Using an application to measure trainees' procedural knowledge before chest tube insertion.

PURPOSE OF THE STUDY: To collect validity evidence for the chest tube insertion (CTI) test mode on the medical simulation application Touch Surgery. This was done by using Messick's contemporary framework. METHODS: Novice, intermediate and experienced participants provided informed consent and demographic information. After familiarisation with the application, they completed the CTI test mode. Validity evidence was collected from four sources: content, response process, relation to other variables and consequences. A post-study questionnaire with 5-point Likert scales assessed the perceived realism, relevance and utility of the assessment. Mean scores of the three groups were compared. RESULTS: A total of 25 novices, 11 intermediates and 19 experienced participants were recruited. Content evidence was collected by an expert in CTI and was based on published literature and guidelines. All users were familiarised with the application, and received standardised instructions throughout the test. Most users rated the simulation as realistic and suitable to assess cognitive skills. Novices received significantly lower (55.9±7.5) test mode scores than intermediates (80.6±4.4) (p<0.001) and experienced participants (82.3±5.3) (p<0.001). There was no significant difference in score between intermediate and experienced participants (p=0.75). Consequences evidence was provided by establishing a pass/fail score of 71% using the contrasting groups method, which resulted in one observed false positive and no false negatives. CONCLUSION: A robust validity argument was constructed for the CTI test mode, which can be implemented in surgical curricula to assess learners' cognitive skills prior to hands-on simulation practice.

Distinct neural mechanisms for body form and body motion discriminations.

Actions can be understood based on form cues (e.g., static body posture) as well as motion cues (e.g., gait patterns). A fundamental debate centers on the question of whether the functional and neural mechanisms processing these two types of cues are dissociable. Here, using fMRI, psychophysics, and transcranial magnetic stimulation (TMS), all within the same human participants, we show that mechanisms underlying body form and body motion processing are functionally and neurally distinct. Multivoxel fMRI activity patterns in the extrastriate body area (EBA), but not in the posterior superior temporal sulcus (pSTS), carried cue invariant information about the body form of an acting human. Conversely, multivoxel patterns in pSTS, but not in EBA, carried information about the body motion of the same actor. In a psychophysical experiment, we selectively impaired body form and body motion discriminations by manipulating different visual cues: misaligning the ellipses that made up a dynamic walker stimulus selectively disrupted body form discriminations, while varying the presentation duration of the walker selectively affected body motion discriminations. Finally, a TMS experiment revealed causal evidence for a double-dissociation between neural mechanisms underlying body form and body motion discriminations: TMS over EBA selectively disrupted body form discrimination, whereas TMS over pSTS selectively disrupted body motion discrimination. Together, these findings reveal complementing but dissociable functions of EBA and pSTS during action perception. They provide constraints for theoretical and computational models of action perception by showing that action perception involves at least two parallel pathways that separately contribute to the understanding of others' behavior.

Orientation-tuned surround suppression in mouse visual cortex.

The firing rates of neurons in primary visual cortex (V1) are suppressed by large stimuli, an effect known as surround suppression. In cats and monkeys, the strength of suppression is sensitive to orientation; responses to regions containing uniform orientations are more suppressed than those containing orientation contrast. This effect is thought to be important for scene segmentation, but the underlying neural mechanisms are poorly understood. We asked whether it is possible to study these mechanisms in the visual cortex of mice, because of recent advances in technology for studying the cortical circuitry in mice. It is unknown whether neurons in mouse V1 are sensitive to orientation contrast. We measured the orientation selectivity of surround suppression in the different layers of mouse V1. We found strong surround suppression in layer 4 and the superficial layers, part of which was orientation tuned: iso-oriented surrounds caused more suppression than cross-oriented surrounds. Surround suppression was delayed relative to the visual response and orientation-tuned suppression was delayed further, suggesting two separate suppressive mechanisms. Previous studies proposed that surround suppression depends on the activity of inhibitory somatostatin-positive interneurons in the superficial layers. To test the involvement of the superficial layers we topically applied lidocaine. Silencing of the superficial layers did not prevent orientation-tuned suppression in layer 4. These results show that neurons in mouse V1, which lacks orientation columns, show orientation-dependent surround suppression in layer 4 and the superficial layers and that surround suppression in layer 4 does not require contributions from neurons in the superficial layers.

