Experimental Brain Research

Saeedpour-Parizi, Mohammad R.; Hassan, Shirin E.; Baniasadi, Tayebeh; Baute, Kelly J.; Shea, John B.

doi: 10.1007/s00221-020-05900-0pmid: 32776171

The purpose of this study was to determine the effect of hierarchical goal structure of a yet-to-be performed task on gait and eye fixation behavior while walking to the location of where the task was to be performed. Subjects performed different goal-directed tasks representing three hierarchical levels of planning. The first level of planning consisted of having the subject walk to a bookcase on which an object (a cup) was located in the middle of a shelf. The second level of planning consisted of walking to the bookcase and picking up the cup which was in the middle, on the right side, or on the left side of the bookcase shelf. The third level of planning consisted of walking to the bookcase, picking up the cup which was located in the middle of the bookcase shelf, and moving it to a higher shelf. Findings showed that hierarchal goals do affect center of mass velocity and eye fixation behavior. Center of mass velocity to the bookcase increased with an increase in the number of goals. Subjects decreased gait velocity as they approached the bookcase and adjusted their last steps to accommodate picking up the cup. The findings also demonstrated the important role of vision in controlling gait velocity in goal-directed tasks. Eye fixation duration was more important than the number of eye fixations in controlling gait velocity. Thus, the amount of information gained through object fixation duration is of greater importance than the number of fixations on the object for effective goal achievement.

Christova, Peka; Joseph, Jasmine; Georgopoulos, Apostolos P.

doi: 10.1007/s00221-020-05893-wpmid: 32776238

The Human Connectome Project (HCP) provides a rich dataset of quantitative and domain-specific behavioral measures from twins and extensive family structures. This makes the dataset a unique and a valuable resource to investigate heritability and determine individual differences. Using a set of measures of behavioral domains (motor, emotion, personality, sensory, and cognition), we estimated the intraclass correlations (ICCs) and heritability of 56 behavioral measures for 4 genetically identified groups of participants: monozygotic (MZ) twins, dizygotic (DZ) twins, non-twin siblings (SB), and unrelated individuals (NR). The ICCs range varied among behavioral domains but systematically so among the four genetic groups. We found the same rank order of ICCs, from the highest values for MZ twins, statistically significantly smaller for the DZ twins and sibling group (compared to MZ), and close to zero for NR. The mean heritability values of the five behavioral domains were: cognition h2 = 0.405, emotion h2 = 0.316, motor h2 = 0.138, personality h2 = 0.444, and sensory h2 = 0.193. These domains share overlapping brain networks. The heritability of motor domain was significantly smaller than cognitive, personality, and emotion domains. These findings provide new insight into the effect of genetics on the various diverse behavioral measures.

Rahdar, Parastoo; Khazali, Homayoun

doi: 10.1007/s00221-020-05860-5pmid: 32783107

RFamide-related peptide-3 (RFRP-3) has been postulated as the suppressor of the reproductive axis at hypothalamic, pituitary and gonadal levels. Considering the hypothalamic level, RFRP-3 can suppress the activity of gonadotropin-releasing hormone (GnRH) neurons and their upstream neuronal stimulator, namely; the kisspeptin neurons. The effects of the RFRP-3 on the other regulators of GnRH neurons, however, are not completely investigated. Furthermore, substance P (SP) has been known as one of the coordinators of GnRH/ luteinizing hormone (LH) and the kisspeptin/G protein-coupled receptor 54 (GPR54) systems. The present study was aimed at investigating the impacts of RFRP-3 on the effects of SP on the reproductive performance in ovariectomized female rats. After intracerebroventricular (ICV) cannulation, the rats were subjected to the ICV injection of either SP or RFRP-3 and simultaneous injection of them and their selective antagonists. Blood and hypothalamic samplings and also sexual behavioral test were carried out on two main groups of rats. The analyses of the results of LH radioimmunoassay, gene expression assay for hypothalamic Gnrh1, Kisspeptin and Gpr54 accompanied by sexual behavioral examination revealed that the SP administration promotes reproductive behavior and GnRH/LH system and upregulates Kisspeptin expression. The RFRP-3 administration suppressed reproductive behavior, GnRH / LH system and Kisspeptin expression; however, the simultaneous injection of SP and RFRP-3 was devoid of significant alterations in the assessed parameters. The results showed that RFRP-3 can modulates the impacts of SP on the reproductive performance in ovariectomized female rats in part through adjusting Kisspeptin expression.

