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Questions and Answers
What is the primary requirement for detecting an electrical signal at the scalp using EEG?
Which of the following categories of oscillation frequencies corresponds to cognitive or physiological functions?
What are K complexes in the context of sleep-wake cycles?
Which statement is true regarding event-related potentials (ERP)?
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How are electrodes placed in the 10-20 system for an EEG?
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Which oscillation band is characterized by the fastest activity levels?
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What is a disadvantage of oscillation-based analyses in EEG?
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What is the role of synchrony in neuron communication?
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What are the two main representations described in the content?
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Which aspect of the action potential indicates the level of firing?
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How does rate coding differ from temporal coding?
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Which of the following is true regarding single-neuron recordings?
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In terms of EEG, what does the technique primarily measure?
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What type of information is electrical activity in the brain primarily linked to according to the EEG technique?
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Which characteristic of neural information transmission is limited by the neuron's location?
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What distinguishes the two electrophysiological techniques, single-neuron recordings and EEG?
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Study Notes
Mental Representation
- Mental Representation is the process by which our brain copies and simulates properties from the outside world (like colors, objects, knowledge) in its cognitive processes
- Neural Representation is how those properties are manifested as signals within the brain, reflected by different neuron firing rates in response to different stimuli
Neural Coding
- Action potential amplitude is fixed and does not reflect the strength of the signal.
- Neural information is coded and transmitted through firing patterns, not stored in a single neuron.
- Firing pattern, interactions between neurons, and firing rate all contribute to information processing.
- Neuron location limits the information it can transmit.
Rate vs Temporal Codes
- Rate coding focuses on the frequency of neuronal responses. Greater firing rate indicates quicker action.
- Temporal coding utilizes the synchronicity of neuronal responses. Neurons firing together encode information differently than those firing separately.
Two Main Electrophysiological Techniques
Single-Neuron Recordings
- Invasive technique with electrodes placed directly in or near a neuron (inside the skull).
- Offers excellent spatial and temporal resolution.
- Primarily uses rate coding to measure action potential frequency per second for individual neurons.
Electroencephalography (EEG)
- Non-invasive technique using electrodes placed on the scalp.
- Provides poor spatial resolution but good temporal resolution.
- Employs temporal coding by measuring synchronous electrical activity of millions of neurons, capturing dendritic currents.
Single-Neuron Recording
- Measures action potentials using a tiny electrode inserted into the axon (intracellular) or positioned outside the axon membrane (extracellular).
- Records neural activity but does not stimulate it.
EEG: Electroencephalography
- Measures post-synaptic electrical currents rather than action potentials.
- Used in cognitive neuroscience to study:
- Different frequency bands of brain oscillations and their relation to cognitive functions.
- Event-related potentials (ERPs).
EEG: Electrode Placement
- Uses the 10-20 system of electrode placement, with electrodes situated 10% or 20% apart based on skull surface area.
EEG: Anatomical Types
- Electrodes are categorized based on their location:
- F: Frontal
- C: Central
- P: Parietal
- O: Occipital
- T: Temporal
- Fp: Frontal polar
- Z: Zero (midline)
Detecting Electrical Signals at the Scalp
- Requires a sufficient number of neurons to generate a strong enough electrical field.
- The neurons need to be aligned parallel to each other so that their activity adds up instead of cancelling out.
Neuron Synchrony
- Neurons firing at the same rate can synchronize their activity.
- Synchronous neurons can communicate by influencing each other’s excitability.
- Asynchronous neurons cannot communicate.
- Millions of neurons firing synchronously create a wave-like structure detectable at the scalp.
Oscillations Detected by EEG
- Neurons tend to fire in synchrony at specific frequencies.
- These frequency ranges are categorized into five bands:
- Delta
- Theta
- Alpha
- Beta
- Gamma
Oscillation Bands and the Sleep-Wake Cycle
- Different oscillation frequencies characterize various sleep-wake stages.
- Examples of micro-events in oscillations:
- K complexes: Large waves that stand out and often occur in response to stimuli (like sounds). They help maintain sleep.
- Sleep spindles: Brief bursts of fast activity that increase and then decrease rapidly. Both types of oscillations link to memory consolidation.
Disadvantages of Oscillation-Based Analyses
- It’s difficult to distinguish task-related activity from the spontaneous activity of other neurons.
Event-Related Potentials (ERPs)
- A method analyzing EEG recordings by averaging the EEG signal over multiple stimulus presentations.
- Positive peaks are denoted as "P" and negative peaks as "N."
- ERP can be used to study cognitive processes like face recognition by comparing differences in peak amplitudes between different groups of people.
Structural Imaging
- Measures spatial distribution of different brain tissue types (like skull, gray matter, white matter, cerebrospinal fluid).
- Different tissue types have unique properties.
- Used to create static, 3D maps of brain structures.
Computerized Tomography (CT)
- Measures x-ray absorption.
- Areas of high density (like bone) absorb more x-rays and appear bright, while areas of low density (like air) absorb less and appear dark.
- Provides a detailed image of the skull and internal structures.
Magnetic Resonance Imaging (MRI)
- Uses magnetic fields and radio waves to create images of the brain.
- Provides better resolution compared to CT scans.
- Different types of MRI: structural MRI, diffusion-tensor imaging (DTI), functional MRI (fMRI).
Structural MRI
- Provides a structural image of the brain tissue.
Diffusion-Tensor Imaging (DTI)
- Measures the direction and extent of water diffusion in brain tissue.
- Used to visualize white matter pathways and their connectivity.
Functional Magnetic Resonance Imaging (fMRI)
- Measures brain activity by detecting changes in blood flow.
- Hemodynamic response: increased blood flow to active brain regions leads to stronger fMRI signal.
- Offers good spatial resolution and reasonable temporal resolution, but slower than EEG.
- Provides information about brain areas involved in specific tasks.
- Can be used to identify brain regions that activate during cognitive tasks.
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Description
Explore the fascinating world of mental and neural representation. This quiz covers the mechanisms through which our brain simulates external properties and how neural coding shapes our perceptions. Challenge your understanding of rate and temporal coding in information processing!
