Galvanic Vestibular Stimulation Activates the Parietal and Temporal Cortex in Humans: A functional near-infrared spectroscopy (fNIRS) Study

Galvanic Vestibular Stimulation (GVS) helps stabilize subjects when balance and posture are compromised. This work aimed to define the cortical regions that GVS activates in normal subjects. We used Functional Near-Infrared Spectroscopy (fNIRS) to test the hypothesis that GVS activates similar cortical areas as a passive movement. We used transcranial current stimulation (cathode in the right mastoid process and anode in the FPz frontopolar point) of bipolar direct current (2 mA), false GVS (sham), vibration (neutral stimulus), and back and forth motion (positive control of vestibular movement) in 18 clinically healthy volunteers. Seventy-two brain scans were performed, applying a crossover-type experimental design. We measured the heart rate, blood pressure, body temperature, head capacitance, and resistance before and after the experiment. The hemodynamic changes of the cerebral cortex were recorded with an arrangement of 26 channels in four regions to perform an ROI-level analysis. The back-and-forth motion produced the most significant oxygenated Hemoglobin (HbO₂ ) increase. The response was similar for the GVS stimulus on the anterior and posterior parietal and right temporal regions. Sham and vibrational conditions did not produce significant changes ROI-wise. The results indicate that GVS produces a cortical activation coherent with displacement percept.

Optical neuroimaging and neurostimulation in surgical training and assessment: A state-of-the-art review

Introduction

Functional near-infrared spectroscopy (fNIRS) is a non-invasive optical neuroimaging technique used to assess surgeons' brain function. The aim of this narrative review is to outline the effect of expertise, stress, surgical technology, and neurostimulation on surgeons' neural activation patterns, and highlight key progress areas required in surgical neuroergonomics to modulate training and performance.

Methods

A literature search of PubMed and Embase was conducted to identify neuroimaging studies using fNIRS and neurostimulation in surgeons performing simulated tasks.

Results

Novice surgeons exhibit greater haemodynamic responses across the pre-frontal cortex than experts during simple surgical tasks, whilst expert surgical performance is characterized by relative prefrontal attenuation and upregulation of activation foci across other regions such as the supplementary motor area. The association between PFC activation and mental workload follows an inverted-U shaped curve, activation increasing then attenuating past a critical inflection point at which demands outstrip cognitive capacity Neuroimages are sensitive to the impact of laparoscopic and robotic tools on cognitive workload, helping inform the development of training programs which target neural learning curves. FNIRS differs in comparison to current tools to assess proficiency by depicting a cognitive state during surgery, enabling the development of cognitive benchmarks of expertise. Finally, neurostimulation using transcranial direct-current-stimulation may accelerate skill acquisition and enhance technical performance.

Conclusion

FNIRS can inform the development of surgical training programs which modulate stress responses, cognitive learning curves, and motor skill performance. Improved data processing with machine learning offers the possibility of live feedback regarding surgeons' cognitive states during operative procedures.

System Derived Spatial-Temporal CNN for High-Density fNIRS BCI

An intuitive and generalisable approach to spatial-temporal feature extraction for high-density (HD) functional Near-Infrared Spectroscopy (fNIRS) brain-computer interface (BCI) is proposed, demonstrated here using Frequency-Domain (FD) fNIRS for motor-task classification. Enabled by the HD probe design, layered topographical maps of Oxy/deOxy Haemoglobin changes are used to train a 3D convolutional neural network (CNN), enabling simultaneous extraction of spatial and temporal features. The proposed spatial-temporal CNN is shown to effectively exploit the spatial relationships in HD fNIRS measurements to improve the classification of the functional haemodynamic response, achieving an average F1 score of 0.69 across seven subjects in a mixed subjects training scheme, and improving subject-independent classification as compared to a standard temporal CNN.

Fuzzy Synchronization of Chaotic Systems with Hidden Attractors

Chaotic systems are hard to synchronize, and no general solution exists. The presence of hidden attractors makes finding a solution particularly elusive. Successful synchronization critically depends on the control strategy, which must be carefully chosen considering system features such as the presence of hidden attractors. We studied the feasibility of fuzzy control for synchronizing chaotic systems with hidden attractors and employed a special numerical integration method that takes advantage of the oscillatory characteristic of chaotic systems. We hypothesized that fuzzy synchronization and the chosen numerical integration method can successfully deal with this case of synchronization. We tested two synchronization schemes: complete synchronization, which leverages linearization, and projective synchronization, capitalizing on parallel distributed compensation (PDC). We applied the proposal to a set of known chaotic systems of integer order with hidden attractors. Our results indicated that fuzzy control strategies combined with the special numerical integration method are effective tools to synchronize chaotic systems with hidden attractors. In addition, for projective synchronization, we propose a new strategy to optimize error convergence. Furthermore, we tested and compared different Takagi-Sugeno (T-S) fuzzy models obtained by tensor product (TP) model transformation. We found an effect of the fuzzy model of the chaotic system on the synchronization performance.

Effect of the level of task abstraction on the transfer of knowledge from virtual environments in cognitive and motor tasks

Introduction

Virtual environments are increasingly being used for training. It is not fully understood what elements of virtual environments have the most impact and how the virtual training is integrated by the brain on the sought-after skill transference to the real environment. In virtual training, we analyzed how the task level of abstraction modulates the brain activity and the subsequent ability to execute it in the real environment and how this learning generalizes to other tasks. The training of a task under a low level of abstraction should lead to a higher transfer of skills in similar tasks, but the generalization of learning would be compromised, whereas a higher level of abstraction facilitates generalization of learning to different tasks but compromising specific effectiveness.

