Experimental Brain Research

Zehr, E.P.; Barss, Trevor; Dragert, Katie; Frigon, Alain; Vasudevan, Erin; Haridas, Carlos; Hundza, Sandra; Kaupp, Chelsea; Klarner, Taryn; Klimstra, Marc; Komiyama, Tomoyoshi; Loadman, Pamela; Mezzarane, Rinaldo; Nakajima, Tsuyoshi; Pearcey, Gregory; Sun, Yao

doi: 10.1007/s00221-016-4715-4pmid: 27421291

During bipedal locomotor activities, humans use elements of quadrupedal neuronal limb control. Evolutionary constraints can help inform the historical ancestry for preservation of these core control elements support transfer of the huge body of quadrupedal non-human animal literature to human rehabilitation. In particular, this has translational applications for neurological rehabilitation after neurotrauma where interlimb coordination is lost or compromised. The present state of the field supports including arm activity in addition to leg activity as a component of gait retraining after neurotrauma.

Simon, Anja; Bock, Otmar

doi: 10.1007/s00221-016-4707-4pmid: 27349994

It is still unknown whether visuomotor adaptation depends on the time during which a person is exposed to distorted vision, or rather on the number of movements executed under the distortion. To find out, we analysed the pointing errors and movement kinematics of 52 participants adapting with online visual feedback to a 60° visual rotation and 39 participants adapting to a 75° visual rotation without time constraints. We found that movement time was not related with participants’ success during adaptation, whereas peak velocity was inversely associated to adaptive success. However, peak velocity lost its association to adaptation when other parameters were taken into account. Movement kinematics during adaptation had little influence on participants’ performance during de-adaptation. Our data suggest that adaptation does not depend primarily on the duration but rather on the number of movements executed under distorted vision. It further suggests that the measured kinematic parameters are consequences of error corrections rather than determinants of the adaptive success. We further have evidence for the view that adaptive recalibration is independent of movement kinematics during adaptation. This outcome generalizes across different visual rotations and is in accordance with earlier work where online visual feedback of the hand was unavailable.

Boytsova, Julia; Danko, Sergey; Medvedev, Svyatoslav

doi: 10.1007/s00221-016-4708-3pmid: 27349995

The main aim of the present study was to investigate effects of partial reductions of electromyogram (EMG) on high-frequency scalp electroencephalogram (EEG) at rest and during performance of certain cognitive tasks. Nineteen healthy women performed the same cognitive tasks before and after cosmetic injections of Dysport in certain sites of facial muscles. Scalp EEG and EMG were recorded. Impact of Dysport injections on changes of spectral power in β2 and low γ frequency ranges (18–40 Hz) in EEG and EMG derivations was investigated. Also changes of spectral power in EEG and EMG derivations during comparisons of different cognitive states were calculated before and after Dysport injections separately. Dysport injections led to EMG decreases in facial muscles around the injection zones and also led to reductions of power of electric processes in scalp derivations. Along with it results of EEG power comparisons between the pairs of the cognitive states were qualitatively similar before and after Dysport injections. These facts to all appearance demonstrate that though scalp EEGs in the range above 15–40 Hz are contaminated by EMG, in certain experimental situations EMG contamination does not preclude qualitative detections of electroencephalographic correlates of mental activities in β2 and low γ frequency ranges. Parallel EEG and EMG registrations can help not to overestimate EMG contamination in psychophysiological EEG studies.

