NEUROSTIMULATION AND NEUROMODULATION TECHNIQUES Flashcards
What is neurostimulation?
Neurostimulation is the purposeful stimulation of the nervous system, both central (CNS) and peripheral (PNS), using non-invasive (TMS, TES) or invasive techniques (e.g., implanted micro-electrodes).
Define non-invasive neurostimulation and provide examples.
Non-invasive neurostimulation involves stimulation from outside the head. Examples include Transcranial Magnetic Stimulation (TMS) and Transcranial Electric Stimulation (TES).
What is the classical method of TMS, and how does it work?
TMS is a classical method involving transcranially applied magnetic currents that stimulate the underlying neural tissue, such as the cortex or nerves.
What is deep brain stimulation (DBS)?
DBS is a neurosurgical implantation of electrodes for precise modulation of the activity of a specific brain area, often used for conditions like Parkinson’s disease with ongoing studies for potential applications in Alzheimer’s disease, depression, and Tourette’s syndrome.
How does TMS modulate neurons, and what is the virtual lesion approach?
TMS modulates the firing rate of neurons and changes excitability. The virtual lesion approach interferes with normal brain functioning, adding noise to specific brain areas, allowing observation of resulting effects on behavior or mental processes.
What are the drawbacks of neuroimaging and surface electrophysiology compared to TMS?
Neuroimaging and surface electrophysiology lack functional resolution, as they can’t demonstrate causal relationships or determine the necessity of a specific brain area for a function.
What are the advantages of TMS in studying brain functions?
TMS offers high functional resolution, focusing on small cortical areas, acute studies minimizing plastic reorganization, flexibility in study designs, and the ability to investigate cortico-cortical connections, neural chronometry, and within-subjects dissociations.
How does TMS differ from other techniques like TES in terms of stimulation?
TMS indirectly stimulates the cortex through magnetic pulses, while techniques like TES (tDCS, tACS, tRNS) administer low voltage current directly over the area of interest with electrodes.
What is optogenetics, and how does it control neuronal activity?
Optogenetics involves using light to control genetically modified neurons expressing light-sensitive ion channels, providing precise neuromodulation and measuring effects in living organisms.
Briefly explain the history of neurostimulation from Galvani to modern TMS.
Galvani and Volta studied electric conduction in animal cells, leading to the discovery of animal electricity. Aldini used transcranial direct electrical current (tDCS) to ameliorate melancholia in 1804. Ferrier in the 1870s demonstrated electrical stimulation of the motor cortex, contributing to the development of neurostimulation techniques.
How recent is TMS, and who were some key figures in its development?
TMS has roots in Faraday’s 1831 discovery of electromagnetic induction. D’Arsonval in 1896 built an inductive device for pulsed magnetic fields. Modern TMS was developed in the 80s by Barker, Freeston, and Jalinous.
What is the aim of TMS, and how does it work according to Faraday-Neumann-Lenz law?
The aim of TMS is to send an electric pulse on a small portion of cortical tissue non-invasively. According to Faraday-Neumann-Lenz law, a current flux in a conductor creates a perpendicular magnetic field, inducing a temporary electric current on the underlying cortical surface.
What are the consequences of TMS at the neural level?
TMS can cause local depolarization or hyperpolarization of neurons, leading to macroscopic responses like evoked neuronal activity, changes in blood flow, muscle twitches, and changes in behavior.
How does the spatial resolution of TMS depend on coil geometry?
The spatial resolution depends on coil geometry. A circular coil stimulates a larger surface, while a figure-of-8 coil is more focal and powerful. Double-cone coils allow stimulation of deeper structures.
How is coil localization achieved in TMS?
Coil localization is achieved by finding functional effects like muscular twitch or phosphenes, using anatomical landmarks, moving towards localized areas, or using neuro-navigation systems.
What are the different types of TMS stimulation waveforms?
Stimulators can have monophasic or biphasic pulses, with the latter being more efficient and allowing faster capacitor recharge for repetitive stimulation at higher frequencies.
Explain the methodology of TMS thresholds.
TMS thresholds include motor threshold (lowest intensity to elicit muscle movement) and phosphene threshold (lowest intensity to elicit visual phosphenes), and they are essential for administering the same amount of energy across subjects.
How does TMS achieve a virtual lesion, and what are its effects?
TMS achieves a virtual lesion by temporarily interfering with a cortical area, compromising its function and leading to transient effects on behavioral performance.
What is the rhythmic non-invasive transcranial stimulation approach?
The rhythmic non-invasive transcranial stimulation approach involves targeting a specific oscillatory frequency to promote the respective oscillatory network.
What is the dual-pulse TMS, and how does it differ from other TMS approaches?
Dual-pulse TMS involves stimulation with two distinct pulses at different time intervals, allowing independent control of stimulation intensity for each pulse.
