Transcranial direct current stimulation (TDCS) is the application of weak electr

Question

Transcranial direct current stimulation (TDCS) is the application of weak electrical stimulation to the brain. It has been reported that application of TDCS can help people suffering from depression and other mental disorders.   A neuroscientist hypothesized that TDCS applied to specific regions of the brain could improve performance on cognitive tasks.   She obtained 100 undergraduate psychology majors from her university’s subject pool and randomly assigned 50 of them to the experimental group (receiving TDCS) and 50 to the control group (no TDCS).    All subjects were connected to the equipment for delivering the weak current to the brain, however only those in the experimental group received actual stimulation.    During the experimental trials they received 2 milliamps of current applied to the right temporal lobe.

The subjects performed 500 trials of a mental rotation task.   In this task subjects are presented with two stimuli that are rotated images of one another.   By mentally rotating one image it is possible to align the images so that they are identical. How on some trials, typically one-half, one image is also flipped front to back so that the two images can never be rotated to identical images.    The subject’s task is to respond as quickly as possible either same or different by pressing one of two keys. The amount of time (in milliseconds) it takes the subjects to respond is recorded. What type of research design was used? Was there a manipulated independent variable?   If so, what was it? What was the dependent variable? How were subjects assigned to the treatment conditions? Why was the equipment hooked up to the control subjects if it wasn’t being used? Can you think of some ways to improve the study?

Explanation / Answer

1. The research design used was experimental hypothesis testing. Because there are control and experimental groups, and we want to find out the effect of application of current to the brain on the cognitive response (visual spatial intelligence test)

2. The independent variable is the amount of current given to the brain. It has 2 options - No current/ current. It was manipulated by providing current and sometimes without current (placebo effect)

3. Dependent variable is the amount of time to identify if one image can be roated to make the second image.This test is a visual spatial intelligence test.

4. All subjects were all connected to the device that produces current. 50 out of 100 were picked at random and were given a small amount of current. This is group1. The group2 consists of the other 50 who were also connected to the device but they weren't given current (placebo effect)

5. The subjects were hooked up with equipment so that they don't get influenced by the fact that current is NOT being passed to the brain. That would add up another factor.

When all subjects are hooked up, it just creates a equal level field that a helmet device was connected to everyone.

Those who weren't passed the current but connected to the device are experiencing a placebo effect i.e. they feel that current is being passed though in reality nothing of that sort happens.

6. May be they could have enhanced the quality of subjects. By directly taking the subjects suffering from depression or disorders, it could have given a much believable effect. The UG students are a proxy and not the actual representatives of population.

The sample could have been stratified. Based on the population characteristics, a similar strata of female and male subjects could have been there instead of completely random sample of x% males and 1-x% females

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.