ViSiElse: an innovative R-package to visualize raw behavioral data over time.

The scientific community encourages the use of raw data graphs to improve the reliability and transparency of the results presented in articles. However, the current methods used to visualize raw data are limited to one or two numerical variables per graph and/or small sample sizes. In the behavioral sciences, numerous variables must be plotted together in order to gain insight into the behavior in question. In this article, we present ViSiElse, an R-package offering a new approach in the visualization of raw data. ViSiElse was developed with the open-source software R to visualize behavioral observations over time based on raw time data extracted from visually recorded sessions of experimental observations. ViSiElse gives a global overview of a process by creating a visualization of the timestamps for multiple actions and all participants into a single graph; individual or group behavior can then be easily assessed. Additional features allow users to further inspect their data by including summary statistics and time constraints.

An observational study using eye tracking to assess resident and senior anesthetists' situation awareness and visual perception in postpartum hemorrhage high fidelity simulation.

BACKGROUND: The postpartum hemorrhage (PPH) is the leading cause of maternal mortality in the world. Human factors and especially situation awareness has primarily responsibility to explain suboptimal cares. Based on eye tracking and behavior analysis in high fidelity simulation of PPH management, the goal of this study is to identify perceptual and cognitive key parameters of the expertise. METHODS: Two groups of fifteen anesthetists (residents and experienced anesthetists) watched the beginning of a severe simulated PPH management. During this first experimental phase, situation awareness was assessed using SAGAT (Situation Awareness Global Assessment Technique) questionnaire and visual behavior was analyzed with eye tracking. In the continuity of the video sequence, they have to step in the PPH situation and to provide care to the simulated patient. Performance of cares was evaluated and self-assessed as well as cognitive load. RESULTS: No statistical difference between the residents and experienced anesthetists was observed on performance of simulated PPH management. The mean expected practice score was 76.9 ± 13.9%). Assessment of situation awareness (65 ± 7%), cognitive load (74.4 ± 11.3%) and theoretical knowledge of PPH (52.4 ± 3.5%) were also not statistically different between the two groups. Only results of self-assessed performance (respectively 66.1 ± 16.6 and 47.0 ± 20.8 for experts and residents) and eye-tracking data revealed that experts tended to get accurate evaluation of their performance and to monitor more the blood loss of the patient. Experts have in average 8.28% more fixating points than Novices and gazed the blood loss region longer (865 ms ± 439 vs. 717 ms ± 362). CONCLUSIONS: This study pointed out the limits of classical assessment of performance, and human factors based on questionnaires to identify expertise in simulated PPH care. A neuroscientific approach with new technology like eye tracking could provide new objective and more sensitive insights on human factors in simulated medical emergency situations.

Single-trial EEG-informed fMRI reveals spatial dependency of BOLD signal on early and late IC-ERP amplitudes during face recognition.

Simultaneous EEG-fMRI has opened up new avenues for improving the spatio-temporal resolution of functional brain studies. However, this method usually suffers from poor EEG quality, especially for evoked potentials (ERPs), due to specific artifacts. As such, the use of EEG-informed fMRI analysis in the context of cognitive studies has particularly focused on optimizing narrow ERP time windows of interest, which ignores the rich diverse temporal information of the EEG signal. Here, we propose to use simultaneous EEG-fMRI to investigate the neural cascade occurring during face recognition in 14 healthy volunteers by using the successive ERP peaks recorded during the cognitive part of this process. N170, N400 and P600 peaks, commonly associated with face recognition, were successfully and reproducibly identified for each trial and each subject by using a group independent component analysis (ICA). For the first time we use this group ICA to extract several independent components (IC) corresponding to the sequence of activation and used single-trial peaks as modulation parameters in a general linear model (GLM) of fMRI data. We obtained an occipital-temporal-frontal stream of BOLD signal modulation, in accordance with the three successive IC-ERPs providing an unprecedented spatio-temporal characterization of the whole cognitive process as defined by BOLD signal modulation. By using this approach, the pattern of EEG-informed BOLD modulation provided improved characterization of the network involved than the fMRI-only analysis or the source reconstruction of the three ERPs; the latter techniques showing only two regions in common localized in the occipital lobe.

Time-Frequency and ERP Analyses of EEG to Characterize Anticipatory Postural Adjustments in a Bimanual Load-Lifting Task.

Anticipatory postural adjustments (APAs) compensate in advance for the destabilizing effect of a movement. This study investigated the specific involvement of each primary motor cortex (M1) during a bimanual load-lifting task in which subjects were required to maintain a stable forearm position during voluntary unloading. Kinematics, electromyographic, and electroencephalographic (EEG) data were recorded in eight right-handed healthy subjects lifting a load placed on their left forearm. Two EEG analyses were performed: a time-frequency (TF) analysis and an event-related potential (ERP) analysis. The TF analysis revealed a mean power decrease in the mu rhythm over the left and right M1 concomitant with lifting onset. Each decrease showed specific features: over the right M1, contralateral to the postural forearm, there was a steeper slope and a greater amplitude than over the left M1. Although a mu rhythm desynchronization has until now been the signature of cortical activity related to a motor component, we show that it can also be related to postural stabilization. We discuss the involvement of the mu rhythm desynchronization over the postural M1 in the high temporal precision enabling efficient APAs. ERP analysis showed a negative wave over the left M1 and a concomitant positive wave over the right M1. While the negative wave classically reflects M1 recruitment related to the forthcoming lifting, the novelty here is that the positive wave reflects the transmission of inhibitory commands toward the postural forearm.