Methods

A total of 25 participants were trained and subsequently evaluated on a cognitive and a motor task following four training regimes, considering real vs. virtual training and low vs. high task abstraction. Performance scores, cognitive load, and electroencephalography signals were recorded. Transfer of knowledge was assessed by comparing performance scores in the virtual vs. real environment.

Results

The performance to transfer the trained skills showed higher scores in the same task under low abstraction, but the ability to generalize the trained skills was manifested by higher scores under high level of abstraction in agreement with our hypothesis. Spatiotemporal analysis of the electroencephalography revealed higher initial demands of brain resources which decreased as skills were acquired.

Discussion

Our results suggest that task abstraction during virtual training influences how skills are assimilated at the brain level and modulates its manifestation at the behavioral level. We expect this research to provide supporting evidence to improve the design of virtual training tasks.

Intraoperative Cerebral Hemodynamic Monitoring during Carotid Endarterectomy via Diffuse Correlation Spectroscopy and Near-Infrared Spectroscopy

Objective: This pilot study aims to show the feasibility of noninvasive and real-time cerebral hemodynamic monitoring during carotid endarterectomy (CEA) via diffuse correlation spectroscopy (DCS) and near-infrared spectroscopy (NIRS). Methods: Cerebral blood flow index (CBFi) was measured unilaterally in seven patients and bilaterally in seventeen patients via DCS. In fourteen patients, hemoglobin oxygenation changes were measured bilaterally and simultaneously via NIRS. Cerebral autoregulation (CAR) and cerebrovascular resistance (CVR) were estimated using CBFi and arterial blood pressure data. Further, compensatory responses to the ipsilateral hemisphere were investigated at different contralateral stenosis levels. Results: Clamping of carotid arteries caused a sharp increase of CVR (~70%) and a marked decrease of ipsilateral CBFi (57%). From the initial drop, we observed partial recovery in CBFi, an increase of blood volume, and a reduction in CVR in the ipsilateral hemisphere. There were no significant changes in compensatory responses between different contralateral stenosis levels as CAR was intact in both hemispheres throughout the CEA phase. A comparison between hemispheric CBFi showed lower ipsilateral levels during the CEA and post-CEA phases (p < 0.001, 0.03). Conclusion: DCS alone or combined with NIRS is a useful monitoring technique for real-time assessment of cerebral hemodynamic changes and allows individualized strategies to improve cerebral perfusion during CEA by identifying different hemodynamic metrics.

Optical imaging and spectroscopy for the study of the human brain: status report

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions.

Diffuse correlation spectroscopy blood flow monitoring for intraventricular hemorrhage vulnerability in extremely low gestational age newborns

In premature infants with an extremely low gestational age (ELGA, < 29 weeks GA), dysregulated changes in cerebral blood flow (CBF) are among the major pathogenic factors leading to germinal matrix/intraventricular hemorrhage (GM/IVH). Continuous monitoring of CBF can guide interventions to minimize the risk of brain injury, but there are no clinically standard techniques or tools for its measurement. We report the feasibility of the continuous monitoring of CBF, including measures of autoregulation, via diffuse correlation spectroscopy (DCS) in ELGA infants using CBF variability and correlation with scalp blood flow (SBF, served as a surrogate measure of systemic perturbations). In nineteen ELGA infants (with 9 cases of GM/IVH) monitored for 6–24 h between days 2–5 of life, we found a strong correlation between CBF and SBF in severe IVH (Grade III or IV) and IVH diagnosed within 72 h of life, while CBF variability alone was not associated with IVH. The proposed method is potentially useful at the bedside for the prompt assessment of cerebral autoregulation and early identification of infants vulnerable to GM/IVH.

An autoencoder-based representation for noise reduction in distant supervision of relation extraction

Distant Supervision is an approach that allows automatic labeling of instances. This approach has been used in Relation Extraction. Still, the main challenge of this task is handling instances with noisy labels (e.g., when two entities in a sentence are automatically labeled with an invalid relation). The approaches reported in the literature addressed this problem by employing noise-tolerant classifiers. However, if a noise reduction stage is introduced before the classification step, this increases the macro precision values. This paper proposes an Adversarial Autoencoders-based approach for obtaining a new representation that allows noise reduction in Distant Supervision. The representation obtained using Adversarial Autoencoders minimize the intra-cluster distance concerning pre-trained embeddings and classic Autoencoders. Experiments demonstrated that in the noise-reduced datasets, the macro precision values obtained over the original dataset are similar using fewer instances considering the same classifier. For example, in one of the noise-reduced datasets, the macro precision was improved approximately 2.32% using 77% of the original instances. This suggests the validity of using Adversarial Autoencoders to obtain well-suited representations for noise reduction. Also, the proposed approach maintains the macro precision values concerning the original dataset and reduces the total instances needed for classification.

Characterization of a Raspberry Pi as the Core for a Low-cost Multimodal EEG-fNIRS Platform

Poor understanding of brain recovery after injury, sparsity of evaluations and limited availability of healthcare services hinders the success of neurorehabilitation programs in rural communities. The availability of neuroimaging ca-pacities in remote communities can alleviate this scenario supporting neurorehabilitation programs in remote settings. This research aims at building a multimodal EEG-fNIRS neuroimaging platform deployable to rural communities to support neurorehabilitation efforts. A Raspberry Pi 4 is chosen as the CPU for the platform responsible for presenting the neurorehabilitation stimuli, acquiring, processing and storing concurrent neuroimaging records as well as the proper synchronization between the neuroimaging streams. We present here two experiments to assess the feasibility and characterization of the Raspberry Pi as the core for a multimodal EEG-fNIRS neuroimaging platform; one over controlled conditions using a combination of synthetic and real data, and another from a full test during resting state. CPU usage, RAM usage and operation temperature were measured during the tests with mean operational records below 40% for CPU cores, 13.6% for memory and 58.85 ° C for temperatures. Package loss was inexistent on synthetic data and negligible on experimental data. Current consumption can be satisfied with a 1000 mAh 5V battery. The Raspberry Pi 4 was able to cope with the required workload in conditions of operation similar to those needed to support a neurorehabilitation evaluation.

