Lecture 25 – Systems Neuroscience and Ethics

Instructor: John ReynoldsDate: 25 September 2024Email: john.reynolds@otago.ac.nzCourse: ANAT242

Page 1: Overview of the Module

• Lecture Topics:

  • Lecture 1: Definition of a brain system and identification methods.

  • Lecture 2: Neuroimaging techniques and introduction to the reward system.

  • Lecture 3: Detailed exploration of the reward system and its dysfunctions.

  • Lecture 4: Foundations of neuroethics and neuromodulation.

  • Lecture 5: Advanced topics in neuroethics.

  • Lecture 6: Applied neuroethics.

  • Lecture 31: Review of relevant papers.

  • Lecture 32: Exam advice and degree planning.

Page 3: Mechanics of the Module

• Module Test:

  • Date: 14 October, 7 PM.

  • Content: Labs 7 and 8, associated lectures on systems, imaging, reward systems, and ethics.

• Final Exam:

  • All content is examinable (MCQs + essay).

• Lecture Slides:

  • Fill in details marked with ‘[...]’.

  • Colored boxes indicate material importance for exams.

Page 4: Objectives of Lecture 1

1. Define a brain system.

2. Understand various neuroimaging modalities.

3. Describe information derived from imaging techniques.

4. Explain CT and PET imaging principles.

5. Explain MRI imaging principles.

6. Differentiate T1-weighted and T2-weighted MRIs.

Page 5: Definition of a Brain System

• Brain System:

  • A collection of structures working together for a common function.

  • Distinction from a 'network' which refers to circuits connecting neurons.

• Examples of Brain Systems:

  • Visual, auditory, vestibular, somatosensory, motor, and reward systems.

• Systems Neuroscience:

  • Analysis of how systems work alone or together to influence behavior.

Page 6: Example of Systems Neuroscience

• Input Sensory Systems:

  • Visual and auditory systems contribute to a single behavioral output (motor system).

• Process:

  • Sensory information is integrated to form perceptions and plans for movement.

Page 7: Identifying Brain System Components

• Neuroimaging Techniques:

  • CT, PET, and MRI scanning.

Page 8: Neuroimaging Methods

• Types of Neuroimaging:

  • CT (Computerized Tomography): Structural imaging.

  • MRI (Magnetic Resonance Imaging): High fidelity structural imaging.

  • PET (Positron Emission Tomography): Metabolic and functional imaging.

• Key Points:

  • CT is structural; PET measures metabolic activity; MRI provides detailed structural images.

Page 9: Principles of CT

• Tomography:

  • Imaging by creating slices using penetrating waves.

• X-ray Principles:

  • Different tissues absorb X-rays to varying degrees, creating contrast in images.

Page 10: CT Imaging Characteristics

• Relative Densities:

  • Air < Fat < CSF < White Matter < Grey Matter < Blood < Bone.

• Advantages:

  • Quick, cost-effective, good for acute bleeding.

• Disadvantages:

  • Limited detail in brain structures, radiation exposure.

Page 11: Principles of PET

• Mechanism:

  • Radiation from a radioisotope is detected externally.

• Functionality:

  • Highlights areas of increased glucose metabolism, useful in cancer detection.

Page 12: PET Imaging Characteristics

• Advantages:

  • Identifies metabolic activity and characterizes tumors.

• Disadvantages:

  • Poor resolution, requires radiation, and localization is approximate.

Page 13: General Principles of MRI

• Mechanism:

  • High-powered magnet aligns hydrogen atoms; uses radiofrequency pulses.

• Considerations:

  • Safety concerns with metal objects in the scanner.

Page 14: MRI Process Overview

• Magnetic Field Effects:

  • Aligns hydrogen atoms, radiofrequency pulse disrupts alignment.

Page 15: MRI Recovery Times

• Recovery Measurement:

  • Time taken for hydrogen atoms to realign after pulse.

• Contrast Mechanism:

  • Different tissues recover at different rates, affecting image brightness.

Page 16: MRI Imaging and Voxel Mapping

• Voxel Definition:

  • 3D pixel used to create anatomical images.

• Tissue Appearance:

  • Variations in brightness based on tissue type and recovery times.

Page 17: CT vs MRI Comparison

• CT:

  • Quick, less detailed, good for fractures.

• MRI:

  • Detailed, longer scanning time, better for soft tissue assessment.

Page 18: MRI Methods

• Types of MRI:

  • Structural, diffusion, functional imaging.

Page 19: T1-Weighted MRI

• Definition:

  • Recovery time for hydrogen atoms to return to resting alignment.

• Image Characteristics:

  • Highlights fat; brighter images indicate quicker recovery.

Page 20: T2-Weighted MRI

• Definition:

  • Recovery time for axial spin of hydrogen atoms.

• Image Characteristics:

  • Useful for investigating water content in the brain.

Page 21: T2-Weighted MRI Differences

• Contrast:

  • T2 images can show opposite effects compared to T1.

• Applications:

  • Differentiates between various tissue types based on water content.

Page 22: T2-FLAIR Imaging

• Purpose:

  • Distinguishes between free-flowing CSF and non-free-flowing edema.

• Image Characteristics:

  • CSF appears dark, while edema appears bright.

Page 23: Summary of Lecture

• Key Takeaways:

  • Definition of a brain system and its components.

  • Introduction to neuroimaging methods.

  • Principles of CT, PET, and MRI.

  • Differences between T1 and T2-weighted images.

  • Introduction to T2