Cognitive strategies in the mental rotation task revealed by EEG spectral power

The roles of symmetry and elongation in developing reference frames

Previous studies showed that elongation and symmetry (two ubiquitous aspects of natural stimuli) are important attributes in object perception and recognition, which in turn suggests that these geometrical factors may contribute to the selection of perceptual reference-frames. However, whether and how these attributes guide the selection of reference-frames is still poorly understood. The goal of this study was to examine systematically the roles of elongation and symmetry, as well as their combination, in the selection of reference axis and how these axes are developed for unfamiliar objects. We designed our experiments to eliminate two potential confounding factors: (i) extraneous environmental cues, such as edges of the screen, etc. (by using VR) and (ii) pre-learned cues for familiar objects and shapes (by using reinforcement learning of novel shapes). We used algorithmically generated textures with different orientations having specified levels of symmetry and elongation as the stimuli. In each trial, we presented only one stimulus and asked observers to report if the stimulus was in its original form or a flipped (mirror-image) one. Feedback was provided at the end of each trial. Based on previous studies on mental rotation, we hypothesized that the selection of a reference-frame defined by symmetry and/or elongation would be revealed by a linear relationship between reaction-times and the angular-deviation from either the most symmetrical or the most elongated orientation. Our results are consistent with this hypothesis. We found that subjects performed mental rotation to transform images to their reference axes and used the most symmetrical or elongated orientation as the reference axis when only one factor was presented, and they used a "winner-take-all" strategy when both factors were presented, with elongation being more dominant than symmetry. We discuss theoretical implications of these findings, in particular in the context of "canonical sensorimotor theory."

The impact of presentation modes on mental rotation processing: a comparative analysis of eye movements and performance

Mental rotation is the ability to rotate mental representations of objects in space. Shepard and Metzler's shape-matching tasks, frequently used to test mental rotation, involve presenting pictorial representations of 3D objects. This stimulus material has raised questions regarding the ecological validity of the test for mental rotation with actual visual 3D objects. To systematically investigate differences in mental rotation with pictorial and visual stimuli, we compared data of N = 54 university students from a virtual reality experiment. Comparing both conditions within subjects, we found higher accuracy and faster reaction times for 3D visual figures. We expected eye tracking to reveal differences in participants' stimulus processing and mental rotation strategies induced by the visual differences. We statistically compared fixations (locations), saccades (directions), pupil changes, and head movements. Supplementary Shapley values of a Gradient Boosting Decision Tree algorithm were analyzed, which correctly classified the two conditions using eye and head movements. The results indicated that with visual 3D figures, the encoding of spatial information was less demanding, and participants may have used egocentric transformations and perspective changes. Moreover, participants showed eye movements associated with more holistic processing for visual 3D figures and more piecemeal processing for pictorial 2D figures.

The relationship between object-based spatial ability and virtual navigation performance

Spatial navigation is a multi-faceted behaviour drawing on many different aspects of cognition. Visuospatial abilities, such as mental rotation and visuospatial working memory, in particular, may be key factors. A range of tests have been developed to assess visuospatial processing and memory, but how such tests relate to navigation ability remains unclear. This understanding is important to advance tests of navigation for disease monitoring in various disorders (e.g., Alzheimer's disease) where spatial impairment is an early symptom. Here, we report the use of an established mobile gaming app, Sea Hero Quest (SHQ), as a measure of navigation ability in a sample of young, predominantly female university students (N = 78; 20; female = 74.3%; mean age = 20.33 years). We used three separate tests of navigation embedded in SHQ: wayfinding, path integration and spatial memory in a radial arm maze. In the same participants, we also collected measures of mental rotation (Mental Rotation Test), visuospatial processing (Design Organization Test) and visuospatial working memory (Digital Corsi). We found few strong correlations across our measures. Being good at wayfinding in a virtual navigation test does not mean an individual will also be good at path integration, have a superior memory in a radial arm maze, or rate themself as having a strong sense of direction. However, we observed that participants who were good in the wayfinding task of SHQ tended to perform well on the three visuospatial tasks examined here, and to also use a landmark strategy in the radial maze task. These findings help clarify the associations between different abilities involved in spatial navigation.