Visual gaze patterns reveal surgeons' ability to identify risk of bile duct injury during laparoscopic cholecystectomy

BACKGROUND

Bile duct injury is a serious surgical complication of laparoscopic cholecystectomy. The aim of this study was to identify distinct visual gaze patterns associated with the prompt detection of bile duct injury risk during laparoscopic cholecystectomy.

METHODS

Twenty-nine participants viewed a laparoscopic cholecystectomy that led to a serious bile duct injury ('BDI video') and an uneventful procedure ('control video') and reported when an error was perceived that could result in bile duct injury. Outcome parameters include fixation sequences on anatomical structures and eye tracking metrics. Surgeons were stratified into two groups based on performance and compared.

RESULTS

The 'early detector' group displayed reduced common bile duct dwell time in the first half of the BDI video, as well as increased cystic duct dwell time and Calot's triangle glances count during Calot's triangle dissection in the control video. Machine learning based classification of fixation sequences demonstrated clear separability between early and late detector groups.

CONCLUSION

There are discernible differences in gaze patterns associated with early recognition of impending bile duct injury. The results could be transitioned into real time and used as an intraoperative early warning system and in an educational setting to improve surgical safety and performance.

Validation of diffuse correlation spectroscopy measures of critical closing pressure against transcranial Doppler ultrasound in stroke patients

SIGNIFICANCE

Intracranial pressure (ICP), variability in perfusion, and resulting ischemia are leading causes of secondary brain injury in patients treated in the neurointensive care unit. Continuous, accurate monitoring of cerebral blood flow (CBF) and ICP guide intervention and ultimately reduce morbidity and mortality. Currently, only invasive tools are used to monitor patients at high risk for intracranial hypertension.

AIM

Diffuse correlation spectroscopy (DCS), a noninvasive near-infrared optical technique, is emerging as a possible method for continuous monitoring of CBF and critical closing pressure (CrCP or zero-flow pressure), a parameter directly related to ICP.

APPROACH

We optimized DCS hardware and algorithms for the quantification of CrCP. Toward its clinical translation, we validated the DCS estimates of cerebral blood flow index (CBFi) and CrCP in ischemic stroke patients with respect to simultaneously acquired transcranial Doppler ultrasound (TCD) cerebral blood flow velocity (CBFV) and CrCP.

RESULTS

We found CrCP derived from DCS and TCD were highly linearly correlated (ipsilateral R2  =  0.77, p  =  9  ×  10  -  7; contralateral R2  =  0.83, p  =  7  ×  10  -  8). We found weaker correlations between CBFi and CBFV (ipsilateral R2  =  0.25, p  =  0.03; contralateral R2  =  0.48, p  =  1  ×  10  -  3) probably due to the different vasculature measured.

CONCLUSION

Our results suggest DCS is a valid alternative to TCD for continuous monitoring of CrCP.

Interpolated functional manifold for functional near-infrared spectroscopy analysis at group level

Significance: Solutions for group-level analysis of connectivity from fNIRS observations exist, but groupwise explorative analysis with classical solutions is often cumbersome. Manifold-based solutions excel at data exploration, but there are infinite surfaces crossing the observations cloud of points. Aim: We aim to provide a systematic choice of surface for a manifold-based analysis of connectivity at group level with small surface interpolation error. Approach: This research introduces interpolated functional manifold (IFM). IFM builds a manifold from reconstructed changes in concentrations of oxygenated Δ c HbO 2 and reduced Δ c HbR hemoglobin species by means of radial basis functions (RBF). We evaluate the root mean square error (RMSE) associated to four families of RBF. We validated our model against psychophysiological interactions (PPI) analysis using the Jaccard index (JI). We demonstrate the usability in an experimental dataset of surgical neuroergonomics. Results: Lowest interpolation RMSE was 1.26 e - 4 ± 1.32 e - 8 for Δ c HbO 2 [A.U.] and 4.30 e - 7 ± 2.50 e - 13 [A.U.] for Δ c HbR . Agreement with classical group analysis was JI = 0.89 ± 0.01 for Δ c HbO 2 . Agreement with PPI analysis was JI = 0.83 ± 0.07 for Δ c HbO 2 and JI = 0.77 ± 0.06 for Δ c HbR . IFM successfully decoded group differences [ANOVA: Δ cHbO 2 : F ( 2,117 ) = 3.07 ; p < 0.05 ; Δ c HbR : F ( 2,117 ) = 3.35 ; p < 0.05 ]. Conclusions: IFM provides a pragmatic solution to the problem of choosing the manifold associated to a cloud of points, facilitating the use of manifold-based solutions for the group analysis of fNIRS datasets.

Association of Residents' Neural Signatures With Stress Resilience During Surgery

Importance

Intraoperative stressors may compound cognitive load, prompting performance decline and threatening patient safety. However, not all surgeons cope equally well with stress, and the disparity between performance stability and decline under high cognitive demand may be characterized by differences in activation within brain areas associated with attention and concentration such as the prefrontal cortex (PFC).

Objective

To compare PFC activation between surgeons demonstrating stable performance under temporal stress with those exhibiting stress-related performance decline.

