NEUROSCIENCE Chapter 3 - Methods of Studying Cognitive Neuroscience

Sagittal Plain

An anatomical plane that divides the body into left and right sections. It runs vertically from the front to the back of the body.

Coronal Plane

A vertical plane that divides the body into anterior and posterior sections.

Axial Plane

A horizontal plane that divides the body into superior and inferior sections, typically running parallel to the ground.

Anterior/Ventral vs Posterior/Dorsal

Front vs Back (separated on the coronal plane)

Superior vs Inferior

Top vs Bottom

Medial vs Lateral

Towards the middle of the body (spinal cord) vs away from the middle of the body

Proximal vs Distal

Near the trunk (torso) vs away from the trunk

Lesion Studies

Research involving damage to specific brain areas to understand their functions. Early scienetists relied on case studies to make inferences about brain functions.

Types of Damage

• Vascular Damage

• Tumors

• Degenerative and Infectious Disorder

• TBI (Traumatic Brain Injury)

• Epilepsy

Vascular Damage (damage type 1/5)

Damage caused by interrupted blood flow to the brain, often leading to stroke. This can result in various cognitive and physical impairments depending on the affected area.

Tumors (damage type 2/5)

Abnormal growths in brain tissue that can interfere with normal brain function, potentially leading to cognitive deficits or neurological symptoms.

Degenerative and Infectious Disorders (damage type 3/5)

Conditions that lead to progressive decline in brain function, including neurodegenerative diseases like Alzheimer's and infections that can damage neural tissue.

TBI (Traumatic Brain Injury) (damage type 4/5)

Traumatic brain injury resulting from external force, causing disruption in brain function.

Epilepsy (damage type 5/5)

A neurological disorder characterized by recurrent seizures, resulting from abnormal electrical activity in the brain.

Single Dissociation Studies

A method in where a specific cognitive function is impaired while others remain intact, often used to understand the relationship between brain regions and cognitive processes.

Double Dissociation Studies

A research method that demonstrates how two cognitive functions can be independently impaired, providing stronger evidence for the separation of brain processes.

Formal Dissociation

A concept that occurs when a cognitive function is affected under certain conditions but remains intact under others, useful for studying the flexibility of brain processes.

Informal Dissociation

A cognitive phenomenon where two functions appear to overlap in brain areas, but can still show differing impairments in certain circumstances.

Transcranial Magnetic Simulation (TMS)

• A non-invasive technique used to stimulate small regions of the brain, employing magnetic fields to induce electrical currents, often used to study neural activity and its effects on behavior

• High temporal resolution, weak spatial resolution

• Temporarily alters brain activity

• Can only activate superficial structures

• Can be either inhibitory or exhibitory

TMS in Practice

• Was used to stimulate the visual cortex in the occipital lobe

• Stimulation prevented subjects from being able to to identify/perceive visual stimuli (letters) on the screen in front of the

• Subjects were unaware of when simulation was happening

• Errors only occurred when stimulation occurred 70-130 milliseconds after stimulus was presented

Transcranial Direct Current Simulation (tDCS)

• A non-invasive brain stimulation technique that uses direct current to modulate neuronal activity, typically enhancing or reducing the excitability of targeted brain areas.

• Device delivers a constant low current to the brain via electrodes on the scalp

• Neurons under the anode become depolarized

• Change in excitability can last up to an hour

Transcranial Alternate Current Simulation (tACS)

• Current oscillates, rather than remaining constant like a tDCS

• Studies show that different oscillating frequencies are associated with different types of cognition

• Can attempt to synchronize differnt brain regions

Electroencephalography (EEG)

• The use of surface electrodes on the scalp to record the ELECTRICAL activity of the brain (measures FUNCTION. Researchers may use as many as 10-256 electrodes embedded into an elastic scalp

• Great temporal precision, but poor spatial precision

• Strength of the signal decreases with distance

EEG Noise

• EEG is very susceptible to many different types of interference

• Outside sources of noise - Electrical activity from AC power lines, lights, and computers. Controlled by using DC equipment or using a factory cage

• Physiological noise - Cardiac Signals and movement artifacts from muscle contractions. Movement can be limited but cardiac noise is constant and needs to be filtered out

• Signal Averaging is believed to help reduce noise

Event Related Potentials (ERP) in EEG Recording

• Data from each electrode is lined up and averaged across trials that are similar, which helps to eliminate EEG Noise

• Specific waves are identified in relation to the timing of the stimulus presentation

• Negative deflections - due to superficial excitatory or deep inhibitory inputs

• Positive deflections - due to deep excitatory or superficial inhibitory inputs

Postsynaptic Potentials

• Changes in the membrane potential of a neuron that occur when neurotransmitters bind to receptors, influencing whether the neuron will fire an action potential. These potentials can be excitatory (depolarizing) or inhibitory (hyperpolarizing) depending on the type of neurotransmitter and receptor involved.

• This makes it so that the soma of the postsynaptic cell is one charge while the cell’s dendrites are another, creating a dipole (a model representing the source of electric or magnetic fields in the brain, characterized by a specific location, orientation, and strength)

Human Brain Waves

• Delta (.5-3 HZ)

• Theta (3-8 HZ)

• Alpha (8-12 HZ)

• Beta (12-30 HZ)

• Gamma (38-42 HZ)

Delta (.5-3 HZ) (Brain Wave 1/5)

Deep meditation and dreamless sleep

Theta (3-8 HZ) (Brain Wave 2/5)

Meditation and REM sleep

Alpha (8-12 HZ) (Brain Wave 3/5)

Drowsiness

Beta (12-30 HZ) (Brain Wave 4/5)

Alert and attentive

Gamma (38-42 HZ) (Brain Wave 5/5)

Integrative activity between regions

Electrocorticography (ECoG)

• Electrodes are laid directly on the surface of the cortex

• Usually used to identify focal points of seizures

• Patients routinely go through the voluntary psychological testing while the electrodes are implanted

• Better spatial precision than an EEG

Magnetoencephalography (MEG)

• Measures the magnetic fields produced by the brains electrical activity (electrical activity produces a circular magnetic field that is perpendicular to the direction of the electric current

• Better spatial resolution than an EEG and similar temporal position

• Can only record from neurons who’s dendrites are parallel with the scalp’s surface. Most recordings then come from the sulci

• Machine is expensive and needs to be in a faraday cage

Single Cell Recording

A technique used to measure the electrical activity of individual neurons. It provides high spatial and temporal resolution, allowing researchers to study specific neural responses during various cognitive tasks.