Effects of two years of physically active lessons on cognitive indicators in children

Our purpose was to evaluate the effect of physically active lessons (PAL) on the cognitive performance of children during two years of follow-up. Four classes (second grade of elementary school) were divided into two intervention classes (n = 34) and two control classes (n = 27). Evaluations were performed before the intervention (M1), after 3 (M2) and 9 (M3) months in the 1st year, and 14 (M4) and 18 (M5) months in the 2nd year. The intervention was based on PAL integrated with the curricular components, which stimulated the children to stand or move in the classroom. Cognitive performance was evaluated using three computerized tests for response inhibition, selective attention, and cognitive flexibility. The children in the intervention classes presented improved cognitive performance in the execution of all tasks along the two years follow-up, in both correct answers and time reactions, with exception of correct answers of visual search. For the intervention classes, in most of the tasks, the mean differences confidence interval of 95% did not include the 0 on the two last moments of evaluation, and in all cases, the mean differences of them between M1 versus M5 were significantly different with high values of effect size (cohen -d > 1). PAL promotes modest improvements in diverse cognitive functions in children.

The spectral profile of cortical activation during a visuospatial mental rotation task and its correlation with working memory

Introduction

The search for a cortical signature of intelligent behavior has been a longtime motivation in Neuroscience. One noticeable characteristic of intelligence is its association with visuospatial skills. This has led to a steady focus on the functional and structural characteristics of the frontoparietal network (FPN) of areas involved with higher cognition and spatial behavior in humans, including the question of whether intelligence is correlated with larger or smaller activity in this important cortical circuit. This question has broad significance, including speculations about the evolution of human cognition. One way to indirectly measure cortical activity with millisecond precision is to evaluate the event-related spectral perturbation (ERSP) of alpha power (alpha ERSP) during cognitive tasks. Mental rotation, or the ability to transform a mental representation of an object to accurately predict how the object would look from a different angle, is an important feature of everyday activities and has been shown in previous work by our group to be positively correlated with intelligence. In the present work, we evaluate whether alpha ERSP recorded over the parietal, frontal, temporal, and occipital regions of adolescents performing easy and difficult trials of the Shepard–Metzler’s mental rotation task, correlates or are predicted by intelligence measures of the Weschler’s intelligence scale.

Methods

We used a database obtained from a previous study of intellectually gifted (N = 15) and average intelligence (N = 15) adolescents.

Results

Our findings suggest that in challenging task conditions, there is a notable difference in the prominence of alpha event-related spectral perturbation (ERSP) activity between various cortical regions. Specifically, we found that alpha ERSP in the parietal region was less prominent relative to those in the frontal, temporal and occipital regions. Working memory scores predict alpha ERSP values in the frontal and parietal regions. In the frontal cortex, alpha ERSP of difficult trials was negatively correlated with working memory scores.

Discussion

Thus, our results suggest that even though the FPN is task-relevant during mental rotation tasks, only the frontal alpha ERSP is correlated with working memory score in mental rotation tasks.

