Neurogenesis

What can one do to improve neurogenesis? Supplements? Practice?

Prediction: Yes, there are supplements and more techniques being discovered.

Article 1:

Erica R. Glasper, Timothy J. Schoenfeld, Elizabeth Gould, Adult neurogenesis: Optimizing hippocampal function to suit the environment, Behavioural Brain Research, Available online 23 May 2011, ISSN 0166-4328, 10.1016/j.bbr.2011.05.013.

(http://www.sciencedirect.com/science/article/pii/S0166432811004025)

Validity: The article was published this year and therefore will be more relevant than older information. The article has been peer reviewed. Members of the Department of Psychology and Neuroscience Institute at Princeton wrote it. No further information was available at this level of access.

Summary: Based on past studies, the researchers are working to come up with a more useful ways to prime the brain for formation of new neurons in the hippocampus. New neurons have been found to be related to improved learning and reduced anxiety. Reduced neurogenesis happens in more severe threat situations and increases chances of survivlal. These situations are accompanied by anxiety. Increase in neurogenesis is found in situations where reward is consistently given.

Reflections and thoughts: While reading the article, I was a bit confused about the phrasing. While the article was clearly looking for a way to optimize neurogenesis, the reduced neurogenesis seemed to have benefits as well. In the sense that anxiety can be useful, I was a bit confused that it seemed as though researchers saw that as a negative. Perhaps in the way that over exhausting adrenals is a bad idea, so is reduced neurogenerative state. I am particularly glad that I can switch easily into “fight-or’flight” and function easily in exigent circumstances. At the same time, I am continuously reminded to beware of non-profit burnout.

Article 2:

T.J. Shors, M.L. Anderson, D.M. Curlik II, M.S. Nokia, Use it or lose it: How neurogenesis keeps the brain fit for learning, Behavioural Brain Research, Available online 22 April 2011, ISSN 0166-4328, 10.1016/j.bbr.2011.04.023.

(http://www.sciencedirect.com/science/article/pii/S0166432811003330)

Validity: The article was published this year and therefore will be more relevant than older information. The article has been peer reviewed. It was written by Department of Psychology, Center for Collaborative Neuroscience, Rutgers University. No further information was available at this level of access. Dr. Schors has published over 100 articles and in several well respected academic journals.

Summary: In order to keep newly made neuron cells, learning must occur. Without this learning, the cells are not integrated into the brain circuitry. The type of learning that is necessary also in turn relies on these cells. This learning is known as “effortful learning, a process that involves concentration in the present moment of experience over some extended period of time.” During this learning, the new and old neuron cells mix together, enabling present memories to integrate with old. This in turn makes the ability to make predictions.

Reflections: It is interesting to think of old neurons to merely be the fodder for the fire of fit brain activity. To think that the old cells require the old to actually function on a higher level shows how the body/the brain works in such harmony. The new cells would die without the old. The old cells reach a ceiling in functioning without the new. This makes me think of how we structure learning in levels; building foundations and then further articulating the subjects. Without an understanding of basics, no specialization can occur. That is why I continue to review introductory courses in preparation for graduate school.

Article 3:

M. Guerra-Crespo, D. Gleason, A. Sistos, T. Toosky, I. Solaroglu, J.H. Zhang, P.J. Bryant, J.H. Fallon, Transforming growth factor-alpha induces neurogenesis and behavioral improvement in a chronic stroke model, Neuroscience, Volume 160, Issue 2, 5 May 2009, Pages 470-483, ISSN 0306-4522, 10.1016/j.neuroscience.2009.02.029.

(http://www.sciencedirect.com/science/article/pii/S0306452209001894)

Validity: The article was published in Neuroscience in 2009. The journal asserts in its Aims and Scopes that articles must be: “Any paper, however short, will be considered for publication provided that it reports significant, new and carefully confirmed findings with full experimental details.” I also feel comforted when there are many departments and institutions involved in research and publication. In this case, the following institutions were involved: Department of Anatomy and Neurobiology, University of California, Irvine, Department of Developmental and Cell Biology, University of California, Irvine, Department of Physiology and Pharmacology, Loma Linda University, and Department of Psychiatry, Human Behavior, University of California, Irvine.