Patterson, Tara; Lenartowicz, Agatha; Berkman, Elliot; Ji, Danni; Poldrack, Russell; Knowlton, Barbara

doi: 10.1007/s00221-016-4709-2pmid: 27349996

The ability to inhibit unwanted responses is critical for effective control of behavior, and inhibition failures can have disastrous consequences in real-world situations. Here, we examined how prior exposure to negative emotional stimuli affects the response-stopping network. Participants performed the stop-signal task, which relies on inhibitory control processes, after they viewed blocks of either negatively emotional or neutral images. In Experiment 1, we found that neural activity was reduced following negative image viewing. When participants were required to inhibit responding after neutral image viewing, we observed activation consistent with previous studies using the stop-signal task. However, when participants were required to inhibit responding after negative image viewing, we observed reductions in the activation of ventrolateral prefrontal cortex, dorsolateral prefrontal cortex, medial frontal cortex, and parietal cortex. Furthermore, analysis of neural connectivity during stop-signal task blocks indicated that across participants, emotion-induced changes in behavioral performance were associated with changes in functional connectivity, such that greater behavioral impairment after negative image viewing was associated with greater weakening of connectivity. In Experiment 2, we collected behavioral data from a larger sample of participants and found that stopping performance was impaired after negative image viewing, as seen in longer stop-signal reaction times. The present results demonstrate that negative emotional events can prospectively disrupt the neural network supporting response inhibition.

Kisler, Lee-Bareket; Granovsky, Yelena; Sinai, Alon; Sprecher, Elliot; Shamay-Tsoory, Simone; Weissman-Fogel, Irit

doi: 10.1007/s00221-016-4710-9pmid: 27342977

Behavioral studies found greater pain sensitivity in females that vanishes fully or partially when controlling for the emotional state. Furthermore, pain-related brain activation hints at the role of limbic structures in sex differences in pain processing. We aimed to investigate the role of pain-related limbic structures in mediating the relation between subjects’ affective state (i.e., anxiety) and pain. Contact heat-evoked potentials (CHEPs) were recorded in 26 healthy subjects (13 males) simultaneously with innocuous (42 °C) baseline and target noxious (52 °C) series of stimuli administered to the left non-dominant volar forearm. The N2 and P2 components were analyzed, and their generators’ activity was estimated using standardized low-resolution brain electromagnetic tomography. Thereafter, structural equation modeling (SEM) was applied separately for females and males, examining the mediatory role of the CHEPs’ limbic structures generators [posterior midcingulate cortex (pMCC), insula, amygdala, and hippocampus] in the anxiety–pain sensitivity association. Females exhibited greater P2 amplitudes that were highly associated with larger pMCC activity (r = 0.910, p < 0.001). This correlation was also evident in males, though with less strength (r = 0.578, p = 0.039). Moreover, the P2 amplitudes were associated both in females (r = 0.645, p = 0.017) and males (r = 0.608, p = 0.028) with the activity of the amygdala\hippocampus\insula. SEM revealed that the relationship between state anxiety and pain ratings was only in females fully mediated via the effect of the pMCC on the P2 amplitude. These findings suggest that sexual dimorphism in anxiety-related brain activity may explain the differences found in CHEPs and the sex-related association between anxiety and pain.

Giabbiconi, Claire-Marie; Jurilj, Verena; Gruber, Thomas; Vocks, Silja

doi: 10.1007/s00221-016-4711-8pmid: 27364143

In cognitive neuroscience, interest in the neuronal basis underlying the processing of human bodies is steadily increasing. Based on functional magnetic resonance imaging studies, it is assumed that the processing of pictures of human bodies is anchored in a network of specialized brain areas comprising the extrastriate and the fusiform body area (EBA, FBA). An alternative to examine the dynamics within these networks is electroencephalography, more specifically so-called steady-state visually evoked potentials (SSVEPs). In SSVEP tasks, a visual stimulus is presented repetitively at a predefined flickering rate and typically elicits a continuous oscillatory brain response at this frequency. This brain response is characterized by an excellent signal-to-noise ratio—a major advantage for source reconstructions. The main goal of present study was to demonstrate the feasibility of this method to study human body perception. To that end, we presented pictures of bodies and contrasted the resulting SSVEPs to two control conditions, i.e., non-objects and pictures of everyday objects (chairs). We found specific SSVEPs amplitude differences between bodies and both control conditions. Source reconstructions localized the SSVEP generators to a network of temporal, occipital and parietal areas. Interestingly, only body perception resulted in activity differences in middle temporal and lateral occipitotemporal areas, most likely reflecting the EBA/FBA.

