geometric shapes. Moreover, bipolar HD cells co-rotate coherently with unipolar HD cells to anchor the external visual cue. The discovery reveals a new spatial cell type of bipolar HD cells, whose unique activity patterns may comprise a potential building block for a sophisticated local neural circuit configuration for the internal representation of direction. These findings may contribute to the understanding of how the brain processes spatial information by shedding light on the role of bipolar HD cells in this process.

Learning to use landmarks for navigation amplifies their representation in retrosplenial cortex.

Visual landmarks provide powerful reference signals for efficient navigation by altering the activity of spatially tuned neurons, such as place cells, head direction cells, and grid cells. To understand the neural mechanism by which landmarks exert such strong influence, it is necessary to identify how these visual features gain spatial meaning. In this study, we characterized visual landmark representations in mouse retrosplenial cortex (RSC) using chronic two-photon imaging of the same neuronal ensembles over the course of spatial learning. We found a pronounced increase in landmark-referenced activity in RSC neurons that, once established, remained stable across days. Changing behavioral context by uncoupling treadmill motion from visual feedback systematically altered neuronal responses associated with the coherence between visual scene flow speed and self-motion. To explore potential underlying mechanisms, we modeled how burst firing, mediated by supralinear somatodendritic interactions, could efficiently mediate context- and coherence-dependent integration of landmark information. Our results show that visual encoding shifts to landmark-referenced and context-dependent codes as these cues take on spatial meaning during learning.

Estimating orientation in natural scenes: A spiking neural network model of the insect central complex.

The central complex of insects contains cells, organised as a ring attractor, that encode head direction. The 'bump' of activity in the ring can be updated by idiothetic cues and external sensory information. Plasticity at the synapses between these cells and the ring neurons, that are responsible for bringing sensory information into the central complex, has been proposed to form a mapping between visual cues and the heading estimate which allows for more accurate tracking of the current heading, than if only idiothetic information were used. In Drosophila, ring neurons have well characterised non-linear receptive fields. In this work we produce synthetic versions of these visual receptive fields using a combination of excitatory inputs and mutual inhibition between ring neurons. We use these receptive fields to bring visual information into a spiking neural network model of the insect central complex based on the recently published Drosophila connectome. Previous modelling work has focused on how this circuit functions as a ring attractor using the same type of simple visual cues commonly used experimentally. While we initially test the model on these simple stimuli, we then go on to apply the model to complex natural scenes containing multiple conflicting cues. We show that this simple visual filtering provided by the ring neurons is sufficient to form a mapping between heading and visual features and maintain the heading estimate in the absence of angular velocity input. The network is successful at tracking heading even when presented with videos of natural scenes containing conflicting information from environmental changes and translation of the camera.

The straight head of rectus femoris: An underdiagnosed cause of chronic pain post hip replacement

Groin pain following hip arthroplasty has a spectrum of aetiologies. Although mild post-operative pain at six months to a year is common, other causative factors should be considered where pain is severe or persistent. The rectus femoris (RF) muscle is the most common of the quadriceps tendons to be injured or strained. Pathologies are known to occur in athletic adults and children and include tendinopathy, tear, and avulsion, but the RF is rarely attributed to hip pain post-arthroplasty. However, tendinopathy may occur as a result of altered biomechanics and muscle loading. We performed a retrospective analysis of 100 patients, at our tertiary orthopedic hospital, who presented with chronic pain post hip arthroplasty. We identified three patients with RF straight (direct) head tendinopathy and one patient with RF straight (direct) head calcific tendinopathy. Established causes of chronic post-operative pain include septic/aseptic loosening, pseudotumor, iliopsoas bursitis/impingement, and bursitis. In this report, we describe the scanning technique, sonographic appearances, and our institutional experience of post-arthroplasty pathologies of the RF straight (direct) head which is an underreported cause of chronic pain following hip replacement. We also recommend including the RF straight (direct) head in routine US protocols of the post-operative hip.

