Biology subjects

Dmochowski, J. P.

Publications and source records attributed to Dmochowski, J. P..

11 recordsLinked to original sources

bioRxiv2026

Focused ultrasound alters neural time irreversibility independently of response amplitude

Transcranial focused ultrasound (tFUS) can modulate activity in deep brain regions non-invasively, yet its effects remain variable and incompletely understood. Because sonication deposits mechanical energy into tissue, we asked whether responses could be clarified through the lens of stochastic thermodynamics, which links nonequilibrium dynamics to dissipation and time-irreversibility. Analyzing previously published fiber-photometry recordings from freely moving mice, we estimated the entropy production rate (EPR) before, during, and after thalamic sonication. GCaMP fluorescence rose monotonically with acoustic dose, but EPR followed a non-monotonic profile peaking at moderate intensity. Immediately after sonication, EPR was elevated yet uncorrelated with GCaMP, and retained a significant dose relationship even after accounting for response amplitude. Finally, trials with lower baseline EPR showed larger subsequent changes in both EPR and GCaMP during sonication. These findings indicate that tFUS reshapes neural dynamics beyond what signal amplitude captures, while highlighting the insights afforded by adopting stochastic thermodynamics in neuromodulation research.

neuroscience↗

bioRxiv2025

Transcranial Focused Ultrasound of the Human Subgenual Anterior Cingulate Reconfigures Resting State Connectivity: A Sham-Controlled fMRI Study

Transcranial focused ultrasound stimulation (tFUS) can modulate human brain activity, but its impact on large-scale functional connectivity (FC) in vivo remains incompletely characterized. Here we asked whether brief tFUS to the subgenual anterior cingulate cortex (sgACC) modulates its FC with other brain regions. In a sham-controlled, within-subject study of healthy adults (N = 16), we measured resting-state blood-oxygen-level dependent (BOLD) activity with functional magnetic resonance imaging (fMRI) before, during, and after five minutes of tFUS (i.e., five 20-second sonications followed by 40 second pauses). Subject-level sgACC-whole-brain FC was analyzed with a linear mixed-effects model (fixed: time, condition, timexcondition; random: subject). tFUS increased sgACC-whole brain connectivity after sonication relative to sham. A smaller, non-significant trend was observed during sonication. Baseline-controlled analyses were employed to rule out the possibility that the observed increase in FC was due to a "regression to the mean" effect. Interestingly, network-level analysis revealed a clear disassociation in the evolution of resting-state FC across the 15 minute recordings: during sham sessions, the sgACCs connectivity with the default mode network (DMN) increased, while FC with other networks was largely unchanged. On the other hand, active tFUS led to a notable increase in FC with non-DMN networks (especially the cognitive control network), while connectivity with the DMN was stable. These results provide whole-brain evidence that tFUS reconfigures network dynamics in the human brain, motivating clinical applications to disorders characterized by dysregulated brain activity.

neuroscience↗

bioRxiv2025

Mechanical Artifacts During Transcranial Focused Ultrasound Mimic Biologically Evoked Responses

Low-intensity transcranial focused ultrasound stimulation (tFUS) has emerged as a promising technique for non-invasive neuromodulation, offering deep brain penetration and high spatial precision. However, the electrophysiological effects of tFUS remain poorly understood, in part due to challenges distinguishing genuine neural responses from mechanical artifacts. Here we investigated the electrophysiological signatures captured during tFUS of the anesthetized rat hippocampus using silicon microelectrodes. We observed a strong, stereotyped local field potential (LFP) response that was time-locked to the onset and offset of sonication and resembled sensory-evoked potentials. Critically, the same waveform was observed in euthanized animals, confirming a non-biological, artifact-driven origin. The artifact scaled with acoustic intensity and was most pronounced under continuous-wave sonication. These findings suggest that electrode movement induced by ultrasound can generate artifactual LFP signals that closely mimic authentic neural responses. Our results underscore the need for caution when interpreting in situ electrophysiological recordings during tFUS and advocate for alternative, artifact-resistant readouts such as fiber photometry to unambiguously detect neuromodulatory effects.

neuroscience↗

bioRxiv2022

Computational modeling of posteroanterior lumbar traction by an automated massage bed: predicting intervertebral disc stresses and deformation

Spinal traction is a physical intervention that provides constant or intermittent stretching axial force to the lumbar vertebrae to gradually distract spinal tissues into better alignment, reduce intervertebral disc (IVD) pressure, and manage lower back pain (LBP). However, such axial traction may change the normal lordotic curvature, and result in unwanted side effects and/or inefficient reduction of the IVD pressure. An alternative to axial traction has been recently tested, consisting of posteroanterior (PA) traction in supine posture, which was recently shown effective to increase the intervertebral space and lordotic angle using MRI. PA traction aims to maintain the lumbar lordosis curvature throughout the spinal traction therapy while reducing the intradiscal pressure. In this study, we developed finite element simulations of mechanical therapy produced by a commercial thermo-mechanical massage bed capable of spinal PA traction. The stress relief produced on the lumbar discs by the posteroanterior traction system was investigated on human subject models with different BMI (normal, overweight, moderate obese and extreme obese BMI cases). We predict typical traction levels lead to significant distraction stresses in the lumbar discs, thus producing a stress relief by reducing the compression stresses normally experienced by these tissues. Also, the stress relief experienced by the lumbar discs was effective in all BMI models, and it was found maximal in the normal BMI model. These results are consistent with prior observations of therapeutic benefits derived from spinal AP traction.

