Unit 2: Methods in Physiological Psychology I

How can researchers study brain structure using observation/correlation?

Measure anatomy and relate it to groups, behavior, or task conditions.

How can researchers study whether brain structure causes behavior?

Study the behavioral and cognitive consequences of structural damage.

How can researchers study brain function using observation/correlation?

Measure brain activity and relate it to groups, behavior, or task conditions

How can researchers study whether brain function causes behavior?

Perturb/manipulate brain activity and test its effects on behavior.

What imaging technique has become the most popular over the years?

fMRI has outscored other imaging techniques in popularity over the years.

What did Raymond Damadian contribute to the history of MRI?

He developed and used MRI technology to produce a full-body human scan to help diagnose cancer/tumors.

What did Ogawa et al. demonstrate in 1990?

They showed measurable MRI changes after physiological manipulation in rats.

What major MRI development occurred in 1992?

The BOLD (blood oxygenation level dependent) contrast era began, allowing MRI to detect changes related to blood oxygenation.

What creates the strong magnetic field in MRI?

The MRI scanner introduces a strong magnetic field.

How does magnetic field strength affect MRI images?

Stronger magnetic fields generally allow for higher imaging resolution and greater detail.

What magnetic field strengths are commonly used in research MRI?

Most research MRIs range from 1.5–7 Tesla (T).

What does Tesla (T) measure in MRI?

The strength of the MRI’s magnetic field.

What does MRI measure from hydrogen atoms?

The energy released from hydrogen (H) atoms.

What can the energy released from hydrogen atoms tell us in MRI?

It can measure fat/water in tissue, water movement, and blood oxygenation.

What does regular MRI measure?

The relative amount of fat and water in tissue.

What does diffusion MRI measure?

The movement of water molecules.

What does fMRI measure?

Changes in blood oxygenation.

Why is hydrogen useful for MRI?

Hydrogen is ubiquitous (found throughout the body) and is the simplest atom.

What is a hydrogen atom primarily composed of?

A single proton.

Why are protons considered MR-active nuclei?

They constantly spin and have magnetic and angular moments.

What is the magnetic moment of a proton?

Its magnetic dipole.

What is the angular moment of a proton?

The directionality of its spin.

What happens to hydrogen protons when there is no external magnetic field?

The protons are randomly oriented, so there is no overall/net magnetization.

What happens to hydrogen protons when placed in the MRI scanner’s strong magnetic field (B₀)?

A small excess of protons align with the magnetic field, creating net magnetization.

Why do hydrogen nuclei behave like tiny magnets?

Their protons have a magnetic moment, so they behave like tiny magnets.

What is precession in MRI?

The wobbling/rotating motion of a proton around the direction of the external magnetic field.

What determines how fast protons precess?

The strength of the external magnetic field (B₀).

What is the Larmor frequency?

The frequency at which a proton precesses in a magnetic field.

What happens to Larmor frequency as magnetic field strength increases?

The Larmor frequency increases—a stronger magnetic field causes faster precessio

What does the radiofrequency (RF) pulse do in MRI?

It transfers energy to the protons.

How does an RF pulse affect net magnetization?

It tips net magnetization away from the main magnetic field.

How does an RF pulse affect proton precession?

It brings the protons’ precession into synchrony (in phase).

What happens after the RF pulse ends?

The magnetization relaxes back toward its original state.

How is the MRI signal detected?

A receiver coil detects the electrical signal produced by changing transverse magnetization.

What happens to the MRI signal when protons are in phase vs. out of phase?

When protons are in phase (synchronized), they produce a stronger combined signal. As they become out of phase, the signal fades.

Why can the receiver coil detect an MRI signal?

The rotating/changing magnetization induces an electrical signal in the receiver coil, similar to a rotating magnet producing a signal in a nearby coil.

Why do white matter, gray matter, and cerebrospinal fluid (CSF) look different on MRI?

They have different relaxation times, which creates tissue contrast.

How does MRI produce different brightness between tissues?

The timing of RF pulses and signal measurement emphasizes differences in tissue relaxation.

How do tissues typically appear on a T1-weighted MRI?

White matter = brighter, gray matter = darker, CSF = dark.

What happens during T1 recovery?

Longitudinal magnetization rebuilds as protons realign with the main magnetic field.

What happens during T2 decay?

What happens during T2 decay?
Protons lose synchrony (become out of phase), causing transverse magnetization and the signal to decrease.

How do white and gray matter differ in relaxation?

They relax at different rates, which helps create contrast between them on MRI.

Why does an MRI scanner need gradients?

To locate where signals come from.

How do gradients help identify signal location?

They vary the magnetic field so different locations have different frequencies.

How does an RF pulse select a slice?

It excites a specific range of frequencies corresponding to that slice.

How does a computer use the location information provided by gradients?

