Lecture Notes: Methods Part II and Neurodevelopment

University of Lethbridge Lecture 3: Methods Part II

  • Date: January 15th, 2026

  • Instructor: Dr. Chelsea Ekstrand

Functional Techniques

Learning Objectives

  • Understanding methods used to study the brain:
      - Functional neuroimaging methods:
        - Positron Emission Tomography (PET)
        - Functional Magnetic Resonance Imaging (fMRI)
        - Electroencephalography (EEG)
        - Magnetoencephalography (MEG)
        - Functional Near-Infrared Spectroscopy (fNIRS)
      - Techniques for modulating brain activity:
        - Transcranial Magnetic Stimulation (TMS)

Positron Emission Tomography (PET)

  • Description: Molecules altered to include a radioactive atom are introduced into the bloodstream.

  • Purpose: Provides insights into neurotransmitter function (e.g., dopamine) and information on absolute levels of brain metabolism.

Mechanism

  • A radioactive isotope is injected into the bloodstream (like radioactive glucose or oxygen).

  • As the molecule decays from radioactive to inert, it releases a positron that collides with an electron, resulting in the emission of two photons of light.

  • The location of the emitted photons helps determine the brain region involved.

Gold Standard Information Provided by PET

  • Blood flow measurement.

  • Oxygen consumption rates.

  • Glucose utilization metrics.

  • Limited use for studying cognitive and emotional functions.

Advantages of PET

  • Allows for examination of specific molecular usage within the brain.

  • Provides absolute brain metabolism levels details.

  • Preferred technique for neurotransmitter function examination.

Disadvantages of PET

  • Restricted number of scans due to ionizing radiation limits.

  • Imaging duration is lengthy, typically taking seconds to minutes.

  • Requires expensive cyclotron for continuous infusion of radioactive isotopes.

Functional Magnetic Resonance Imaging (fMRI)

  • Key Concept: Experimental stimulus correlates with neural activity, blood flow, and the Blood Oxygen Level Dependent (BOLD) signal.

BOLD Signal Explanation

  • When a brain area is active, oxygen demand increases.

  • The level of oxygenated blood rises compared to deoxygenated blood in that area.

  • The resultant increase in oxygenated blood leads to a more prominent MRI signal.

fMRI Task-Based Approaches

  • Evaluates changes in brain activity signal during task performance.

  • Results are interpreted based on the difference between task conditions and a baseline task.

Advantages of fMRI

  • Widely available and non-invasive (no high energy radiation).

  • Multiple scans allowed per individual over time.

  • Applicable for various demographics (children, reproductive-aged women).

  • Higher temporal resolution in comparison to PET.

Disadvantages of fMRI

  • Temporal resolution is still limited.

  • It provides an indirect measure of neural activity.

  • Some participant restrictions exist regarding scanning capabilities.

  • Patients may be uncomfortable due to confined spaces.

  • High operational costs.

Electroencephalography (EEG)

  • Mechanism: The brain's communication through electrical activity, with raw EEG signals recorded on the scalp via electrode caps.

  • Applications: Frequently utilized to identify seizures in epilepsy.

Event-Related Potentials (ERPs)

  • These are EEG signals recorded in relation to specific events.

  • Each ERP is characterized by distinct components (e.g., N170 linked to face processing).

EEG Signal Characteristics

  • The EEG signal comprises complex waveforms with varying frequencies, amplitudes, and shapes.

  • Signals can be analyzed across electrodes to ascertain the underlying frequency components (akin to ripples in a lake).

Power Spectrum Analysis

  • To understand frequency compositions in waveforms, spectral analysis, such as Fast Fourier Transform (FFT) is employed.

  • Power relates to wave amplitude where higher amplitude equates to more pronounced signals (e.g., louder noises = higher amplitude).

Advantages of EEG

  • High temporal resolution allows for accurate measurement of brain activity.

  • Relatively inexpensive and portable compared to other techniques.

  • Direct measurement of neural activity is possible.

  • Silent operation.

Disadvantages of EEG

  • Spatial resolution is low, which can affect detail.

  • Sensitive to motion artifacts and may be challenging to use with certain hair types.

  • Only captures signals from a specific subset of neurons.

Magnetoencephalography (MEG)

  • Mechanism: Maps brain activity by tracking magnetic fields stemming from electrical currents in neurons.

  • Detectors (SQUIDs) identify signals; around 50,000 active neurons are necessary for effective detection.

Advantages of MEG

  • Silent operation with good spatial resolution and excellent temporal resolution.

Disadvantages of MEG

  • Requires specialized magnetically shielded environments.

  • High expenses associated with operation.

