A1. Please report the answer that you’ve digested by posting as lots of following tasks will be based on your previous reply.

A2. Feel free to use any figures or any multimedia materials as the answers.

A3. Please site the ref. for the materials you majorly read or use for your current post

A1. Please report the answer that you’ve digested by posting as lots of following tasks will be based on your previous reply.

A2. Feel free to use any figures or any multimedia materials as the answers.

A3. Please site the ref. for the materials you majorly read or use for your current post

Q2: I deal with these jargons by using online neuroscience glossary (WashU Medicine) or google them.

Q3:

Structures in the brain

• Human telencephalon

• Thalamocortical axon

• White matter

• Basal ganglia

• Cortical gyri and sulci

• Corpus callosum

• Coronal radiata

• Right amygdala 

• Bilateral entorhinal cortex 

• Left insula 

Aforementioned jargons as brain structures:

• Inferior/superior cerebellar peduncles

• Ventrolateral nuclei of the thalamus

• Telencephalon

• Lentiform nucleus

• Coronal radiata

• Centrum semiovale

• Bilateral entorhinal cortex

• Left insula

I recently read a book called Almond by Sohn Won-pyung about a boy with alexithymia, a condition associated with the inability to identify and understand emotions. The boy in the story had a smaller amygdala, which made me wonder what exactly about the amygdala contributes to this condition. The amygdala is part of the limbic system, a structure that acts as the center for emotions. It partly controls one’s attitude towards stress, hunger, and sex. The amygdala itself regulates people’s emotions, especially anger and fear. It is connected to circuits associated with one’s ability to infer intentions of others’ language, gaze, and gestures. Lastly, it also plays a role in memory due to its consolidation of memories that evoke strong emotional responses. 

2. Brainstem & Cerebral Cortex

In AP Psychology, I learned about the Activation-Synthesis Theory of dreams, which is a topic in neuroscience that still remains quite undiscovered. The Activation-Synthesis Theory states that the brainstem fires random electrical impulses during REM sleep and the cerebral cortex makes sense of these impulses by spinning them into stories our minds perceive as dreams. Besides its role in forming dreams, the brainstem is a structure that connects the cerebrum to the spinal cord and cerebellum. It contains other structures such as the midbrain, pons, and medulla oblongata. It controls our body’s involuntary processes such as breathing and heart rate. On the other hand, the cerebral cortex serves as an outer layer of nerve tissue with many grooves and crevices. It is responsible for many high-level functions such as memory, learning, emotions, and consciousness. 

- Basal Ganglia

The basal ganglia are a group of structures near the center of the brain, including the striatum, globus pallidus, and subthalamic nucleus. The major function of this structure is movement, decision-making, and a reward system. For motor control, the basal ganglia control the selection and initiation of action through two pathways: direct and indirect. The direct pathway causes motion by inhibiting GPi(Globus Pallidus Internus), which allows the thalamus to excite the motor cortex. The indirect pathway, on the other hand, inhibits motor activity by inhibiting GPe (Globus Pallidus Externus), which excites the subthalamic nucleus and the GPi. Dysfunction in this system leads to movement disorders such as Parkinson’s disease (too little movement) and Huntington’s disease (excessive involuntary movement).

- Myelin sheath + Oligodendrocytes

While watching The Resident, one of the main characters, Dr. Bell, was diagnosed with Multiple Sclerosis. This is a disease that causes the breakdown of the protective covering of nerves, the myelin sheath. Composed of fat and protein, it insulates axons and enables rapid conduction by allowing electrical impulses to jump between nodes of Ranvier. The glial cell that forms this protective layer is known as the oligodendrocyte. In addition to myelination, oligodendrocytes provide metabolic support to neurons by supplying energy substrates, ensuring long-term axonal survival. When oligodendrocytes are destroyed, remyelination often fails, which can lead to chronic neurodegeneration and progressive disability.