Design, Setting, and Participants

Cohort study conducted from July 2015 to September 2016 at the Imperial College Healthcare National Health Service Trust, England. One hundred two surgical residents (postgraduate year 1 and greater) were invited to participate, of which 33 agreed to partake.

Exposures

Participants performed a laparoscopic suturing task under 2 conditions: self-paced (SP; without time-per-knot restrictions), and time pressure (TP; 2-minute per knot time restriction).

Main Outcomes and Measures

A composite deterioration score was computed based on between-condition differences in task performance metrics (task progression score [arbitrary units], error score [millimeters], leak volume [milliliters], and knot tensile strength [newtons]). Based on the composite score, quartiles were computed reflecting performance stability (quartile 1 [Q1]) and decline (quartile 4 [Q4]). Changes in PFC oxygenated hemoglobin concentration (HbO2) measured at 24 different locations using functional near-infrared spectroscopy were compared between Q1 and Q4. Secondary outcomes included subjective workload (Surgical Task Load Index) and heart rate.

Results

Of the 33 participants, the median age was 33 years, the range was 29 to 56 years, and 27 were men (82%). The Q1 residents demonstrated task-induced increases in HbO2 across the bilateral ventrolateral PFC (VLPFC) and right dorsolateral PFC in the SP condition and in the VLPFC in the TP condition. In contrast, Q4 residents demonstrated decreases in HbO2 in both conditions. The magnitude of PFC activation (change in HbO2) was significantly greater in Q1 than Q4 across the bilateral VLPFC during both SP (mean [SD] left VLPFC: Q1, 0.44 [1.30] μM; Q4, -0.21 [2.05] μM; P < .001; right VLPFC: Q1, 0.46 [1.12] μM; Q4, -0.15 [2.14] μM; P < .001) and TP (mean [SD] left VLPFC: Q1, 0.44 [1.36] μM; Q4, -0.03 [1.83] μM; P = .001; right VLPFC: Q1, 0.49 [1.70] μM; Q4, -0.32 [2.00] μM; P < .001) conditions. There were no significant between-group differences in Surgical Task Load Index or heart rate in either condition.

Conclusions and Relevance

Performance stability within TP is associated with sustained prefrontal activation indicative of preserved attention and concentration, whereas performance decline is associated with prefrontal deactivation that may represent task disengagement.

Gaze patterns hold key to unlocking successful search strategies and increasing polyp detection rate in colonoscopy

BACKGROUND

The adenoma detection rate (ADR) is an important quality indicator in colonoscopy. The aim of this study was to evaluate the changes in visual gaze patterns (VGPs) with increasing polyp detection rate (PDR), a surrogate marker of ADR.

METHODS

18 endoscopists participated in the study. VGPs were measured using eye-tracking technology during the withdrawal phase of colonoscopy. VGPs were characterized using two analyses - screen and anatomy. Eye-tracking parameters were used to characterize performance, which was further substantiated using hidden Markov model (HMM) analysis.

RESULTS

Subjects with higher PDRs spent more time viewing the outer ring of the 3 × 3 grid for both analyses (screen-based: r = 0.56, P = 0.02; anatomy: r = 0.62, P < 0.01). Fixation distribution to the "bottom U" of the screen in screen-based analysis was positively correlated with PDR (r = 0.62, P = 0.01). HMM demarcated the VGPs into three PDR groups.

CONCLUSION

This study defined distinct VGPs that are associated with expert behavior. These data may allow introduction of visual gaze training within structured training programs, and have implications for adoption in higher-level assessment.

[Sensor-based mobile system for the promotion and real-time monitoring of physical activity]

[No disponible]

Imperial College near infrared spectroscopy neuroimaging analysis framework

This paper describes the Imperial College near infrared spectroscopy neuroimaging analysis (ICNNA) software tool for functional near infrared spectroscopy neuroimaging data. ICNNA is a MATLAB-based object-oriented framework encompassing an application programming interface and a graphical user interface. ICNNA incorporates reconstruction based on the modified Beer-Lambert law and basic processing and data validation capabilities. Emphasis is placed on the full experiment rather than individual neuroimages as the central element of analysis. The software offers three types of analyses including classical statistical methods based on comparison of changes in relative concentrations of hemoglobin between the task and baseline periods, graph theory-based metrics of connectivity and, distinctively, an analysis approach based on manifold embedding. This paper presents the different capabilities of ICNNA in its current version.

Automation of motor dexterity assessment

Motor dexterity assessment is regularly performed in rehabilitation wards to establish patient status and automatization for such routinary task is sought. A system for automatizing the assessment of motor dexterity based on the Fugl-Meyer scale and with loose restrictions on sensing technologies is presented. The system consists of two main elements: 1) A data representation that abstracts the low level information obtained from a variety of sensors, into a highly separable low dimensionality encoding employing t-distributed Stochastic Neighbourhood Embedding, and, 2) central to this communication, a multi-label classifier that boosts classification rates by exploiting the fact that the classes corresponding to the individual exercises are naturally organized as a network. Depending on the targeted therapeutic movement class labels i.e. exercises scores, are highly correlated-patients who perform well in one, tends to perform well in related exercises-; and critically no node can be used as proxy of others - an exercise does not encode the information of other exercises. Over data from a cohort of 20 patients, the novel classifier outperforms classical Naive Bayes, random forest and variants of support vector machines (ANOVA: p < 0.001). The novel multi-label classification strategy fulfills an automatic system for motor dexterity assessment, with implications for lessening therapist's workloads, reducing healthcare costs and providing support for home-based virtual rehabilitation and telerehabilitation alternatives.

Robot training for hand motor recovery in subacute stroke patients: A randomized controlled trial

BACKGROUND

Evidence of superiority of robot training for the hand over classical therapies in stroke patients remains controversial. During the subacute stage, hand training is likely to be the most useful.

