TMS Study Guide With Complete Questions And Answers.

What is TMS (transcranial magnetic stimulation)? - correct answer a *non-invasive* technique use to create a virtual cortical *lesion* What does TMS involve? - correct answer [small, brief, localised lesions] they are temporary and don't cause harm How is TMS applied? - correct answer Externally, using a coil placed on the scalp that produces a rapidly changing magnetic field to induce electrical currents in the brain What can the currents applied in TMS do? - correct answer They can depolarise neurons in a small area of the cortex This causes neurons to fire randomly, increasing the level of neural noise (and masking the neurons that are firing correctly) Who were first to stimulate the brain? - correct answer Fritz and Hitzig (1870) Animal models Who discovered magnetic stimulation of the visual cortex? - correct answer D'Arsouval (1896) Discovered that magnetic stimulation of the visual cortex can elicit 'phosphenes' Sensation of light entering eye with not light stimulation Who invented the TMS head coil (historical version of TMS)? - correct answer Magnusson and Stevens (1911) Who invented today's TMS? - correct answer Barker, Jalinous and Freestone (1985) Capacitator is charged and immediately discharged to create a magnetic field Creation of a magnetic field - correct answer Fast loading times (~100-200s) and short durations (1ms) are required to create a strong enough magnetic field for stimulation Figure eight coil - correct answer Most common Generates magnetic field in opposite direction = more precision of stimulation generation Round coil - correct answer Less focal area of cortex is stimulated But you can get a clearer idea of area what part of the cortex is affected Four methods of TMS application in research - correct answer 1) Neural noise 2) Probing excitability 3) Virtual lesion 4) Paired-pulse 1) Neural noise approach - correct answer using single-pulse TMS to *disrupt* cognitive processing can determine *causality* can be used to understand the *timing* of cognitive functions 1) Neural noise approach Study A - Aim - correct answer to investigate the effects of TMS on letter perception when varying interval between visual stimuli and TMS stimulation (time) 1) Neural noise approach Study A - Method - correct answer Amassian et al (1989) - 3 x letters as stimuli presented under difficult viewing conditions - illuminated backgrounds - magnetic stimulation applied to visual cortex (above inion - bone) 1) Neural noise approach Study A - Results (main result) - correct answer Was found that a [critical period (40-120ms)] affected detection performance 1) Neural noise approach Study A - Results (LR) - correct answer shifting the stimulation site from left to right (letters displayed horizontally) caused perception of letters in the *contra-lateral visual field* to be predominantly impaired 1) Neural noise approach Study A - Results (TB) - correct answer When moving stimulation from top to bottom at midline (letters displayed vertically), stimulation above reference line suppressed letters at the bottom (couldn't stimulate at the bottom because of bone - inion) 1) Neural noise approach Study B - Aim - correct answer test whether a visual mask can be masked using single-pulse stimulation, thereby unmasking stimulus 1) Neural noise approach Study B - Theory behind it - correct answer TMS can work like a mask Usually, backwards 'masks' are presented after the stimulus, used to disrupt the visual processing of the target 1) Neural noise approach Study B - Method - correct answer [Target] 3 x letters I I [Mask] 3 x letters I I [Mask stimulus] TMS pulse 1) Neural noise approach Study B - Results - correct answer Without TMS = detection rate of 0.37 With TMS = detection rate of 0.90 (blocked out mask - second letter set) 'Unmasking' occurred between *60-140ms* after the mask was exposed 2) Probing excitability - correct answer Using [single-pulse TMS] to test the *responsiveness* of brain region For the motor system in particular Degree of additional movement noted if motor cortex is required for a cognitive task 2) Probing excitability approach - How does it work? - correct answer Excitability measured by recording MEPs (motor evoked potentials - amplitudes) using EMG Measure MEPs for each stimulation, then compare average MEPs between experimental conditions 2) Probing excitability approach Study A - Aim/ Research Q - correct answer Eisenegger et al. (2007) Is primary motor cortex (M1) involved in mental rotation of objects? Or involved in inner speech?