It places the measured signals in their correct locations to build an image.

What determines tissue brightness in an MRI image?

Tissue properties and scan settings.

What is the main role of the magnetic field in MRI?

It prepares net magnetization.

What is the role of the RF pulse and detection in MRI?

The RF pulse creates a signal that the receiving coil can measure.

What do relaxation and contrast explain in MRI?

Why different tissues produce different signal strengths.

What do gradients and location explain in MRI?

How the scanner places signals in an image.

What does diffusion MRI measure?

The movement of water molecules within tissue.

How do tissue barriers affect water movement in white matter?

They restrict movement across axon bundles more than along them.

In white matter, does water generally diffuse more easily along or across axon bundles?

Along axon bundles.

Why does diffusion MRI measure diffusion in different directions?

To estimate local fiber orientation.

What is tractography?

A method that uses estimated local fiber orientations from diffusion MRI to map possible white matter pathways.

What happens to local blood flow when a brain region becomes active, such as when viewing a flashing checkerboard?

Local blood flow increases, delivering more oxygen than the tissue’s increased consumption requires.

How does this increased oxygen delivery affect deoxygenated hemoglobin?

The amount of deoxygenated hemoglobin decreases.

Why does a decrease in deoxygenated hemoglobin increase the MRI signal?

It reduces disruption of the local magnetic field.

What does BOLD stand for?

Blood oxygen level dependent.

What is the BOLD signal?

A change in the MRI signal caused by changes in blood oxygenation associated with brain activity.

Does the BOLD signal measure neurons’ electrical activity directly?

No. It measures associated changes in blood oxygenation.

What two types of fields does neurons’ electrical activity produce?

Electrical and magnetic fields.

What does EEG record, and how?

Electrical voltage differences using electrodes on the scalp.

What does MEG record, and how?

Magnetic fields using sensors around the head.

What makes EEG and MEG useful for studying when processing happens?

Both track rapid changes in brain activity.

What does NIBS stand for?

Non-invasive brain stimulation.

What are two types of non-invasive brain stimulation?

Transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES).

How does TMS stimulate the cortex?

It uses a strong, changing magnetic field to induce a transient electrical current in the cortex.

How does TES stimulate the brain?

It applies a weak electrical current directly to the scalp, which is conducted to the brain.

What is the main difference between how TMS and TES deliver stimulation?

TMS induces electrical current using a changing magnetic field; TES applies electrical current through the scalp.

What clinical use do brain stimulation techniques have?

They are used to treat neurological and psychiatric disorders.

How can brain stimulation help researchers study causal links between brain function and behavior?

Researchers alter brain activity and observe the resulting changes in behavior.

What induces electrical current during TMS?

Flux, or change, in the magnetic field.

What rule relates the directions of current and the magnetic field?

The right-hand rule.

What kind of magnetic pulses does TMS use?

Brief but strong magnetic pulses that induce electrical current.

How quickly do TMS pulses rise and fall? How long does a TMS pulse last?

In approximately 0.1 milliseconds. last Approximately 1 millisecond.

What magnetic field strength does TMS produce?

Approximately 1.5–3 tesla.

Why does TMS have different effects from the main magnetic field in MRI?

The TMS magnetic field changes rapidly, inducing electrical current.

How does TMS magnetic field strength change with distance from the coil?

It drops off rapidly with distance; your notes describe this as exponentially.

How does coil size relate to the size of the magnetic field produced?

A larger coil generally produces a larger magnetic field region.

Approximately how far below the scalp does TMS stimulation penetrate, according to these notes?

About 1.5 cm.

How focal is the spread of TMS stimulation, according to these notes?

Approximately 3.5 × 3.5 cm.

What affects the spread and precision of TMS stimulation?

Coil design and the precision of coil placement.

Why is targeting a specific brain region with TMS challenging?

The coil must be positioned accurately over the intended region, and individual brain anatomy varies.

What is ideal for identifying a participant’s precise anatomy before TMS?

Having an MRI scan of that participant.

What tools can improve TMS targeting?

Neuro-navigation software and brain templates.

How can stimulation of primary motor or visual areas help confirm TMS targeting?

Observable responses, such as muscle movements or perceived flashes of light, help identify the stimulated location.

What example was used in class to illustrate non-invasive brain stimulation (NIBS)?

The Twizzlers example.

What is a major advantage of single-pulse TMS?

High temporal precision.

What does the high temporal precision of single-pulse TMS allow researchers to do?

Isolate specific stages of information processing.

What happens when a TMS pulse is delivered 80–100 ms after a target letter appears?

It disrupts the ability to detect the letter.

What happens when a TMS pulse is delivered 80–150 ms after a visual mask appears?
It disrupts the masking effect, making the target easier to detect.

It disrupts the masking effect, making the target easier to detect.