AIM

To establish whether robot active assisted therapies provides any additional motor recovery for the hand when administered during the subacute stage (<4 months from event) in a Mexican adult population diagnosed with stroke.

HYPOTHESIS

Compared to classical occupational therapy, robot based therapies for hand recovery will show significant differences at subacute stages.

TRIAL DESIGN

A randomized clinical trial.

METHODS

A between subjects randomized controlled trial was carried out on subacute stroke patients (n = 17) comparing robot active assisted therapy (RT) with a classical occupational therapy (OT). Both groups received 40 sessions ensuring at least 300 repetitions per session. Treatment duration was (mean ± std) 2.18 ± 1.25 months for the control group and 2.44 ± 0.88 months for the study group. The primary outcome was motor dexterity changes assessed with the Fugl-Meyer (FMA) and the Motricity Index (MI).

RESULTS

Both groups (OT: n = 8; RT: n = 9) exhibited significant improvements over time (Non-parametric Cliff's delta-within effect sizes: dwOT-FMA = 0.5, dwOT-MI = 0.5, dwRT-FMA = 1, dwRT-MI = 1). Regarding differences between the therapies; the Fugl-Meyer score indicated a significant advantage for the hand training with the robot (FMA hand: WRS: W = 8, p <0.01), whilst the Motricity index suggested a greater improvement (size effect) in hand prehension for RT with respect to OT but failed to reach significance (MI prehension: W = 17.5, p = 0.080). No harm occurred.

CONCLUSIONS

Robotic therapies may be useful during the subacute stages of stroke - both endpoints (FM hand and MI prehension) showed the expected trend with bigger effect size for the robotic intervention. Additional benefit of the robotic therapy over the control therapy was only significant when the difference was measured with FM, demanding further investigation with larger samples. Implications of this study are important for decision making during therapy administration and resource allocation.

The impact of expert visual guidance on trainee visual search strategy, visual attention and motor skills

Minimally invasive and robotic surgery changes the capacity for surgical mentors to guide their trainees with the control customary to open surgery. This neuroergonomic study aims to assess a "Collaborative Gaze Channel" (CGC); which detects trainer gaze-behavior and displays the point of regard to the trainee. A randomized crossover study was conducted in which twenty subjects performed a simulated robotic surgical task necessitating collaboration either with verbal (control condition) or visual guidance with CGC (study condition). Trainee occipito-parietal (O-P) cortical function was assessed with optical topography (OT) and gaze-behavior was evaluated using video-oculography. Performance during gaze-assistance was significantly superior [biopsy number: (mean ± SD): control = 5.6 ± 1.8 vs. CGC = 6.6 ± 2.0; p < 0.05] and was associated with significantly lower O-P cortical activity [ΔHbO2 mMol × cm [median (IQR)] control = 2.5 (12.0) vs. CGC 0.63 (11.2), p < 0.001]. A random effect model (REM) confirmed the association between guidance mode and O-P excitation. Network cost and global efficiency were not significantly influenced by guidance mode. A gaze channel enhances performance, modulates visual search, and alleviates the burden in brain centers subserving visual attention and does not induce changes in the trainee's O-P functional network observable with the current OT technique. The results imply that through visual guidance, attentional resources may be liberated, potentially improving the capability of trainees to attend to other safety critical events during the procedure.

Gesture therapy: an upper limb virtual reality-based motor rehabilitation platform

Virtual reality platforms capable of assisting rehabilitation must provide support for rehabilitation principles: promote repetition, task oriented training, appropriate feedback, and a motivating environment. As such, development of these platforms is a complex process which has not yet reached maturity. This paper presents our efforts to contribute to this field, presenting Gesture Therapy, a virtual reality-based platform for rehabilitation of the upper limb. We describe the system architecture and main features of the platform and provide preliminary evidence of the feasibility of the platform in its current status.

Neural reorganization accompanying upper limb motor rehabilitation from stroke with virtual reality-based gesture therapy

BACKGROUND

Gesture Therapy is an upper limb virtual reality rehabilitation-based therapy for stroke survivors. It promotes motor rehabilitation by challenging patients with simple computer games representative of daily activities for self-support. This therapy has demonstrated clinical value, but the underlying functional neural reorganization changes associated with this therapy that are responsible for the behavioral improvements are not yet known.

OBJECTIVE

We sought to quantify the occurrence of neural reorganization strategies that underlie motor improvements as they occur during the practice of Gesture Therapy and to identify those strategies linked to a better prognosis.

METHODS

Functional magnetic resonance imaging (fMRI) neuroscans were longitudinally collected at 4 time points during Gesture Therapy administration to 8 patients. Behavioral improvements were monitored using the Fugl-Meyer scale and Motricity Index. Activation loci were anatomically labelled and translated to reorganization strategies. Strategies are quantified by counting the number of active clusters in brain regions tied to them.

RESULTS

All patients demonstrated significant behavioral improvements (P < .05). Contralesional activation of the unaffected motor cortex, cerebellar recruitment, and compensatory prefrontal cortex activation were the most prominent strategies evoked. A strong and significant correlation between motor dexterity upon commencing therapy and total recruited activity was found (r2 = 0.80; P < .05), and overall brain activity during therapy was inversely related to normalized behavioral improvements (r2 = 0.64; P < .05).

CONCLUSIONS

Prefrontal cortex and cerebellar activity are the driving forces of the recovery associated with Gesture Therapy. The relation between behavioral and brain changes suggests that those with stronger impairment benefit the most from this paradigm.