Multiunit recording

A method for simultaneously recording the electrical activity of multiple neurons to analyze their collective firing patterns and interactions during cognitive processes.

Single cell & Multiunit recording

• Mostly done with model systems (animals, not humans)

• Very big advancement for neuroscience

• Electrodes are inserted into the extracellular space of the brain and measure ion concentration

• Allows neuroscientists to map receptive fields of sensory neurons

• Advances in singe cell recording techniques led to multiunit recording devices

Brain Computer Interfaces (BCI)

• The same devices used in Multiunit recording have been implanted in human patients

• Some are used to detect seizure activity, some are used to restore paralyzed patients

• Electrodes can be inserted into the motor cortex and can use the signals to move robotic arms or to control digital displays

• Neurons will actually wire themselves to the device to give it a better signal

Neuroimaging

• Techniques used to visualize brain activity and structure, including fMRI, PET, and CT scans. These methods help understand brain function and identify abnormalities.

• Pioneered by a team led by Marcus Raichle, Mike Posner, and Steven Peterson

• Measure metabolic activities of the brain

• This type of research is correlational research

Functional Magnetic Resonance Imaging (fMRI)

• A neuroimaging technique that measures brain activity by detecting changes associated with blood flow, allowing researchers to observe brain function during various cognitive tasks

• Great spatial resolution, weak temporal resolution

• BOLD oxygen changes reflect neural activity (Measures ratios of oxygenated to deoxygenated hemoglobin in the brain)

Blood Oxygenation Level Dependence (BOLD)

• A measure of the changes in blood oxygen levels associated with neural activity, commonly used in fMRI studies to map brain activity

• All of our blood has a ratio of oxygenated to deoxygenated hemoglobin in a given location

• BOLD signals peak at 6-10 seconds after neuronal activation, reflecting increased blood flow to regions of the brain that are more active.

Issues with BOLD

Challenges related to the variability and interpretation of BOLD signals, including the influence of physiological noise and delayed hemodynamic response, which can complicate the understanding of neural activity.

Positron Emmission Tomography (PET)

• A neuroimaging technique that uses radioactive tracers to visualize metabolic processes in the brain. It provides information about brain activity and can identify abnormalities.

• Poor temporal Precision, time lag occurs, and limited spatial resolution

• Delivered to the areas of the brain that are active and need additional blood

• Sensors pick up radioactivity (gamma rays)

Magnetic Resonance Imaging (MRI)

• A neuroimaging technique that uses strong magnetic fields and radio waves to create detailed images of the brain's structure. It is critical for diagnosing conditions such as tumors, brain injuries, and neurological diseases.

• Poor temporal precision but excellent spatial resolution

• Measures the structures of the brain

• Functional imaging measures blood flow

• Involves manipulating the orientation of hydrogen atoms

Computerized Tomography (CT)

• X-Ray based neural imaging

• High spatial resolution, average temporal resolution

Block Design

A method used in neuroimaging experiments where stimuli are presented in blocks or grouped together to measure brain activity, allowing for better signal detection and analysis. This design enhances the statistical power of fMRI studies by reducing noise.

Event Related Design

A neuroimaging experimental design that presents stimuli in a quasi-randomized fashion, allowing for the study of brain activity associated with individual events or trials.

MR Physics

The principles and concepts of physics that underpin the operation of Magnetic Resonance Imaging, including the interaction of magnetic fields and radio waves with atomic nuclei.

Voxels

The smallest distinguishable box-shaped units in an MRI scan, representing a volume of brain tissue and used to analyze spatial data.

T1 Weighted Structural Scan

• A type of MRI scan that provides detailed images of brain anatomy based on the T1 relaxation time of tissue, commonly used to assess structural changes in the brain

• Can be used to measure cortical thickness and surface area

• More 1mm-2mm Voxels to differentiate between gray matter and white matter, useful in various neurological assessments.

T2/T2* Weighted Functional Imaging

• A type of MRI imaging that detects changes in the magnetic resonance signal related to the T2 relaxation time, useful for examining brain function and connectivity

• Fewer voxels that are 2mm-4mm in size that can help identify areas of activation in response to specific tasks or stimuli.

The Big Data Problem

The challenges of processing, analyzing, and interpreting vast amounts of data generated by modern neuroscience research (specifically from voxels), which can affect the integration of findings across studies.

Comparing Multiple People

• Each individual person has a uniquely shaped brain

• In order to compare brain activity, we need to line up the same regions from person to person

• Each subjects brain is warped into a standard space using nonlinear transformations (via a process called registration)

Resting State Networks

Functional connections in the brain that are active during rest, showing patterns of connectivity that reflect underlying neural networks; these networks have been linked to various cognitive functions.

Stroop Effect

Demonstrates that when viewing words, we cannot help but activate word representations even when they are irrelevant to the task.

Optogenetics

A technique that uses light to control neurons which have been genetically modified to express light-sensitive ion channels, allowing for precise manipulation of neural activity in living tissue.