116 research outputs found
Distributed networks for auditory memory differentially contribute to recall precision
Re-directing attention to objects in working memory can enhance their representational fidelity. However, how this attentional enhancement of memory representations is implemented across distinct, sensory and cognitive-control brain network is unspecified. The present fMRI experiment leverages psychophysical modelling and multivariate auditory-pattern decoding as behavioral and neural proxies of mnemonic fidelity. Listeners performed an auditory syllable pitch-discrimination task and received retro-active cues to selectively attend to a to-be-probed syllable in memory. Accompanied by increased neural activation in fronto-parietal and cingulo-opercular networks, valid retro-cues yielded faster and more perceptually sensitive responses in recalling acoustic detail of memorized syllables. Information about the cued auditory object was decodable from hemodynamic response patterns in superior temporal sulcus (STS), fronto-parietal, and sensorimotor regions. However, among these regions retaining auditory memory objects, neural fidelity in the left STS and its enhancement through attention-to-memory best predicted individuals’ gain in auditory memory recall precision. Our results demonstrate how functionally discrete brain regions differentially contribute to the attentional enhancement of memory representations
Changes of hand switching costs during bimanual sequential learning
Many tasks in our daily life demand not only the use of different fingers of one hand in a serial fashion, but also to alternate from one hand to the other. Here, we investigated performance in a bimanual serial reaction time task (SRTT) with particular emphasis on learning-related changes in reaction time (RT) for consecutive button presses for homologous index- and middle fingers. The bimanual SRTT consisted of sequential button presses either with the left or right index- and middle-finger to a series of visual letters displayed on a computer screen. Each letter was assigned a specific button press with one of four fingers. Two outcome measures were investigated: (a) global sequence learning as defined by the time needed to complete a 15-letter SRTT sequence and (b) changes in hand switch costs across learning. We found that bimanual SRTT resulted in a global decrease in RT during the time course of learning that persisted for at least two weeks. Furthermore, RT to a button press showed an increase when the previous button press was associated with another hand as opposed to the same hand. This increase in RT was defined as switch costs. Hand switch costs significantly decreased during the time course of learning, and remained stable over a time of approximately two weeks. This study provides evidence for modulations of switch costs during bimanual sequence learning, a finding that might have important implications for theories of bimanual coordination and learning
Rapid Quantification of White Matter Disconnection in the Human Brain
With an estimated five million new stroke survivors every year and a rapidly
aging population suffering from hyperintensities and diseases of presumed
vascular origin that affect white matter and contribute to cognitive decline,
it is critical that we understand the impact of white matter damage on brain
structure and behavior. Current techniques for assessing the impact of lesions
consider only location, type, and extent, while ignoring how the affected
region was connected to the rest of the brain. Regional brain function is a
product of both local structure and its connectivity. Therefore, obtaining a
map of white matter disconnection is a crucial step that could help us predict
the behavioral deficits that patients exhibit. In the present work, we
introduce a new practical method for computing lesion-based white matter
disconnection maps that require only moderate computational resources. We
achieve this by creating diffusion tractography models of the brains of healthy
adults and assessing the connectivity between small regions. We then interrupt
these connectivity models by projecting patients' lesions into them to compute
predicted white matter disconnection. A quantified disconnection map can be
computed for an individual patient in approximately 35 seconds using a single
core CPU-based computation. In comparison, a similar quantification performed
with other tools provided by MRtrix3 takes 5.47 minutes.Comment: 2020 42nd Annual International Conference of the IEEE Engineering in
Medicine and Biology Society (EMBC
a comparison between young and old adults
Healthy aging is associated with a variety of functional and structural brain
alterations. These age-related brain alterations have been assumed to
negatively impact cognitive and motor performance. Especially important for
the execution of everyday activities in older adults (OA) is the ability to
perform movements that depend on both hands working together. However,
bimanual coordination is typically deteriorated with increasing age. Hence, a
deeper understanding of such age-related brain-behavior alterations might
offer the opportunity to design future interventional studies in order to
delay or even prevent the decline in cognitive and/or motor performance over
the lifespan. Here, we examined to what extent the capability to acquire and
maintain a novel bimanual motor skill is still preserved in healthy OA as
compared to their younger peers (YA). For this purpose, we investigated
performance of OA (n = 26) and YA (n = 26) in a bimanual serial reaction time
task (B-SRTT), on two experimental sessions, separated by 1 week. We found
that even though OA were generally slower in global response times, they
showed preserved learning capabilities in the B-SRTT. However, sequence
specific learning was more pronounced in YA as compared to OA. Furthermore, we
found that switching between hands during B-SRTT learning trials resulted in
increased response times (hand switch costs), a phenomenon that was more
pronounced in OA. These hand switch costs were reduced in both groups over the
time course of learning. More interestingly, there were no group differences
in hand switch costs on the second training session. These results provide
novel evidence that bimanual motor skill learning is capable of reducing age-
related deficits in hand switch costs, a finding that might have important
implications to prevent the age-related decline in sensorimotor function
Anodal Transcranial Direct Current Stimulation Does Not Facilitate Dynamic Balance Task Learning in Healthy Old Adults
Older adults frequently experience a decrease in balance control that leads to
increased numbers of falls, injuries and hospitalization. Therefore,
evaluating older adults’ ability to maintain balance and examining new
approaches to counteract age-related decline in balance control is of great
importance for fall prevention and healthy aging. Non-invasive brain
stimulation techniques such as transcranial direct current stimulation (tDCS)
have been shown to beneficially influence motor behavior and motor learning.