Neural and cognitive correlates of performance in dynamic multi-modal settings

The endeavour to understand human cognition has largely relied upon investigation of task-related brain activity. However, resting-state brain activity can also offer insights into individual information processing and performance capabilities. Previous research has identified electroencephalographic resting-state characteristics (most prominently: the individual alpha frequency; IAF) that predict cognitive function. However, it has largely overlooked a second component of electrophysiological signals: aperiodic 1/ƒ activity. The current study examined how both oscillatory and aperiodic resting-state EEG measures, alongside traditional cognitive tests, can predict performance in a dynamic and complex, semi-naturalistic cognitive task. Participants' resting-state EEG was recorded prior to engaging in a Target Motion Analysis (TMA) task in a simulated submarine control room environment (CRUSE), which required participants to integrate dynamically changing information over time. We demonstrated that the relationship between IAF and cognitive performance extends from simple cognitive tasks (e.g., digit span) to complex, dynamic measures of information processing. Further, our results showed that individual 1/ƒ parameters (slope and intercept) differentially predicted performance across practice and testing sessions, whereby flatter slopes and higher intercepts were associated with improved performance during learning. In addition to the EEG predictors, we demonstrate a link between cognitive skills most closely related to the TMA task (i.e., spatial imagery) and subsequent performance. Overall, the current study highlights (1) how resting-state metrics - both oscillatory and aperiodic - have the potential to index higher-order cognitive capacity, while (2) emphasising the importance of examining these electrophysiological components within more dynamic settings and over time.

Individual differences in processing ability to transform visual stimuli during the mental rotation task are closely related to individual motor adaptation ability

Mental rotation (MR) is a well-established experimental paradigm for exploring human spatial ability. Although MR tasks are assumed to be involved in several cognitive processes, it remains unclear which cognitive processes are related to the individual ability of motor adaptation. Therefore, we aimed to elucidate the relationship between the response time (RT) of MR using body parts and the adaptive motor learning capability of gait. In the MR task, dorsal hand, palmar plane, dorsal foot, and plantar plane images rotated in 45° increments were utilized to measure the RTs required for judging hand/foot laterality. A split-belt treadmill paradigm was applied, and the number of strides until the value of the asymmetrical ground reaction force reached a steady state was calculated to evaluate the individual motor adaptation ability. No significant relationship was found between the mean RT of the egocentric perspectives (0°, 45°, and 315°) or allocentric perspectives (135°, 180°, and 225°) and adaptive learning ability of gait, irrespective of body parts or image planes. Contrarily, the change rate of RTs obtained by subtracting the RT of the egocentric perspective from that of the allocentric perspective in dorsal hand/foot images that reflect the time to mentally transform a rotated visual stimulus correlated only with adaptive learning ability. Interestingly, the change rate of RTs calculated using the palmar and plantar images, assumed to reflect the three-dimensional transformation process, was not correlated. These findings suggest that individual differences in the processing capability of visual stimuli during the transformation process involved in the pure motor simulation of MR tasks are precisely related to individual motor adaptation ability.

The Influence of Mental Imagery Expertise of Pen and Paper Players versus Computer Gamers upon Performance and Electrocortical Correlates in a Difficult Mental Rotation Task

We investigated the influence of mental imagery expertise in 15 pen and paper role-players as an expert group compared to the gender-matched control group of computer role-players in the difficult Vandenberg and Kuse mental rotation task. In this task, the participants have to decide which two of four rotated figures match the target figure. The dependent measures were performance speed and accuracy. In our exploratory investigation, we further examined midline frontal theta band activation, parietal alpha band activation, and parietal alpha band asymmetry in EEG as indicator for the chosen rotation strategy. Additionally, we explored the gender influence on performance and EEG activation, although a very small female sample section was given. The expected gender difference concerning performance accuracy was negated by expertise in pen and paper role-playing women, while the gender-specific difference in performance speed was preserved. Moreover, gender differences concerning electro-cortical measures revealed differences in rotation strategy, with women using top-down strategies compared to men, who were using top-down strategies and active inhibition of associative cortical areas. These strategy uses were further moderated by expertise, with higher expertise leading to more pronounced activation patters, especially during successful performance. However, due to the very limited sample size, the findings of this explorative study have to be interpreted cautiously.

Testing the Darwinian function of lateralization. Does separation of workload between brain hemispheres increase cognitive performance?