Robot-assisted Partial Nephrectomy Using Intra-arterial Renal Hypothermia for Highly Complex Endophytic or Hilar Tumors: Case Series and Description of Surgical Technique.

Background: In partial nephrectomy for highly complex tumors with expected long ischemia time, renal hypothermia can be used to minimize ischemic parenchymal damage. Objective: To describe our case series, surgical technique, and early outcomes for robot-assisted partial nephrectomy (RAPN) using intra-arterial cold perfusion through arteriotomy. Design setting and participants: A retrospective analysis was conducted of ten patients with renal tumors (PADUA score 9-13) undergoing RAPN between March 2020 and March 2023 with intra-arterial cooling because of expected arterial clamping times longer than 25 min. Surgical procedure: Multiport transperitoneal RAPN with full renal mobilization and arterial, venous, and ureteral clamping was performed. After arteriotomy and venotomy, 4°C heparinized saline is administered intravascular through a Fogarty catheter to maintain renal hypothermia while performing RAPN. Measurements: Demographic data, renal function, console and ischemia times, surgical margin status, hospital stay, estimated blood loss, and complications were analyzed. Results and limitations: The median warm and cold ischemia times were 4 min (interquartile range [IQR] 3-7 min) and 60 min (IQR 33-75 min), respectively. The median rewarming ischemia time was 10.5 min (IQR 6.5-23.75 min). The median pre- and postoperative estimated glomerular filtration rate values at least 1 mo after surgery were 90 ml/min (IQR 78.35-90 ml/min) and 86.9 ml/min (IQR 62.08-90 ml/min), respectively. Limitations include small cohort size and short median follow-up (13 [IQR 9.1-32.4] mo). Conclusions: We demonstrate the feasibility and first case series for RAPN using intra-arterial renal hypothermia through arteriotomy. This approach broadens the scope for minimal invasive nephron-sparing surgery in highly complex renal masses. Patient summary: We demonstrate a minimally invasive surgical technique that reduces kidney infarction during complex kidney tumor removal where surrounding healthy kidney tissue is spared. The technique entails arterial cold fluid irrigation, which temporarily decreases renal metabolism and allows more kidneys to be salvaged.

Distinct mechanisms for coding of visual actions in macaque temporal cortex.

Temporal cortical neurons are known to respond to visual dynamic-action displays. Many human psychophysical and functional imaging studies examining biological motion perception have used treadmill walking, in contrast to previous macaque single-cell studies. We assessed the coding of locomotion in rhesus monkey (Macaca mulatta) temporal cortex using movies of stationary walkers, varying both form and motion (i.e., different facing directions) or varying only the frame sequence (i.e., forward vs backward walking). The majority of superior temporal sulcus and inferior temporal neurons were selective for facing direction, whereas a minority distinguished forward from backward walking. Support vector machines using the temporal cortical population responses as input classified facing direction well, but forward and backward walking less so. Classification performance for the latter improved markedly when the within-action response modulation was considered, reflecting differences in momentary body poses within the locomotion sequences. Responses to static pose presentations predicted the responses during the course of the action. Analyses of the responses to walking sequences wherein the start frame was varied across trials showed that some neurons also carried a snapshot sequence signal. Such sequence information was present in neurons that responded to static snapshot presentations and in neurons that required motion. Our data suggest that actions are analyzed by temporal cortical neurons using distinct mechanisms. Most neurons predominantly signal momentary pose. In addition, temporal cortical neurons, including those responding to static pose, are sensitive to pose sequence, which can contribute to the signaling of learned action sequences.

Functional differentiation of macaque visual temporal cortical neurons using a parametric action space.

