Biology subjects

Schmid, A.-C.

Publications and source records attributed to Schmid, A.-C..

4 recordsLinked to original sources

bioRxiv2023

Not only a matter of age: Machine learning-based characterization of the differential effect of brain stimulation on skill acquisition

Brain stimulation shows potential at enhancing cognitive and motor functions in humans. However, multiple studies assessing its effects on behavior show heterogeneous results, especially in healthy older subjects. We propose a new method to predict an individuals likelihood and the magnitude of the benefit from stimulation, based on the baseline performance of a sequential motor task, framed in the context of their age. Our results show a differential effect of stimulation, in which individuals with less efficient learning mechanisms benefit from stimulation, while those possessing optimal learning strategies resent a detrimental effect. Importantly, this differential effect was determined by ones ability to integrate task-relevant information at the early stages of training, and not the age. This study paves the way towards the personalized application of stimulation to maximize its effects, and constitutes the first steps to implement an individualized translational clinical intervention, based on the state of the neural system. TeaserAge notwithstanding, brain stimulation is most effective in deficient neural systems, while being detrimental to optimal systems Visual abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=121 SRC="FIGDIR/small/544579v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@bcfab0org.highwire.dtl.DTLVardef@ee55e9org.highwire.dtl.DTLVardef@14a7519org.highwire.dtl.DTLVardef@14de600_HPS_FORMAT_FIGEXP M_FIG C_FIG Main findingAnodal transcranial direct current stimulation (atDCS), applied over the hand representation of the motor cortex concomitant to the training of a sequential motor sequence, has differential effects as a function of the recipients ability to integrate task-relevant information at the early stages of training. Stimulation benefits individuals with seemingly less efficient learning mechanisms, enabling the rapid storage of the spatial coordinates of the motor sequence and an accelerated optimization of the accuracy of execution. In contrast, individuals possessing optimal learning mechanisms experience detrimental effects of stimulation, leading to drops in the accuracy of execution.

neuroscience↗

bioRxiv2021

Black-box testing in motor sequence learning

During learning of novel motor sequences, practice leads to the consolidation of hierarchical structures, namely motor chunks, facilitating the accurate execution of sequences at increasing speeds. Recent studies show that such hierarchical structures are largely represented upstream of the primary motor cortex in the motor network, suggesting their function to be more related to the encoding, storage, and retrieval of sequences rather than their sole execution. We isolated different components of motor skill acquisition related to the consolidation of spatiotemporal features and followed their evolution over training. We found that optimal motor skill acquisition relies on the storage of the spatial features of the sequence in memory, followed by the optimization of its execution and increased execution speeds (i.e., a shift in the speed-accuracy trade-off) early in training, supporting the model proposed by Hikosaka in 1999. Contrasting the dynamics of these components during ageing, we identified less-than-optimal mechanisms in older adults explaining the observed differences in performance. We applied noninvasive brain stimulation in an attempt to support the aging brain to compensate for these deficits. The present study found that anodal direct current stimulation applied over the motor cortex restored the mechanisms involved in the consolidation of spatial features, without directly affecting the speed of execution of the sequence. This led older adults to sharply improve their accuracy, resulting in an earlier yet gradual emergence of motor chunks. The results suggest the early storage of the sequence in memory, largely independent of motor practice, is crucial for an optimal motor acquisition and retrieval of this motor behavior. Nevertheless, the consolidation of optimal temporal patterns, detected as motor chunks at a behavioral level, is not a direct consequence of storing the sequence elements, but rather of motor practice.

neuroscience↗

bioRxiv2021

Prolonged tonic pain in healthy humans enhances functional connectivity of descending pain modulation networks involving the amygdala, periaqueductal gray and parabrachial nucleus to cortical sensory-discriminative areas

