Browsing by Author "Crowell, Courtney A"

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    Application of long-interval paired-pulse transcranial magnetic stimulation to motion-sensitive visual cortex does not lead to changes in motion discrimination.
    (Neuroscience letters, 2020-05-12) Gamboa, Olga Lucia; Brito, Alexandra; Abzug, Zachary; D'Arbeloff, Tracy; Beynel, Lysianne; Wing, Erik A; Dannhauer, Moritz; Palmer, Hannah; Hilbig, Susan A; Crowell, Courtney A; Liu, Sicong; Donaldson, Rachel; Cabeza, Roberto; Davis, Simon W; Peterchev, Angel V; Sommer, Marc A; Appelbaum, Lawrence G
    The perception of visual motion is dependent on a set of occipitotemporal regions that are readily accessible to neuromodulation. The current study tested if paired-pulse Transcranial Magnetic Stimulation (ppTMS) could modulate motion perception by stimulating the occipital cortex as participants viewed near-threshold motion dot stimuli. In this sham-controlled study, fifteen subjects completed two sessions. On the first visit, resting motor threshold (RMT) was assessed, and participants performed an adaptive direction discrimination task to determine individual motion sensitivity. During the second visit, subjects performed the task with three difficulty levels as TMS pulses were delivered 150 and 50 ms prior to motion stimulus onset at 120% RMT, under the logic that the cumulative inhibitory effect of these pulses would alter motion sensitivity. 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 by tilting the coil 90°. 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. Active-versus-sham stimulation differences did not interact with either stimulation location (p = 0.12) or difficulty (p = 0.33). These findings fail to support the hypothesis that long-interval ppTMS recruits inhibitory processes in motion-sensitive cortex but must be considered within the limited parameters used in this design.
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    Effects of online repetitive transcranial magnetic stimulation (rTMS) on cognitive processing: A meta-analysis and recommendations for future studies.
    (Neuroscience and biobehavioral reviews, 2019-12) Beynel, Lysianne; Appelbaum, Lawrence G; Luber, Bruce; Crowell, Courtney A; Hilbig, Susan A; Lim, Wesley; Nguyen, Duy; Chrapliwy, Nicolas A; Davis, Simon W; Cabeza, Roberto; Lisanby, Sarah H; Deng, Zhi-De
    Online repetitive transcranial magnetic stimulation (rTMS), applied while subjects are performing a task, is widely used to disrupt brain regions underlying cognition. However, online rTMS has also induced "paradoxical enhancement". Given the rapid proliferation of this approach, it is crucial to develop a better understanding of how online stimulation influences cognition, and the optimal parameters to achieve desired effects. To accomplish this goal, a quantitative meta-analysis was performed with random-effects models fitted to reaction time (RT) and accuracy data. The final dataset included 126 studies published between 1998 and 2016, with 244 total effects for reaction times, and 202 for accuracy. Meta-analytically, rTMS at 10 Hz and 20 Hz disrupted accuracy for attention, executive, language, memory, motor, and perception domains, while no effects were found with 1 Hz or 5 Hz. Stimulation applied at and 10 and 20 Hz slowed down RTs in attention and perception tasks. No performance enhancement was found. Meta-regression analysis showed that fMRI-guided targeting and short inter-trial intervals are associated with increased disruptive effects with rTMS.
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    Site-Specific Effects of Online rTMS during a Working Memory Task in Healthy Older Adults.
    (Brain sciences, 2020-04-27) Beynel, Lysianne; Davis, Simon W; Crowell, Courtney A; Dannhauer, Moritz; Lim, Wesley; Palmer, Hannah; Hilbig, Susan A; Brito, Alexandra; Hile, Connor; Luber, Bruce; Lisanby, Sarah H; Peterchev, Angel V; Cabeza, Roberto; Appelbaum, Lawrence G
    The process of manipulating information within working memory is central to many cognitive functions, but also declines rapidly in old age. Improving this process could markedly enhance the health-span in older adults. The current pre-registered, randomized and placebo-controlled study tested the potential of online repetitive transcranial magnetic stimulation (rTMS) applied at 5 Hz over the left lateral parietal cortex to enhance working memory manipulation in healthy elderly adults. rTMS was applied, while participants performed a delayed-response alphabetization task with two individually titrated levels of difficulty. Coil placement and stimulation amplitude were calculated from fMRI activation maps combined with electric field modeling on an individual-subject basis in order to standardize dosing at the targeted cortical location. Contrary to the a priori hypothesis, active rTMS significantly decreased accuracy relative to sham, and only in the hardest difficulty level. When compared to the results from our previous study, in which rTMS was applied over the left prefrontal cortex, we found equivalent effect sizes but opposite directionality suggesting a site-specific effect of rTMS. These results demonstrate engagement of cortical working memory processing using a novel TMS targeting approach, while also providing prescriptions for future studies seeking to enhance memory through rTMS.