Brain lateralization is a fundamental aspect of the organization of brain and behavior in the animal kingdom, begging the question about its Darwinian function. We tested the possibility that lateralization enhances cognitive performance in single- and dual-tasks. Previous studies reported mixed results on this topic and only a handful of studies have measured functional brain lateralization and performance independently and simultaneously. We therefore examined a possible positive effect of the strength and direction of lateralization on two demanding cognitive tasks: A visuospatial task (mental rotation MR), and a language task (word generation WG), executed either as a singletask or as dual-task. Participants (n = 72) performed these tasks while their single-task brain lateralization was assessed with functional Transcranial Doppler for both tasks. From these measurements we determined strength and direction of lateralization for both tasks and the individual pattern of lateralization (contralateral or ipsilateral) was derived. These factors, along with sex, were used in a GLM analysis to determine if they predicted the respective performance measure of the tasks. We found that for MR there was a significant medium effect of direction of lateralization on performance with better performance in left-lateralized (atypical) participants (partial eta squared 0.061; p = .039). After correction for outliers, there was a significant effect for strength (p = .049). For the dual-task, there was a significant positive medium effect of strength of lateralization on performance (partial eta squared 0.062; p = .038, respectively) No other association between direction or strength in either tests were found. We conclude that there is no evidence for hemispheric crowding, and that strength of lateralization may be a factor that contributes to the evolutionary selection of functional brain lateralization. Pattern of lateralization does not, explaining the large inter-individual variation in these traits.

Effects of Physically Active Lessons on Movement Behaviors, Cognitive, and Academic Performance in Elementary Schoolchildren: ERGUER/Aracaju Project

BACKGROUND

To evaluate the effects of the introduction of physically active lessons on movement behaviors, cognitive, and academic performance in schoolchildren.

METHODS

This was a cluster-controlled trial. A total of 61 students from the second year of elementary school in a public school in Brazil made up 2 intervention classes (n = 34) with the introduction of physically active lessons and 2 control classes (n = 27). Sedentary behavior, physical activity, cognitive, and academic performance were evaluated in 3 moments, which were compared using models of generalized estimating equations.

RESULTS

The intervention was effective for reducing the standing time between the baseline and 3 months while increasing the walking time between baseline and 3 months and baseline and 9 months. There was a reduction in time in stationary activities and increased time in light physical activities between all moments. The intervention group increased their performance in the go/no go test, showing a smaller number of errors between the baseline and 3 months and baseline and 9 months, and a reduction in the test time between baseline and 3 months. No impact on students' academic performance was observed.

CONCLUSION

Physically active lessons improve movement behaviors and cognitive functions among elementary schoolchildren.

Neuropsychological effect of working memory capacity on mental rotation under hypoxia environment

High-altitude exposure induces the decline of spatial manipulation such as mental rotation which is limited by working memory capacity, but the underlying neuropsychological effect remains to be identified. We evaluated the mental rotation task and the contralateral delay activity (CDA) task under hypoxia environment using the event-related potential. When compared with the controls, the behavior response was slowed on two tasks in the high-altitude group. The declined mental rotation and the decreased working memory capacity were synchronously related to the amplitudes of P50 and CDA, respectively. The P50 during mental rotation was positively correlated to that of rotation-related negativity (RRN) component, so was with the CDA. Time-frequency analysis showed that the beta/alpha power in mental rotation and the theta/alpha/beta power in CDA were enhanced in the high-altitude group. The present study might suggest that the decline of working memory capacity induced poor performance of mental rotation, which may be derived from a bottom-up sensory gating deficit reflected by P50.

A Positive Relationship Between Sign Language Comprehension and Mental Rotation Abilities

Past work investigating spatial cognition suggests better mental rotation abilities for those who are fluent in a signed language. However, no prior work has assessed whether fluency is needed to achieve this performance benefit or what it may look like on the neurobiological level. We conducted an electroencephalography experiment and assessed accuracy on a classic mental rotation task given to deaf fluent signers, hearing fluent signers, hearing non-fluent signers, and hearing non-signers. Two of the main findings of the study are as follows: (1) Sign language comprehension and mental rotation abilities are positively correlated and (2) Behavioral performance differences between signers and non-signers are not clearly reflected in brain activity typically associated with mental rotation. In addition, we propose that the robust impact sign language appears to have on mental rotation abilities strongly suggests that "sign language use" should be added to future measures of spatial experiences.