When the fingers need to act faster than the arm: coordination between grip force and load force during oscillation of a hand-held object.

Using a precision grip, 12 participants horizontally oscillated a lightweight object at different movement frequencies (1.0, 1.5, and 2.0 Hz) under two types of elastic load. In the first (CENT), the center of oscillation coincided with the neutral position of the object in the elastic force field, leading to two peaks in load force (LF) per cycle of movement (2:1 frequency ratio). In the second (BACK and FRONT), the neutral elastic force position of the object was located outside the range of movement, thus leading to only one LF peak per cycle of movement (1:1 frequency ratio). Results showed that in BACK and FRONT the coupling between grip force (GF) and LF (as reflected by coefficients of correlations) remained strong for all movement frequencies. In contrast, this coupling decreased in CENT as movement frequency increased, with participants switching progressively from two to one GF modulation per cycle of movement. Specific evaluation of performance under conditions giving rise to comparable LF frequencies (CENT at 1.0 Hz vs. BACK/FRONT at 2.0 Hz) confirmed the effect of frequency ratio on GF-LF coupling. We conclude that the control of GF is more efficient when LF varies at the frequency of movement than when it varies at twice this frequency, especially when movement frequency is high. These results are interpreted in the context of coordination dynamics and forward modeling approach.

Aging affects the predictive control of grip force during object manipulation.

We examined the effects of aging on the predictive control of grip force during object manipulation under various external force fields. Participants rhythmically moved a hand-held object (m = 0.4 kg) in the horizontal plane under three experimental conditions: (1) with an elastic cord attached to the upper arm (ARM), (2) with the elastic cord attached to the object (OBJECT), and (3) without any elastic cord (NO ELAST). Performance was evaluated in terms of both metric and spectral characteristics of the grip force (GF) profile, in relation to the movement-induced variations in load at the object-finger interface (LFO). The performance of a group of 12 older adults (mean age = 66.3 years) was compared to the performance of a group of 12 young adults (mean age = 25.0 years), whose metric characteristics were reported earlier (Exp. Brain Res. 172:331, 2006). Although elderly participants exerted a larger mean GF, a tight linear coupling between GF and LFO was found for both groups in OBJECT. In ARM and NO ELAST, coefficients of cross-correlations were markedly lower, the more so for the elderly participants. Adjustments in GF occurred slightly in advance of variations in LFO in young adults (+7 ms) and somewhat delayed in the elderly (-26 ms). Spectral analyses revealed that in OBJECT, LFO and GF varied primarily at the frequency of movement. In ARM and NO ELAST, where LFO varied at twice this frequency, GF modulations contained a substantial frequency component at the frequency of movement, with this effect being more pronounced for the elderly participants. We conclude that both young and older adults demonstrate a predictive control of GF, capable of separating external force fields acting on the arm or on object-finger interface. However, in the presence of variations in LFO occurring at twice the frequency of movement, the spectral profile of GF exhibits a non-functional component of variation at the frequency of movement. Aging amplifies this latter effect, thereby affecting the efficiency of the predictive control of grip force.

Predictive control of grip force when moving object with an elastic load applied on the arm.

Skilled object manipulation relies on the capability to adjust the grip force according to the consequences of our movements in terms of the resulting load force of the object. Such predictive grip force control requires (at least) two neural processes: (1) predicting the kinematic characteristics of the unfolding arm trajectory and (2) predicting the load force on the object resulting, among other factors, from the arm movement. The goal of this study was to examine whether subjects can still anticipate the resulting load force on the object when the moving arm is submitted to a type of load that does not contribute to the object load. To this end, 12 subjects were asked to rhythmically move a 0.4 kg object under three different conditions. In the first condition (ARM), an elastic cord was attached to the upper arm. In the second condition, the elastic cord was attached to the object (OBJECT). In the third condition, the elastic cord was absent (NO ELAST). At the kinematic level, results showed no influence of the elastic cord on the pattern of movement of the object. At the kinetic level, cross-correlation analyses between grip force and load force acting on the object revealed significant correlations with minimal delays. In addition, grip force profiles were similar under the ARM and NO ELAST conditions, both differing from the OBJECT condition. Overall, we interpret these results as evidence that the neural processes involved in the prediction of the arm trajectory and those involved in the prediction of the load on the object held can take into account different external force fields, thereby preserving the functionality of the behaviour.