A quantitative scale to define endoscopic torque control during natural orifice surgery

INTRODUCTION

The drive to perform procedures with the least impact on the patient has meant that interest in natural orifice translumenal endoscopic surgery (NOTES) continues to proliferate. However, endoscope control within the extralumenal environment remains a significant challenge. This study aims to define a method to quantitatively assess endoscopic torque control as an indication of performance.

MATERIAL AND METHODS

Fourteen endoscopists performed a ten-target navigational task within a simulated NOTES environment whilst wrist movements were tracked with an optical motion tracker. Patterns of wrist movements were translated to a binary form enabling differentiation of the specified movement from no movement. Three patterns were discernable suggesting the discrimination of purposeful over random manipulations. Three independent assessors scored 140 patterns on a scale of 1 to 3 determined by which pattern was the most appropriate fit.

RESULTS

Mean score for novices was 16 (± 3) and for clinicians 22 (± 7). Inter-rater reliability (kappa statistic function) between the assessors ranged from 0.637 to 0.751 p < 0.001 referred to as a substantial assessment tool. The internal consistency between all variables using Chronbach's alpha function was 0.948 (p < 0.001).

CONCLUSIONS

Pattern of movements extrapolated from the wrist can be used as a method of measuring endoscope torque control during a translumenal navigation task.

Collaborative gaze channelling for improved cooperation during robotic assisted surgery

The use of multiple robots for performing complex tasks is becoming a common practice for many robot applications. When different operators are involved, effective cooperation with anticipated manoeuvres is important for seamless, synergistic control of all the end-effectors. In this paper, the concept of Collaborative Gaze Channelling (CGC) is presented for improved control of surgical robots for a shared task. Through eye tracking, the fixations of each operator are monitored and presented in a shared surgical workspace. CGC permits remote or physically separated collaborators to share their intention by visualising the eye gaze of their counterparts, and thus recovers, to a certain extent, the information of mutual intent that we rely upon in a vis-à-vis working setting. In this study, the efficiency of surgical manipulation with and without CGC for controlling a pair of bimanual surgical robots is evaluated by analysing the level of coordination of two independent operators. Fitts’ law is used to compare the quality of movement with or without CGC. A total of 40 subjects have been recruited for this study and the results show that the proposed CGC framework exhibits significant improvement (p < 0.05) on all the motion indices used for quality assessment. This study demonstrates that visual guidance is an implicit yet effective way of communication during collaborative tasks for robotic surgery. Detailed experimental validation results demonstrate the potential clinical value of the proposed CGC framework.

Spatial awareness in Natural Orifice Transluminal Endoscopic Surgery (NOTES) navigation

OBJECTIVE

To characterise navigational patterns in the abdominal cavity associated with different spatial awareness status of the operator during navigation of Natural Orifice Transluminal Endoscopic Surgery (NOTES). It is hypothesised that poor spatial awareness will manifest as erratic navigational patterns and poor performance.

SUBJECTS AND METHODS

Ten endoscopic novices navigated a defined course in a NOTES phantom (NOSsE) simulating the path of peritoneoscopic examination. Subjects performed the task three times without and once with an additional laparoscopic camera. Electromagnetic tracking was used to trace the tip of the endoscope during the navigation. Metrics of performance included the number of correctly visualised course targets, between targets localisation time and path length, and total completion time. Spatial awareness was explored by means of topological modelling of the navigation trace. Spatial navigation maps were generated from the tip trace footprint, differentiated using the Earth Movers Distance (EMD) and captured in a two dimensional chart where proximity in the projected space reflects similarity of navigation behaviour. Groups were identified displaying idiosyncratic target to target transitions in endoscopic navigation behaviour.

RESULTS

No significant differences were found between four sessions in terms of the path length. Time was statistically improved when using supplemental visualisation (p<0.05). Four awareness groups were identified based on the subjects exhibited navigation footprint over the frontal plane, namely: (1) consistent navigation and performance; (2) inconsistent navigation and performance; (3) improvements in navigation and performance despite undifferentiated behavioural signatures; and (4) inconsistent navigation with improvements in performance.

CONCLUSIONS

Tracking the tip of the endoscope permits reconstruction of the navigation path during extraluminal navigation. The spatial location of the tip of the endoscope during navigation was used to unveil the operator's spatial awareness. Navigation routes in this study have been projected onto a 2D scene, related to performance and classified according to exhibited spatial awareness. Our assessment of this relationship suggests that poor spatial awareness is accompanied by erratic manoeuvres, often leading to poor performances, and vice versa. Tracking the location of the tip of the endoscope is an important issue in NOTES, and similarly understanding the spatial awareness of the operator is crucial in terms of the safety in NOTES. This work may have significant implications for training and assessment of new NOTES or minimally invasive surgeons. It may also lead to the new designs of endoscopes for NOTES.

Value of orientation training in laparoscopic cholecystectomy

BACKGROUND

It is well established that disorientation during laparoscopic operations such as cholecystectomy is associated with increased morbidity and mortality. The aim of the present study was to evaluate whether high-performance orientation strategies could be taught to a cohort without relevant experience of laparoscopic cholecystectomy, resulting in improved performance and spatial awareness, thereby reducing the need for operative experience to command this skill.

METHODS

Thirty medical students participated in a randomized controlled trial, with half randomized to a tutorial teaching orientation strategies at specific stages of laparoscopic cholecystectomy and half to a control group without any teaching. Attention as represented by gaze was captured using eye tracking as subjects were presented with 12 images of various stages of the operation, with the task of interpreting the orientation of the image. The primary outcome measure was subject performance in orientation. Secondary outcome measures were gaze dwell time on relevant anatomical structures within the images and comparison of individual behaviour using a visual behaviour profiling algorithm.

