Transcranial Magnetic Stimulation & Rat Experiments

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Questions and Answers

What is the main purpose of subtracting the baseline in experimental tasks?

  • To isolate the activity of interest (correct)
  • To enhance the quality of fMRI imaging
  • To compare different tasks without any controls
  • To increase the overall brain activity measured

Which of the following is considered a limitation of functional MRI (fMRI)?

  • It shows the specific function of brain regions clearly.
  • It has limited temporal resolution compared to EEG. (correct)
  • It can accurately measure individual differences without averaging.
  • It provides a direct measure of causation in brain activity.

What is the function of the Default Mode Network (DMN)?

  • Associated with external sensory processing only
  • Involved in resting states and mind-wandering activities (correct)
  • Active primarily during specific tasks requiring concentration
  • Active only during sleep or unconscious states

Why is spatial averaging a problem in interpreting fMRI results?

<p>It can mask the underlying neural functions by averaging results. (B)</p> Signup and view all the answers

What does resting-state functional connectivity MRI (rsfcMRI) specifically measure?

<p>Functional connections between brain regions at rest (B)</p> Signup and view all the answers

What is a key limitation associated with analyzing fMRI data on a voxel-by-voxel basis?

<p>Every voxel is analyzed independently, causing statistical challenges. (C)</p> Signup and view all the answers

What does functional connectivity in the brain indicate?

<p>Regions show synchronized activity with each other. (D)</p> Signup and view all the answers

Which of the following statements about the limitations of fMRI is TRUE?

<p>It may not clarify the specific functions indicated by observed brain activity. (C)</p> Signup and view all the answers

Which brain regions are part of the Default Mode Network?

<p>Medial prefrontal cortex, posterior parietal cortex, lateral temporal cortex (C)</p> Signup and view all the answers

What issue was raised in the case study comparing heavy metal lovers and classical music lovers?

<p>No behavioral measurements were taken alongside the fMRI data. (B)</p> Signup and view all the answers

What is the primary purpose of rTMS?

<p>To induce electrical changes in the brain. (A)</p> Signup and view all the answers

What is assessed using the Forced-Swim Test?

<p>Depression-like symptoms. (D)</p> Signup and view all the answers

Which behavioral test is utilized to study spatial learning in rats?

<p>Morris Water Maze. (B)</p> Signup and view all the answers

What is a major benefit of using a within-subjects design in animal studies?

<p>No separate control group needed. (D)</p> Signup and view all the answers

What type of lesion method allows for temporary inactivation of brain regions?

<p>Reversible Lesions. (D)</p> Signup and view all the answers

Which injection method provides rapid entry of drugs into the bloodstream?

<p>Intramuscular (IM). (D)</p> Signup and view all the answers

What is a major challenge of conducting intracellular unit recording?

<p>Movement may dislodge the electrode from the cell. (B)</p> Signup and view all the answers

What is the primary benefit of optogenetics in neural research?

<p>It allows precise control of neural activity using light. (C)</p> Signup and view all the answers

Which type of stain is best for visualizing individual neurons?

<p>Golgi Stain. (A)</p> Signup and view all the answers

What type of brain imaging captures structural differences over time?

<p>Static (Structural) Imaging. (D)</p> Signup and view all the answers

What is a significant limitation of chemical lesions?

<p>Excess excitatory chemicals can damage neurons. (B)</p> Signup and view all the answers

Which of the following accurately describes a characteristic of the hippocampal disruption in rats?

<p>Hippocampal damage leads to difficulty in finding platforms. (B)</p> Signup and view all the answers

What is used to bypass the blood-brain barrier in drug administration?

<p>Intraventricular injection. (D)</p> Signup and view all the answers

What is the main advantage of using Computerized Axial Tomography (CAT/CT) over traditional X-rays?

<p>Lower radiation risk (A)</p> Signup and view all the answers

Which imaging technique relies on the alignment and relaxation of hydrogen atoms?

<p>Magnetic Resonance Imaging (MRI) (A)</p> Signup and view all the answers

What does Diffusion Tensor Imaging (DTI) primarily track in the brain?

<p>Movement of water molecules (A)</p> Signup and view all the answers

Which technique measures brain activity by detecting changes in blood oxygen levels?

<p>Functional MRI (fMRI) (B)</p> Signup and view all the answers

What is a significant limitation of Positron Emission Tomography (PET)?

