Older adults use fewer muscles to overcome perturbations during a seated locomotor task.

Older adults use fewer muscles to overcome perturbations during a seated locomotor task

Older adults often demonstrate greater co-contraction and motor errors than young adults in response to motor perturbations. We demonstrated that older adults reduced their motor errors more than young adults with brief perturbations during recumbent stepping while maintaining greater muscle co-contraction. In doing so, older adults largely used one muscle pair to drive the stepper, tibialis anterior and soleus, while young adults used all muscles. These two muscles are crucial for maintaining upright balance.

March 2024 · Seyed Yahya Shirazi, Helen Huang
The overall design of the Lab Streaming Layer (LSL) for synchronized data recording.

The Lab Streaming Layer for Synchronized Multimodal Recording

The Lab Streaming Layer (LSL) presents a software-based solution for synchronizing data streams across multiple instruments in neurophysiological research. Utilizing per-sample time stamps and LAN-based time synchronization, LSL ensures accurate, continuous recording despite varying device clocks. It automatically corrects for network delays and jitters, maintaining data integrity through disruptions. Supporting over 150 device classes and compatible with numerous programming languages, LSL has become a vital tool for integrating diverse data acquisition systems. Its robustness and adaptability have extended its application beyond research, into art, performance, and commercial realms, making it a cornerstone for multimodal data collection and synchronization.

February 2024 · Christian Kothe, Seyed Yahya Shirazi, Tristan Stenner, David Medine, Chadwick Boulay, Matthew I. Grivich, Tim Mullen, Arnaud Delorme, Scott Makeig
Muscle faitgue can be characterized using a non-parametric functional muscle network.

Non-Parametric Functional Muscle Network as a Robust Biomarker of Fatigue

We show that the effects of fatigue on muscle coordination and neural drive can be reliably characterized using a non-parametric functional muscle network. The network demonstrated a consistent decrease in connectivity after the fatigue intervention, as indicated by network degree, weighted clustering coefficient (WCC), and global efficiency. The graph metrics displayed consistent and significant decreases at the group level, individual subject level, and individual muscle level. The proposed approach has the potential to be a sensitive biomarker of fatigue with superior performance to conventional spectrotemporal measures.

January 2023 · Rory O' Keeffe, Seyed Yahya Shirazi, Jingui Yang, Sarmad Mehrdad, Smita Rao, S Farokh Atashzar
The effect of fiducial mismarking on EEG source estimation.

Nonlinear functional muscle network based on information theory tracks sensorimotor integration post stroke

We show that InfoMuNet, a novel functional biomarker based on a nonlinear network graph of muscle connectivity, can quantify the role of sensory information on motor performance. We demonstrate its potential use in precision rehabilitation interventions.

July 2022 · Rory O'Keeffe, Seyed Yahya Shirazi, Seda Bilaloglu, Shayan Jahed, Ramin Bighamian, Preeti Raghavan, S. Farokh Atashzar
The effect of fiducial mismarking on EEG source estimation.

Perilaryngeal-Cranial Functional Muscle Network Differentiates Vocal Tasks: A Multi-Channel sEMG Approach

We explored the potential of a functional muscle network to differentiate vocal tasks. The network robustly differentiated vocal tasks, while classic muscle activation assessment failed to differentiate. The study also discovered tasks with the highest network involvement, which may be utilized in the future to monitor voice disorders and rehabilitation.

May 2022 · Rory O' Keeffe, Seyed Yahya Shirazi, Sarmad Mehrdad, Tyler Crosby, Aaron M Johnson, S Farokh Atashzar
The effect of fiducial mismarking on EEG source estimation.

Differential Theta-Band Signatures of the Anterior Cingulate and Motor Cortices During Seated Locomotor Perturbations

We demonstrate that seated locomotor perturbations produce differential theta-band responses in the anterior cingulate and supplementary motor areas, suggesting that tuning perturbation parameters can potentially modify electrocortical responses.

February 2021 · Seyed Yahya Shirazi, Helen Huang
The five digitizing methods tested in this study.

More Reliable EEG Electrode Digitizing Methods Can Reduce Source Estimation Uncertainty, but Current Methods Already Accurately Identify Brodmann Areas

Download Paper Code and data Abstract Electroencephalography (EEG) and source estimation can be used to identify brain areas activated during a task, which could offer greater insight on cortical dynamics. Source estimation requires knowledge of the locations of the EEG electrodes. This could be provided with a template or obtained by digitizing the EEG electrode locations. Operator skill and inherent uncertainties of a digitizing system likely produce a range of digitization reliabilities, which could affect source estimation and the interpretation of the estimated source locations....

November 2019 · Seyed Yahya Shirazi, Helen Huang
The effect of fiducial mismarking on EEG source estimation.

Influence of Mismarking Fiducial Locations on EEG Source Estimation

Mismarking fiducial locations can systematically change EEG source locations. We inestigated this effect by systematically moving the fiducial locations to simulate such errors.

March 2019 · Seyed Yahya Shirazi, Helen Huang