The Effect of Planning, Strategy Learning, and Working Memory Capacity on Mental Workload

In our modern society, planning and problem solving are crucial for handling a wide range of situations. Investigation of the experienced mental workload connected to planning, strategy learning, and working memory capacity is of particular interest for adjusting conditions according to the mental state of the individual. In our study, we examined 21 subjects during a planning and a working memory task. We applied the method of Dual Frequency Head Maps (DFHM) from the electroencephalogram for capturing mental workload objectively. We evaluated the DFHM-workload index and performance data during the learning and main phase of the planning task and linked the results to subjects' working memory capacity. The DFHM-workload index indicated that subjects with higher working memory capacity experienced a gradual decrease in mental workload during strategy learning of the planning task. However, the effect of learning on mental workload disappeared during the main phase.

Indexing Mental Workload During Simulated Air Traffic Control Tasks by Means of Dual Frequency Head Maps

In our digitized society, advanced information and communication technology and highly interactive work environments impose high demands on cognitive capacity. Optimal workload conditions are important for assuring employee's health and safety of other persons. This is particularly relevant in safety-critical occupations, such as air traffic control. For measuring mental workload using the EEG, we have developed the method of Dual Frequency Head Maps (DFHM). The method was tested and validated already under laboratory conditions. However, validation of the method regarding reliability and reproducibility of results under realistic settings and real world scenarios was still required. In our study, we examined 21 air traffic controllers during arrival management tasks. Mental workload variations were achieved by simulation scenarios with different number of aircraft and the occurrence of a priority-flight request as an exceptional event. The workload was assessed using the EEG-based DFHM-workload index and instantaneous self-assessment questionnaire. The DFHM-workload index gave stable results with highly significant correlations between scenarios with similar traffic-load conditions (r between 0.671 and 0.809, p ≤ 0.001). For subjects reporting that they experienced workload variation between the different scenarios, the DFHM-workload index yielded significant differences between traffic-load levels and priority-flight request conditions. For subjects who did not report to experience workload variations between the scenarios, the DFHM-workload index did not yield any significant differences for any of the factors. We currently conclude that the DFHM-workload index reveals potential for applications outside the laboratory and yields stable results without retraining of the classifiers neither regarding new subjects nor new tasks.

Schizophrenia diagnosis using innovative EEG feature-level fusion schemes

Electroencephalogram (EEG) has become a practical tool for monitoring and diagnosing pathological/psychological brain states. To date, an increasing number of investigations considered differences between brain dynamic of patients with schizophrenia and healthy controls. However, insufficient studies have been performed to provide an intelligent and accurate system that detects the schizophrenia using EEG signals. This paper concerns this issue by providing new feature-level fusion algorithms. Firstly, we analyze EEG dynamics using three well-known nonlinear measures, including complexity (Cx), Higuchi fractal dimension (HFD), and Lyapunov exponents (Lya). Next, we propose some innovative feature-level fusion strategies to combine the information of these indices. We evaluate the effect of the classifier parameter (σ) adjustment and the cross-validation partitioning criteria on classification accuracy. The performance of EEG classification using combined features was compared with the non-combined attributes. Experimental results showed higher classification accuracy when feature-level features were utilized, compared to when each feature was used individually or all fed to the classifier simultaneously. Using the proposed algorithm, the classification accuracy increased up to 100%. These results establish the suggested framework as a superior scheme compared to the state-of-the-art EEG schizophrenia diagnosis tool.