<p>Requires fresh radioactive tracers (C)</p> Signup and view all the answers

What does the BOLD response refer to in the context of Functional MRI?

<p>Blood Oxygen Level Dependent response (B)</p> Signup and view all the answers

What is a common use of the technique known as resting-state functional connectivity MRI?

<p>Identifying default brain network activity (D)</p> Signup and view all the answers

Which imaging technique has the highest risk associated with radiation exposure?

<p>X-Ray (A)</p> Signup and view all the answers

In what way can Functional MRI (fMRI) be said to have a limitation compared to EEG methods?

<p>Temporally slower than EEG methods (A)</p> Signup and view all the answers

Which of the following techniques is specifically designed to provide clear images of white matter bundles?

<p>Diffusion Tensor Imaging (DTI) (C)</p> Signup and view all the answers

What method improves the image quality of CT scans?

<p>Advanced image processing software (B)</p> Signup and view all the answers

What is one main reason why Positron Emission Tomography (PET) is considered expensive?

<p>It uses a radioactive tracer (B)</p> Signup and view all the answers

Which imaging method has the lowest radiation risk?

<p>Magnetic Resonance Imaging (MRI) (A), Functional MRI (fMRI) (D)</p> Signup and view all the answers

What does the mechanism of X-ray imaging primarily rely on?

<p>Tissue absorption of X-rays (A)</p> Signup and view all the answers

Flashcards

Baseline Subtraction

A technique used to analyze fMRI data by subtracting baseline activity from the activity of interest. This helps researchers isolate specific brain activity related to a particular event or task.

Event-Related Design

A type of fMRI design that involves averaging data across many trials, allowing researchers to analyze brain activity related to a specific event or task.

Resting-State Functional Connectivity MRI (rsfcMRI)

A type of fMRI that measures functional connections between different brain regions while the participant is at rest.

Seed Region

A brain region that serves as the starting point for measuring functional connectivity in rsfcMRI. Activity in the seed region is compared to other regions to determine their functional relationship.

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Default Mode Network (DMN)

A network of brain regions that are highly active during resting states and mind-wandering. It is associated with internal thoughts, self-reflection, and processing information related to the past and future.

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Spatial Averaging

A limitation of fMRI interpretation where results average out individual differences in brain activity. Variations across individuals are lost.

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Temporal Resolution

A limitation of fMRI data interpretation due to a temporal delay in the BOLD signal. This delay makes it difficult to pin down the precise timing of brain activity.

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Ambiguity in Interpreting fMRI Results

A limitation of fMRI interpretation because the fMRI signal only shows activity, it cannot tell us the specific function of that activation. For example, language activation might show up in both hemispheres of the brain, but we need further analysis to understand which specific function it represents.

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Regional Hemodynamics

A limitation of fMRI interpretation that arises from slight timing differences in blood flow across different brain regions. These differences can lead to misalignment of results and make it difficult to accurately interpret the timing of brain activity.

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Reliability of fMRI Data

A limitation of fMRI interpretation because every voxel is analyzed independently, using statistical approaches. This means there are inherent limitations in the reliability and accuracy of the results due to statistical noise and potential errors.

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Computerized Axial Tomography (CAT/CT)

A type of structural imaging technique that uses multiple X-ray images from different angles to create a 3D image of the brain.

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CAT scan strengths

CAT scans are good at differentiating between tissue and fluids in the brain.

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CAT scan strengths

CAT scans have a lower radiation risk than traditional X-rays.

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CAT scan strengths

CAT scans can be improved by using modern image processing software.

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CAT scan limitations

CAT scans cannot easily distinguish between white matter and gray matter in the brain.

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CAT scan limitations

CAT scans have relatively low resolution compared to MRI.

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Magnetic Resonance Imaging (MRI)

A type of structural imaging technique that uses strong magnetic fields to create detailed 3D images of the brain.

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MRI process

MRI aligns hydrogen atoms in the brain using a strong magnetic field.

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MRI process

MRI uses a second magnetic pulse to knock hydrogen atoms out of alignment.

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MRI process

The relaxation process of hydrogen atoms returning to alignment releases energy that is measured by the MRI.

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MRI strengths

MRI produces high-quality 3D images of the brain with better resolution than CT.

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MRI strengths

MRI does not involve any radiation exposure.

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MRI limitations

MRI relies on extremely low temperatures to maintain the strong magnetic fields.