RESULTS

The intervention group was significantly more likely to orientate correctly than the control group (mean 75·6 versus 56·1 per cent; P = 0·019). A difference in visual attention behaviour between the two groups was apparent for the majority of images when examining the output of the visual profiling algorithm, in the form of increased homogeneity of visual behaviour and/or an overall difference in orientation strategy. The mean orientation rate of all surgeons under identical conditions in a previously published study was 78·6 per cent.

CONCLUSION

Training novices in orientation strategies improved their performance significantly and it could reach the level of a surgeon with several years of experience in laparoscopic surgery.

Transgastric or trans-sigmoidal? The impact of the choice of access on task performance in target natural orifice translumenal endoscopic surgery procedures

INTRODUCTION

The effect of the choice of access upon endoscope control during a navigational task is explored within a simulator model.

MATERIALS AND METHODS

The study was conducted within the endoscopic-laparoscopic interdisciplinary training entity (ELITE) model (Minimally Invasive Therapy and Intervention Research Group [MITI], Technische Universität, Germany)--a validated natural orifice translumenal endoscopic surgery (NOTES) simulator. Seventeen subjects, 15 with no endoscopic experience, navigated the endoscope from predefined trans-sigmoidal and transgastric access points to the appendix and the gallbladder. A previously defined and validated quantitative analysis of endoscope control, in addition to time taken to complete the task, was used to evaluate overall performance. The quantitative analysis extrapolated the movements of the subject's wrist in control of the endoscope and rated the movements using a scoring system of 0-3 based upon the smoothness of the movements recorded.

RESULTS

Although no significant difference in terms of performance time was demonstrated between the two approaches to the appendix (36.6 ± 14.7 seconds TG and 29.8 ± 16 seconds TS) (P = .214), when the endoscope control score was compared, a significant difference was confirmed (3 TG and 7 TS) (P < .001). With regard to the approach to the gallbladder, a significant difference in terms of both the performance time (19.8 seconds TG and 35.6 seconds TS) (P < .001) and the quality of endoscope control (7 TG and 5 TS) (P = .001) was demonstrated.

CONCLUSION

The choice of access route impacts directly on the ease with which the endoscopist navigates to the target. Within this study, the trans-sigmoidal appears the most appropriate to access the appendix and the transgastric for the gallbladder.

The ergonomics of natural orifice translumenal endoscopic surgery (NOTES) navigation in terms of performance, stress, and cognitive behavior

BACKGROUND

The evolution toward minimally invasive surgery and subsequently to natural orifice translumenal endoscopic surgery (NOTES) poses challenges to the surgeon in terms of increased task complexity requiring greater visuospatial and navigational ability. Neuroergonomics is the study of the brain and behavior at work, and establishing the baseline cortical response for NOTES procedures will help to ascertain whether technological innovation such as navigational aids can alleviate the task-induced cognitive burden. The aims of the current study are to characterize the impact of navigation within a NOTES environment on the subject in terms of (1) performance, (2) stress, (3) prefrontal cortical activity, and (4) how this is influenced by expertise.

METHODS

In all, 29 subjects were assessed for performance, stress response, and prefrontal cortical activity during a NOTES navigational task within a validated NOTES simulator.

RESULTS

Experts performed significantly better than novices (P < .05). Expertise was not a predictor for overall changes in prefrontal cortical activity. The differences between experts and novices were modulated by the location of prefrontal cortical activity, with experts demonstrating more pronounced lateral prefrontal cortical activation compared with novices. Stress was not an independent predictor of changes in prefrontal cortical hemodynamics.

CONCLUSION

This study is the first to characterize the performance, stress, and neurocognitive behavior associated with natural orifice translumenal endoscopic surgery navigation. The results indicate the relevance of visuospatial centers in successful task execution, and they serve as a baseline within the neuroergonomic paradigm for investigating performance-enhancing technology.

Gaze-Contingent Motor Channelling, haptic constraints and associated cognitive demand for robotic MIS

The success of MIS is coupled with an increasing demand on surgeons' manual dexterity and visuomotor coordination due to the complexity of instrument manipulations. The use of master-slave surgical robots has avoided many of the drawbacks of MIS, but at the same time, has increased the physical separation between the surgeon and the patient. Tissue deformation combined with restricted workspace and visibility of an already cluttered environment can raise critical issues related to surgical precision and safety. Reconnecting the essential visuomotor sensory feedback is important for the safe practice of robot-assisted MIS procedures. This paper introduces a novel gaze-contingent framework for real-time haptic feedback and virtual fixtures by transforming visual sensory information into physical constraints that can interact with the motor sensory channel. We demonstrate how motor tracking of deforming tissue can be made more effective and accurate through the concept of Gaze-Contingent Motor Channelling. The method is also extended to 3D by introducing the concept of Gaze-Contingent Haptic Constraints where eye gaze is used to dynamically prescribe and update safety boundaries during robot-assisted MIS without prior knowledge of the soft-tissue morphology. Initial validation results on both simulated and robot assisted phantom procedures demonstrate the potential clinical value of the technique. In order to assess the associated cognitive demand of the proposed concepts, functional Near-Infrared Spectroscopy is used and preliminary results are discussed.

