Browsing by Author "Liu, Sicong"

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Open Access
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.
Open Access
Intensity- and timing-dependent modulation of motion perception with transcranial magnetic stimulation of visual cortex.
(Neuropsychologia, 2020-10) Gamboa Arana, Olga Lucia; Palmer, Hannah; Dannhauer, Moritz; Hile, Connor; Liu, Sicong; Hamdan, Rena; Brito, Alexandra; Cabeza, Roberto; Davis, Simon W; Peterchev, Angel V; Sommer, Marc A; Appelbaum, Lawrence G
Despite the widespread use of transcranial magnetic stimulation (TMS) in research and clinical care, the dose-response relations and neurophysiological correlates of modulatory effects remain relatively unexplored. To fill this gap, we studied modulation of visual processing as a function of TMS parameters. Our approach combined electroencephalography (EEG) with application of single pulse TMS to visual cortex as participants performed a motion perception task. During each participants' first visit, motion coherence thresholds, 64-channel visual evoked potentials (VEPs), and TMS resting motor thresholds (RMT) were measured. In second and third visits, single pulse TMS was delivered at one of two latencies, either 30 ms before the onset of motion or at the onset latency of the N2 VEP component derived from the first session. TMS was delivered at 0%, 80%, 100%, or 120% of RMT over the site of N2 peak activity, or at 120% over vertex. Behavioral results demonstrated a significant main effect of TMS timing on accuracy, with better performance when TMS was applied at the N2-Onset timing versus Pre-Onset, as well as a significant interaction, indicating that 80% intensity produced higher accuracy than other conditions at the N2-Onset. TMS effects on the P3 VEP showed reduced amplitudes in the 80% Pre-Onset condition, an increase for the 120% N2-Onset condition, and monotonic amplitude scaling with stimulation intensity. The N2 component was not affected by TMS. These findings reveal the influence of TMS intensity and timing on visual perception and electrophysiological responses, with optimal facilitation at stimulation intensities below RMT.
Open Access
Visual-motor expertise in athletes: Insights from semiparametric modelling of 2317 athletes tested on the Nike SPARQ Sensory Station.
(Journal of sports sciences, 2020-02) Burris, Kyle; Liu, Sicong; Appelbaum, Lawrence
Elite athletes not only run faster, hit harder, and jump higher, but also see and react better. However, the specific visual-motor skills that differentiate high-achieving athletes are still not well understood. In this paper we examine 2317 athletes (1871 male) tested on the Nike SPARQ Sensory Station, a digital test battery measuring visual, perceptual and motor skills relevant for sports performance. We develop a multivariate Gaussian transformation model to robustly estimate visual-motor differences by level, gender, and sport type. Results demonstrate that visual-motor performance is superior for athletes at higher levels, with males faster at near-far eye movements and females faster at eye-hand reaction times. Interestingly, athletes who play interceptive sports such as baseball and tennis exhibit better measures of visual clarity, contrast sensitivity and simple reaction time, while athletes from strategic sports like soccer and basketball have higher measures of spatial working memory. These findings provide quantitative evidence of domain-specific visual expertise in athletes.