Brainstem: Both rodents and humans have brainstems. They have similar functions in regulating involuntary functions such as breathing and heart rate, which keep us alive. However, the brainstems in rodents are much smaller with differences in their neuronal soma shape. The shape of their soma are almost spherical while those of humans come in more complex shapes (triangular, ovoid, granular). Humans also have extended structures within the brainstem such as the nucleus paramedian dorsalis (PMD), which play a role in processing vestibular information

Basal Ganglia

• Both humans and rodents contain this structure in their brains, and their role in motor control is also similar. However, humans have a more complex and clearly defined substructure, like the caudate, putamen, and globus pallidus. Since human brains are larger and more complex, they can perform more complicated behaviors than rodents.

Myelin sheath + Oligodendrocytes

• Both humans and rodents contain myelin sheath and oligodendrocytes in their brains. However, due to the difference in brain size, the myelin sheaths in humans are longer, which requires more oligodendrocytes per neuron. In addition, humans and rodents share a majority of myelin proteins, but some are still species-specific.

Brainstem: In the gestational period, the brainstem greatly increases in volume and proportion. After birth, myelination occurs most actively in the first two years and continues at a slower rate as the child grows. At the neonatal stage, the functional organization of the brainstem is also localized or “segregated.” Later on as the brainstem matures into adulthood, new neurons form via neurogenesis and networks become more integrated or connected together. 

For the basal ganglia, their structural development is largely restricted to embryonic development, which means that the neonatal basal ganglia are structurally similar to the adult basal ganglia. However, the function in the neonatal basal ganglia isn’t fully developed yet, and the motor behaviors are still poorly coordinated. As the function becomes mature, it allows better motor control and procedural learning.

Myelin sheath+oligodendrocytes

The myelin sheath in a neonate has just started to form, which is thin and loosely compacted. As the structure matures, it gets thicker, allowing for fast neural transmission and supporting complex thoughts. 

For oligodendrocytes, neonates mostly contain oligodendrocyte progenitor cells (OPCs) and only have a few mature oligodendrocytes, but as they grow older, the mature oligodendrocyte population increases and stabilizes, which helps to form a thick myelin sheath.

• Since it is a gray matter structure, a conventional MRI can be used to depict the change. It measures changes by giving a contrast between gray and white matter, making the basal ganglia clearly visible.

Myelin sheath and oligodendrocytes

• White matter is more myelinated than the gray matter, so a DTI can be used to depict the change. In addition, the myelin sheath is a lipid layer surrounding the axons, meaning that it can affect water diffusion. DTI can measure the change in water diffusion to show the change in the Myelin sheath and oligodendrocytes.

https://www.sciencedirect.com/science/article/pii/S187892932100116X

To Eva

https://pmc.ncbi.nlm.nih.gov/articles/PMC6666647/

Brainstem: T1-weight and T2-weighted images are often used to measure changes in the brainstem. For example, if lesions appear on the brainstem such as in patients with multiple sclerosis (MS), using T1-weighted images can help identify areas of tissue loss or atrophy, which appear as dark spots.

• How do the volumes of various subcortical and cortical brain structures change from childhood through young adulthood?

2. The study aims

• Describe and compare the developmental trajectories of several subcortical structures. (The cerebral cortex, cerebral WM, caudate, putamen, pallidum, accumbens area, hippocampus, amygdala, thalamus, brainstem, cerebellar GM, cerebellar WM, lateral ventricles, inferior lateral ventricles, third ventricle, and fourth ventricle)

3. The major method to prove the questions.

• Recruited one hundred seventy-one children and young adults (87 females and 84 males).

• Data were collected through a 1.5 tesla Siemens Avanto scanner with three-dimensional T1-weighted scans.

• Datasets were processed and analyzed at the Neuroimaging Analysis Lab, Center for the Study of Human Cognition, University of Oslo.

• Regression plots showing the relationship between age and bilateral volumes of each subcortical and cortical structure.