Summary: Transforming growth factor-alpha (TGFα) already exists in our bodies and is produced in several areas of the body from macrophages to epithelial cells. Researchers administered TGFa to rats who brains had been subjected to a stroke. Up to four weeks after the brain damage, the TGFa was able to encourage cell growth. The cells were able to “migrate preferentially along and ventral to the corpus callosum (CC) and external capsule to the site of the injury where many of them differentiate into several site-appropriate neuronal phenotypes in association with near complete (99%) behavioral recovery.” Thusly TGFa is useful for brain recovery for chronic stroke and potentially other neurological damage.

Reflections: I find it interesting that something that our own bodies make can help so efficiently. The experimenting and use of different growth factors is very exciting. Our bodies already have what we are looking for to repair. The fact that the action of introducing TGFa up to a month later still showed such positive results amazed me. Perhaps neurological issues will less plague future older populations. This gives me faith in a world that seems to be lessening and lessening our access to consistent and efficient eldercare.

Article 4:

T. Kobilo, M.C. Potter, H. van Praag, Neurogenesis and Exercise, In: Editors-in-Chief: George F. Koob, Michel Le Moal and Richard F. Thompson, Editor(s)-in-Chief, Encyclopedia of Behavioral Neuroscience, Academic Press, Oxford, 2010, Pages 404-409, ISBN 9780080453965, 10.1016/B978-0-08-045396-5.00239-6.

(http://www.sciencedirect.com/science/article/pii/B9780080453965002396)

Validity: National Institute on Aging published the article in 2010. Initially, I was nervous about its validity. I did find that the Institute is part of the National Institute of Health. It has a very strong research department in the Division of Neuroscience. The reputation of the institution gives me more faith.

Summary: Some of the obvious detriments of a sedentary lifestyle are increased chances of heart disease and cancer. Exercise also helps the brain function best by helping with cognition and memory. New neurons grow in the hippocampus with exercise.

Reflections: The benefits of exercise impress me all the time. Yes, we know exercise is good for you but it becomes increasingly better with further research. I know that for myself when I incorporate exercise into my week, I am more alert. I sleep better and tend to recall information more easily.

Intelligence Measurement

How is intelligence measured? Do those with higher intelligence actually have more synapse? Is there a difference in structure or neural pathways?

Prediction: IQ is well known measure of intelligence. I propose that the entire process of intelligence testing needs to revitalized. I believe that we will not see a structural difference and that there must be another measure of intelligence.

Article 1:

Ramsden S, Richardson FM, Josse G, Thomas MS, Ellis C, Shakeshaft C, Seghier ML, and Price CJ. Verbal and non-verbal intelligence changes in the teenage brain. Nature. 2011 Oct 19. doi: 10.1038/nature10514.

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10514.html

Validity: My initial attention to this article came from NPR. I was unsatisfied with using a non-scientific journal. I went to the source and went directly to the study conducted by University College London and the University of London. With further research, I was able to see how the Wellcome Trust Centre for Neuroimaging, University College London and the Developmental Neurocognition Laboratory, Department of Psychological Sciences, Birkbeck College, University of London had conducted the study. The study was designed by one individual then a separate team recruited participants. Another team was put together to collect the data. Yet another team was put together to analyze the data. And finally a writing team wrote the paper. All these levels of transparency as well as the availability of supplemental data made me feel very comfortable with validity.

IQ is the standard measure of intelligence. The belief was that this would stay consistent through the life span. Neuroimaging was also used to see if changes occurred whether or not they corresponded with changes in brain development. Teenagers did show fluctuations and that during these years that IQ could change. More specifically:

“By using longitudinal assessments of the same individuals, we obviated the many sources of variation in brain structure that confound cross-sectional studies. This allowed us to dissociate neural markers for the two types of IQ and to show that general verbal and non-verbal abilities are closely linked to the sensorimotor skills involved in learning.”

It makes sense to use this information to my own experiences. As a child, I was seen as intelligent child. I scored relatively well but more so saw results by surrounding myself with other high achievers. By the time, I was 15 years old I was in the gifted and talented crowd. Therefore just like the researchers found intellectual potential did improve. Furthermore the researchers found that changes in grey matter were clearly measures. This completely derailed my hypothesis.

