Chapter 2-cognitive Neuroscience Flashcards
Cognitive Neuroscience
- the study of the physiological basis of cognition
- involves an understanding of the nervous system and the individual units that comprise that system
Nerve net
Early concept of interconnected neurons creating a nerve net (similar to a highway network)
This allows for almost non stop continuous communication of signals throughout the network
Neuron doctrine
- Contradicts the nerve net
- Ramon y Cajal
- individual nerve cells transmit signals and are not continuously linked with other cells
Neurons
Cells specialized to receive and transmit information in nervous system
Cell body
Contains mechanisms to keep cell alive
Axon
Tube filled with fluid that transmits electrical signal to other neurons
Dendrites
Multiple branches reaching from the cell body, which receives information from other neurons
Sensory receptors
Specialized to respond to information received from the senses
Action potential
- Neuron receives signal from environment
- information travels down the axon of that neuron to the dendrite of another neuron
- all or none propagation
Measuring action potentials
- microelectrodes pick up electrical signal
- placed near axon
Measuring action potentials
- size is not measured: it remains consistent
- the rate of firing is measured:
Low intensity stimulus: slow firing
High intensity stimulus: fast firing
Synapse
Space between axon of one neuron and dendrite or cell body of another
When the action potential reaches the end of the axon, synaptic vesicles open and release chemical neurotransmitters
Neurotransmitters
Chemicals that affect the electrical signal of the receiving neuron, cross the synapse and bind with the receiving dendrites
Excitatory neurotransmitter
Increases chance neuron will fire
Inhibitory neurotransmitter
Decreases chance neuron will fire
Definition of the mind
A system that creates representations of the world, so that we can act on it to achieve goals
Principle of neural representation
Everything a person experiences is based on representations in the person’s nervous system
Feature detectors
Huber and Wiesel research with visual stimuli in cats
Feature detectors are neurons that respond best to a specific element
Experience-dependent plasticity (feature detectors)
The structure of the brain changes with experience
Kittens exposed to vertical only stimuli over time could only perceive verticals in normal stimuli
-demonstrated that perception is determined by neurons that fire to specific qualities of a stimulus
Hierarchical Processing
When we perceive different objects, we do so in a specific order that moves from lower to higher areas of the brain
The ascension from lower to higher areas of the brain corresponds to perceiving objects that range from lower (simple) to higher levels of complexity
Specificity coding (grandma cell)
Representation of a stimulus by the firing of specifically tuned neurons specialized to respond only to a specific stimulus
Population coding
Representation of a stimulus by the pattern of firing of a large number of neurons
All neurons fire but in different patterns
Sparse coding
Representation of a stimulus by a pattern of firing of only a small group of neurons, with the majority of neurons remaining silent
Localization of Function
- specific functions are served by specific areas of the brain
- cognitive functioning declines in specific ways when certain areas of the brain are damaged
What part of the brain contains mechanisms responsible for most cognitive functions
Cerebral cortex (3mm thick layer covering the brain)
Localization of Function: Language
Language production is impaired by damage to Broca’s area (frontal lobe)
Language comprehension is impaired by damage to Wernicke’s area (temporal lobe)
Localization of Function: Perception
Primary receiving areas for the senses:
- occipital lobe: vision
- parietal lobe: touch, temp, pain
- temporal lobe: smell, taste
Coordination of information received from all senses:
-frontal lobe
Double Dissociation
-when damage to one part of the brain causes function A to be absent while function B is present, and damage to another area cause function B to be absent while Function A is present
Allows us to identify functions that are controlled by different parts of the brain
Position Emission Tomography (PET)
- blood flow increases in areas of the brain activated by a cognitive task
- radioactive tracer is injected into person’s blood stream
- measure signal from tracer at each location of the brain
- higher signals indicate higher levels of brain activity
Subtraction technique
Measures brain activity before and during stimulation presentation
Difference between activation determines what areas of the brain are active during manipulation
Functional magnetic resonance imaging (fMRI)
Measure brain activity by identifying highly oxygenated hemoglobin molecules
Activity recorded in voxels (3-D pixels)
Method: Event-Related Potential (ERP)
Neuron “firing” is an electrical event
Measure electrical activity on the scalp and make inferences about underlying brain activity
Averaged over a large number of trials to calculate ERPs
Advantage: continuous and rapid measurements
Disadvantage: does not give precise location
Localization demonstrated by brain imaging
- Fusiform face area (FFA) responds specifically to faces. Damage to this area causes prosopagnosia (inability to recognize faces)
- Parahippocampal place area (PPA) responds specifically to places (indoor/outdoor scenes)
- Extrastriate body area (EBA) responds specifically to pictures of bodies and parts of bodies
Central principle of cognition
Most of our experience is multidimensional
In addition to localization of Function, specific functions are processed by many different areas of the brain (concepts are complementary)
Neural networks
Interconnected areas of the brain that communicate with each other
Connectome
Structural description of the network of elements and connections forming the human brain
Based on detection of how water diffuses along the length of nerve fibres
Structural connectivity
The brains “wiring diagram” created by axons that connect brain areas
As unique to individuals as fingerprints
Functional connectivity
How groups of neurons within the connectome function in relation to types of cognition
Determined by the amount of correlated neural activity in two brain areas
Resting-state functional connectivity
Use task related fMRI to determine a brain location associated with carrying out a specific task. This location is called the seed location.
Measure the resting state fMRI at the seed location which is called the time series response because it indicates how the response changes over time.
Measure the resting state fMRI at another location, which is called the test location.
Calculate the correlation between the seed and test location response
Six common functions determined by Resting State fMRI
- visual: vision and visual perception
- Somato-motor: movement and touch
- Dorsal Attention: attention to visual stimuli and spatial locations
- Executive control: higher level cognitive tasks involved in working memory and directing attention during tasks
- Salience: attending to survival-relevant events in the environment
- Default mode: mind wandering, and cognitive activity related to personal life-story, social functions, and monitoring internal emotional states
Dynamics of cognition
The flow and activity within and across the brain’s functional networks change based on conditions
Change within and across network is constant
Default mode network
Mode of brain function that occurs when it is at rest (activation at rest is higher than at tasks)
One of the brain’s largest networks