How does the amygdala develop from childhood to adolescence? What are the most reliable and accurate techniques to study amygdala development?

The study aims:

Examine how different tracing methods lead to trajectory differences in amygdala development by comparing the segmentation processes of amygdala volumes extracted manually from FreeSurfer, volBrain, and FSL-FIRST

The major method to prove the questions:

• Combined cross-sectional and longitudinal methods 

• Participants did not have any neurological/mental health problems and were not on psychotropic medication

• Included data from 201 typically developing controls (TDCs) from 6-17 years old (invited to participate in 3 consecutive waves of data collection at an interval of approximately 1.25 years)

• Conducted a T1-weighted MRI at each interval

• Included a final sample of 427 samples from 198 participants (105 females and 93 males)

• Compared amygdala volumes taken from the three previously mentioned methods

https://www.sciencedirect.com/science/article/pii/S187892932100116X

To Eva

https://pmc.ncbi.nlm.nih.gov/articles/PMC6666647/

Figure 1

• The plots show that most gray-matter structures, like the cortex and pallidum, gradually decrease in size as age increases. In contrast, white matter structures, such as cerebral WM, increase in size with age.

Table 2

• The table lists the volume of each structure for different age groups. The pattern shows that gray-matter regions, such as the cortex, get smaller, while white-matter regions grow larger.

Figure 3

• The figure shows that all four lobes’ volume, thickness, and surface area decrease over time at a slightly different rate.

Table 6

• The table quantifies how much each structure changes over time. The column about the percentage change of the raw volume shows that cerebellum GM has a negative value(-8.9), while cerebellum WM has a positive value (27.3). This suggests that the volume for gray-matter structures decreases, while the volume for white-matter structures increases.

Table 7

• The table highlights that different lobes change at different rates. The parietal lobe shows the fastest decrease in volume (-28.5%), while the temporal lobe shows the slowest (-15.0%).

Different methods of amygdala-segmentation tools produce size-dependent biases in children and adolescents, which leads to inconsistent developmental trajectories. Only manual tracing and volBrain after GMV-adjustment reveals the true pattern of amygdala growth across school-age years. 

Figure 1:

FreeSurfer over-covers tissue (over-segmentation). VolBrain marks a smaller region (under-segmentation). FSL results in a better shape, but mismatched edges still remain. These differences confirm that different tools in amygdala segmentation generate different volumes relative to manual tracing. 

Table 3:

Again, FreeSurfer estimates larger volumes. VolBrain estimates smaller volumes. FSL has inconsistent performance, so this data does not reliably reflect its individual difference. None of these methods have correlations big enough to substitute for manual tracing. 

Figure 2:

VolBrain has lower false positive rates and the highest false negative rates, meaning it rarely adds wrong tissue but undercovers actual amygdala tissue. FreeSurfer has higher false positive rates, meaning it overcovers amygdala tissue. FSL is, again, inconsistent across all charts (overlap, false-positive, and false-negative. 

Figure 4:

Manual tracing produces a steady, linear increase in amygdala volume as age increases, similar to volBrain. FreeSurfer shows flattened curves that don’t resemble true growth. FSL shows a concave down shape. 

Figure 6:

After adjusting amygdala volume by gray matter volume (GMV), the results for volBrain start to resemble results produced by manual tracing (steady and linear). However, after adjusting by intracranial volume (ICV), the results don’t resemble manual tracing. 

https://www.sciencedirect.com/science/article/pii/S187892932100116X

To Eva

https://pmc.ncbi.nlm.nih.gov/articles/PMC6666647/

1. Please list two findings in this paper showing SIMILAR results with any published study (cite the references).

2. Please list two findings in this paper showing DIFFERENT results from any published study (cite the references).

3. Please list two most important LIMITATIONS of the study.

4. Do you think the results of the paper FULLY answer the aim of the study? Why or why not?