Nooristani, M.; Moïn-Darbari, K.; Pagé, S.; Bacon, B. A.; Champoux, F.

doi: 10.1007/s00221-020-05903-xpmid: 32839854

Mental imagery can induce audiovisual integration, but whether it can induce interactions in other modalities remains uncertain. It has been demonstrated that audiomotor interaction can be generated following training, but whether such audiomotor interaction can be induced by auditory imagery training remains unknown. The present study aims at determining whether auditory mental imagery could induce a multimodal association with postural control. We examined static postural control in the presence of a frequency-modulated sound in three groups of participants, prior to and following a short period of training designed to create an association between auditory mental imagery of sounds and postural swaying. Results suggest that mental imagery impacted performance, as a significant decrease in postural control was observed in the experimental group following mental imagery training. Results of the control groups confirmed that the effect of mental imagery was not due to response bias, but to a significant multimodal interaction following training. These findings are in accordance with previous studies suggesting that mental imagery stimuli can interact with perceptual stimuli of a different sensory modality and lead to multisensory integration. The results also confirm that audiomotor interaction can be generated a mental imagery training. However, the full extent of mental imagery influence on multimodal interaction remains to be determined.

Hernandez-Sarabia, Jesus A.; Luera, Micheal J.; Barrera-Curiel, Alejandra; Estrada, Carlos A.; DeFreitas, Jason M.

doi: 10.1007/s00221-020-05906-8pmid: 32844233

The purpose of this study was to determine if the implementation of a strict validation procedure, designed to limit the inclusion of inaccuracies from the decomposition of surface electromyographic (sEMG) signals, affects population-based motor unit (MU) analyses. Four sEMG signals were obtained from the vastus lateralis of 59 participants during isometric contractions at different relative intensities [30%, 70%, and 100% of maximal voluntary contraction (MVC)], and its individual motor unit potential trains (MUPTs) were extracted. The MUPTs were then excluded (ISIval) based on the coefficient of variation and histogram of the interspike intervals (ISI), the absence of additional clusters that reveals missed or additional firings, and more. MU population-based regression models (i.e., modeling the entire motor unit pool) were performed between motor unit potential size (MUPSIZE), mean firing rate (MFR), and recruitment threshold (RT%) separately for DSDCOnly (includes all MUPTs without the additional validation performed) and ISIval data at each contraction intensity. The only significant difference in regression coefficients between DSDCOnly and ISIval was for the intercepts of the MUPSIZE/MFR at 100% MVC. The validation had no other significant effect on any of the other regression coefficients for each of the contraction intensities. Our findings suggest that even though the decomposition of surface signals leads to some inaccuracies, these errors have limited effects on the regression models used to estimate the behavior of the whole pool. Therefore, we propose that motor unit population-based regression models may be robust enough to overcome decomposition-induced errors at the individual MU level.

Abou Khalil, G.; Doré-Mazars, K.; Senot, P.; Wang, D. P.; Legrand, A.

doi: 10.1007/s00221-020-05858-zpmid: 32851460

It is now accepted that performing a cognitive task impacts postural control (Polskaia and Lajoie 2016; Vuillerme et al. Neurosci Lett 291: 77–80, 2000). However, the reverse impact of posture on cognitive performance is less documented. The present study investigated performance in two cognitive activities (memory and arithmetic) performed in three different postural conditions (sitting, standing, and walking). Overall, our data suggest that the posture adopted during a task can improve cognitive performance with a better answer for arithmetic in the sitting position than during walking but more correctly recalled words while walking. This study, thus, suggests that there could be preferential association between cognition and posture, i.e., memory cognitive performance can be improved when walking and mental arithmetic while sitting.

Bojsen-Møller, E.; Ekblom, M. M.; Tarassova, O.; Dunstan, D. W.; Ekblom, O.

doi: 10.1007/s00221-020-05866-zpmid: 32860117

Paired associative stimulation (PAS) can induce plasticity in the motor cortex, as measured by changes in corticospinal excitability (CSE). This effect is attenuated in older and less active individuals. Although a single bout of exercise enhances PAS-induced plasticity in young, physically inactive adults, it is not yet known if physical activity interventions affect PAS-induced neuroplasticity in middle-aged inactive individuals. Sixteen inactive middle-aged office workers participated in a randomized cross-over design investigating how CSE and short-interval intracortical inhibition (SICI) were affected by PAS preceded by 3 h of sitting (SIT), 3 h of sitting interrupted every 30 min by 3 min of frequent short bouts of physical activity (FPA) and 2.5 h of sitting followed by 25 min of moderate-intensity exercise (EXE). Transcranial magnetic stimulation was applied over the primary motor cortex (M1) of the dominant abductor pollicis brevis to induce recruitment curves before and 5 min and 30 min post-PAS. Linear mixed models were used to compare changes in CSE using time and condition as fixed effects and subjects as random effects. There was a main effect of time on CSE and planned within-condition comparisons showed that CSE was significantly increased from baseline to 5 min and 30 min post-PAS, in the FPA condition, with no significant changes in the SIT or EXE conditions. SICI decreased from baseline to 5 min post-PAS, but this was not related to changes in CSE. Our findings suggest that in middle-aged inactive adults, FPAs may promote corticospinal neuroplasticity. Possible mechanisms are discussed.

