Biology subjects

Appelbaum, L. G.

Publications and source records attributed to Appelbaum, L. G..

12 recordsLinked to original sources

bioRxiv2022

Concurrent fMRI demonstrates propagation of TMS effects across task-related networks

Transcranial magnetic stimulation (TMS) has become an important technique in both scientific and clinical practices, and yet our understanding of how the brain responds to TMS is still limited. Concurrent neuroimaging during TMS may bridge this gap, and emerging evidence suggests widespread that modulatory effects of TMS may be best captured through changes in functional connectivity between distributed networks, rather than local changes in cortical activity. However, the relationship between TMS stimulation parameters and evoked changes in functional connectivity is unknown. In this study, 24 healthy volunteers received concurrent TMS-fMRI while performing a dot-motion direction discrimination task. An MR-compatible coil was used to apply trains of three pulses at 10 Hz rTMS over the primary visual cortex (V1) at the onset of the dot stimuli with four levels of stimulation intensity (20%, 40%, 80%, and 120% of resting motor threshold, RMT). Behavioral results demonstrated impairment of motion discrimination at 80% RMT. FMRI results yielded three findings. First, functional connectivity between visual and non-visual areas increased as a function of rTMS intensity. Second, connectivity within the visual network was positively associated with motion accuracy, while the connectivity between visual and non-visual regions was negatively associated with motion accuracy. Lastly, we found that reductions in the similarity between functional and structural connectivity associated with increasing TMS intensity were constrained to the visual network. These findings demonstrate spatially dependent nonlinear effects of TMS intensity on brain functional connectivity that proceed beyond the site of stimulation and influence associated behavior.

neuroscience↗

bioRxiv2020

The effect of functionally-guided-connectivity-based rTMS on amygdala activation.

Repetitive transcranial magnetic stimulation (rTMS) has fundamentally transformed how we treat psychiatric disorders, but is still in need of innovation to optimally correct dysregulation that occurs throughout the fronto-limbic network. rTMS is often applied over the prefrontal cortex, a central node in this network, but less attention is given to subcortical areas because they lie at depths beyond the electric field penetration of rTMS. Recent studies have demonstrated that the effectiveness of rTMS is dependent on the functional connectivity between deep subcortical areas and superficial targets, indicating that leveraging such connectivity may improve dosing approaches for rTMS interventions. The current preliminary study, therefore, sought to test whether task-related, fMRI-connectivity-based rTMS could be used to modulate amygdala activation through its connectivity with the medial prefrontal cortex (mPFC). For this purpose, fMRI was collected on participants to identify a node in the mPFC that showed the strongest negative connectivity with right amygdala, as defined by psychophysiological interaction analysis. To promote long-lasting Hebbian-like effects, and potentially stronger modulation, 5Hz rTMS was then applied to this target as participants viewed frightening video-clips that engaged the fronto-limbic network. Post-rTMS fMRI results revealed promising increases in both the left mPFC and right amygdala, for active rTMS compared to sham. While these modulatory findings are promising, they differ from the a priori expectation that excitatory 5Hz rTMS over a negatively connected node would reduce amygdala activity. As such, further research is needed to better understand how connectivity influences TMS effects on distal structures, and to leverage this information to improve therapeutic applications.

