Biology subjects

Labruna, L.

Publications and source records attributed to Labruna, L..

5 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↗

bioRxiv2020

A single mechanism for global and selective response inhibition under the influence of motor preparation

In our everyday behavior, we frequently cancel one movement while continuing others. Two competing models have been suggested for the cancellation of such specific actions: 1) the abrupt engagement of a unitary global inhibitory mechanism followed by reinitiation of the continuing actions, or 2) a balance between distinct global and selective inhibitory mechanisms. To evaluate these models, we examined behavioral and physiological markers of proactive control, motor preparation, and response inhibition using a combination of behavioral task performance measures, electromyography, electroencephalography, and motor evoked potentials elicited with transcranial magnetic stimulation. Healthy participants performed two versions of a stop signal task with cues incorporating proactive control: A unimanual task involving the initiation and inhibition of a single response, and a bimanual task involving the selective stopping of one of two prepared responses. Stopping latencies, motor evoked potentials, and frontal beta power (13-20 Hz) did not differ between the uni- and bimanual tasks. However, evidence for selective proactive control before stopping was manifest in the bimanual condition as changes in corticomotor excitability, mu (9-14 Hz), and beta (15-25 Hz) oscillations over sensorimotor cortex. Altogether, our results favor the recruitment of a single inhibitory stopping mechanism with the net behavioral output depending on the levels of action-specific motor preparation. Significance statementResponse inhibition is a core function of cognitive flexibility and movement control. Previous research has suggested separate mechanisms for selective and global inhibition, yet the evidence is inconclusive. Another line of research has examined the influence of preparation for action stopping, or what is called proactive control, on stopping performance, yet the neural mechanisms underlying this interaction are unknown. We combined transcranial magnetic stimulation, electroencephalography, electromyography and behavioral measures to compare selective and global inhibition models and to investigate markers of proactive control. The results favor a single inhibitory mechanism over separate selective and global mechanisms, but indicate a vital role for preceding motor activity in determining whether and which actions will be stopped.

neuroscience↗

bioRxiv2019

Planning Face, Hand, and Leg Movements: Anatomical Constraints on Preparatory Inhibition.

Motor-evoked potentials (MEPs), elicited by Transcranial Magnetic Stimulation (TMS) over the motor cortex, are reduced during the preparatory period in delayed response tasks. Here we examine how MEP suppression varies as a function of the anatomical organization of the motor cortex. MEPs were recorded from a left index muscle while participants prepared a hand or leg movement in Experiment 1, or prepared an eye or mouth movement in Experiment 2. In this manner, we assessed if the level of MEP suppression in a hand muscle varied as a function of the anatomical distance between the agonist for the forthcoming movement and the muscle targeted by TMS. MEPs suppression was attenuated when the cued effector was anatomically distant from the hand (e.g., leg or facial movement compared to finger movement). A similar effect was observed in Experiment 3 in which MEPs were recorded from a muscle in the leg and the forthcoming movement involved the upper limb or face. These results demonstrate an important constraint on preparatory inhibition: It is sufficiently broad to be manifest in a muscle that is not involved in the task, but is not global, showing a marked attenuation when the agonist muscle belongs to a different segment of the body. New & NoteworthyUsing TMS, we examine changes in corticospinal excitability as people prepare to move. Consistent with previous work, we observe a reduction in excitability during the preparatory period, an effect observed in both task relevant and task irrelevant muscles. However, this preparatory inhibition is anatomically constrained, attenuated in muscles belonging to a different body segment than the agonist of the forthcoming movement.

neuroscience↗