Chow, John; Stokic, Dobrivoje

doi: 10.1007/s00221-016-4712-7pmid: 27370944

We compared variability, frequency composition, and temporal regularity of submaximal isometric elbow flexion force at 10, 20, 35, and 50 % of peak torque between 34 stroke subjects (5–48 days post-onset, both arms) and 24 age-matched controls (dominant arm), and related the findings in the paretic arm to motor impairment. Force variability was quantified by the coefficient of variation (CV), frequency composition by the median frequency and relative power in 0–3-, 4–6-, and 8–12-Hz bands, and regularity by the sample entropy (SampEn). The paretic elbow flexors showed significantly increased CV and relative power in 0–3-Hz band, decreased power in 4–6- and 8–12-Hz bands, and decreased SampEn compared to both the non-paretic and control elbow flexors (P ≤ 0.0002), with no differences between the latter two (P ≥ 0.012). With increasing contraction intensity, the relative power in different frequency bands was insufficiently modulated and SampEn excessively decreased in the paretic elbow flexors. Also, CV in the paretic elbow flexors was non-linearly related to the relative power in different frequency bands and SampEn across contraction intensities (rectangular hyperbolic fit, 0.21 ≤ R 2 ≤ 0.55, P ≤ 0.006), whereas no force parameter correlated with arm motor impairment. These results largely extend our previous findings in the paretic knee extensors to the elbow flexors in subacute stroke, except that here force variability was increased only in the paretic elbow flexors and modulation of force regularity with increasing contraction intensity showed the opposite, decreasing pattern, which was considerably exaggerated in the paretic muscles.

Massol, Stéphanie; Carreiras, Manuel; Duñabeitia, Jon

doi: 10.1007/s00221-016-4713-6pmid: 27372835

This study investigates the processing of letter position coding by exploring whether or not two explicitly presented words that share the same consonants, but that differ in their vowels, exert mutual interference more than two words that do not share their consonants. In an explicit perceptual matching task, word targets were preceded by a word reference that could share all the consonants either at the same position or in a different absolute position (while keeping their relative position intact) or preceded by an unrelated reference. Experiment 1 showed larger discrimination costs for pairs sharing the consonants at the same position than for pairs sharing their consonants in a different position. Experiment 2 investigated when and how the types of overlap influence word target processing by using event-related potential recordings. The ERP results showed a Relatedness effect only for targets that share the consonants at the same position from 120 to 600 ms post-target onset, whereas targets that share their consonants in different positions in the string produced null effects. Altogether, these data suggest that targets containing the same consonants included in the references in the same positions are processed as being highly similar to them, thus distorting target processing. Furthermore, these data suggest possible mechanisms of competition between lexical representations of the reference and target stimuli.

Fine, Michael; Lum, Peter; Brokaw, Elizabeth; Caywood, Matthew; Metzger, Anthony; Libin, Alexander; Terner, Jill; Tsao, Jack; Norris, Jacob; Milzman, David; Williams, Diane; Colombe, Jeff; Dromerick, Alexander

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Qaiser, Taha; Chisholm, Amanda; Lam, Tania

doi: 10.1007/s00221-016-4716-3pmid: 27380635

Sensorimotor integration is essential for controlling movement and acquiring new motor tasks in humans. The aim of this project was to understand how lower limb proprioceptive sense contributes to the acquisition of a skilled walking task. We assessed lower limb joint position and movement detection sense in healthy human subjects using the Lokomat robotic exoskeleton. Subjects walked on a treadmill to practice a skilled motor task (200 trials) requiring them to match their foot height during the swing phase to the height of a virtual obstacle displayed on a monitor in front of them. Subjects were given visual feedback on their error relative to the obstacle height after it was crossed. Lower limb joint position sense was related to the final performance error, but not the learning rate of the skilled walking task. The findings from this study support the role of lower limb proprioceptive sense on locomotor skill performance in healthy adult subjects.