In the present study, we investigated the influence of tDCS applied over the
leg area of the primary motor cortex (M1) on balance task learning of healthy
elderly in a dynamic balance task (DBT). In total, 30 older adults were
enrolled in a cross-sectional, randomized design including two consecutive DBT
training sessions. Only during the first DBT session, either 20 min of anodal
tDCS (a-tDCS) or sham tDCS (s-tDCS) were applied and learning improvement was
compared between the two groups. Our data showed that both groups successfully
learned to perform the DBT on both training sessions. Interestingly, between-
group analyses revealed no difference between the a-tDCS and the s-tDCS group
regarding their level of task learning. These results indicate that the
concurrent application of tDCS over M1 leg area did not elicit DBT learning
enhancement in our study cohort. However, a regression analysis revealed that
DBT performance can be predicted by the kinematic profile of the movement, a
finding that may provide new insights for individualized approaches of
treating balance and gait disorders
Neural correlates of mirror visual feedback-induced performance improvements: A resting-state fMRI study
Mirror visual feedback (MVF) is a promising approach to enhance motor performance without training in healthy adults as well as in patients with focal brain lesions. There is preliminary evidence that a functional modulation within and between primary motor cortices as assessed with transcranial magnetic stimulation (TMS) might be one candidate mechanism mediating the observed behavioral effects. Recently, studies using task-based functional magnetic resonance imaging (fMRI) have indicated that MVF-induced functional changes might not be restricted to the primary motor cortex (M1) but also include higher order regions responsible for perceptual-motor coordination and visual attention. However, aside from these instantaneous task-induced brain changes, little is known about learning-related neuroplasticity induced by MVF. Thus, in the present study, we assessed MVF-induced functional network plasticity with resting-state fMRI (rs-fMRI). We performed rs-fMRI of 35 right-handed, healthy adults before and after performing a complex ball-rotation task. The primary outcome measure was the performance improvement of the untrained left hand (LH) before and after right hand (RH) training with MVF (mirror group [MG], n = 17) or without MVF (control group [CG], n = 18). Behaviorally, the MG showed superior performance improvements of the untrained LH. In resting-state functional connectivity (rs-FC), an interaction analysis between groups showed changes in left visual cortex (V1, V2) revealing an increase of centrality in the MG. Within group comparisons showed further functional alterations in bilateral primary sensorimotor cortex (SM1), left V4 and left anterior intraparietal sulcus (aIP) in the MG, only. Importantly, a correlation analysis revealed a linear positive relationship between MVF-induced improvements of the untrained LH and functional alterations in left SM1. Our results suggest that MVF-induced performance improvements are associated with functional learning-related brain plasticity and have identified additional target regions for non-invasive brain stimulation techniques, a finding of potential interest for neurorehabilitation
A Resting-State fMRI Study
Mirror visual feedback (MVF) is a promising approach to enhance motor
performance without training in healthy adults as well as in patients with
focal brain lesions. There is preliminary evidence that a functional
modulation within and between primary motor cortices as assessed with
transcranial magnetic stimulation (TMS) might be one candidate mechanism
mediating the observed behavioral effects. Recently, studies using task-based
functional magnetic resonance imaging (fMRI) have indicated that MVF-induced
functional changes might not be restricted to the primary motor cortex (M1)
but also include higher order regions responsible for perceptual-motor
coordination and visual attention. However, aside from these instantaneous
task-induced brain changes, little is known about learning-related
neuroplasticity induced by MVF. Thus, in the present study, we assessed MVF-
induced functional network plasticity with resting-state fMRI (rs-fMRI). We
performed rs-fMRI of 35 right-handed, healthy adults before and after
performing a complex ball-rotation task. The primary outcome measure was the
performance improvement of the untrained left hand (LH) before and after right
hand (RH) training with MVF (mirror group [MG], n = 17) or without MVF
(control group [CG], n = 18). Behaviorally, the MG showed superior performance
improvements of the untrained LH. In resting-state functional connectivity
(rs-FC), an interaction analysis between groups showed changes in left visual
cortex (V1, V2) revealing an increase of centrality in the MG. Within group
