Combined MRI-TMS Investigations of Working Memory
Study Purpose: There is a lot of data that has been collected using magnetic resonance imaging (fMRI), a machine to collect brain images, that suggests that a variety of brain regions are involved in the short-term maintenance of information. Although fMRI and other techniques can provide a lot of information, these techniques cannot provide strong causal evidence for the role of specific brain regions in a certain task. Transcranial magnetic stimulation (TMS) is a useful tool that can be used to activate, or stimulate, parts of the brain temporarily. TMS can provide the evidence that a given brain region is necessary for certain processes that happen in a brain, and it can be used on normal healthy adults. This study will seek to understand the causal contribution of specific brain regions to mental processes of interest by (1) scanning participants using fMRI, (2) individually targeting TMS to specific brain regions, and (3) assessing behavior and brain activity post-TMS to begin to expand our knowledge of the neural underpinnings of working memory.
Who is eligible: Healthy, English-speaking, right handed adults between the ages of 18-35.
What to expect:
Time commitment: Up to 10 sessions.
Compensation: $15 per hour.
Recruitment status: Not currently recruiting. However, please feel free to reach out to us if you are interested in participating and we can let you know once this study is active!
Collaboration: Dr Taraz Lee, director of the CoCoA Lab, is the principal investigator for the study [co-Investigators Dr. Michael Vesia].
IRBMED HUM00203427Date of approval: November 2022
What are TMS and tDCS?
Transcranial magnetic stimulation (TMS) and Transcranial direct current stimulation (tDCS) are both forms of non-invasive brain stimulation (NIBS). This process is considered non-invasive because it does not involve placing anything under your skin or inside your body.
TMS involves sending magnetic fields into a person’s brain to stimulate nerve cells. Using TMS to stimulate the brain and measure brain activity is not currently FDA-approved for healthy people and is considered experimental.
Before testing, we will place electrodes on the skin of your hands. These electrodes will record muscle activity from your hands. A device called a coil will rest on your head, as shown here in the picture. We will send an electric current through the coil to create a magnetic field. The magnetic field will pass through your skin and skull and into your brain. You will not feel the magnetic field, and it will not hurt or damage your body. During this part of the experiment, you will hear a click, and it may feel like someone has lightly tapped your head. We will determine the intensity of stimulation needed for you; this is because everyone’s brain is different.
You will be seated in a chair with your arms placed in molded hand rests during the experiment. We will place one coil over the part of your brain called the motor cortex. We will place a second coil over a different part of your brain involved in planning voluntary hand movements. During the TMS procedure, you will experience slight twitching and muscle contractions in your arm and hand. During stimulation, we will measure your hand muscle activity through the electrodes. We will use TMS to study the excitability of the two parts of your brain and how different regions of your brain send commands to your hand muscles.
tDCS involves sending a weak electrical current through the brain via electrodes attached to the scalp. The tDCS device used in this study has not received FDA approval and is limited to investigational use in the US.
We will apply tDCS using a battery-operated stimulator delivered through a pair of saline soaked surface sponge electrodes or gelled electrodes placed in holes of a neoprene cap (see picture) for ~20 minutes. You might feel a slight itch under the electrode. This is normal, and it will not hurt or damage your body. During the tDCS procedure, you likely will experience a tingling sensation on the scalp where electrodes are attached; this tingling sensation usually diminishes after several seconds. The goal of the tDCS portion of our study is to determine the roles of brain regions used to control hand movement, by measuring behavior and brain activity during stimulation.
When we remove the electrodes, a small amount of gel may remain in your hair; this generally comes out easily with water and shampoo.
Brain Behavior Lab
at the Kinesiology Building
Functional MRI Laboratory