Neurons in the rostral superior temporal sulcus (STS) are responsive to displays of body movements. We employed a parametric action space to determine how similarities among actions are represented by visual temporal neurons and how form and motion information contributes to their responses. The stimulus space consisted of a stick-plus-point-light figure performing arm actions and their blends. Multidimensional scaling showed that the responses of temporal neurons represented the ordinal similarity between these actions. Further tests distinguished neurons responding equally strongly to static presentations and to actions ("snapshot" neurons), from those responding much less strongly to static presentations, but responding well when motion was present ("motion" neurons). The "motion" neurons were predominantly found in the upper bank/fundus of the STS, and "snapshot" neurons in the lower bank of the STS and inferior temporal convexity. Most "motion" neurons showed strong response modulation during the course of an action, thus responding to action kinematics. "Motion" neurons displayed a greater average selectivity for these simple arm actions than did "snapshot" neurons. We suggest that the "motion" neurons code for visual kinematics, whereas the "snapshot" neurons code for form/posture, and that both can contribute to action recognition, in agreement with computation models of action recognition.

Signatures of knee osteoarthritis in women in the temporal and fractal dynamics of human gait.

BACKGROUND: Osteoarthritis of the knee is characterized by progressive cartilage deterioration causing pain and function loss. Symptoms develop late with limited disease-modifying opportunities. Osteoarthritis is a major cause of immobility, with a higher prevalence above 60 years. This age-related increase in prevalence is further amplified by the female gender. Imaging and biochemical analyses for detection of osteoarthritis of the knee are expensive and labor-intensive. Continuous movement tracking could aid in detecting onset and/or worsening of symptoms. METHODS: We used portable technology to investigate kinematic differences in female patients with knee osteoarthritis, weight-matched healthy female volunteers and obese female patients with osteoarthritis of the knee. Knee osteoarthritis was established radiographically and corroborated using magnetic resonance imaging. FINDINGS: The total amount, type and level of activity did not differ significantly between groups. The temporal activity pattern during the day was however significantly different with a bimodal signature in healthy volunteers only. Sequence analyses revealed more time to recuperate after dynamic activity in both patient groups. Analysis of walking bouts revealed significant differences in stride interval dynamics, indicative of gait naturalness, only in healthy volunteers. Temporal activity, sequence and walking patterns were independent of body weight. INTERPRETATION: We thus provide for the first-time evidence of temporal specific kinematic signatures in amount and quality of movement also in stride interval dynamics between people with and without osteoarthritis of the knee independent of body weight. These findings could allow early and non-intrusive diagnosis of osteoarthritis enabling concordant treatment.

Stimulus similarity-contingent neural adaptation can be time and cortical area dependent.

Repetition of a stimulus results in decreased responses in many cortical areas. This so-called adaptation or repetition suppression has been used in several human functional magnetic resonance imaging studies to deduce the stimulus selectivity of neuronal populations. We tested in macaque monkeys whether the degree of neural adaptation depends on the similarity between the adapter and test stimulus. To manipulate similarity, we varied stimulus size. We recorded the responses of single neurons to different-sized shapes in inferior temporal (IT) and prefrontal cortical (PFC) areas while the animals were engaged in a size or shape discrimination task. The degree of response adaptation in IT decreased with increasing size differences between the adapter and the test stimuli in both tasks, but the dependence of adaptation on the degree of similarity between the adapter and test stimuli was limited mainly to the early phase of the neural response in IT. PFC neurons showed only weak size-contingent repetition effects, despite strong size selectivity observed with the same stimuli. Thus, based on the repetition effects in PFC, one would have erroneously concluded that PFC shows weak or no size selectivity in such tasks. These findings are relevant for the interpretation of functional magnetic resonance adaptation data: they support the conjecture that the degree of adaptation scales with the similarity between adapter and test stimuli. However, they also show that the temporal evolution of adaptation during the course of the response, and differences in the way individual regions react to stimulus repetition, may complicate the inference of neuronal tuning from functional magnetic resonance adaptation.

Discrimination of locomotion direction in impoverished displays of walkers by macaque monkeys.

A vast literature exists on human biological motion perception in impoverished displays, e.g., point-light walkers. Less is known about the perception of impoverished biological motion displays in macaques. We trained 3 macaques in the discrimination of facing direction (left versus right) and forward versus backward walking using motion-capture-based locomotion displays (treadmill walking) in which the body features were represented by cylinder-like primitives. The displays did not contain translatory motion. Discriminating forward versus backward locomotion requires motion information while the facing-direction/view task can be solved using motion and/or form. All monkeys required lengthy training to learn the forward-backward task, while the view task was learned more quickly. Once acquired, the discriminations were specific to walking and stimulus format but generalized across actors. Although the view task could be solved using form cues, there was a small impact of motion. Performance in the forward-backward task was highly susceptible to degradations of spatiotemporal stimulus coherence and motion information. These results indicate that rhesus monkeys require extensive training in order to use the intrinsic motion cues related to forward versus backward locomotion and imply that extrapolation of observations concerning human perception of impoverished biological motion displays onto monkey perception needs to be made cautiously.

