Abdul Naji Professor Melara Psych 102 B7 Monday September 24
Psych 102 B7
Monday September 24, 2018
Using the Correlational Method to Study the Divided Brain
The purpose of this paper is to evaluate the correlational method as a means for examining the relationship between functions of the left and right hemispheres. I will compare the performance of people with intact brains with the performance of so-called split-brain patients. In many ways, the brains of these two groups are very similar. 1a. The location of the brain stem in a normal brain is above the spinal cord. Its base is the medulla and the top part is the pons. It is placed under the thalamus. The function of the brainstem is to connect different areas of the brain. It receives and sends information from one side of the brain to another and also controls actions that the body does, that we don’t consciously focus on. For example, breathing, heartbeat, sleep, etc. In a split-brain, the brainstem’s function is the same. 1b. The hippocampus helps us create new memories and stores facts that we come across. As we age it shrinks in size and loses some of its ability to hold memories. The hippocampus is a part of the limbic system and is located in the medial temporal lobe in the center of the brain. The hippocampus functions similarly in both normal and split-brain patients. 1c. The corpus callosum is located in the center of the cerebral cortex and connects both the left and right hemispheres. The corpus callosum carries messages between both hemispheres and helps them communicate. Split-brain patients must have their corpus callosum severed, to help stop seizures, therefore they will be unable to communicate information between both hemispheres of the brain. 1d. The cerebral cortex is located in the top part of the brain and is made up of four lobes. The frontal, temporal, parietal and occipital and also covers both hemispheres of the brain. It is the largest part of the brain. The cerebral cortex has many functions which include thought, action, personality, etc. The functions are different between a cerebral cortex in a normal brain and that of a split-brain. The split-brain patient will experience partial paralysis and losing the ability to speak.
The split-brain patient provides scientists with a window into the normal functions of the brain. 2b. A split-brain patient is someone who previously suffered from major epileptic seizures, where they needed to go through a procedure called corpus callosotomy. This procedure cuts through the corpus callosum which limits the abnormal brain activity from bouncing back and forth between both hemispheres. The neural pathway was blocked and after the corpus callosotomy, these epileptic episodes stopped occurring. 2b. One test that was used to demonstrate the that language function is lateralized to one hemisphere was administered by Michael Gazzaniga. He would ask split-brain patients to stare at a dot in the middle of a screen. He would then flash the word “Heart” but with “HE” on the left side of the screen and the word “ART” on the right side of the screen. He knew that since there wouldn’t be any communication between the hemispheres, the left side of the brain (which is responsible for language) would only be able to process the right side of the screen which was the word “Art.” He asked them to read what they saw and they responded with “Art.” However, when asked to point at what they saw, they would point at the word “HE” because that is what their right hemisphere visually processed which was on the left side of the screen. This showed that they weren’t able to put the two words together because their right and left hemispheres couldn’t communicate. Additionally, they weren’t able to conclude what a person with a fully functional corpus callosum would have. This shows that the right hemisphere is visually dominant while the left hemisphere is dominant in language. 2c. These results with split-brain patients can be used to understand laterality in the general population because it shows that certain operations are done in one hemisphere. These results help show the different functions of both hemispheres and what each one is more dominant in certain areas. Both hemispheres still function in their own ways but can’t communicate to each other or put certain aspects of the same problem together. They can individually solve what they can without the help of the other.
Cognitive tests performed on split-brain patients have identified a division of labor between hemispheres. It is conceivable that functions handled by different hemispheres will show a strong relationship in the general population, but not in split-brain patients. 3a. Both hemispheres have their own abilities. The right hemisphere is able to recognize faces, is able to listen to music, draw and has the ability to control the left side of the human body. The left hemisphere on the other hand is able to control the right side of the human body, process language, do mathematical and logical problems. 3b. The hypothesis which will be evaluated is, whether or not there is a stronger relationship between both hemispheres in an intact brain versus those with a split-brain. People with intact brains will be able to use both hemispheres whereas split-brain participants will have to rely on either the right or the left alone. 3c. The correlational method will be used to calculate the correlation between the participants and their scores, and how strong of a relationship there is between those within their own group. Both correlation coefficients will be compared, and the results will determine whether or not the hypothesis was correct or incorrect.
Data were collected from a group of split-brain patients and a group from the general population to test the hypothesis using the correlational method. Each group completed three tasks shown previously to be lateralized: (1) a vocabulary test, (2) a logical reasoning task, and (3) a face recognition task. 4a. The vocabulary test will be lateralized in the left hemisphere of the brain. The logical reasoning task will also be lateralized in the left hemisphere, whereas the third task, the face recognition test will be lateralized in the right hemisphere. 4b. If the hypothesis is correct, then the pattern of the correlations in the intact brain group will be similar to the split-brain group when comparing the vocabulary test and the logical reasoning task. This is because these two tasks are both lateralized on the same left hemisphere, but when comparing the facial recognition to the vocabulary test and then again to the logical reasoning, it is expected that the intact brain group will have stronger correlation patterns in comparison to the split-brain group. This is predicted because these tasks are lateralized in different hemispheres, and the split-brain group are at a disadvantage in that regard. 4c. Below is a table detailing the results of the gathered data:
Intact Brain Data
Tests r I II III
Vocab ; Logical R. .71 78176 60 1542
Vocab ; Face R. .63 78176 116,785.84 60669.58
Logical R. ; Face R. .87 60 116,785.84 2,303.46
Split-Brain Brain Data
Tests r I II III
Vocab ; Logical R. .72 88909 95.6 2085.95
Vocab ; Face R. .34 88909 108737.55 33889.21
Logical R. ; Face R. .04 95.6 108737.55 159.15
The results of the correlational method were valuable in addressing the hypothesis under study. However, future investigations may need to adopt techniques that improve upon those used here. 5a. The hypothesis stated before the results was, whether or not there is a stronger relationship between both hemispheres in an intact brain versus those with a split-brain. People with intact brains will be able to use both hemispheres whereas split-brain participants will have to rely on either the right or the left alone. This has come to be true after receiving the results. The relationships between tasks that compared right and left were much stronger in intact brain participants compared to split-brain participants. For the solely left hemisphere lateralized tasks (vocabulary ; logical reasoning) both groups had almost identical relationships with the split-brain group having a slightly higher correlation coefficient of +.72 whereas the intact brain group had a correlation coefficient of +.71. 5b. All of the data fit with the previously stated hypothesis, although the relationship between logical reasoning task and facial recognition for the split-brain group was a lot lower than anticipated. There was almost no correlation at all, which makes sense since their right and left hemispheres are not able to communicate with one another. 5c. A feature of the current correlational method that should be changed is the size of the groups. There should be larger groups in order to make the results more accurate. When there are too few participants, then a few extreme scores will have a huge effect on the outcomes. Another aspect that should be changed is adding one or more tasks that target other potential lateralized responsibilities of the different hemispheres. 5d. Correlational studies can be used to evaluate hypothesis. For instance, the hypothesis for this study was to see if there is or there isn’t some sort of relationship between certain groups, which we were successful in figuring out that there was a relationship. Correlational methods are suitable for evaluating hypotheses. 5e. One experiment that would test the hypothesis in this paper is by adding evening out the tasks assigned to both the right and left hemispheres. Another task to add to this experiment would be an art awareness exercise which would stimulate the right side of the brain. This way both have an even workload and we can more accurately look at the relationship between them and see the differences between the groups with the intact brain and those with the split-brain.