Mohammad Daneshzand

Harvard Medical School | HMS · Athinoula A. Martinos Center for Biomedical Imaging

Higher-order cognitive and affective functions are supported by large-scale networks in the brain. Dysfunction in different networks is proposed to associate with distinct symptoms in neuropsychiatric disorders. However, the specific networks targeted by current clinical transcranial magnetic stimulation (TMS) approaches are unclear. While standard...

Objective: Transcranial focused ultrasound (tFUS) is an emerging neuromodulation approach that has been demonstrated in animals but is difficult to translate to humans because of acoustic attenuation and scattering in the skull. Optimal dose delivery requires subject-specific skull porosity estimates which has traditionally been done using CT. We p...

Background Transcranial focused ultrasound (tFUS) neuromodulation has shown promise in animals but is challenging to translate to humans because of the thicker skull that heavily scatters ultrasound waves. Objective We develop and disseminate a model-based navigation (MBN) tool for acoustic dose delivery in the presence of skull aberrations that i...

Previously, we regressed TMS-induced electric fields (e-fields) on motor evoked potentials (MEPs) to pinpoint muscle representations in the primary motor cortex (M1). This approach relies on e-field variance across TMS pulses and, thus, is limited by the significant spatial autocorrelation of TMS-induced e-field patterns. Here, we explore potentia...

Working memory (WM), short term maintenance of information for goal directed behavior, is essential to human cognition. Identifying the neural mechanisms supporting WM is a focal point of neuroscientific research. One prominent theory hypothesizes that WM content is carried in a dynamic fashion, involving an activity-silent brain state based on syn...

Background: Current noninvasive brain stimulation methods are incapable of directly modulating subcortical brain regions critically involved in psychiatric disorders. Transcranial Focused Ultrasound (tFUS) is a newer form of noninvasive stimulation that could modulate the amygdala, a subcortical region implicated in fear. Objective: We investigate...

When modeling transcranial magnetic stimulation (TMS) in the brain, a fast and accurate electric field solver can support interactive neuronavigation tasks as well as comprehensive biophysical modeling. We formulate, test, and disseminate a direct (i.e., non-iterative) TMS solver that can accurately determine global TMS fields for any coil type eve...

Speech and language processing involve complex interactions between cortical areas necessary for articulatory movements and auditory perception and a range of areas through which these are connected and interact. Despite their fundamental importance, the precise mechanisms underlying these processes are not fully elucidated. We measured BOLD signal...

Objective: This study aims to describe a MATLAB software package for transcranial magnetic stimulation (TMS) coil analysis and design. Approach: Electric and magnetic fields of the coils as well as their self- and mutual (for coil arrays) inductances are computed, with or without a magnetic core. Solid and stranded (Litz wire) conductors are also t...

BACKGROUND: The association between brain regions involved in speech production and those that play a role in speech perception is not yet fully understood. We compared speech production related brain activity with activations resulting from perceptual categorization of syllables using high field 7 Tesla functional magnetic resonance imaging (fMRI)...

Background: When modeling transcranial magnetic stimulation (TMS) in the brain, a fast and accurate electric field solver can support interactive neuronavigation tasks as well as comprehensive biophysical modeling. Objective: We formulate, test, and disseminate a direct (i.e., non-iterative) TMS solver that can accurately determine global TMS field...

Purpose: Multichannel Transcranial Magnetic Stimulation (mTMS) [1] is a novel non-invasive brain stimulation technique allowing multiple sites to be stimulated simultaneously or sequentially under electronic control without movement of the coils. To enable simultaneous mTMS and MR imaging, we have designed and constructed a whole-head 28-channel r...

Repetitive transcranial magnetic stimulation (TMS), when applied to the dorsolateral prefrontal cortex (dlPFC), treats depression. Therapeutic effects are hypothesized to arise from propagation of local dlPFC stimulation effects across distributed networks; however, the mechanisms of this remain unresolved. dlPFC contains representations of differe...

Multichannel Transcranial Magnetic Stimulation (mTMS) provides the capability of stimulating multiple cortical areas simultaneously or in rapid succession by electronic shifting of the E-field hotspots. However, in order to target the desired brain region with intended intensity, the intracranial E-field distribution for all coil elements needs to...

Transcranial Magnetic Stimulation (TMS) is a non-invasive method for safe and painless activation of cortical neurons. On-line visualization of the induced Electric field (E-field) has the potential to improve quantitative targeting and dosing of stimulation, however present commercially available systems are limited by simplified approximations of...

The Transcranial Magnetic Stimulation (TMS) inverse problem (TMS-IP) investigated in this study aims to focus the TMS induced electric field close to a specified target point defined on the gray matter interface in the M1HAND area while otherwise minimizing it. The goal of the study is to numerically evaluate the degree of improvement of the TMS-IP...