Investigating sex differences, cognitive effort, strategy, and performance on a computerised version of the mental rotations test via eye tracking

Mental rotation tests (MRTs) have previously shown one of the most prominent sex differences in cognitive psychology, marked by a large male performance advantage. However, debate continues over the reasons for these sex differences. Previously, we used pupillometry to demonstrate sex differences in the cognitive effort invoked during the original MRT. Here, we evaluated the magnitude of sex differences during performance on a computerized version of the Vandenberg and Kuse MRT. Secondly, we examined whether fixation metrics could illuminate strategy use by participants. Finally, we used pupillometry to investigate whether cognitive effort differed between sexes and trials of different difficulty. While our results demonstrate no performance differences between sexes on the computerized MRT, fixation patterns provided evidence that gaze strategy was associated with performance on different parts of the test. Moreover, we show the cognitive demand of the V&K MRT, evidenced by large task dependent increases in participants’ pupil diameters.

Revisiting mental rotation with stereoscopic disparity: A new spin for a classic paradigm

To understand how the presence of stereoscopic disparity influences cognitive and neural processing, we recorded participants' behavior and scalp electrical activity while they performed a mental rotation task. Participants wore active shutter 3D goggles, allowing us to present stimuli with or without stereoscopic disparity on a trial-by-trial basis. Participants were more accurate and faster when stimuli were presented with stereoscopic disparity. This improvement in performance was accompanied by changes in neural activity recorded from scalp electrodes at parietal and occipital regions; stereoscopic disparity produced earlier P2 peaks, larger N2 amplitudes, and earlier, smaller P300 peak amplitudes. The presence of stereoscopic disparity also produced greater neural entropy at occipital electrode sites, and lower entropy at frontal sites. These findings suggest that the nature of the benefit afforded by stereoscopic disparity occurs at both low-level perceptual processing and higher-level cognitive processing, and results in more accurate and rapid performance.

Beta and gamma synchronous oscillations in neural network activity in mice-induced by food deprivation

Food deprivation is known to trigger hunger sensation and motivation to eat for energy replenishing. However, brain mechanisms associated with hunger and neural circuitries that mediate hunger driven responses remained to be investigated. To understand neural signaling of hunger, local field potentials (LFPs) in the lateral hypothalamus (LHa), nucleus accumbens (NAc), dorsal hippocampus (HP) and olfactory bulb (OB) and their interconnectivities were studied in freely moving adult male Albino mice during 18-20 h food deprivation and fed periods. Raw LFP signals were recorded and analyzed for mean values of spectral frequency power and coherence values. One-way repeated measures ANOVA revealed significant increases in spectral powers of beta and gamma frequency ranges induced by food deprivation in the LHa, HP, NAc but not OB. No change of spectral power in these brain regions was induced by food feeding. The analyses of coherent activity between brain regions also deliniated some distributed neural network activities correlated with hunger. In particular, coherent function indicated the increased beta and gamma phase synchrony between the pairs of LHa-HP and NAc-OB regions, and decreased gamma synchrony between the pairs of LHa-NAc and NAc-HP induced by food deprivation. It was found that plasma glucose level, locomotor count, travelled distance and time spent on moving were not altered by food deprivation. These results suggest that changes in LFP hallmarks in these brain regions were associated with hunger driven by negative energy balance.

Decoding electroencephalographic signals for direction in brain-computer interface using echo state network and Gaussian readouts

BACKGROUND

Noninvasive brain-computer interfaces (BCI) for movement control via an electroencephalogram (EEG) have been extensively investigated. However, most previous studies decoded user intention for movement directions based on sensorimotor rhythms during motor imagery. BCI systems based on mapping imagery movement of body parts (e.g., left or right hands) to movement directions (left or right directional movement of a machine or cursor) are less intuitive and less convenient due to the complex training procedures. Thus, direct decoding methods for detecting user intention about movement directions are urgently needed.

METHODS

Here, we describe a novel direct decoding method for user intention about the movement directions using the echo state network and Gaussian readouts. Importantly parameters in the network were optimized using the genetic algorithm method to achieve better decoding performance. We tested the decoding performance of this method with four healthy subjects and an inexpensive wireless EEG system containing 14 channels and then compared the performance outcome with that of a conventional machine learning method.

RESULTS

We showed that this decoding method successfully classified eight directions of intended movement (approximately 95% of an accuracy).