neuroscience↗

bioRxiv2020

Skill acquisition and gaze behavior during laparoscopic surgical simulation

BackgroundExperts consistently exhibit more efficient gaze behaviors than non-experts during motor tasks. In surgery, experts have been shown to gaze more at surgical targets than surgical tools during simple simulations and when watching surgical recordings, suggesting a proactive control strategy with greater use of feedforward visual sampling. To investigate such expert gaze behaviors in a more dynamic and complex laparoscopic surgery simulation, the current study measured and compared gaze patterns between surgeons and novices who practiced extensively with laparoscopic simulation. MethodsThree surgeons were assessed in a testing visit and five novices were trained and assessed (at pre-, mid-, and post-training points) in a 5-visit protocol on the Fundamentals of Laparoscopic Surgery peg transfer task. The task was adjusted to have a fixed action sequence to allow recordings of dwell durations based on pre-defined areas of interest (AOIs). Novices individualized learning curves were analyzed using an inverse function model, and group-level differences were tested using analysis of variance on both behavioral performance and dwell duration measures. ResultsTrained novices were shown to reach more than 98% (M = 98.62%, SD = 1.06%) of their behavioral learning plateaus, leading to equivalent behavioral performance to that of surgeons. Despite this equivalence in behavioral performance, surgeons continued to show significantly shorter dwell durations at visual targets of current actions and longer dwell durations at future steps in the action sequence than trained novices (ps [≤] .03, Cohens ds > 2). ConclusionThis study demonstrates that, whereas novices can train to match surgeons on behavioral performance, their gaze pattern is still less efficient than that of surgeons, suggesting that eye-tracking metrics might be more sensitive than behavioral performance in detecting surgical expertise. Such insight can be applied to develop training protocols so non-experts can internalize experts "gaze templates" to accelerate learning. Article SummaryGaze pattern differences persist between laparoscopic surgery experts and novices who have been trained to reach over 98% of individualized behavioral learning plateaus in the Fundamentals of Laparoscopic Surgery (FLS) peg transfer task. The importance of this finding lies in motivating the decision and method of including gaze behaviors via eyetracking technology in the present surgical training programs.

neuroscience↗

bioRxiv2020

Dynamic Vision Training Transfers Positively to Batting Performance Among Collegiate Baseball Batters

A growing body of evidence demonstrates visual, perceptual, and oculomotor abilities contribute to batting performance in baseball and there is interest in whether training such abilities can transfer positively to batting performance. The current study tested this question through a pre-registered randomized, and placebo-controlled intervention, conducted with 24 collegiate baseball players at two Division 1 universities. Athletes were randomized to receive either dynamic vision training consisting of stroboscopic, anticipatory timing, and eye quickness drills, or placebo drills stylized after control procedures in previous vision therapy studies. Generalized near-transfer was tested via a digital visual-motor task battery (n = 20), while sports-specific intermediate and far transfer of training were evaluated through instrumented batting practice metrics (n = 14) and box score performance in NCAA-sanctioned games (n = 12). The effects of training group were tested on these outcome measures while controlling for covariates such as pre-training expectations and site. Participants averaged 8.50 hours of training with no significant training group differences in adherence, expectations, or baseline assessments. ANCOVA revealed no group differences in measures of visual-motor skills or NCAA game statistics. However, batting practice demonstrated significant improvements in launch angle (p = 0.002, Cohens d = 0.74) and hit distance (p < 0.001, Cohens d = 0.70) for the active cohort relative to the placebo control. This controlled and pre-registered pilot study therefore provides preliminary evidence that vision training may improve batting practice performance, creating new opportunities for the transfer of skill training and warranting further study. Pre-RegistrationAt Open Science Framework on August 9, 2018. DOI 10.17605/OSF.IO/496RX. Accessible at https://osf.io/jxh8u

neuroscience↗

bioRxiv2020

Visual and oculomotor abilities predict professional baseball batting performance

Scientists and practitioners have long debated about the specific visual skills needed to excel at hitting a pitched baseball. This study aimed to advance the debate by evaluating the relationship between pre-season visual and oculomotor evaluations and pitch-by-pitch season performance data from professional baseball batters. Eye tracking, visual-motor, and optometric evaluations collected during spring training 2018 were obtained from 71 professional baseball players. Pitch-level data from Trackman 3D Doppler radar were obtained from these players during the subsequent season and used to generate batting propensity scores for swinging at pitches out of the strike zone (O-Swing), swinging at pitches in the strike zone (Z-Swing), and swinging at, but missing pitches in the strike zone (Z-Miss). Nested regression models were used to test which vision-related evaluation(s) could best predict the standardized plate discipline scores as well as the batters highest attained league levels during the season. Results indicated that visual evaluations relying on eye tracking (e.g., smooth pursuit accuracy and oculomotor processing speed) significantly predicted the highest attained league level and the propensity scores associated with O-Swing and Z-Swing, but not Z-Miss. These exploratory findings indicate that batters with superior visual and oculomotor abilities are generally more discerning at the plate. When combined with other known performance advantages in perceptual and cognitive abilities for elite athletes, these results provide a wholistic view of visual expertise in athletes.

neuroscience↗

bioRxiv2019

Structural controllability predicts functional patterns and neuromodulatory benefits associated with working memory

