PSY 340 Week 2 Brain Structure and Research Methods Example

Finding the Words: Brain Structure, a Left-Hemisphere Stroke and the Methods That Locate Function

[Student Name]

University of Phoenix

PSY/340: Biological Foundations in Psychology

Week 2 Assignment

[Instructor Name]

[Date]

The person described is a composite written for a model paper; research findings come from the sources listed.

The brain is organized into regions and networks that contribute to different functions, and researchers use a range of methods to discover which structures support which behaviors. This paper reviews the major structures, applies them to a case of stroke and compares the methods used to link brain and behavior.

The Case

Hector is forty-seven and works as a commercial electrician in Mesa, Arizona. One afternoon, while on a ladder, he felt his right arm go weak and could not get words out to his apprentice. At the hospital, imaging showed a blockage in a branch of the left middle cerebral artery and damage in the left frontal lobe. A week later, his right arm had largely recovered, but his speech remained slow and effortful, with short phrases such as "Truck... job... tomorrow." He understands most conversation, follows instructions and is frustrated by his difficulty speaking.

A Tour of the Brain

The nervous system divides into the central nervous system, the brain and spinal cord, and the peripheral nervous system, which connects them to the body. Within the brain, the hindbrain includes the medulla and pons, which regulate breathing and heart rate, and the cerebellum, which coordinates movement and contributes to learning motor skills. The midbrain relays sensory and motor information. The forebrain includes the thalamus, a relay station for sensory input; the hypothalamus, which regulates hunger, temperature and hormones; the limbic structures, including the amygdala, involved in emotion, and the hippocampus, involved in forming memories; and the cerebral cortex.

The cortex has four lobes in each hemisphere. The occipital lobe processes vision. The temporal lobe handles hearing, language comprehension and aspects of memory. The parietal lobe processes touch and spatial information. The frontal lobe controls movement, planning, decision-making and, in the left hemisphere for most people, speech production.

Locating Hector's Damage

Hector's symptoms point to the left frontal lobe. Weakness in his right arm reflects damage near the motor cortex, which controls the opposite side of the body. His halting speech with relatively good comprehension fits a pattern traditionally called Broca's aphasia, associated with damage to the lower part of the left frontal lobe. Because comprehension relies more on the temporal lobe, which was spared, he understands far better than he speaks.

Revisiting Broca's Patients

In the 1860s, Paul Broca described patients who lost fluent speech and, after their deaths, found damage in the left frontal lobe. Dronkers et al. (2007) scanned the preserved brains of Broca's first two patients with high-resolution MRI. They found that the damage extended well beyond the surface region now called Broca's area into deeper structures and white matter pathways. Their findings suggest that lasting speech production problems depend on damage to a wider network, not a single spot, which fits Hector's case: his lesion involves both the cortical area and the connections beneath it.

Methods for Linking Brain and Behavior

Lesion studies, like Broca's and Hector's case, examine what changes when a region is damaged. They can show that a region is necessary for a function, but natural damage rarely respects neat boundaries.

Structural imaging shows anatomy. CT scans are fast and useful in emergencies, which is why Hector received one first to rule out bleeding. MRI gives far finer detail of soft tissue and revealed the extent of his lesion.

Functional imaging shows activity. PET tracks radioactive tracers that reveal metabolism or neurotransmitter activity. fMRI tracks changes in blood oxygen that follow neural activity.

Electrical methods such as EEG record activity from the scalp with millisecond timing, though with poor spatial precision. Transcranial magnetic stimulation briefly disrupts or excites a cortical region, allowing researchers to test whether it is needed for a task in healthy people.

What fMRI Can and Cannot Show

Logothetis (2008) reviewed the basis of the fMRI signal and argued that it reflects changes in blood flow and oxygen linked to neural activity, particularly the input and local processing within a region, rather than the output firing of neurons. Because blood flow changes over seconds and each image element contains many thousands of neurons, fMRI cannot resolve fast events or distinguish excitation from inhibition. He concluded that fMRI is powerful when combined with other methods but cannot on its own reveal how neural circuits compute.

A bright spot on a brain scan shows where blood flowed during a task, not proof that the spot produced the behavior.

Why Small Studies Mislead

Button et al. (2013) analyzed meta-analyses in neuroscience and estimated that the median statistical power of studies was very low, around 20 percent. Low power means that real effects are often missed and that significant findings are more likely to be false or exaggerated. Many early imaging studies used small samples, which helps explain why some widely reported brain-behavior links have not replicated. For students reading imaging research, sample size is one of the first things to check.

Converging Evidence

No single method answers every question. For language, lesion studies show which areas are necessary, fMRI shows which regions are active in healthy speakers, EEG shows the timing of language processing and stimulation can test whether disrupting a region briefly impairs speech. When these methods agree, the case for a structure's role is strong.

Hector's Recovery

Hector began speech therapy within two weeks. Therapists use repetition, melodic intonation, which draws on the right hemisphere's role in rhythm and melody, and practice with work-related phrases. Recovery is often fastest in the first months, as swelling falls and surviving areas, including regions in the right hemisphere, take on more of the work.

Conclusion

Hector's halting speech and weak arm reflect damage to the left frontal lobe and its connections. A tour of brain structures explains the pattern, a modern look at Broca's patients shows that speech depends on networks, a review of fMRI clarifies what imaging measures and research on statistical power urges caution about small studies. Combining methods gives the clearest picture of how brain structure supports behavior.

References

Button, K. S., Ioannidis, J. P. A., Mokrysz, C., Nosek, B. A., Flint, J., Robinson, E. S. J., & Munafò, M. R. (2013). Power failure: Why small sample size undermines the reliability of neuroscience. Nature Reviews Neuroscience, 14(5), 365-376. https://doi.org/10.1038/nrn3475

Dronkers, N. F., Plaisant, O., Iba-Zizen, M. T., & Cabanis, E. A. (2007). Paul Broca's historic cases: High resolution MR imaging of the brains of Leborgne and Lelong. Brain, 130(5), 1432-1441. https://doi.org/10.1093/brain/awm042

Logothetis, N. K. (2008). What we can do and what we cannot do with fMRI. Nature, 453(7197), 869-878. https://doi.org/10.1038/nature06976