Mirror-Neuron System: Girl vs. Boy

Amber Badgerow

October 16, 2011

PSY 213

John Olmsted

Mirror-Neuron System: Girl vs. Boy

Question:

It is often said that women are more empathetic than men or at least show it very differently. The mirror-neuron system has been indicated in helping a person feel empathetic. Is there a difference between the female and male mirror-neuron system?

Prediction:

There may be differences seen in the volume or in the usage of the mirror-neuron system between men and women. Women may have greater volume than men in the area of the mirror-neuron system. Another possibility is that men and women use different areas in the mirror-neuron system. Both of these hypotheses would help explain why women and men do not display empathy in the same way.

Article 1: “Sex Differences in the Neuroanatomy of Human Mirror-Neuron System: A Voxel-based Morphometric Investigation”

This article was written by Y. Cheng, K.-H. Chou, J. Decety, I.-Y. Chen, D. Hung, O. J.-L. Tzeng, and C.-P. Lin to discuss their findings from a study to find sex differences in regional brain volume regarding the mirror-neuron system (MNS). They explained that other studies have shown that women do better at several cognitive tasks involving emotional recognition, verbal fluency, and sensitivity. Their study used voxel-based morphometry (VBM) to find structural differences in regions of the brain to support or contradict previous findings. Twenty-five women and twenty-five men participated in the study. MRI scans were taken to obtain VBM, which revealed that women had larger global white matter volume, but men had larger global gray matter volume and intracranial volume. However, regionally, women displayed greater volume of gray matter in the social cognition network, including the medial prefrontal cortex, the lateral occipital cortex, and the MNS. Notably, larger volume was seen in the fundamental MNS areas, which are the right pars opercularis and the right anterior inferior parietal lobule. Men showed greater gray matter volume in the parahippocampus, lentiform nucleus, and amygdala. These VBM results concurred with previous research regarding sex differences in brain structure and social regions. Combined with other studies, such findings slightly support the idea of women having better empathetic skills.

Article 2: “Gender differences in brain networks supporting empathy”

Martin Schulte-Rüther, Hans J. Markowitsch, N. Jon Shah, Gereon R. Fink, and Martina Piefkea wrote this article about their study involving the discovery of sex-related differences in the brain’s empathetic network- the mirror-neuron system specifically. They first discussed that women have rated higher on tests of empathy and noted that men are more prone to disorders distinguished by a lack of empathy, such as antisocial personality disorder, autism spectrum disease, and conduct disorder. Previous studies indicated that men and women may use different systems to process cognitive and emotional information, which could play a part in the sex differences of empathy. There were 12 men and 14 women in their study. Participants were shown emotional faces that expressed fear or anger. They were told to either decide what emotional state was expressed by the face (OTHER-task) or to focus on what feelings were stimulated in themselves when looking at the face (SELF-task). They also were asked to decide on the age and gender of neutral faces for a high-level baseline condition. Functional magnetic resonance imaging was used to record participant's brain activity during these tasks. MRI scans showed that, in both sexes, the SELF- and OTHER- tasks activated the inferior frontal gyrus, the superior temporal sulcus, the temporal poles, the middle frontal gyrus, the left medial prefrontal cortex, the right cerebellum, and the pre-supplementary motor area- areas associated with the mirror-neuron system. The SELF versus the high-level baseline also revealed activation in the precuneus/posterior cingulate cortex and the temporoparietal juction. However, women had stronger activation of the right cerebellum, right inferior frontal cortex, and right superior temporal sulcus in comparing SELF- and high-level baseline tasks, whereas men had stronger activation in the left temporoparietal junction. Women also showed more activation in the inferior frontal cortex comparing the OTHER-task to the high-level baseline task. These results indicate that women rely more on the MNS when evaluating other people's emotional states and when their own emotional response to others' feelings is produced, which may relate to an increased ability to empathize. The fact that men recruited more temporoparietal junction activation than women could indicate that men cannot as easily restrain the distinction between one's own emotional response to others' feelings and assessing others' emotional states during social interactions and therefore find empathizing more difficult.

Source Validity:

Both sources came from credible authors and provide reliable results as far as methods go. However, both sources could have had a larger subject group to improve reliability. The first article’s study also consisted of only Chinese participants, which may have resulted in a sample that cannot apply to the general population since ethnicity can alter brain morphology. Although both sources relied on several previous studies that were similar, these studies should be repeated to ensure validity. The results of this research raise questions into the difference of the mirror-neuron system in individuals with autism spectrum disease and antisocial personality disorder since both occur more frequently in men than women.

Reflection on Hypothesis:

The research supports my hypothesis that women have greater volume in the mirror-neuron system than men, although the hypothesis that men and women use different areas of the mirror-neuron system was not completely supported by this research.

Works Cited:

Cheng, Y. et al. “Sex Differences in the Neuroanatomy of Human Mirror-Neuron System: A

Voxel-based Morphometric Investigation.” Neuroscience 158 (2009): 713–720. Elsevier Ltd.

Web (Google Scholar: “Sex difference mirror-neuron system voxel-based”). Oct. 14, 2011.

http://home.uchicago.edu/decety/publications/Cheng_N2009.pdf

Schulte-Rüther, Martin et al. “Gender differences in brain networks supporting empathy.”

NeuroImage 42.1 (2008): 393-403. Elsevier Inc. ScienceDirect. Web. Oct. 14, 2011.

http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S1053811908004886