CONCLUSIONS

We suggest that the echo state network and Gaussian readouts can be a useful decoding method to directly read user intention of movement directions even using an inexpensive and portable EEG system.

Effect of Complexity on Frontal Event Related Desynchronisation in Mental Rotation Task

A complexity (orientation and shape of stimuli) in the mental rotation (MR) task often affects reaction time (RT) and response accuracy, but the nature of such reflections in neuroscientific research is commonly undocumented. A number of studies have explored the effect of complexity and subsequently noted down the differences in performance. However, a few studies explored complexity (in the term of angular disparity) and cognitive strategies with respect to correct responses only. In contrast, the present study investigated frontal alpha desynchronization with reference to the complexity and proportions of correct and incorrect responses. Behavioral and neurophysiological responses were investigated to understand the switching between strategies (Analytic vs. Holistic). Results showed longer response time with respect to increased complexity. Frontal alpha desynchronization increased for difficult trials and incorrect responses, suggesting a higher utilization of cognitive resources at the frontal region during the MR task. Higher left frontal desynchronization reflected a trading off between strategies for difficult trials. Taken together, these findings suggest that the effect of stimuli complexity is more nuanced than implied by a simple hemispheric dichotomy for frontal cortex and discuss possible future directions to better understand the multitudinous brain mechanisms involved in MR.

Alpha and beta band correlates of haptic perceptual grouping: Results from an orientation detection task

Behavioral and neurophysiological findings in vision suggest that perceptual grouping is not a unitary process and that different grouping principles have different processing requirements and neural correlates. The present study aims to examine whether the same occurs in the haptic modality using two grouping principles widely studied in vision, spatial proximity and texture similarity. We analyzed behavioral responses (accuracy and response times) and conducted an independent component analysis of brain oscillations in alpha and beta bands for haptic stimuli grouped by spatial proximity and texture similarity, using a speeded orientation detection task performed on a novel haptic device (MonHap). Behavioral results showed faster response times for patterns grouped by spatial proximity relative to texture similarity. Independent component clustering analysis revealed the activation of a bilateral network of sensorimotor and parietal areas while performing the task. We conclude that, as occurs in visual perception, grouping the elements of the haptic scene by means of their spatial proximity is faster than forming the same objects by means of texture similarity. In addition, haptic grouping seems to involve the activation of a network of widely distributed bilateral sensorimotor and parietal areas as reflected by the consistent event-related desynchronization found in alpha and beta bands.

Combination of a short cognitive training and tDCS to enhance visuospatial skills: A comparison between online and offline neuromodulation

Visuospatial skills can be enhanced thanks to specific intervention programs, but the additional benefits of neuromodulation on these skills have not been fully investigated yet, although transcranial direct current stimulation (tDCS) has demonstrated to boost the effects of cognitive trainings. When combining cognitive intervention with neuromodulation, the time-window of tDCS application in relation to task execution has to be taken into account since it has been shown to affect stimulation outcomes. The aim of the present experiment was to investigate the influence of tDCS in enhancing the effects of a training for visuospatial skills. We hypothesized that tDCS applied during training execution (online) would improve the cognitive performance at a larger extent than tDCS applied before training execution (offline). Participants received anodal tDCS over the dorsolateral prefrontal cortex during (online) or before (offline) the completion of the training. A control sham condition was included. Visuospatial abilities were measured 24 h before (day 1, pre-test) and 24 h after (day 3, post-test) the stimulation and training session (day 2). tDCS enhanced gains for mental folding performance when applied during the execution of the training (online). Participants' mental rotation and mental folding performance improved from pre-test to post-test regardless of the stimulation condition. However participants in the online tDCS condition showed the largest improvement in mental folding performance. Findings indicate that tDCS enhanced the effects of the training when applied during its execution, showing cumulative positive aftereffects on visuospatial performance 24 h after the stimulation session. The time-dependent effect points out the importance of the time-window of tDCS application in influencing behavior when combined with cognitive programs.