The brain is an inherently dynamic system, and much work has focused on the ability to modify neural activity through both local perturbations and changes in the function of global network ensembles. Network controllability is a recent concept in network science that purports to predict the influence of individual cortical sites on global network states and state changes, thereby creating a unifying account of local influences on global brain dynamics. Here, we present an integrated set of multimodal brain-behavior relationships, acquired from functional magnetic resonance imaging during a transcranial magnetic stimulation intervention, that demonstrate how network controllability influences network function, as well as behavior. This work helps to outline a clear technique for integrating structural network topology and functional activity to predict the influence of a potential stimulation target on subsequent behaviors and prescribes next steps towards predicting neuromodulatory and behavioral responses after brain stimulation.\n\nHighlights- This study tested the strength of network controllability using fMRI and rTMS\n- Controllability correlates with functional modulation of working memory demand load\n- Controllability is also correlated with the memory improvement from applied rTMS\n- These findings link network control theory with physiology and behavior.\n\n\nIn briefBeynel et al. show that the benefits of functionally targeted brain stimulation on working memory performance can be predicted by network control properties at the stimulated site. Structural controllability and functional activity independently predict this cognitive benefit.\n\nAuthor ContributionsConceptualization & Methodology: L.B, S.W.D., B.L., R.C., L.G.A.; Investigation: L.B., L.D., S.W.D., C.A.C., M.D., H.P., S.H.; Writing--Original Draft: L.B., L.D., S.W.D.; Writing--Review & Editing: L.B., L.D., S.W.D., L.G.A., A.V.P.; Funding Acquisition: S.W.D., R.C., B.L., S.H.L., A.V.P.; Resources: L.G.A., B.L., R.C.; Supervision: L.G.A., S.W.D.

neuroscience↗

bioRxiv2019

Application of long-interval paired-pulse transcranial magnetic stimulation to motion-sensitive visual cortex does not lead to changes in motion perception

The perception of visual motion is dependent on a set of occipitotemporal regions which are readily accessible to neuromodulation. Previous studies using paired-pulse Transcranial Magnetic Stimulation (ppTMS) have provided evidence of the capacity of this type of protocols to modulate cognitive processes. To test whether such cortical modulation can be observed in the visual system, particularly during motion perception, ppTMS was applied to the occipital cortex using both scalp-based and meta-analytic targeting coordinates. In this within-subject, sham-controlled study, fifteen subjects completed two sessions in two consecutive weeks. On the first visit, subject-specific resting motor threshold (RMT) was determined and participants performed an adaptive motion discrimination task to determine individual motion sensitivity. During the second visit, subjects performed the same task with three individualized difficulty levels as two TMS pulses were delivered respectively -150 and -50 ms prior to motion stimulus onset at 120% RMT, under the logic that the cumulative inhibitory effect of these two pulses would alter motion sensitivity as measured by the individually calibrated task. The ppTMS was delivered at one of two locations: 3 cm dorsal and 5 cm lateral to inion (scalp-based coordinate), or at the site of peak activation for \"motion\" according to the NeuroSynth fMRI database (meta-analytic coordinate). Sham stimulation was delivered on one-third of trials and evenly between the two targets. Analyses showed no significant active-versus-sham effects of ppTMS when stimulation was delivered to the meta-analytic (p = 0.15) or scalp-based coordinates (p = 0.17), which were separated by 29 mm on average. Additionally, there was no was significant interaction between ppTMS at either location and task difficulty level (p = 0.12 and p = 0.33, respectively). These findings fail to support the hypothesis that long-interval ppTMS recruits inhibitory processes in motion-sensitive cortex, but must be considered within the limits of the current design choices.\n\nHIGHLIGHTSO_LILong-interval paired-pulse TMS was applied to visual cortex during a motion task\nC_LIO_LIThe ppTMS was delivered according to scalp and meta-analytic coordinates, as well as sham\nC_LIO_LINo effects of active-versus-sham stimulation were observed on motion task performance\nC_LI

neuroscience↗

bioRxiv2019

Older adults benefit from more widespread brain network integration during working memory