Article 2:

Isabell Wartenburger, Esther Kühn, Uta Sassenberg, Manja Foth, Elizabeth A. Franz, Elke van der Meer, On the relationship between fluid intelligence, gesture production, and brain structure, Intelligence, Volume 38, Issue 1, January-February 2010, Pages 193-201, ISSN 0160-2896, 10.1016/j.intell.2009.11.001.

http://www.sciencedirect.com/science/article/pii/S0160289609001457

Validity: The research was conducted at the Humboldt University Berlin (Department of Psychology, Humboldt University Berlin, Rudower Chausee 18, 12489 Berlin, Germany) and the Berlin NeuroImaging Center (Berlin NeuroImaging Center, Department of Neurology, Charité University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany). I could not find more information at this level of article access. I did look into the Intelligence journal itself. I found it promising that it preferred original research and not derivatives. The journal has a standard of ethics in publishing and a conflict of interest clause. The clinical research also must be as follows:

“All randomised controlled trials submitted to Intelligence whose primary purpose is to affect clinical practice (phase 3 trials) must be registered in accordance with the principles outlined by the International Committee of Medical Journal Editors (ICMJE; http://www.icmje.org/).”

The purpose of the study was to see any relationships between fluid intelligence, gesture production, and brain structure. Relationships were clearly seen: “Our results thus indicate that cortical thickness of those brain regions is related to both high fluid intelligence and the production of gestures.”

I found this amusing. I find that those who I see as more intelligent tend to be more purposeful with their physical gestures. More deliberate. I was not surprised after reading the first article that there was a region corresponding with this region. Obviously intelligence can be structurally observed. Although I was surprised that on its own that gesture production was from the same region. I wonder if those who are more innovative and deliver presentations on their revolutionary thoughts are more demonstrative as well in addition to more highly stimulated in the same region.

Article 3:

Aljoscha C. Neubauer, Andreas Fink, Intelligence and neural efficiency, Neuroscience & Biobehavioral Reviews, Volume 33, Issue 7, July 2009, Pages 1004-1023, ISSN 0149-7634, 10.1016/j.neubiorev.2009.04.001.

http://www.sciencedirect.com/science/article/pii/S0149763409000591

Validity: The article again had limited access. It is often cited but this did not actually speak to validity. I was left to only analyze the journal validity. Similar to Intelligence, it had the same clauses in ethics and conflict of interest. It did however also mention that funding must come directly from those doing the research. I do think there was a need to speak to funding.

The basis of the research jumped of a previous study that found that those who are more neurally efficient (use less brain activation energy) in cognitive tasks are brighter as well. This study found that further research was necessary. Results could be varied by amount and quality of learning. Although conclusively: “In very complex tasks more able individuals seem to invest more cortical resources resulting in positive correlations between brain usage and cognitive ability.”

As far as my hypothesis, I found it interesting that intelligence could be studied as far as how brain-energy-efficient one could be. I like the idea that indeed it could be another indicator. I do want to see more research and feel unsatisfied with the results. This is the first time I have really been let down as far as not being able to get more information.

Article 4:

John C Wickett, Philip A Vernon, Donald H Lee, Relationships between factors of intelligence and brain volume, Personality and Individual Differences, Volume 29, Issue 6, December 2000, Pages 1095-1122, ISSN 0191-8869, 10.1016/S0191-8869(99)00258-5.

http://www.sciencedirect.com/science/article/pii/S0191886999002585

Validity: The study only concerns a small population. More specifically, the adult male sibling in London ON Canada. This seems so small scoped. Again access level left me wanting more. The journal had similar requirements as the ones in the previous article.

This study wanted to look more into brain volume and head size in intelligence. The study was consistent with the previous studies. Thusly there was a correlation: “The sum of the data suggested that although brain volume (and to a lesser extent, head size) is predictive of g, fluid ability, and memory, it does not predict crystallized ability.”

After our previous research in male and female brains, I was already aware of studies in volume and brain abilities. I was hoping to find more information about cognitive abilities in relation with specific brain regions and intelligence. I was pleased that the study did find outliers that crystallized ability and spatial image loading.

Restoration of the Brain after Damage

Amber Badgerow

October 19, 2011

PSY 213

John Olmsted

Restoration of the Brain after Damage

Question:

There are amazing stories of people with brain damage regaining use of limbs, speech, etc. What changes occur in the brain after damage that could aid in recovery and must those changes be facilitated?

Prediction:

Neuroplasticity occurs during maturation, learning, and after an injury. The changes in the brain after damage may be new connections, strengthened connections, and/or new growth in order for the area of the brain that is undamaged to partially take over the tasks of the damaged area. In order for changes to occur, effort toward rehabilitation may be needed or an effort could expedite recovery since it means relearning tasks, which may promote neuroplasticity.