Feltmate, Brett B. T.; Hurst, Austin J.; Klein, Raymond M.

doi: 10.1007/s00221-020-05902-ypmid: 32860512

As part of a larger study on the effects of fatigue on various attentional and behavioural measures, we had participants complete a modified version of Luna et al.’s (J Neurosci Methods 306:77–87, Luna et al., J Neurosci Methods 306:77–87, 2018) ANTI-Vea task (mANTI-Vea) at the beginning and end (pre/post) of each of two 8-h testing sessions. Between these administrations of the mANTI-Vea our participants spent ~ 6 h performing an intervening task. Our intent in this project was two-fold: first, to replicate the pattern of effects reported in Luna et al.’s original presentation of the ANTI-Vea; second, to assay the impact of fatigue on vigilance and attention by observing shifts in mANTI-Vea performance as a function of time on task and before versus after the intervening task. With time-on-task (the mANTI-Vea is divided into six sub-blocks) we observed that participants became increasingly conservative in their biases to respond towards infrequent targets, showed a decline in sensitivity, and lapsed in responding in the psychomotor vigilance task with greater frequency. In the pre/post comparison, we observed an increase in the proportion of lapses, but not in participants’ response biases. Attentional network scores were found to be somewhat insensitive to our fatigue manipulations; the effect of time-on-task was only significant for orienting scores on RT, and our pre/post comparison was only significant for RT derived executive functioning scores.

Ucar, Buket; Yusufogullari, Sedef; Humpel, Christian

doi: 10.1007/s00221-020-05907-7pmid: 32862235

Vessel damage is a general pathological process in many neurodegenerative disorders, as well as spinal cord injury, stroke, or trauma. Biomaterials can present novel tools to repair and regenerate damaged vessels. The aim of the present study is to test collagen hydrogels loaded with different angiogenic factors to study vessel repair in organotypic brain slice cultures. In the experimental set up I, we made a cut on the organotypic brain slice and tested re-growth of laminin + vessels. In the experimental set up II, we cultured two half brain slices with a gap with a collagen hydrogel placed in between to study endothelial cell migration. In the experimental set up I, we showed that the number of vessels crossing the cut was tendencially increased with the addition of fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor, or platelet-derived growth factor-BB compared to the control group. In the experimental set up II, we demonstrated that a collagen hydrogel loaded with FGF-2 resulted in a significantly increased number of migrated laminin + cells in the gap between the slices compared to the control hydrogel. Co-administration of several growth factors did not further potentiate the effects. Taken together, we show that organotypic brain slices are good models to study brain vessels and FGF-2 is a potent angiogenic factor for endothelial cell proliferation and migration. Our results provide evidence that the collagen hydrogels can be used as an extracellular matrix for the vascular endothelial cells.

McCambridge, Alana B.; Hay, Kayla; Levin, Kumbelin; Philpott, Kirsty; Wood, Kunal; Bradnam, Lynley V.

doi: 10.1007/s00221-020-05887-8pmid: 32862278

Transcranial magnetic stimulation (TMS) produces motor-evoked potentials (MEP) used to infer changes in corticomotor excitability. In humans, neck rotation can probe reticulospinal input on corticomotor output. This study investigated the effect of neck rotation on MEP duration in a proximal and distal upper limb muscle and compared responses between rest and preactivation. Single-pulse TMS to motor cortex was used to evoke MEPs at two stimulus intensities in 18 healthy adults (20–40 years). Surface electromyography recorded MEPs from the non-dominant biceps brachii (BB) and first dorsal interosseous (FDI). Participants were seated with the target muscle at rest or 10% preactivated, and head rotated ipsilateral, contralateral, or in neutral position. The primary outcome was MEP tail, defined as the mean difference in MEP duration between active and rest trials. Secondary outcomes were MEP duration and amplitude. MEP tail was modulated by neck rotation in the proximal BB (P = 0.03) but not distal FDI (P > 0.19), with shorter duration during ipsilateral or contralateral rotation relative to neutral. In a neutral neck position, MEP duration was prolonged by muscle preactivation and higher TMS intensities in the FDI and BB (P < 0.03). Neck rotation attenuated the prolongation of MEP duration during preactivation in the BB, but not the FDI. Neck rotation had no effect on MEP amplitude for either muscle (P > 0.05). Modulation of the late portion of the MEP by rotation of the neck could indicate subcortical projections to alpha-motoneuron pools are stronger in proximal than distal upper limb muscles. These findings may have relevance for using MEP duration as a neural biomarker in neurological diseases.