Neuroimaging evidence suggests that the aging brain relies on a more distributed set of cortical regions than younger adults in order to maintain successful levels of performance during demanding cognitive tasks. However, it remains unclear how task demands give rise to this age-related expansion in cortical networks. To investigate this issue, we used functional magnetic resonance imaging to measure univariate activity, network connectivity, and cognitive performance in younger and older adults during a working memory (WM) task. In the WM task investigated, participants hold letters online (maintenance) while reordering them alphabetically (manipulation). WM load was titrated to obtain four individualized difficulty levels. Network integration--defined as the ratio of within-versus between-network connectivity--was linked to individual differences in WM capacity. The study yielded three main findings. First, as task difficulty increased, network integration decreased in younger adults, whereas it increased in older adults. Second, age-related increases in network integration were driven by increases in right hemispheric connectivity to both left and right cortical regions, a finding that helps to reconcile extant theories of compensatory recruitment in aging to address the multivariate dynamics of global network functioning. Lastly, older adults with higher WM capacity demonstrated higher levels of network integration in the most difficult condition. These results shed light on the mechanisms of age-related network reorganization by suggesting that changes in network connectivity may act as an adaptive form of compensation, with older adults recruiting a more distributed cortical network as task demands increase.\n\nSignificance statementOlder adults often activate brain regions not engaged by younger adults, but the circumstances under which this widespread network emerges are unclear. Here, we examined the effects of aging on network connectivity between task regions recruited during a working memory (WM) manipulation task, and the rest of the brain. We found an age-related increase in the more global network integration in older adults, and an association between this integration and working memory capacity in older adults. The findings are generally consistent with the compensatory interpretation of these effects.

neuroscience↗

bioRxiv2019

Site-specific effects of online rTMS during a working memory task in healthy older adults.

The process of manipulating information within working memory (WM) is central to many cognitive functions, but also declines rapidly in old age. Given the importance of WM manipulation for maintaining healthy cognition, improving this process could markedly enhance health-span in older adults. The current pre-registered study tested the potential of online repetitive transcranial magnetic stimulation (rTMS) to enhance WM manipulation in healthy elderly adults. Online 5Hz rTMS was applied over the left lateral parietal cortex of 15 subjects to test the hypothesis that active rTMS would significantly improve performance compared to sham stimulation, and that these effects would be most pronounced in conditions with the highest cognitive demand. rTMS was applied while participants performed a delayed-response alphabetization task with two individually-titrated levels of difficulty. Sham stimulation was applied using an electrical sham coil that produced similar clicking sounds and somatosensory sensation as active stimulation but induced negligible effects on the brain. A stimulation site in left lateral parietal cortex was identified from fMRI activation maps and was targeted using individualized electric field modeling, stereotactic neuronavigation, and real-time robotic positioning, allowing optimal coil placement during the stimulation. Contrary to the a priori hypothesis, active rTMS significantly decreased accuracy relative to sham, and only in the hardest difficulty level. These results, therefore, demonstrate engagement of cortical WM processing, but not the anticipated facilitation, and provide a prescription for future studies that may attempt to enhance memory through application of different stimulation parameters.\n\nHighlightsO_LIThis study is one of the first attempts to enhance WM manipulation with online rTMS\nC_LIO_LIOnline 5Hz rTMS and sham were applied over the left parietal cortex of older adults\nC_LIO_LIIndividualized fMRI and electric field modeling were used to optimize targeting\nC_LIO_LIContrary to expectations, rTMS disrupted working memory manipulation abilities\nC_LIO_LIThis demonstrates that parietal cortex is involved in WM and modifiable with rTMS\nC_LI

neuroscience↗

bioRxiv2018

Utilizing Transcranial Direct Current Stimulation to Enhance Laparoscopic Technical Skills Training: A Randomized Controlled Trial