IntroductionResting state functional connectivity (FC) is widely used to assess functional brain alterations in patients with chronic pain. However, reports of FC changes accompanying tonic pain in pain-free persons is rare. A brain network disrupted during chronic pain is a network we term the Descending Pain Modulatory Network (DPMN). Here, we evaluate the effect of tonic pain on FC of this network: anterior cingulate cortex (ACC), amygdala (AMYG), periaqueductal gray (PAG), and parabrachial nuclei (PBN). MethodsIn 50 pain-free participants (30F), we induced tonic pain using a capsaicin-heat pain model. We used functional MRI to measure resting BOLD signal during pain-free rest where participants experienced warmth and tonic pain where participants experienced the same temperature thermode combined with capsaicin. We evaluated FC from ACC, AMYG, PAG, and PBN with correlation of self-report pain intensity with FC during both states. We hypothesized tonic pain would disrupt FC dyads within the DPMN. We used partial correlation to determine FC correlated with pain intensity and BOLD signal. ResultsOf hypothesized FC dyads, PAG and subgenual ACC was weakly disrupted during tonic pain (F=3.34; p=0.074; pain-free>pain d=0.25). sgACC-PAG FC became positively related to pain intensity (R=0.38; t=2.81; p=0.007). Right PBN-PAG FC during pain-free rest positively correlated with subsequently experienced pain (R=0.44; t=3.43; p=0.001). During tonic pain, FC of this connection was abolished (paired t=-3.17; p=0.0026). During pain-free rest, FC between left AMYG and right superior parietal lobule and caudate nucleus were positively correlated with subsequent pain. During tonic pain, FC between left AMYG and right inferior temporal and superior frontal gyri negatively correlated with pain. Subsequent pain positively correlated with right AMYG FC and right claustrum; left and right primary visual cortex; right middle temporal gyrus and right temporo-occipitoparietal junction. Finally, subsequent pain positively correlated with PAG FC and left cerebellum, left dorsolateral prefrontal, right posterior cingulate cortex and paracentral lobule, inferior parietal lobule, medial precuneus and PBN. ConclusionWe demonstrate 1) tonic pain weakly disrupts of sgACC-PAG FC; 2) sgACC-PAG tonic pain FC positively correlates with pain; 3) right PBN-PAG FC predicts subsequent pain and is abolished during tonic pain. Finally, we reveal PAG- and right AMYG-anchored networks which predict intensity of tonic pain. Our findings suggest specific connectivity patterns within the DPMN at rest predict experienced pain and are modulated by tonic pain. These nodes and their functional modulation may reveal new therapeutic targets for neuromodulation and biomarkers to guide interventions. HighlightsO_LIParabrachial-periaqueductal gray (PAG) functional connectivity (FC) predicts pain C_LIO_LISubgenual anterior cingulate cortex-PAG FC correlates with pain during tonic pain C_LIO_LIPAG- and amydalocortical networks at rest predict tonic pain intensity C_LIO_LIResting FC of PAG supports cortical targets of neuromodulation to control pain C_LI

neuroscience↗

bioRxiv2019

Prolonged tonic pain in healthy humans disrupts intrinsic brain networks implicated in pain modulation

Neural mechanisms of ongoing nociceptive processing in the human brain remain largely obscured by the dual challenge of accessing neural dynamics and safely applying sustained painful stimuli. Recently, pain-related neural processing has been measured using fMRI resting state functional connectivity (FC) in chronic pain patients. However, ongoing pain-related processing in normally pain-free humans remains incompletely understood. Therefore, differences between chronic pain patients and controls may be due to comorbidities with chronic pain. Decreased FC among regions of the descending pain modulation network (DPMN) are associated with presence and severity of chronic pain disorders. We aimed to determine if the presence of prolonged tonic pain would lead to disruption of the DPMN. High (10%) concentration topical capsaicin was combined with a warm thermode applied to the leg to create a flexible, prolonged tonic pain model to study the FC of brain networks in otherwise healthy, pain-free subjects in two separate cohorts (n=18; n=32). We contrasted seed-based FC during prolonged tonic pain with a pain-free passive task. In seed-based FC analysis prolonged tonic pain led to enhanced FC between the anterior middle cingulate cortex (aMCC) and the somatosensory leg representation. Additionally, FC was enhanced between the pregenual anterior cingulate cortex (pACC), right mediodorsal thalamus and the posterior parietal cortex bilaterally. Further, in the seed-driven PAG network, positive FC with the left DLPFC became negative FC during prolonged tonic pain. These data suggest that some altered DPMN FC findings in chronic pain could partially be explained by the presence of ongoing pain.

neuroscience↗