Causal evidence of a line attractor encoding an affective state

Continuous attractors are an emergent property of neural population dynamics that have been hypothesized to encode continuous variables such as head direction and eye position1–4. In mammals, direct evidence of neural implementation of a continuous attractor has been hindered by the challenge of targeting perturbations to specific neurons within contributing ensembles2,3. Dynamical systems modelling has revealed that neurons in the hypothalamus exhibit approximate line-attractor dynamics in male mice during aggressive encounters5. We have previously hypothesized that these dynamics may encode the variable intensity and persistence of an aggressive internal state. Here we report that these neurons also showed line-attractor dynamics in head-fixed mice observing aggression6. This allowed us to identify and manipulate line-attractor-contributing neurons using two-photon calcium imaging and holographic optogenetic perturbations. On-manifold perturbations yielded integration of optogenetic stimulation pulses and persistent activity that drove the system along the line attractor, while transient off-manifold perturbations were followed by rapid relaxation back into the attractor. Furthermore, single-cell stimulation and imaging revealed selective functional connectivity among attractor-contributing neurons. Notably, individual differences among mice in line-attractor stability were correlated with the degree of functional connectivity among attractor-contributing neurons. Mechanistic recurrent neural network modelling indicated that dense subnetwork connectivity and slow neurotransmission7 best recapitulate our empirical findings. Our work bridges circuit and manifold levels3, providing causal evidence of continuous attractor dynamics encoding an affective internal state in the mammalian hypothalamus.

Brain Punch: K-1 Fights Affect Brain Wave Activity in Professional Kickboxers.

Kickboxing is a popular striking combat sport, and K-1 is a type of kickboxing. Direct head blows can cause significant long-term injury and affect brain wave activity. We aim to compare the changes in brain wave activities of fighters during a K-1 kickboxing contest to those in a control group, who were striking a punching bag and were not hit by another K-1 athlete. A total of 100 professional Polish K-1 kickboxers were split evenly into experimental (n = 50, age 25.5 ± 4.63years) and control (n = 50, age 26.6 ± 5.22years) groups. We used quantitative electroencephalography (QEEG) to assess the spectrum of brain wave activity (delta, theta, alpha, sensorimotor rhythm (SMR), beta-1 and beta-2) before and after an intervention (experimental: K-1 contest, control: simulated contest), with eyes open and then closed. The number of direct blows to the head was also recorded for all bouts. Comparative and statistical analyses between selected variables were performed. K-1 fighters showed elevated baseline brain activity for the entire delta band (p < 0.001). There was significant variation in brain activity among the experimental group following the intervention and compared with the control group for all wave types (p < 0.001). No significant variation in activity was found in the control group. The number of direct head blows was positively correlated with brain activity, at delta and beta-2 wave frequencies. K-1 kickboxing is associated with detectable changes in brain wave activity. It is presently unclear what the long-term effects of these changes in brain wave activities are, and longitudinal studies are necessary to study the brain health of kickboxers.

Direct Fetal Head Injury after Maternal Motor Vehicle Crash

Direct Fetal Head Injury after Maternal Motor Vehicle Crash

The effect of safety modifications on head kinematics experienced during common skills in women’s artistic gymnastics

ABSTRACT The objective of this study was to evaluate the effect of skill modifications on head motion experienced during women’s artistic gymnastics skills. Nine gymnasts (four beginner and five advanced) completed three trials of up to 24 skill progressions, each consisting of a skill and two progressive safety modifications. Gymnasts were instrumented with mouthpiece sensors embedded with an accelerometer and gyroscope collecting motion data at 200, 300, and 500 Hz during each skill performance. Peak-to-peak linear and rotational kinematics during contact phases and peak rotational kinematics during non-contact phases were computed. A mixed-effects model was used to compare differences in modification status nested within skill categories. Timer skills (i.e. drills that simulate performance of a gymnastics skill) resulted in the highest median ΔLA and ΔRA of all skill categories, and 132 skill performances exceeded 10 g ΔLA during a contact phase. Modifications were associated with significant reductions in head kinematics during contact phases of timers, floor skills, bar releases, and vault skills. Gymnasts can be exposed to direct and indirect head accelerations at magnitudes consistent with other youth contact sports, and common safety modifications may be effective at reducing head motion during contact and non-contact phases of gymnastics skills.