Article 1: “Remodeling the Brain Plastic Structural Brain Changes Produced by Different Motor Therapies After Stroke”

Lynne V. Gauthier, MA, Edward Taub, PhD, Christi Perkins, BS, Magdalene Ortmann, Victor W. Mark, MD, and Gitendra Uswatte, PhD wrote this article to find evidence for structural brain changes induced by an effective rehabilitation program. Sixteen stroke patients received constraint-induced (CI) movement therapy (that also encouraged use of the affected arm in daily activities at home) and twenty received a comparison therapy. Structural MRI scans were taken on patients before and after therapy for voxel-based morphometry (VBM). Results showed that not only did CI therapy patients obtain more use of the affected arm than the comparison therapy patients, but that they also displayed significant increases in ipsilateral and contralateral sensory and motor area gray matter. There was also in increase in the gray matter of the hippocampus, which is associated with learning and memory. Comparison therapy patients did not show an increase in gray matter. This indicated that changes in brain morphology may be responsive to a motor task's behavioral relevance. The observed neuroplasticity (growth in gray matter) could have been due to increased generation of neuronal or glial stem cells to aid in repair, reorganization or increased size of dendrites and greater synaptic density, proliferation of astrocytes, and/or angiogenesis.

Article 2: “Dynamic Neuroplasticity after Human Prefrontal Cortex Damage”

This article by Bradley Voytek, Matar Davis, Elena Yago, Francisco Barcelo´, Edward K. Vogel, and Robert T. Knight discussed their study that was conducted to provide evidence that, depending on the situation and cognitive load, the intact prefrontal cortex (PFC) compensates for the PFC with a unilateral lesion. They used electroencephalography (EEG) to measure the compensation. First, six patients performed lateralized visual working memory tasks. Contralesional stimuli produced sustained frontal theta activity that increased with memory load over the intact PFC. Ipsilesional stimuli did not produce electrophysiological changes and such changes were not observed in the control group. After the memory tasks patients performed a lateralized visual attention task, which was to find targets in swiftly progressing stimuli presented to the left or right visual field. When targets were presented to the damaged hemisphere there was late frontal activity that increased over the intact PFC. The fact that the undamaged hemisphere showed activity in less time and with less of a load when the damaged PFC was challenged suggested a powerful compensatory process involving neural changes to aid the damaged hemisphere.

Source Validity:

The first article has a few limitations that were noted: the experiment needs to be repeated, the

VBM method does not allow for the identification of the means of gray matter changes, and there was a small sample group. Article two also has a couple issues that may affect reliability: there was a very small subject group and an imbalance of right and left hemisphere lesions in patients. Despite these issues both articles were written by reputable authors, had experiments that controlled for age, education, and medical conditions, and provided evidence from other research that supported their results.

Reflection on Hypothesis:

This research supports my hypothesis that there are possible strengthened connections and/or new connections and that there is growth in the brain after damage. There is also evidence that the undamaged hemisphere compensates for the damaged one. Although the study in the first article indicates that morphologic neuroplasticity after brain damage only occurs with specific rehabilitation programs, more research must be done on the subject to fully support the hypothesis that neuroplasticity for recovery must be facilitated. There is still the question of whether the observed neuroplasticity is an effect of the functional changes or if it causes the functional changes.

Works Cited:

Gauthier Lynne V. et al. “Remodeling the Brain Plastic Structural Brain Changes Produced

by Different Motor Therapies After Stroke.” Stroke 39.5 (2008):1520-1525. American Heart

Association. GoogleScholar (“Structural Neuroplasticity Stroke”, PDF from

stroke.ahajournals.org). Web. Oct. 19, 2011.

< http://stroke.ahajournals.org/content/39/5/1520.full.pdf+html>

Voytek Bradley et al. “Dynamic Neuroplasticity after Human Prefrontal Cortex Damage.”

Neuron 68 (2010): 401–408. Elsevier Inc. GoogleScholar (“Neuroplasticity Cortex Damage”).

Web. <http://psychweb.uoregon.edu/~pk_lab/documents/

Voytek%20et%20al%202010%20Neuron.pdf>

The Brain's Response to Learning

Amber Badgerow

October 19, 2011

PSY 213

John Olmsted

The Brain’s Response to Learning

Question:

The brain’s capacity to learn is a fascinating feature. There is obviously a method the brain must use in order to process and store information. What changes occur in the brain with learning?

Prediction:

In order to process and store information gained in learning, the brain may strengthen connections between neurons and may grow in the area needed for the particular task.