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Diffusion Tensor Imaging (DTI)

A type of structural imaging technique that is a variation of MRI that tracks the movement of water molecules in the brain.

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DTI strengths

DTI is useful for identifying white matter differences across individuals or groups.

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Transcranial Magnetic Stimulation (TMS)

A technique that uses magnetic fields to stimulate specific areas of the brain, inducing changes in brain activity. It can be used to create temporary "virtual lesions" by briefly turning off a specific brain region.

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Repetitive TMS (rTMS)

A repeated form of TMS, where magnetic pulses are applied repeatedly to a specific brain region. It's often used for research and therapeutic applications.

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Morris Water Maze

A well-known behavioral task used to study spatial learning and memory in rodents. Rats learn to find a hidden platform in a pool of opaque water, using visual cues in their environment.

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5-Choice Serial Reaction Time Task

A behavioral task in which a rat must quickly identify which of five holes will light up and then poke its nose into that correct hole. It's used to study attention and impulsivity.

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T-maze

A simple maze where an animal chooses between two arms, used to study decision-making, learning, and memory.

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Forced-Swim Test (FST)

A standardized behavioral assay for assessing depression-like behaviors in rodents. Animals are placed in a pool of water with no escape and their swimming behavior is observed.

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Acute Drug Administration

The administration of a drug in a single instance, often to study its immediate effects on behavior.

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Chronic Drug Administration

The regular administration of a drug over an extended period, often to study its long-term effects.

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Dose-Response Curve

A graphical representation of the relationship between different doses of a drug and the resulting behavioral responses.

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Within-Subjects Design

A research design where a single animal is exposed to all experimental conditions (e.g., different drug doses), allowing for comparisons within the same subject.

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Intracellular Unit Recording

A powerful technique that allows researchers to record the electrical activity within a single neuron.

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Extracellular Unit Recording

A technique for recording electrical activity from outside of a neuron, providing data about the overall activity of a group of neurons.

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Multiple-Unit Recording

A technique involving multiple electrodes to record electrical activity from many neurons simultaneously, providing information about the coordinated activity of neural ensembles.

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Stereotaxic Surgery

A surgical technique used to precisely target specific brain regions in animals for procedures such as lesioning, electrode implants, or optogenetic manipulations.

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Reversible Lesion

A method of temporarily inactivating a specific brain region by injecting drugs, allowing for within-subjects experimental designs without permanent damage to the brain.

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Study Notes

Transcranial Magnetic Stimulation (TMS)

  • TMS is repeated transcranial magnetic stimulation
  • Uses magnetic fields to induce electrical changes in brain activity
  • Targets the cortex to briefly turn off a brain region
  • Used for therapeutic applications, like treating depression resistance

Deep Thoughts by the Rat

  • Morris Water Maze:
    • Rats are placed in a pool of opaque water with a hidden platform
    • Rats swim randomly to locate the platform
    • Repeated trials decrease the time to find the platform
    • Swimming route becomes more direct
    • Visual markers (e.g., stars, trees) help spatial navigation
    • Hippocampal dependent
    • Rats with hippocampal damage have difficulty finding the platform
  • 5-Choice Serial Reaction Time Task:
    • Conducted in an operant chamber with 5 lighted holes
    • Rats must identify which hole lights up and poke their nose into the correct hole, for a sugar reward
    • Measures accuracy, implying attention
    • Avoid poking their heads into holes before the light fires (in order to avoid the 5 seconds timeout penalty)
    • Measures impulsivity, focusing on the lights
    • Success depends on focusing on lit holes.
    • Failure to wait for the light demonstrates impulsive behavior

Drug Administration in Animal Models

  • Drugs can be administered acutely or chronically
  • Intramuscular (IM): Injection into shoulder muscle.
    • Advantages: Rapid entry to bloodstream
    • Disadvantages: Disrupts the muscle's pH causing soreness and pain
  • Intravenous (IV): Injection into a vein
    • Advantages: Used for self-administration studies
    • Disadvantages: Risk of the animal removing the catheter, or infection risk
  • Subcutaneous (SC): Injection just under the skin
    • Advantages: Minimal discomfort, good for injection
    • Disadvantages: Slower absorption rate
  • Intraperitoneal (IP): Injection into the abdominal cavity
    • Advantages: Quick absorption
    • Disadvantages: Slower absorption rate compared to IM
  • Intraventricular (IVT): Injection directly into the brain ventricles
    • Allows drugs to bypass blood-brain barrier