bioengineering↗

bioRxiv2022

Computational modeling of deep tissue heating by an automatic thermal massage bed: predicting the effects on circulation

Automatic thermal and mechanical massage beds support selfmanaged treatment, including reduction of pain and stress, enhanced circulation, and improved mobility. As the devices become more sophisticated (increasing the degrees of freedom), it is essential to identify the settings that best target the desired tissue. To that end, we developed an MRI-derived model of the lower back and simulated the physiological effects of a commercial thermal-mechanical massage bed. Here we specifically estimated the tissue temperature and increased circulation under steady-state conditions for typical thermal actuator settings (i.e., 45-65{degrees}C). Energy transfer across nine tissues was simulated with finite element modeling (FEM) and the resulting heating was coupled to blood flow with an empirically-guided model of temperature-dependent circulation. Our findings indicate that thermal massage increases tissue temperature by 3-8{degrees}C and 1-3{degrees}C at depths of 2 and 3 cm, respectively. Importantly, due to the rapid (non-linear) increase of circulation with local temperature, this is expected to increase blood flow four-fold (4x) at depths occupied by deep tissue and muscle. These predictions are consistent with prior clinical observations of therapeutic benefits derived from spinal thermal massage.

bioengineering↗

bioRxiv2021

Neuronal responses to focused ultrasound are gated by pre-stimulation brain rhythms

BackgroundOwing to its high spatial resolution and penetration depth, transcranial focused ultrasound stimulation (tFUS) is one of the most promising approaches to non-invasive neuromodulation. Identifying the impact of the stimulation waveform and endogenous neural activity on neuromodulation outcome is critical to harnessing the potential of tFUS. ObjectiveHere we tested a new form of tFUS where the amplitude of the ultrasonic waveform is modulated at a rate much slower than the operating frequency. Moreover, we sought to identify the relationship between pre-stimulation neural activity and the neuronal response to tFUS. MethodsWe applied three minutes of amplitude modulated (AM) tFUS at 40 Hz to the rat hippocampus while recording local field potentials (LFP) and multi-unit activity (MUA)from the sonicated region. To assess the role of AM, we also tested continuous-wave (CW) stimulation. ResultsAM tFUS reduced firing rate during and immediately after stimulation. On the other hand, CW tFUS produced an acute firing rate increase that was abolished after sonication. For both waveforms, firing rate changes were stronger in units exhibiting high baseline LFP power, particularly in the gamma band (30-250 Hz). The neuromodulatory effect was also influenced by the prevalence of sharp wave ripples (SWR) during the pre-stimulation period, with firing rates modulated by up to 33% at units showing frequent baseline SWR. ConclusionOur findings suggest that AM and CW tFUS produce qualitatively different neuronal outcomes, and that baseline rhythms may effectively "gate" the response to tFUS.

neuroscience↗

bioRxiv2021

Inter-Subject Correlation during New Music Listening: A Study of Electrophysiological and Behavioral Responses to Steve Reich's Piano Phase

Musical minimalism utilizes the temporal manipulation of restricted collections of rhythmic, melodic, and/or harmonic materials. One example, Steve Reichs Piano Phase, offers listeners readily audible formal structures containing unpredictable events at local levels. Pattern recurrences may generate strong expectations which are violated by small temporal and pitch deviations. A hyper-detailed listening strategy prompted by these minute deviations stands in contrast to the type of listening engagement typically cultivated around functional tonal Western music. Recent research has suggested that the inter-subject correlation (ISC) of electroencephalographic (EEG) responses to natural audio-visual stimuli objectively indexes a state of "engagement", demonstrating the potential of this approach for analyzing music listening. But can ISCs capture engagement with minimal music, which features less obvious expectation formation and has historically received a wide range of reactions? To approach this question, we collected EEG and continuous behavioral (CB) data while 30 adults listened to an excerpt from Steve Reichs Piano Phase, as well as three controlled manipulations and a popular-music remix of the work. Our analyses reveal that EEG and CB ISC are highest for the remix stimulus and lowest for our most repetitive manipulation. In addition, we found no statistical differences in overall EEG ISC between our most musically meaningful manipulations and Reichs original piece. We also found that aesthetic evaluations corresponded well with overall EEG ISC. Finally we highlight co-occurrences between stimulus events and time-resolved EEG and CB ISC. We offer the CB paradigm as a useful analysis measure and note the value of minimalist compositions as a limit case for studying music listening using EEG ISC. We show that ISC is less effective at measuring engagement with this minimalist stimulus than with popular music genres and argue that this may be due to a difference between the type of engagement measured by ISC and the particular engagement patterns associated with minimalism.

neuroscience↗

bioRxiv2021

Inter-Subject EEG Correlation Reflects Time-Varying Engagement with Natural Music

