Cortex - Lecture 2

Question 1

What is the role of the Subthalamic Nucleus (STN) in Parkinson’s disease?

Answer 1

The STN is targeted for Deep Brain Stimulation (DBS) to relieve motor symptoms of Parkinson’s disease. DBS modulates STN activity to improve motor control.

Question 2

What are the three primary functional subdivisions of the STN?

Answer 2

The motor, associative, and limbic subdivisions.

Question 3

How does the STN impact motor function?

Answer 3

The motor subdivision of the STN influences motor inhibition and movement control, and lesions here can cause involuntary movements like hemiballismus.

Question 4

What type of neurotransmitter is primarily used by the STN, and what effect does it have?

Answer 4

Glutamate; it provides excitatory signals within the basal ganglia, particularly impacting motor control regions.

Question 5

Describe the role of dopamine in STN function.

Answer 5

Dopamine influences the STN by modulating activity related to reward and motivation. Dysregulation in dopamine affects STN function and is related to symptoms in Parkinson’s disease.

Question 6

What imaging techniques are used to study the STN, and what is their primary limitation?

Answer 6

Structural and functional MRI, as well as in vivo imaging, are used. A primary limitation is the low anatomical detail, which complicates precise analysis.

Question 7

How does DBS impact other functions outside of motor control in Parkinson’s patients?

Answer 7

DBS can have effects on mood, motivation, and behavior, sometimes causing neuropsychiatric side effects, such as apathy, hypomania, or changes in emotional regulation.

Question 8

What are calcium-binding proteins, and why are they significant in STN studies?

Answer 8

Calcium-binding proteins, like parvalbumin and calretinin, are markers used to differentiate neuronal populations within the STN, supporting theories of functional zonation.

Question 9

Describe the role of tracing studies in understanding STN connectivity.

Answer 9

Tracing studies help map anatomical connections within the STN, providing insight into the convergence and overlap of motor, associative, and limbic circuits within this nucleus.

Question 10

What neuroanatomical changes are noted in Parkinson’s disease within the STN?

Answer 10

The STN does not degenerate in Parkinson’s, but its dysregulated activity due to loss of dopaminergic input from the substantia nigra contributes to motor symptoms.

Question 11

Explain the significance of the indirect pathway involving the STN.

Answer 11

The indirect pathway, with the STN as a relay, helps regulate motor control by modulating inhibitory output through connections with the globus pallidus and substantia nigra.

Question 12

What are the two main methods used in STN studies for anatomical and functional analysis?

Answer 12

Histological (post-mortem studies) and imaging (MRI, in vivo) methods are commonly used, each with strengths and limitations regarding anatomical detail and connectivity insights.

Question 13

What are GABAergic inputs, and what is their role in the STN?

Answer 13

GABAergic inputs inhibit STN neurons, balancing excitatory signals and contributing to the regulation of motor output within the basal ganglia.

Question 14

What challenges do researchers face in studying subdivisions within the STN?

Answer 14

Challenges include variability in findings across species, limited observations, and technical limitations in identifying precise subdivisions within the STN.

Question 15

How does STN activity differ between obsessive-compulsive disorder (OCD) and Parkinson’s disease?

Answer 15

STN firing rates are lower in OCD compared to Parkinson’s, indicating functional differences within the STN subdivisions for different conditions.

Question 16

Why is the tripartite subdivision hypothesis of the STN debated?

Answer 16

Some researchers argue that the motor, associative, and limbic subdivisions overlap, challenging the notion of clear, anatomically separated zones within the STN.

Question 17

What is the relationship between beta-band activity and the STN in Parkinson’s disease?

Answer 17

Increased beta-band activity in the STN is associated with motor dysfunction in Parkinson’s, particularly in the dorsal STN region.

Question 18

Describe how event-related potentials (ERPs) are used in STN studies.

Answer 18

ERPs help assess STN responses to emotional stimuli, with dopamine medication impacting ERP magnitude, especially in the ventral STN.