This study aimed to test the efficacy of transcranial direct current stimulation (tDCS) during laparoscopic skill training to determine if it has the capacity to accelerate technical skill acquisition. tDCS is a non-invasive brain stimulation technique that delivers constant, low electrical current resulting in changes to cortical excitability and prior work suggests it may enhance motor learning. We evaluate for the first time the potential of tDCS, coupled with motor skill training, to accelerate the development of laparoscopic technical skills. In this pre-registered, double-blinded and sham-controlled study, 60 healthy subjects were randomized into sham or active tDCS in either bilateral primary motor cortex (bM1) or supplementary motor area (SMA) electrode configurations. All subjects practiced the Fundamental of Laparoscopic Surgery Peg Transfer Task during a pre-test, six 20-minute training sessions, and a post-test. The primary outcome was change in laparoscopic skill performance over time, quantified by improvement in performance according to a seconds-per-object calculated score accounting for errors. Sixty participants were randomized equally into the three training cohorts (active bM1, active SMA, sham). The active groups had significantly greater improvement in performance from pre-test to post-test compared to the sham groups (108 vs 76 seconds, p = 0.018). Both bM1 and SMA active cohorts had significantly greater improvement in learning (p < 0.01), achieving the same skill level in 4 sessions compared to the 6 sessions required of the sham cohort. The SMA cohort had more variability in performance compared to the bM1 and control cohorts. Laparoscopic skill training with active, bM1 or SMA, tDCS exhibited significantly greater learning relative to training with sham tDCS. The potential for tDCS to enhance the training of surgical skills merits further investigation to determine if these preliminary results may be replicated.

clinical trials↗

bioRxiv2018

Spatio-temporally specific transcranial magnetic stimulation to test the locus of perceptual decision making in the human brain

Previous research modeling EEG, fMRI and behavioral data has identified three spatially distributed brain networks that activate in temporal sequence, and are thought to enable perceptual decision-making during face-versus-car categorization. These studies have linked late activation (>300ms post stimulus onset) in the lateral occipital cortex (LOC) to object discrimination processes. We applied paired-pulse transcranial magnetic stimulation (ppTMS) to LOC at different temporal latencies with the specific prediction, based on these studies, that ppTMS beginning at 400ms after stimulus onset would slow reaction time (RT) performance. Thirteen healthy adults performed a two-alternative forced choice task selecting whether a car or face was present on each trial amidst visual noise pre-titrated to approximate 79% accuracy. ppTMS, with pulses separated by 50ms, was applied at one of five stimulus onset asynchronies: -200, 200, 400, 450, or 500ms, and a sixth no-stimulation condition. As predicted, TMS at 400ms resulted in significant slowing of RTs, providing causal evidence in support of LOC contribution to perceptual decision processing. In addition, TMS delivered at -200ms resulted in faster RTs, indicating early stimulation may result in performance enhancement. These findings build upon correlational EEG and fMRI observations and demonstrate the use of TMS in predictive validation of psychophysiological models.

neuroscience↗

bioRxiv2018

A systematic study of repetitive transcranial magnetic stimulation to enhance working memory manipulation abilities

A core element of human working memory (WM) is the ability to perform mental operations on information that is stored in a flexible, limited capacity buffer. Given the profound importance of such WM manipulation (WM-M) abilities, there is a concerted effort aimed at developing approaches to improve them. Past research has identified neural substrates of WM-M centered in the dorsolateral prefrontal cortex (DLPFC), thereby providing a plausible and accessible target for noninvasive neuromodulatory stimulation that can be used to alter cortical excitability and potentially lead to facilitation of WM-M. In the current study, 5Hz online repetitive transcranial magnetic stimulation (rTMS), applied over the left DLPFC, was used to test the hypothesis that active rTMS would lead to significant improvements in memory recall accuracy compared to sham stimulation, and that these effects would be most pronounced in the WM-M conditions with the highest cognitive demand (registered Clinical Trial: #NCT02767323). Participants performed a delayed response alphabetization task with three individually-titrated levels of difficulty during active and sham rTMS. Analyses revealed that active rTMS led to numerically greater accuracy relative to sham stimulation for the hardest condition; however, this effect did not survive Bonferroni correction over all task conditions. Despite the lack of robust, study-wise significant effects, when considered in isolation, the magnitude of behavioral improvement in the hardest condition was negatively correlated with parametric difficulty-related fMRI activity in the targeted brain region, suggesting that individuals with less activation benefit more from rTMS. The present findings therefore suggest evidence towards the hypothesis that active rTMS can enhance performance during difficult memory manipulation conditions; however, firm conclusions cannot be drawn given the lack of overall significant effects. These findings are discussed in the context of individualized targeting and other factors that might moderate rTMS effects.

neuroscience↗