Vital discoveries in neuroscience can be made in resource limited environments. Here, we detail how to employ transcranial magnetic stimulation using valid and reliable methods. Single pulse and low frequency TMS provides causal, not correlational brain behavior relationships.
This allows one to make much stronger conclusions about brain behavior relationships. TMS is used routinely to treat depression. By training minorities and other resource limited students in TMS, we are expanding the pool of trained professionals.
TMS is used in almost every clinical and scientific application. However, it has been able to answer questions on consciousness and self-awareness that have baffled great thinkers for centuries. Anyone starting out with TMS should work on motor systems because you can actually see the effects of TMS immediately with a hand or leg movement.
The other possibility is working on the visual system and asking participants to report the phosphenes that they see. Both systems give feedback immediately to the learning student. Begin by marking swim caps along the nasion or inion line and the midpoint taken using a magic marker.
Measure pre-auricular points and take those midpoints, as well. From here, plot 10/20 coordinates. Using the right hemisphere pre-auricular line, go 33%down in the ventral direction and begin searching for the optimal location for the Abductor Pollicis Brevis or APB using the TMS coil.
Discharge the TMS machine using the coil trigger, the foot switch, and disengaging the safety. Orient the TMS coil at 45 degrees for all searches in TMS deliveries, then start the stimulation output at 20%total machine output by using the dial on the front of the machine. Raise in 2%increments using the dial until a movement is noted.
Here, as the stimulation is increased in terms of intensity, move the location also. There is a careful interplay between coil movement and stimulation intensity. Mark the coil tip site on the cap to allow an accurate placement and trace the entire anterior portion of the coil onto the swim cap using a magic marker.
Once the optimal location is found, that is the site that provided the maximum APB response, determined the MT.For the visual inspection method, start at 20%of machine intensity and workup. The dial should be raised and lowered in response to increased or decreased finger movements. Use approximately 20 pulses to find what stimulation level results in 5 out of 10 APB responses.
Once 5 out of 10 responses have been obtained, record the individual's MT by noting what the machine is displaying as the intensity. For the MEP method, place disposable electrodes on the APB and the tendon of the thumb and a ground. Define a positive MEP response as an MEP with greater than or equal to 50 microvolts peak-to-peak amplitude.
Similar to visual inspection, stimulate until 5 out of 10 positive MEPs are observed. The MEPs should be greater than 50 microvolts. If 50%of the MEPs are above, it can be said that MT has been identified.
Set the TMS machine to the appropriate stimulation level. 90%of the motor threshold is an ideal balance between effective, active TMS and safety. Randomly select the order of all sites.
Place the coil over the active site and start a presentation software. Stimulation should proceed automatically and in sync with stimuli. Collect all behavioral data using the presentation software.
Give two practice trials and introduce the analog scale to the participants. All participants easily adjust to the equipment. The instructions are given orally and the participants are told to rate how well they know the word.
If the word is familiar to them, it should be given a high rating. If they sort of know the word, they are to give a medium rating. If the word is not that familiar to them, they will assign a low rating.
A total of 144 words should be used. Participants have unlimited time to respond. Following the response on the analog scale, the next word is presented.
Self-deception can be modulated using TMS. Participants were given social pressure to know words in one condition and no social pressure in another condition. The social pressure was a series of verbal prompts that indicated that every person knew these words and they were easy or that the words were difficult and most people did not know them.
Means and the standard errors are presented here. Because social cognition is a medial prefrontal cortex, or MPFC function, it was assumed that TMS delivered in an inhibitory manner would decrease overclaiming. This was found to be the case.
Measuring out the 10/20 system and correctly gauging motor threshold is important for safety and reliable results. Instead of the 10/20 system, narrow navigation can be used. TMS was a first major technique that determined causal relationships between brain and behavior.
Additionally, it is now a major therapeutic technique using the treatment of depression.