comparisons showed further functional alterations in bilateral primary
sensorimotor cortex (SM1), left V4 and left anterior intraparietal sulcus
(aIP) in the MG, only. Importantly, a correlation analysis revealed a linear
positive relationship between MVF-induced improvements of the untrained LH and
functional alterations in left SM1. Our results suggest that MVF-induced
performance improvements are associated with functional learning-related brain
plasticity and have identified additional target regions for non-invasive
brain stimulation techniques, a finding of potential interest for
neurorehabilitation
Decreased thalamo-cortico connectivity during an implicit sequence motor learning task and 7Â days escitalopram intake
Evidence suggests that selective serotonin reuptake inhibitors (SSRIs) reorganize neural networks via a transient window of neuroplasticity. While previous findings support an effect of SSRIs on intrinsic functional connectivity, little is known regarding the influence of SSRI-administration on connectivity during sequence motor learning. To investigate this, we administered 20 mg escitalopram or placebo for 1-week to 60 healthy female participants undergoing concurrent functional magnetic resonance imaging and sequence motor training in a double-blind randomized controlled design. We assessed task-modulated functional connectivity with a psycho-physiological interaction (PPI) analysis in the thalamus, putamen, cerebellum, dorsal premotor, primary motor, supplementary motor, and dorsolateral prefrontal cortices. Comparing an implicit sequence learning condition to a control learning condition, we observed decreased connectivity between the thalamus and bilateral motor regions after 7 days of escitalopram intake. Additionally, we observed a negative correlation between plasma escitalopram levels and PPI connectivity changes, with higher escitalopram levels being associated with greater thalamo-cortico decreases. Our results suggest that escitalopram enhances network-level processing efficiency during sequence motor learning, despite no changes in behaviour. Future studies in more diverse samples, however, with quantitative imaging of neurochemical markers of excitation and inhibition, are necessary to further assess neural responses to escitalopram
Transnational partisanship: idea and practice
That parties might successfully organize transnationally is an idea often met with scepticism. This article argues that while certain favourable conditions are indeed absent in the transnational domain, this implies not that partisanship is impossible but that it is likely to be marked by certain traits. Specifically, it will tend to be episodic, structured as a low-density network and delocalized in its ideational content. These tendencies affect the normative expectations one can attach to it. Transnational partisanship should be valued as a transitional phenomenon, e.g. as a pathway to transnational democracy, more than as a desirable thing in itself
Quadrupedal movement training improves markers of cognition and joint repositioning
Introduction - Exercise, and in particular balance and coordination related activities such as dance, appear to have positive effects on cognitive function, as well as neurodegenerative conditions such as dementia and Parkinson’s disease. Quadrupedal gait training is a movement system requiring coordination of all four limbs that has previously been associated with cognitive development in children. There is currently little research into the effect of complex QDP movements on cognitive function in adults.
Purpose - To determine the effects of a novel four-week quadrupedal gait training programme on markers of cognitive function and joint reposition sense in healthy adults.
Methods - Twenty-two physically active sports science students (15 male and 7 female) were divided into two groups: a training group (TG) and a control group (CG). All participants completed the Wisconsin Card Sorting Task (WCST) and were tested for joint reposition sense before and after a four-week intervention, during which time the TG completed a series of progressive and challenging quadrupedal movement training sessions.
Results - Participants in the TG showed significant improvements in the WCST, with improvements in perseverative errors, non-perseverative errors, and conceptual level response. This improvement was not found in the CG. Joint reposition sense also improved for the TG, but only at 20 degrees of shoulder flexion.
Conclusions - Performance of a novel, progressive, and challenging task, requiring the coordination of all 4 limbs, has a beneficial impact on cognitive flexibility, and in joint reposition sense, although only at the specific joint angle directly targeted by the training. The findings are consistent with other studies showing improvements in executive function and joint reposition sense following physical activity
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