Article 1: “Neuroplasticity of semantic representations for musical instruments in professional musicians”

Klaus Hoenig, Cornelia Müller, Bärbel Herrnberger, Eun-Jin Sim, Manfred Spitzer, Günter Ehret, and Markus Kiefer from the University of Ulm in Germany conducted a study to investigate the effects of musical learning on the brain's abstract higher-level cognition. Previous studies have proven that the brain undergoes basic noncognitive and motor map changes due to musical experience. Hoenig et al. used fMRI scans to find neuroplastic changes induced by visual depictions of musical instruments while participants (20 professional musicians and 20 control subjects) performed two different tasks. One task was picture and word matching (a conceptual task) and the other was listening to sounds (a perceptual task). Activation of the posterior superior temporal gyrus, right middle temporal gyrus, and superior temporal sulcus in the abstract processing of musical instruments was produced only by professional musicians. Moreover, the right middle temporal gyrus was also activated when the musicians listened to sounds, which indicated a link between auditory perceptual and conceptual brain systems in musicians. Non-musicians were not able to incorporate the auditory association cortex when accessing abstract knowledge about musical instruments. Professional musicians also evidenced more activation outside auditory areas (including the parietal and inferior temporal areas, the bilateral angular gyrus, the superior frontal gyrus, and the precuneus) for musical instruments. All those areas had previously been associated with processing certain aspects of music. These results suggested that musicians' brains undergo experience-based neuroplasticity that forms higher-level auditory conceptual feature maps for musical instruments depicted in and next to the auditory association cortex. Learning a skill can cause the brain to form new connections.

Article 2: “Distinct patterns of functional and structural neuroplasticity associated with learning Morse code”

This article, written by T. Schmidt-Wilcke, K. Rosengarth, R. Luerding, U. Bogdahn, and M.W. Greenlee, discussed a study to further elucidate the association between learning and alterations in neural activity and gray matter density. Functional magnetic resonance imaging (fMRI) and voxel-based morphology (VBM) was used to observe such changes. Sixteen participants were studied, before and after they learned Morse code, against 15 control subjects. The study revealed that learning was associated with brain activity in the supramarginal gyrus, the superior temporal gyrus, the precuneus/posterior cingulate gyrus, the middle temporal gyrus, the right fusiform gyrus, the left angular gyrus, the left middle frontal gyrus, and the medial frontal gyrus/superior frontal gyrus. Furthermore, learners showed a significant increase in gray matter density in the left occipitotemporal cortex extending to the fusiform gyrus when comparing scans before and after learning. These areas are all associated with different aspects of language perception. The data from this study indicates that learning a new skill produces functional reorganization and regional structural changes in the brain.

Source Validity:

Both sources provided evidence from previous research that was similar to or contributed to their research to help ensure that results were not contingent. The authors of both articles were well credited. However, like many studies, they both had small sample groups, which can affect the reliability of their findings. Article two noted that the methods used were not able to allow for the analysis of functional connectivity between activated brain regions.

Reflection on Hypothesis:

The research found supports my hypothesis and even adds that neural connections are not only strengthened, but new ones formed. More information could be studied to further clarify the effects of learning on brain morphology and neural connections. One aspect not found in this research is whether or not white matter density is affected.

Works Cited:

Hoenig Klaus, Cornelia Müller, et al. “Neuroplasticity of semantic representations for musical

instruments in professional musicians.” NeuroImage 56.3 (2011): 1714-1725. Elsevier Inc.

ScienceDirect. Web. Oct. 18, 2011.

< http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S1053811911002217>

Schmidt-Wilcke T., Rosengarth K. et al. “Distinct patterns of functional and structural

neuroplasticity associated with learning Morse code.” NeuroImage 51.3 (2010): 1234-1241.

Elsevier Inc. ScienceDirect. Web. Oct. 18, 2011.

< http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S1053811910003290>

The Impact of Sex Hormones on the Brain

Amber Badgerow

October 16, 2011

PSY 213

John Olmsted

The Impact of Sex Hormones on the Brain

Question:

There are distinct differences between male and female brains, but numerous things can influence the brain’s structure. How do sex hormones contribute to the difference in the structure of the male and female brain?

Prediction:

Sex hormones may be involved with the difference of gray and white matter volume in the male and female brain. Therefore, they could also contribute to the difference in regional volume in various parts of the male or female brain.

