Biology subjects

Ruddy, K. L.

Publications and source records attributed to Ruddy, K. L..

6 recordsLinked to original sources

bioRxiv2024

A robust brain network for sustained attention from adolescence to adulthood that predicts later substance use

Substance use, including cigarettes and cannabis, is associated with poorer sustained attention in late adolescence and early adulthood. Previous studies were predominantly cross-sectional or under-powered and could not indicate if impairment in sustained attention was a predictor of substance-use or a marker of the inclination to engage in such behaviour. This study explored the relationship between sustained attention and substance use across a longitudinal span from ages 14 to 23 in over 1,000 participants. Behaviours and brain connectivity associated with diminished sustained attention at age 14 predicted subsequent increases in cannabis and cigarette smoking, establishing sustained attention as a robust biomarker for vulnerability to substance use. Individual differences in network strength relevant to sustained attention were preserved across developmental stages and sustained attention networks generalized to participants in an external dataset. In summary, brain networks of sustained attention are robust, consistent, and able to predict aspects of later substance use. TeaserA robust brain network for sustained attention at age 14 predicts cigarette and cannabis use from ages 14 to 23.

neuroscience↗

bioRxiv2021

Self-regulation of the brain's Beta rhythm using a brain-computer interface improves inhibitory control

Neural oscillations, or brain rhythms, fluctuate in a manner reflecting ongoing behavior. Whether these fluctuations are instrumental or epiphenomenal to the behavior remains elusive. Attempts to experimentally manipulate neural oscillations exogenously using non-invasive brain stimulation have shown some promise, but difficulty with tailoring stimulation parameters to individuals has hindered progress in this field. We demonstrate here using electroencephalography (EEG) neurofeedback in a brain-computer interface that human participants (n=44) learned over multiple sessions across a 6-day period to self-regulate their Beta rhythm (13-20 Hz) over the right inferior frontal cortex (rIFC). The modulation was evident only during neurofeedback task performance but did not lead to offline alteration of Beta rhythm characteristics at rest, nor to changes in subsequent cognitive behavior. Likewise, a control group (n=38) who underwent training of the Alpha rhythm (8-12 Hz) did not exhibit behavioral changes. Although the right frontal Beta rhythm has been repeatedly implicated as a key component of the brains inhibitory control system, the present data suggest that its manipulation offline prior to cognitive task performance does not result in behavioral change. Thus, this form of neurofeedback training of the tonic Beta rhythm would not serve as a useful therapeutic target for disorders with dysfunctional inhibitory control as their basis.

neuroscience↗

bioRxiv2021

Mental individuation of imagined finger movements can be achieved using TMS-based neurofeedback

Neurofeedback (NF) in combination with motor imagery (MI) can be used for training individuals to volitionally modulate sensorimotor activity without producing overt movements. However, until now, NF methods were of limited utility for mentally training specific hand and finger actions. Here we employed a novel transcranial magnetic stimulation (TMS) based protocol to probe and detect MI-induced motor activity patterns in the primary motor cortex (M1) with the aim to reinforce selective facilitation of single finger representations. We showed that TMS-NF training but not MI training with uninformative feedback enabled participants to selectively upregulate corticomotor excitability of one finger, while simultaneously downregulating excitability of other finger representations within the same hand. Successful finger individuation during MI was accompanied by strong desynchronisation of sensorimotor brain rhythms, particularly in the beta band, as measured by electroencephalography. Additionally, informative TMS-NF promoted more dissociable EEG activation patterns underlying single finger MI, when compared to MI of the control group where no such feedback was provided. Our findings suggest that selective TMS-NF is a new approach for acquiring the ability of finger individuation even if no overt movements are performed. This might offer new treatment modality for rehabilitation after stroke or spinal cord injury.

neuroscience↗

bioRxiv2019

Steady-state responses in the somatosensory system interact with endogenous beta activity

Brain oscillations have been related to many aspects of human behavior. To understand a potential causal relationship, it is of great importance to develop methods for modulating ongoing neural activity. It has been shown that external rhythmic stimulation leads to an oscillatory brain response that follows the temporal structure of the presented stimulus and is assumed to reflect the synchronization of ongoing neural oscillations with the stimulation rhythm. This interaction between individual brain activity and so called steady-state evoked potentials (SSEPs) is the fundamental requirement of neural entrainment. Here, we investigate whether neural responses to rhythmic vibrotactile stimulation, measured with EEG, are dependent on ongoing individual brain oscillations, and therefore reflect entrained oscillatory activity. For this, we measured phase synchronization in response to rhythmic stimulation across various frequencies in the alpha and beta band. Three different stimulation intensities were applied for each frequency relative to the individual sensory threshold. We found that a higher stimulation intensity, compared to lower intensities, resulted in a more pronounced phase synchronization with the stimulation signal. Moreover, EEG responses to low stimulation frequencies closer to individual beta peak frequencies revealed a higher degree of entrainment, compared to stimulation conditions with frequencies that were more distant to endogenous oscillations. Our findings provide evidence that the efficacy of vibrotactile rhythmic beta stimulation to evoke a SSEPs is dependent on ongoing brain oscillations.

neuroscience↗

bioRxiv2018

A different state of mind: neural activity related to volitionally up- versus downregulating cortical excitability

To date there exists no reliable method to non-invasively upregulate or downregulate the state of the resting motor system over a large dynamic range. Here we show that an operant conditioning paradigm which provides neurofeedback of the size of motor evoked potentials (MEPs) in response to transcranial magnetic stimulation (TMS), enables participants to self-modulate their own brain state. Following training, participants were able to robustly increase (by 83.8%) and decrease (by 30.6%) their MEP amplitudes. This volitional up-versus down-regulation of corticomotor excitability caused an increase of late-cortical disinhibition (LCD), a TMS derived read-out of presynaptic GABAB disinhibition, which was accompanied by an increase of gamma and a decrease of alpha oscillations in the trained hemisphere. This approach paves the way for future investigations into how altered brain state influences motor neurophysiology and recovery of function in a neurorehabilitation context.

neuroscience↗

bioRxiv2017

Improving the quality of combined EEG-TMS neural recordings: Introducing the ‘Coil Spacer’

BackgroundIn the last decade, interest in combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) approaches has grown substantially. Aside from the obvious artifacts induced by the magnetic pulses themselves, separate and more sinister signal disturbances arise as a result of contact between the TMS coil and EEG electrodes.\n\nNew methodHere we profile the characteristics of these artifacts and introduce a simple device - the coil spacer - to provide a platform allowing physical separation between the coil and electrodes during stimulation.\n\nResultsEEG data revealed high amplitude signal disturbances when the TMS coil was in direct contact with the EEG electrodes, well within the physiological range of viable EEG signals. The largest artifacts were located in the Delta and Theta frequency range, and standard data cleanup using independent components analysis (ICA) was ineffective due to the artifacts similarity to real brain oscillations.\n\nComparison with Existing MethodWhile the current best practice is to use a large coil holding apparatus to fixate the coil hovering over the head with an air gap, the spacer provides a simpler solution that ensures this distance is kept constant throughout testing.\n\nConclusionsThe results strongly suggest that data collected from combined TMS-EEG studies with the coil in direct contact with the EEG cap are polluted with low frequency artifacts that are indiscernible from physiological brain signals. The coil spacer provides a cheap and simple solution to this problem and is recommended for use in future simultaneous TMS-EEG recordings.

neuroscience↗