Functional prefrontal reorganization accompanies learning-associated refinements in surgery: a manifold embedding approach

The prefrontal cortex (PFC) is known to be vital for acquisition of visuomotor skills, but its role in the attainment of complex technical skills which comprise both perceptual and motor components, such as those associated with surgery, remains poorly understood. We hypothesized that the prefrontal response to a surgical knot-tying task would be highly dependent on technical expertise, and that activation would wane in the context of learning success following extended practice. The present series of experiments investigated this issue, using functional Near Infrared Spectroscopy (fNIRS) and dexterity analysis to compare the PFC responses and technical skill of expert and novice surgeons performing a surgical knot-tying task in a block design experiment. Applying a data-embedding technique known as Isomap and Earth Mover's Distance (EMD) analysis, marked differences in cortical hemodynamic responses between expert and novice surgeons have been found. To determine whether refinement in technical skill was associated with reduced PFC demands, a second experiment assessed the impact of pre- and post-training on the PFC responses in novices. Significant improvements (p < 0.01) were observed in all performance parameters following training. Smaller EMD distances were observed between expert surgeons and novices following training, suggesting an evolving pattern of cortical responses. A random effect model demonstrated a statistically significant decrease in relative changes of total hemoglobin (Delta HbT) [coefficient = -3.825, standard error (s.e.) = 0.8353, z = -4.58, p < 0.001] and oxygenated hemoglobin (Delta HbO(2)) [coefficient = -4.6815, s.e = 0.6781, z = -6.90, p < 0.001] and a significant increase in deoxygenated hemoglobin (Delta HHb) [coefficient = 0.8192, s.e = 0.3034, z = 2.66, p < 0.01] across training. The results indicate that learning-related refinements in technical performance are mediated by temporal reductions in prefrontal activation.

Modelling dynamic fronto-parietal behaviour during minimally invasive surgery--a Markovian trip distribution approach

Learning to perform Minimally Invasive Surgery (MIS) requires considerable attention, concentration and spatial ability. Theoretically, this leads to activation in executive control (prefrontal) and visuospatial (parietal) centres of the brain. A novel approach is presented in this paper for analysing the flow of fronto-parietal haemodynamic behaviour and the associated variability between subjects. Serially acquired functional Near Infrared Spectroscopy (fNIRS) data from fourteen laparoscopic novices at different stages of learning is projected into a low-dimensional 'geospace', where sequentially acquired data is mapped to different locations. A trip distribution matrix based on consecutive directed trips between locations in the geospace reveals confluent fronto-parietal haemodynamic changes and a gravity model is applied to populate this matrix. To model global convergence in haemodynamic behaviour, a Markov chain is constructed and by comparing sequential haemodynamic distributions to the Markov's stationary distribution, inter-subject variability in learning an MIS task can be identified.

Changes in prefrontal cortical behaviour depend upon familiarity on a bimanual co-ordination task: an fNIRS study

To investigate neurocognitive mechanisms associated with task-related expertise development, this paper investigates serial changes in prefrontal activation patterns using functional near infrared spectroscopy (fNIRS). We evaluate cortical function in 62 healthy subjects with varying experience during serial evaluations of a knot-tying task. All tasks were performed bimanually and self paced, with fixed episodes of motor rest for five repetitions. Improvements in technical skill were evaluated using dexterity indices to quantify time, total movements and pathlength required to complete trials. Significant improvements in technical skills were observed in novices between the 2nd and 3rd trials, associated with increasing task familiarity. In trained subjects, minimal fluctuation in task-related oxyhaemoglobin (HbO(2)) and deoxyhaemoglobin (HHb) changes were observed in association with more stable task performance. In contrast, two significant transitions in prefrontal haemodynamic change were observed in novices. Greater task-related increases in HbO(2) and decreases in HHb were identified on the second trial compared to the first. Relative decreases in HbO(2) and increases in HHb change were observed between the third and fourth, and fourth and fifth trials respectively. These data suggest that prefrontal processing across five knot-tying trials is influenced by the level of experience on a task. Modifications in prefrontal activation appear to confer technical performance adaptation in novices.

Functional near infrared spectroscopy in novice and expert surgeons--a manifold embedding approach

Monitoring expertise development in surgery is likely to benefit from evaluations of cortical brain function. Brain behaviour is dynamic and nonlinear. The aim of this paper is to evaluate the application of a nonlinear dimensionality reduction technique to enhance visualisation of multidimensional functional Near Infrared Spectroscopy (fNIRS) data. Manifold embedding is applied to prefrontal haemodynamic signals obtained during a surgical knot tying task from a group of 62 healthy subjects with varying surgical expertise. The proposed method makes no assumption about the functionality of the data set and is shown to be capable of recovering the intrinsic low dimensional structure of in vivo brain data. After manifold embedding, Earth Mover's Distance (EMD) is used to quantify different patterns of cortical behaviour associated with surgical expertise and analyse the degree of inter-hemispheric channel pair symmetry.

Quantitative analysis of multi-spectral fundus images

We have developed a new technique for extracting histological parameters from multi-spectral images of the ocular fundus. The new method uses a Monte Carlo simulation of the reflectance of the fundus to model how the spectral reflectance of the tissue varies with differing tissue histology. The model is parameterised by the concentrations of the five main absorbers found in the fundus: retinal haemoglobins, choroidal haemoglobins, choroidal melanin, RPE melanin and macular pigment. These parameters are shown to give rise to distinct variations in the tissue colouration. We use the results of the Monte Carlo simulations to construct an inverse model which maps tissue colouration onto the model parameters. This allows the concentration and distribution of the five main absorbers to be determined from suitable multi-spectral images. We propose the use of "image quotients" to allow this information to be extracted from uncalibrated image data. The filters used to acquire the images are selected to ensure a one-to-one mapping between model parameters and image quotients. To recover five model parameters uniquely, images must be acquired in six distinct spectral bands. Theoretical investigations suggest that retinal haemoglobins and macular pigment can be recovered with RMS errors of less than 10%. We present parametric maps showing the variation of these parameters across the posterior pole of the fundus. The results are in agreement with known tissue histology for normal healthy subjects. We also present an early result which suggests that, with further development, the technique could be used to successfully detect retinal haemorrhages.