Synaptic ring attractor: A unified framework for attractor dynamics and multiple cues integration

Effective cue integration is essential for an animal's survival. The ring attractor network has emerged as a powerful framework for understanding how animals seamlessly integrate various cues. This network not only elucidates neural dynamics within the brain, especially in spatial encoding systems like the heading direction (HD) system, but also sheds light on cue integration within decision-making processes. Yet, many significant phenomena across different fields lack clear explanations. For instance, in physiology, the integration mechanism of Drosophila's compass neuron when confronted with conflicting self-motion cues and external sensory cues with varying gain control settings is not well elucidated. Similarly, in ethology, the decision-making system shows Bayesian integration (BI) under minimal cue conflicts, but shifts to a winner-take-all (WTA) mode as conflicts surpass a certain threshold. To address these gaps, we introduce a ring attractor network with asymmetrical neural connections and synaptic dynamics in this paper. A thorough series of simulations has been conducted to assess its ability to track external cues and integrate conflicting cues. The results from these simulations demonstrate that the proposed model replicates observed neural dynamics and offers a framework for modeling biologically plausible cue integration behaviors. Furthermore, our findings yield several testable predictions that could inform future neuroethological research, providing insights into the role of ring attractor dynamics in the animal brain.

Context-dependence of deterministic and nondeterministic contributions to closed-loop steering control.

In natural circumstances, sensory systems operate in a closed loop with motor output, whereby actions shape subsequent sensory experiences. A prime example of this is the sensorimotor processing required to align one's direction of travel, or heading, with one's goal, a behavior we refer to as steering. In steering, motor outputs work to eliminate errors between the direction of heading and the goal, modifying subsequent errors in the process. The closed-loop nature of the behavior makes it challenging to determine how deterministic and nondeterministic processes contribute to behavior. We overcome this by applying a nonparametric, linear kernel-based analysis to behavioral data of monkeys steering through a virtual environment in two experimental contexts. In a given context, the results were consistent with previous work that described the transformation as a second-order linear system. Classically, the parameters of such second-order models are associated with physical properties of the limb such as viscosity and stiffness that are commonly assumed to be approximately constant. By contrast, we found that the fit kernels differed strongly across tasks in these and other parameters, suggesting context-dependent changes in neural and biomechanical processes. We additionally fit residuals to a simple noise model and found that the form of the noise was highly conserved across both contexts and animals. Strikingly, the fitted noise also closely matched that found previously in a human steering task. Altogether, this work presents a kernel-based analysis that characterizes the context-dependence of deterministic and non-deterministic components of a closed-loop sensorimotor task.

A neural compass in the human brain during naturalistic virtual navigation.

A central component of wayfinding is the ability to maintain a consistent representation of one's facing direction when moving about the world. In rodents, head direction cells are believed to support this "neural compass", but identifying a similar mechanism in humans during dynamic naturalistic navigation has been challenging. To address this issue, we acquired fMRI data while participants freely navigated through a virtual reality city. Encoding model analyses revealed voxel clusters in retrosplenial complex and superior parietal lobule that exhibited reliable tuning as a function of facing direction. Crucially, these directional tunings were consistent across perceptually different versions of the city, spatially separated locations within the city, and motivationally distinct phases of the behavioral task. Analysis of the model weights indicated that these regions may represent facing direction relative to the principal axis of the environment. These findings reveal specific mechanisms in the human brain that allow us to maintain a sense of direction during naturalistic, dynamic navigation.