Article 1: “Regional sex differences in grey matter volume are associated with sex hormones in the young adult human brain”

This article was written by A. Veronica Witte, Markus Savli, Alexander Holik, Siegfried Kasper, and Rupert Lanzenberger (most of whom are on the Functional Neuroimaging Group- PET & fMRI from the Medical University of Vienna) to describe their study that was conducted to clarify the function of sex hormones in the sex differences of gray matter volume in the brain. They used MRI scans to obtain voxel-based morphometry (VBM) from 34 participants (17 males and 17 females). Previous studies had shown that males exhibit greater cerebral spinal fluid volume and white matter volume, but women have greater cortical grey matter volume. Specific regions of the brain also tend to be distinctly different between the sexes. The results of their study revealed that there was a relation between 17ß-estradiol levels and cluster mean gray matter volumes in the left superior parietal gyrus. The circulating 17ß-estradiol levels explained 12.6% of the variance in gray matter volumes. Cluster mean gray matter volumes in the right middle temporal pole were correlated with progesterone levels, which explained 13% of the variance. Progesterone was associated with larger temporal gray matter volume in men. Testosterone levels were related to greater cluster mean gray matter volumes in the opercular part of the left inferior frontal gyrus. Circulating testosterone levels explained 2.2% of the variance. These findings indicate that sex hormones organizationally influence regional gray matter volumes.

Article 2: “Sex steroids and brain structure in pubertal boys and girls”

Jiska S. Peper, Rachel M. Brouwer, Hugo G. Schnack, G. Caroline van Baal, Marieke van Leeuwen, Ste´phanie M. van den Berg, Henrie¨tte A. Delemarre-Van de Waal, Dorret I. Boomsma, Rene´ S. Kahn, and Hilleke E. Hulshoff Pol conducted a study on the association between brain structure and pubertal rises in testosterone and estradiol levels. There were 37 boys and 41 girls who participated in the study. Volumetric-MRI was used to measure global brain volumes. Higher estradiol levels in girls were associated with smaller global gray matter volume. In boys, higher testosterone levels were related to greater global gray matter volume. VBM was used to measure regional gray and white matter volumes. A correlation was found between higher estradiol levels in girls and lower gray matter volume in the parietal (supramarginal gyrus and angular gyrus), middle temporal, and prefrontal (superior gyrus, inferior gyrus, and orbitofrontal gyrus) areas. However, greater gray matter volume in parts of the middle frontal gyrus, inferior temporal gyrus, and middle occipital gyrus was also related to higher estradiol levels. Although testosterone levels had no indicative correlations with gray or white matter volume in boys or girls, a trend was seen between higher testosterone levels in girls and decreased gray matter volume in the left inferior frontal gyrus, left middle temporal gyrus, and right fusiform gyrus. The absence of a relationship between sex steroid levels and regional brain structures in boys could be explained by the possibility of the male and female brain reacting differently to sex steroids' effects. Yet, the results still indicate that sex steroid hormones have an effect on the brain structure of males and females, with estradiol levels in females having an observable effect.

Source Validity:

Despite the fact that both sources were reliably authored and used appropriate and dependable techniques, they each had some limitations. The sample size could be larger, especially regarding the first study, to ensure more accurate results. In article one, it could be noted that the methods used were unable to reveal causal dependencies and other factors could have caused differences in brain structure independent of sex hormones. However, the narrow age range, the education similarity, and the fact that there was no variance in the menstrual cycle phase in women positively affected validity. Article two also had some limitations, namely that the girls were older than boys and that the method used may not have been able to detect more subtle brain changes from hormones. However, this source also ensured similarity between the participants. Bias is possible, but not likely since both sources used previous impartial research on which to base their own studies.

Reflection on Hypothesis:

My hypothesis was supported by these findings. However, there is still research that needs to be conducted to further elucidate the relationship between sex hormones and brain structure differences between men and women.

Works Cited:

Witte A. Veronica, Savli Markus, Holik Alexander, Kasper Siegfried, Lanzenberger Rupert.

“Regional sex differences in grey matter volume are associated with sex hormones in the

young adult human brain.” NeuroImage 49. 2 (2010): 1205-1212. Elsevier Inc. ScienceDirect.

Web. Oct. 14, 2011.

< http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S1053811909010258>

Peper Jiska S. et al. “Sex steroids and brain structure in pubertal boys and girls.”

Psychoneuroendocrinology 34.3 (2009): 332-342. Elsevier Ltd. ScienceDirect. Web. Oct.

14, 2011.

< http://0-www.sciencedirect.com.library.pcc.edu/science/article/pii/S0306453008002539>