Musical engagement can be conceptualized through various activities, modes of listening, and listener states--among these a state of focused engagement. Recent research has reported that this state can be indexed by the inter-subject correlation (ISC) of EEG responses to a shared naturalistic stimulus. While statistically significant ISC has been reported during music listening, these reports have considered only correlations computed across entire excerpts and do not provide insights into time-varying engagement. Here we present the first EEG-ISC investigation of time-varying engagement within a musical work. From a sample of 23 adult musicians who listened to a cello concerto movement, we find varying levels of ISC throughout the excerpt. In particular, significant ISC is observed during periods of musical tension that build to climactic highpoints, but not at the highpoints themselves. In addition, we find that a control stimulus retaining envelope characteristics of the intact music, but little other temporal structure, also elicits significant neural correlation, though to a lesser extent than the original excerpt. In all, our findings shed light on temporal dynamics of listener engagement during music listening, establish connections between salient musical events and EEG ISC, and clarify specific listener states that are indexed by this measure.

neuroscience↗

bioRxiv2021

Neural responses to natural visual motion are spatially selective across the visual field, with selectivity differing across brain areas and task

It is well established that neural responses to visual stimuli are enhanced at select locations in the visual field. While spatial selectivity and the effects of spatial attention are well-understood for discrete tasks (e.g., visual cueing paradigms), little is known about neural response during a naturalistic visual experience that involves complex dynamic visual stimuli, for instance, driving. In this study, we assess the strength of neural responses across the visual space during a kart race video game. Specifically, we measure the correlation strength of scalp evoked potentials with optical flow magnitude at individual locations on the screen. We find the strongest neural responses for task-relevant locations in visual space, selectively extending to areas beyond the focus of overt attention: while the drivers gaze is directed upon the heading direction at the center of the screen, we observe robust neural evoked responses also to peripheral areas such as the road and surrounding buildings. Importantly, this spatial selectivity of neural responses differs across scalp locations. Moreover, during active gameplay, the strength of the spatially-selective neural responses are enhanced compared to passive viewing. Spatially selective neural gains have previously been interpreted as an attentional gain mechanism. In this view, the present data suggest that different brain areas focus attention on different task-relevant portions of the visual field, reaching beyond the focus of overt attention.

neuroscience↗

bioRxiv2020

Differential effects of amplitude-modulated transcranial focused ultrasound on excitatory and inhibitory neurons

Although stimulation with ultrasound has been shown to modulate brain activity at multiple scales, it remains unclear whether transcranial focused ultrasound stimulation (tFUS) exerts its influence on specific cell types. Here we propose a novel form of tFUS where a continuous waveform is amplitude modulated (AM) at a slow rate (i.e., 40 Hz) targeting the temporal range of electrophysiological activity: AM-tFUS. We stimulated the rat hippocampus while recording multi-unit activity (MUA) followed by classification of spike waveforms into putative excitatory pyramidal cells and inhibitory interneurons. At low acoustic intensity, AM-tFUS selectively reduced firing rates of inhibitory interneurons. On the other hand, higher intensity AM-tFUS increased firing of putative excitatory neurons with no effect on inhibitory firing. Interestingly, firing rate was unchanged during AM-tFUS at intermediate intensity. Consistent with the observed changes in firing rate, power in the theta band (3-10 Hz) of the local field potential (LFP) decreased at low-intensity, was unchanged at intermediate intensity, and increased at higher intensity. Temperature increases at the AM-tFUS target were limited to 0.2{degrees}C. Our findings indicate that inhibitory interneurons exhibit greater sensitivity to ultrasound, and that cell-type specific neuromodulation may be achieved by calibrating the intensity of AM-tFUS.

neuroscience↗

bioRxiv2019

Natural Music Evokes Correlated EEG Responses Reflecting Temporal Structure and Beat

The brain activity of multiple subjects has been shown to synchronize during salient moments of natural stimuli, suggesting that correlation of neural responses indexes a brain state operationally termed engagement. While past electroencephalography (EEG) studies have considered both auditory and visual stimuli, the extent to which these results generalize to music--a temporally structured stimulus for which the brain has evolved specialized circuitry--is less understood. Here we investigated neural correlation during natural music listening by recording dense-array EEG responses from N = 48 adult listeners as they heard real-world musical works, some of which were temporally disrupted through shuffling of short-term segments (measures), reversal, or randomization of phase spectra. We measured neural correlation across responses (inter-subject correlation) and between responses and stimulus envelope fluctuations (stimulus-response correlation) in the time and frequency domains. Stimuli retaining basic musical features evoked significantly correlated neural responses in all analyses. However, while unedited songs were self-reported as most pleasant, time-domain correlations were highest during measure-shuffled versions. Frequency-domain measures of correlation (coherence) peaked at frequencies related to the musical beat, although the magnitudes of these spectral peaks did not explain the observed temporal correlations. Our findings show that natural music evokes significant inter-subject and stimulus-response correlations, and suggest that the neural correlates of musical engagement may be distinct from those of enjoyment.

neuroscience↗