Biology subjects

Sheltraw, D.

Publications and source records attributed to Sheltraw, D..

3 recordsLinked to original sources

bioRxiv2026

Manipulating speech perception with amplitude-modulated kilohertz magnetic perturbation (AM-kTMP)

Speech perception has been hypothesized to exploit neural activity that entrains to the rhythmic properties of the utterance. Perceptual sensitivity varies with the phase of oscillatory activity induced by speech, and with an external oscillatory perturbation induced by transcranial alternating current stimulation (tACS) over the temporal lobe. Here we used a new form of non-invasive brain stimulation (NIBS), kilohertz transcranial magnetic perturbation (kTMP), in which a low frequency perturbation is created by the amplitude modulation (AM) of a continuous high-frequency carrier signal (3.5 kHz). As a magnetic induction method, kTMP can produce much higher electrical fields at the cortical surface than tACS and reduces cutaneous co-stimulation. Human participants (n=40) listened to sequences of rhythmic speech while receiving kTMP with an AM component of 3.125 Hz. The phasic modulation of perceptual sensitivity was greater during AM-kTMP than during sham stimulation, suggesting that AM-kTMP entrains neural activity underlying speech perception. Participants ratings of rhythmic sensations and other side effects did not differ between AM-kTMP and sham stimulation. Together with its reduced peripheral stimulation, our results highlight kTMP as a promising NIBS method for modulating frequency-specific brain dynamics in speech perception.

neuroscience↗

bioRxiv2026

Amplitude-Modulated Kilohertz Stimulation Targeting Beta-Band Activity Disrupts Motor Learning

Sensorimotor learning is associated with the modulation of neural rhythms in the primary motor cortex (M1). Beta-band activity ("beta"; 15-30 Hz) is suppressed during learning, while delta oscillations (1-4 Hz) become increasingly correlated with movement kinematics as skill improves. These observations have been complemented by experimental manipulations designed to perturb oscillatory activity with externally applied electric fields (E-fields). In non-human primates, invasive beta stimulation has been shown to disrupt motor learning whereas delta stimulation enhanced motor recovery in a stroke model. Causal evidence in humans remains limited, partly because established non-invasive methods cannot achieve continuous, narrowband E-fields at sufficient amplitude in the brain. To address this gap, we employed kilohertz transcranial magnetic perturbation (kTMP), a non-invasive magnetic induction technique that delivers continuous narrowband kilohertz E-fields which can be amplitude-modulated (AM) to target cortical rhythms. We applied AM-kTMP to test the functional relevance of beta and delta activity in human motor learning. In a double-blind mixed design, 40 participants performed a force-control task while receiving AM-kTMP at E-field amplitudes of 8 V/m in M1. We targeted either beta or delta, each paired with a sham condition. AM-kTMP influenced motor performance in a frequency-dependent manner: Beta-kTMP suppressed performance gains relative to both delta-kTMP and sham, whereas delta-kTMP showed no effect. These results suggest that increased beta activity in human M1 can interfere with motor learning. More broadly, kTMP offers a novel approach to probe frequency-specific cortical dynamics.

neuroscience↗

bioRxiv2021

kTMP: A New Non-invasive Magnetic Induction Method to Modulate Cortical Excitability.

Non-invasive brain stimulation (NIBS) provides a method for safely perturbing brain activity, and has been employed in basic research to test hypotheses concerning brainbehavior relationships with increasing translational applications. We introduce and evaluate a novel subthreshold NIBS method: kilohertz transcranial magnetic perturbation (kTMP). kTMP is a magnetic induction method that delivers continuous kHz-frequency cortical electric fields (E-fields) which may be amplitude-modulated to potentially mimic electrical activity at endogenous frequencies. We used TMS to compare the amplitude of motor-evoked potentials (MEPs) in a hand muscle before and after kTMP. In Experiment 1, we applied kTMP for 10 min over motor cortex to induce an E-field amplitude of approximately 2.0 V/m, comparing the effects of waveforms at frequencies of 2.0, 3.5, or 5.0 kHz. In Experiments 2 and 3 we used two forms of amplitude-modulated kTMP with a carrier frequency at 3.5 kHz and modulation frequencies of either 20 or 140 Hz. The only percept associated with kTMP was an auditory tone, making kTMP amenable for doubleblind experimentation. Relative to sham stimulation, non-modulated kTMP at 2.0 and 3.5 kHz resulted in an increase in cortical excitability, with Experiments 2 and 3 providing a replication of this effect for the 3.5 kHz condition. Although amplitude-modulated kTMP increased MEP amplitude compared to sham, no enhancement was found compared to non-modulated kTMP. kTMP opens a new experimental NIBS space inducing relatively large amplitude subthreshold E-fields able to increase cortical excitability with minimal sensation.

neuroscience↗