Functional Near-Infrared Spectroscopy (fNIRS)

  • Description: A relatively new method based on how hemoglobin absorbs near-infrared light.

  • Provides information regarding neural activity sources and the timeline of conditions.

Mechanisms of fNIRS

  • Distinctions in optical properties for oxygenated vs. deoxygenated blood.

  • Involves shining infrared light on the scalp, with detectors a few centimeters away capturing alterations in light paths due to brain tissues and blood.

Advantages of fNIRS

  • Non-invasive nature.

  • Silent and portable, providing flexibility for studies.

  • Less sensitive to motion artifacts and more affordable than fMRI.

Disadvantages of fNIRS

  • Limited to measuring surface brain activity (within 2-3 cm).

  • Poor temporal resolution (though better compared to fMRI).

  • Low spatial resolution at least 1 cm³.

  • Reduction in measurement quality based on hair color (e.g., dark hair is problematic).

Summary of Techniques

Comparative Summary

  • PET: Good for understanding neurotransmitters; invasive and expensive.

  • fMRI: Good spatial resolution; non-invasive but with some temporal limitations.

  • EEG: Low cost and excellent temporal resolution; suffers in spatial resolution.

  • MEG: High temporal and spatial resolution but expensive.

  • fNIRS: Non-invasive and low cost; limited to cortex surface scanning.

Transcranial Magnetic Stimulation (TMS)

  • Technique allows for the temporary increase or decrease of brain activity using a pulsed magnetic field over the scalp, altering the membrane potential of neurons.

  • TMS helps in establishing cause and effect relationships.

  • Most effectively used for cortical structures, with limitations on deeper brain areas.

Study Recommendations

  • Familiarize with functional methods:
      - PET
      - fMRI
      - EEG
      - MEG
      - fNIRS

  • Understand the operational mechanisms, advantages, and disadvantages of each.

  • Study modulation methods like TMS.

Upcoming Classes

  • Next Class: Neurodevelopment, January 20, 2026

  • Activity 1 opens on January 19 at 9 AM and closes January 25 at 11:59 PM.

University of Lethbridge Lecture 4: Neurodevelopment

  • Date: January 20th, 2026

  • Instructor: Dr. Chelsea Ekstrand

Learning Objectives

  • Understand the six stages of neural development:
      - Neurogenesis
      - Cell migration
      - Differentiation
      - Synaptogenesis
      - Neuronal death
      - Synapse rearrangement

  • Analyze how these stages may be affected in autism.

Stages of Brain Development

1. Neurogenesis

  • Formation of new nerve cells from the neural tube.

  • Occurs around the ventricles.

2. Cell Migration

  • Glial cells create pathways for neuron migration.

  • Most neurons are produced by six months of gestation.

  • Development issues such as Fetal Alcohol Spectrum Disorder (FASD) can impact this stage.

3. Differentiation

  • Stem cells divide and differentiate into various neuron types.

  • Includes neuroblasts and glioblasts responsible for specialized functions.

4. Synaptogenesis

  • Significant increase in synaptic connections among neurons, marked initially by explosive growth.

  • Surfaces area for connections increases dramatically.

  • The initial synaptic formation leads to overproduction, which is refined later.

5. Neuronal Death

  • Synaptic overproduction (“blooming”) followed by pruning (elimination).

  • Timing varies across regions, with sensory/motor regions maturing first, followed by frontal cortex development during adolescence.

6. Synapse Rearrangement

  • Neurons that fail to secure neurotrophic support die.

  • Successful connections maintain and strengthen their synaptic ties reinforced by neurotrophic factors.

Neurotrophic Factors

  • Provide necessary nutrients for neuronal growth.

  • Direct where growth occurs, crucial for proper development.

Implications in Autism Spectrum Disorder (ASD)

  • Theory suggests excessive target neurons result in connectivity issues.

  • Evidence of disrupted cell layering has been observed in autism brains, indicating atypical prenatal development.

Cortical Development Sequence

  • Order:
      1. Sensory Systems (Visual, Auditory)
      2. Motor Systems
      3. Speech/Language
      4. Social/Emotional
      5. Cognitive

Myelination

  • Critical for enhancing signal transmission across the nervous system.

  • Begins around the fourth gestational month, extending into early years after birth.

  • The developmental timeline differs by area; for example, basic sensory and motor systems are myelinated within the first year but more complex integrative systems mature later.

Study Recommendations

  • Be able to explain each of the six stages of neural development and underlying processes.

  • Recognize the sequence of cortical development, along with the implications of ASD.

Upcoming Class

  • Next Class: Neuroanatomy, January 25, 2026

  • Activity 1 opened on January 19 at 9 AM and closes January 25 at 11:59 PM.