Activity in Lateral Visual Areas Contributes to Surround Suppression in Awake Mouse V1.

Neuronal response to sensory stimuli depends on the context. The response in primary visual cortex (V1), for instance, is reduced when a stimulus is surrounded by a similar stimulus [1-3]. The source of this surround suppression is partially known. In mouse, local horizontal integration by somatostatin-expressing interneurons contributes to surround suppression [4]. In primates, however, surround suppression arises too quickly to come from local horizontal integration alone, and myelinated axons from higher visual areas, where cells have larger receptive fields, are thought to provide additional surround suppression [5, 6]. Silencing higher visual areas indeed decreased surround suppression in the awake primate by increasing responses to large stimuli [7, 8], although not under anesthesia [9, 10]. In smaller mammals, like mice, fast surround suppression could be possible without feedback. Recent studies revealed a small reduction in V1 responses when silencing higher areas [11, 12] but have not investigated surround suppression. To determine whether higher visual areas contribute to V1 surround suppression, even when this is not necessary for fast processing, we inhibited the areas lateral to V1, particularly the lateromedial area (LM), a possible homolog of primate V2 [13], while recording in V1 of awake and anesthetized mice. We found that part of the surround suppression depends on activity from lateral visual areas in the awake, but not anesthetized, mouse. Inhibiting the lateral visual areas specifically increased responses in V1 to large stimuli. We present a model explaining how excitatory feedback to V1 can have these suppressive effects for large stimuli.

The representation of subordinate shape similarity in human occipitotemporal cortex.

We investigated the coding of subordinate shape similarity in human object-selective cortex in two event-related functional magnetic resonance adaptation (fMR-A) experiments. Previous studies using faces have concluded that there is a narrow tuning of neuronal populations selective to each face, and that tuning is relative to the expected "average" face (norm-based encoding). Here we investigated these issues using outlines of animals and tools occupying a particular position on different morphing sequences per category. In a first experiment, we inferred the width of neural tuning to exemplars by examining whether the release from adaptation with increasing shape changes between two stimuli asymptotes. In a second experiment, we compared the response to central and extreme positions in shape space while controlling for the number of presentations of each unique stimulus to study whether the expected "average" category exemplar plays a role. The current fMR-A results show that a small change in exemplar shape produces a large release of adaptation, but only for outline shape changes of animals and not for man-made tools. Furthermore, our results suggested that central and extreme positions were not treated differently. Together, these results suggest a narrow tuning in object-selective cortex for individual exemplars from natural object categories, consistent with an exemplar-based encoding principle.

Similarity, typicality, and category-level matching of morphed outlines of everyday objects.

During visual object categorisation, a match must be found between the input image and stored information about basic-level categories. Graf [2002 Form, Space and Object (Berlin: Wissenschaftlicher Verlag Berlin)] suggested the involvement of analogue transformational, shape-changing processes in aligning the memory representation of the category with the perceptual representation of the current stimulus. Here we compare the predictions of alignment models with those of exemplar-based models, using morphing between four exemplar outlines within each of eleven categories. Overall, with increasing transformational distance between two exemplars of the same category, reaction times to decide whether they belong to the same category in a sequential matching paradigm increased, while rated similarity between the two exemplars decreased. However, in contrast to alignment accounts, exemplar-based accounts can correctly predict the observed dissociation between typicality and categorisation time, and allow the observed deviations from sequential additivity and nonlinear relations between transformational distance and rated similarity. Discussion of integrations of exemplar-based theories with neglected processes, such as information accumulation, response competition, response priming, and gain-modulation leads to a view of the recognition process from input to response, which increases the validity and scope of modern exemplar-based categorisation and recognition models.