Question 19

What is the role of high-resolution MRI in STN-targeted DBS?

Answer 19

High-resolution MRI aids in precise DBS electrode placement within the STN, enhancing the specificity of treatment and reducing side effects.

Question 20

What future research directions are suggested to better understand STN functions?

Answer 20

Future studies are encouraged to explore anatomical overlap within subdivisions, improved imaging techniques, and computational modeling to clarify parallel versus convergent pathways.

Question 21

What are the two main types of cortex in the human brain?

Answer 21

Neocortex and allocortex.

Question 22

What are the subdivisions of the allocortex?

Answer 22

Archicortex and paleocortex.

Question 23

What is the field called that studies the differences between cortical regions based on cell type distribution?

Answer 23

Cytoarchitectonics.

Question 24

Who developed the concept of Brodmann areas and in what year?

Answer 24

Korbinian Brodmann in 1909.

Question 25

Which Brodmann areas correspond to Broca’s area?

Answer 25

Brodmann’s Areas 44 and 45.

Question 26

Approximately what percentage of the cortex volume is located within the sulci?

Answer 26

66%.

Question 27

What are the main sources of afferent inputs to the cortex?

Answer 27

Other cortical areas (association and commissural fibers) and subcortical sites, predominantly the thalamus.

Question 28

What is the function of the primary motor cortex (M1)?

Answer 28

It is activated directly by peripheral stimulation and is responsible for the execution of movements and adaptation of movements to new conditions.

Question 29

What role does the dorsal premotor area (PMA) play?

Answer 29

PMA is involved in action selection, sensorimotor transformations, and externally triggered movements.

Question 30

What is the function of the ventral PMA?

Answer 30

It helps in conforming the hand to the shape of objects, action selection, and sensorimotor transformations.

Question 31

What does the supplementary motor area (SMA) do?

Answer 31

It prepares motor sequences from memory and sends massive projections to M1 and the spinal cord.

Question 32

What are the characteristics of the pre-SMA compared to the SMA?

Answer 32

The pre-SMA has no direct projections to M1 or the spinal cord and is associated with motor sequence learning.

Question 33

What is the main function of the visual cortex (V1)?

Answer 33

It is involved in retinotopic mapping and processes visual input from the retina via the lateral geniculate nucleus (LGN).

Question 34

Which visual areas follow V1 in the processing sequence?

Answer 34

V2, V3, V4, and V5/MT.

Question 35

What role does the lateral intraparietal lobe (LIP) play in visual processing?

Answer 35

It acts as a possible accumulator and its activity is correlated with the direction of eye movements during responses.

Question 36

What functions are associated with the dorsolateral prefrontal cortex (PFC)?

Answer 36

Maintaining and manipulating information in working memory, inductive reasoning, rule-based processing, and complex decision-making.

Question 37

What is the function of the pMFC (posterior medial frontal cortex)?

Answer 37

It is involved in performance monitoring and signaling other brain areas to adjust cognitive control when there is a failure to obtain an expected reward.

Question 38

What does ultra-high field MRI allow researchers to study in more detail?

Answer 38

The complex biophysical and computational input/output properties of cortical components and their spatiotemporal interactions across layers.

Question 39

What is the difference between the Talairach and MNI standard spaces?

Answer 39

The Talairach space is based on a smaller, older brain (a 60-year-old French woman) with unequal slice spacing relative to the AC-PC line, while the MNI space is based on an average of multiple T1, T2, and PD images registered to a larger, more representative template.

Question 40

Name three sources of variability in brain structure.

Answer 40

Sex differences (e.g., grey matter volume), age (e.g., iron levels, atrophy), and genetic factors.

Question 41

Why are interindividual variations important in cortical studies?

Answer 41

They affect the accuracy and interpretation of cortical models, as older models do not account for these variations, which are significant for deeper cortical structures and the subcortex.