Dose-Response Curve

  • Drugs typically exhibit a dose-response relationship
  • Example: Alcohol in small doses may stimulate, and in higher doses may be depressive

Invasive Electrical Recording Methods

  • Intracellular Unit Recording: Records activity inside a single cell
    • Very difficult, especially in awake/behaving animals
    • Movement can dislodge the electrodes
  • Extracellular Unit Recording: Records activity outside a neuron
    • More common and reliable method
    • Electrodes are stable
  • Multiple-Unit Recording: Simultaneous recording from multiple neurons
    • Monitors activity from multiple neurons at once
  • Invasive EEG Recording: Places EEG electrodes near the brain
    • Used to study sleep in animal models
  • Stereotaxic Surgery: Used to access specific brain regions via lesions, optogenetics, or electrode implants.
    • Stereotaxic atlases pinpoint specific brain regions in millimeters
    • Bregma is used as a reference point on the skull

Lesion Methods

  • Chemical Lesions: Using chemicals to target specific neuron types
    • Excitotoxic Lesions (e.g., quinolinic acid, ibotenic acid): Excess excitatory chemicals cause harmful neuron damage
    • Selective Chemical Lesions: Chemicals (e.g., 6-hydroxydopamine or 5,7-hydroxytryptamine) target specific neurotransmitters
  • Reversible Lesions: Temporary inactivation of brain regions
    • Injected drugs (e.g., baclofen + muscimol)
    • Allows for within-subjects design without permanent damage
  • Electrical Lesions: Using electric currents to affect neurons. Imprecise nature leads to unintended widespread damage, a drawback

Optogenetics

  • Uses light-gated ion channels to precisely control or target neurons
  • Light exposure affects the protein shape for ion flow
  • Genetic model needed to introduce light-gated protein gene

Stains

  • Nissl Stain/Cresyl Violet Stain: Visualizes neuron cell bodies
  • Fibre Stains (e.g., Luxol-fast blue, Toluidine blue): Visualizes white matter
  • Green Fluorescent Protein (GFP): Fluorescent protein from jellyfish allowing visualization inside neurons/cells
  • Brainbow Mouse: Modified GFP to visualize neurons in multiple colors

Neuroimaging

  • Static (Structural Imaging): Captures a single point in time
    • Computerized Axial Tomography (CAT/CT): Multiple X-ray images create 3D image.
    • Strengths: Good for identifying tissue, low radiation risk
    • Limitations: Lower resolution compared to MRI, high radiation risk
  • Magnetic Resonance Imaging (MRI): Aligns hydrogen atoms in the brain using a magnetic field, then measures energy release as atoms return to alignment
  • Strengths: High quality 3D images, no radiation risk
  • Limitations: Requires extremely low temperatures to maintain the strong magnetic field
  • Diffusion Tensor Imaging (DTI): Tracks water movement within axons, focusing on white matter tracts, and helping differentiate across individuals
  • Strengths: Provides clear white matter images, helps identify white matter issues
  • Limitations: High radiation exposure and low detail compared to other modalities

Dynamic (Functional Imaging)

  • Positron Emission Tomography (PET): Radioactive tracer is injected into the patient; brain activity measured by distribution and concentration.

Paired Image Subtraction

  • Two sessions to isolate specific activity that happened during the second session.
  • Baseline activity is subtracted to isolate the activity of interest.
  • Averaging many trials to reveal consistent activity patterns

fMRI

  • Functional Magnetic Resonance Imaging (fMRI): Measures brain activity by detecting changes in blood oxygen levels (BOLD signal). - Strengths: High spatial resolution, non-invasive.
  • Limitations: Slower time resolution than other methods.

Functional Connectivity (rsfcMRI)

  • Used to measure functional connections between brain regions during rest
  • Starts with a Seed Region (e.g., medial prefrontal cortex) and compares its activity to other regions
  • Synchronized activity signifies functional connectivity

Default Mode Network (DMN)

  • Active during rest and mind-wandering
  • Includes medial prefrontal cortex, posterior cingulate cortex, and lateral temporal cortex

Case Study: Heavy Metal Brain

  • Compared functional connectivity in heavy metal lovers and classical music lovers
  • Found differences in brain activity but no direct link to behavior was established
  • The study had limitations, and the interpretation of results could have been biased

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