introduction and neuroimaging Flashcards by Hannah Brown

mathematical model

The use of mathematical language and equations
to describe psychological and/or neural processes.

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computational model

The use of mathematical language and equations to describe steps in psychological and/ or neural processes (often implemented on a computer).

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efficient coding models

Theoretical and/or computational models that
explain neural processing by assuming that sensory systems become tuned to predictability in natural environments in ways that economically encode predict- able sensory inputs while highlighting inputs that are less predictable.

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bayesian models

Theoretical and/ or computational models that employ Bayesian statistical methods to gen- erate an internal model of the source of sensory inputs based upon prior experience.

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predictive coding

The use of Bayesian models to predict future inputs. If pre- dictions do not match inputs (prediction error), the model is adjusted to improve future predictions.

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artificial neural networks

Also referred to as connectionist models,
are computational methods that consist of networks of nodes with weighted connections between them. Connection weights increase and decrease following experience in ways that resemble orga- nization of biological neural networks

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deep neural networks

Artificial neural networks that have a very large num- ber of layers of nodes with millions of connections.

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What’s the difference between sensation and perception?

A similar distinction:
Sensation is the immediate, basic experience generated by external stimuli.
Perception involves the interpretation of these sensations, giving them meanings and organization.

No clear boundary-fuzzy distinction

Think of sensation as the initial processing carried out by our sensory systems and perception as the interpretive processing of this sensory information

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Cajal

Cajal- made drawing of organization of neurons in the brain.Neurons do not actually touch( separate cells with tiny gaps(synapse))

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Loewl

Loewl-excitatory( increase response of next neuron). Inhibatory( decrease response response of next neuron)

Chemical instead of electrical NT travel from axon across the synapse to bind to receptor molecules on the dendrite of the next neuron - some excite or inhibit from firing

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Neuroimaging

A set of methods that generate images of the structure and/or function of the brain.
Allow us to examine the brain in healthy, living, behaving humans.

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Dendrite

Receives info

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Soma

Contains nucleus & multicell organelles

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Terminal

Synapse with target cell

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Axon

Conducts AP away from cell body

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Axon Hillock

Info integrated here.
Generates AP

Types of structural NeuroImaging Technologies

Structural techniques:
Computerized Tomography(CT)
Magnetic Resonance Imaging(MRI)

Types of functional NeuroImaging Technologies

Functional techniques:
Functioning Magnetic Resonance Imaging(fMRI)
Positron Emission Tomography(PET)
Electroencephalography(EEG)
Event-Related Potential(ERP)
Magnetoencephalography(MEG)

Advantages of MRI over CT

Higher resolution(clearer images)
No radiation
Versatile

Advantages of CT over MRI

Advantages of CT over MRI:

Advantages of CT over MRI:
More comfortable environment
MRI is very loud
No danger of asphyxiation
No danger of foreign materials

How can we determine function?

(B❤️H)

Metabolic imaging: indirect measure of brain activity
based on changes in blood flow
Functional MRI (fMRI)
Positron Emission Tomography (PET)

Electromagnetic:direct measure of brain activity

Electroencephalography (EEG), event-related potentials (ERPs)
Magnetoencephalography (MEG)

Metabolic Imaging: The Timecourse of Blood Flow

Changes in cerebral blood flow (CBF) are very slow.

Typically 5-20 seconds post-stimulus.

Consequently, metabolic imaging techniques suffer

Functional magnetic resonance imaging (fMRI)

Blood oxygen level-dependent (BOLD) signal:
The ratio of oxygenated to deoxygenated hemoglobin that permits the localization of brain neurons that are most involved in a task.

Active brain tissue needs oxygen. Which is delivered by blood( active brain demands more).

See the activity of the brain.

Temporal resolution is slow.

Machines noisy,expensive.

Looks at increase metabolic activity

Positron emission tomography (PET)

Small amount of safe, biologically active, radioactive material( a tracer) is introduced in the participants bloodstream. Camera directs gamma rays emitted from brain region where the tracer is being used the most.

Advantages of fMRI

Slightly higher spatial resolution Does not require a radioactive tracer

Advantages of PET

Different radioisotopes provide more flexibility for PET Radiopharmacology

The Subtractive Approach

All parts of the brain are active at all times Interested in small changes in blood flow during cognitive processes Need to use a good control condition to isolate the cognition-related activity

Example of Subtractive Approach- Peterson, Fox, Posner, Mintun, & Raichle (1989) -Experimental conditions

1) Subjects stared at a crosshair on a computer monitor while their brain activity was monitored via PET imaging 2) Common English nouns appeared on the screen (visual), or were heard over earphones (auditory). The presentation rate was 40 words a minute. 3) The subjects were asked to speak the words that they saw or heard. 4) The subjects were asked to say aloud a use appropriate for the noun they either viewed or heard (e.g., if the word was ‘hammer’ an appropriate response would be ‘hit’)

Example of Subtractive Approach-Subtractions

Hearing words: Condition 2 (Auditory) – Condition 1 Seeing words: Condition 2 (Visual) – Condition 1 Speaking words: Condition 3 – Condition 2 Generating words: Condition 4 – Condition 3

Electroencephalography (EEG)

Measures brain electrical activity at the scalp from the rapid post-synaptic potential changes of of pyramidal cells in the cortex Dozens of electrodes on the scalp Can’t learn what individual neurons are doing or pinpoint exact are of neural activity Localize population of neurons and measure their activities with excellent temporal accuracy

MRI

Uses responses of atoms to strong magnetic fields to form images of structure in the brain

Event related potential (ERP

Created by averaging together many EEG trials time locked top a specific event Tells us about temporal processing of a stimulus

Magnetoencephalography MEG

A technique similar to eeg that measures changes in magnetic activity across populations of many neurons in the brain Has the same high temporal resolution as EEG, but better spatial resolution Provides good measure of neuronal timing Shows where in the brain neurons are. Most active Shows that very small changes in local magnetic fields accompany the small electrical changes that take place when a neuron fires - use small devices to measure these tiny magnetic field changes Simple and cheap

EEG vs Meg

EEG: Relatively inexpensive Portable Equivalent: Safe/non-invasive Very high temporal resolution (1 ms accuracy) MEG Better spatial resolution (though not as good as fMRI)