To enable concurrent non-invasive stimulation (TMS) and whole-head multimodal imaging (EEG-fMRI), we propose to apply Bexible RF coil technology to build a Erst-of-its-kind TMS compatible integrated multimodal imaging array, the “RF- EEG cap”. The proposed system allows unrestricted positioning of the TMS coil across the entire scalp. We built a 2-...

Background: TMS neuronavigation with on-line display of the induced electric field (E-field) has the potential to improve quantitative targeting and dosing of stimulation, but present commercially available solutions are limited by simplified approximations. Objective: Developing a near real-time method for accurate approximation of TMS induced...

Purpose: Multichannel Transcranial Magnetic Stimulation (mTMS) arrays enable multiple sites to be stimulated simultaneously or sequentially under electronic control without moving the system's stimulation coils. Here, we build and characterize the performance of a novel modular 3-axis TMS coil that can be utilized as a unit element in large-scale...

Objective To present and disseminate our transcranial magnetic stimulation (TMS) modeling software toolkit, including several new algorithmic developments, and to apply this software to realistic TMS modeling scenarios given a high-resolution model of the human head including cortical geometry and an accurate coil model. Approach The recently deve...

A particular yet computationally successful solution of an inverse transcranial magnetic stimulation (TMS) problem is reported. The goal has been focusing the normal unsigned electric field at the inner cortical surface and its vicinity (the D wave activation site) given a unique high-resolution gyral pattern of a subject and a precise coil model....

The hyperkinetic symptoms of Parkinson’s Disease (PD) are associated with the ensembles of interacting oscillators that cause excess or abnormal synchronous behavior within the Basal Ganglia (BG) circuitry. Delayed feedback stimulation is a closed loop technique shown to suppress this synchronous oscillatory activity. Deep Brain Stimulation (DBS) v...

Neuronal dynamics, firing patterns, LFP recordings, PSD and EC data. (PDF)

Neural oscillations within the Basal Ganglia (BG) circuitry are associated with Parkinson’s Disease (PD) and are observable through the Local Field Potential (LFP) of the Subthalamic Nucleus (STN) or Globus Pallidus externa (GPe) neurons. LFP amplitude modulation in a delayed feedback protocol for Deep Brain Stimulation (DBS) is shown to destabiliz...

To investigate how different types of neurons can produce well-known spiking patterns, a new computationally efficient model is proposed in this paper. This model can help realize the neuronal interconnection issues. The model can demonstrate various neuronal behaviors observed in vivo through simple parameter modification. The behaviors include to...

Deep brain stimulation (DBS) has compelling results in the desynchronization of the basal ganglia neuronal activities and thus, is used in treating the motor symptoms of Parkinson's disease (PD). Accurate definition of DBS waveform parameters could avert tissue or electrode damage, increase the neuronal activity and reduce energy cost which will pr...

This work represents the design and verification of three different finite impulse response (FIR) filter implementations for removing the noise of electrocardiogram (ECG) signals. Generally, ECG signals may be contaminated with different noise sources such as body movement and respiration, electromyography (EMG) interference, power line interferenc...

Most applications dealing with wireless sensor networks need a strategy to reduce the energy usage. Each node in a wireless sensor network has a certain amount of energy, in which in some applications is crucial for a system to have stable nodes with the ability of working properly. One of the recent algorithms to have an energy efficient topology...

In all mammalian brain billions of neurons exist and these neurons are working together through synapses and spike responses. Through numerous models presented to describe neuronal response and how the membrane potential would vary due to different tasks, still a big question stand still in the field of neuroscience. Why a neuron can produce differ...

To investigate how different types of neurons in brain can produce well known spiking patterns, a new computationally efficient model is proposed in this poster. The model can demonstrate various neuronal behavior observed in vivo such as abnormal pattern of subthalamic nucleus (STN) in Parkinson's disease. The irregular and arrhythmic behavior of...

A Superposed Quantum Model of Brain Spiking Neurons in all mammalian brain billions of neurons exist and these neurons are working together through synapses and spike responses. A big question stand still in the field of neuroscience. Why a neuron can produce different types of spikes under same conditions? We showed that unknown and random behavio...

In this work, an efficient digital system is designed using hardware to filter the Electrocardiogram (ECG) signal and to detect the QRS complex (beats). The system implementation has been done by using a Field Programmable Gate Array (FPGA). In the first phase of the hardware system implementation, Finite Impulse Response (FIR) filters are designed...

In medical diagnosis and therapy, finding an appropriate method to evaluate the effect of various drugs is crucial. There are several ways to qualify a drug for a specific disease and one way is through medical image analysis. This process varies with the tissues we want to analyze and the imaging technique that is employed. For hydrous tissue...

Coronary artery heart disease is one of the main reasons of death in under development countries such as Iran. Based on vagueness in data and uncertainty in decision making finding an optimal way for diagnosis would be helpful. The main goal of this article is to change the linguistic terms which doctors use for representing coronary heart disease...