Chapter 2: Cognitive Neuroscience Flashcards
What are the levels of analysis for cognitive functions/ Principles of the nervous system
- neuronal representation: how neurons represent information
- localized representation: how specific brain regions represent information
- distributed representation: how multiple brain regions represent information
- neural networks (DMN): how large networks of brain regions represent information
What is a neuron?
- the basic unit of the brain and the nervous system
How many neurons and connections do we have in the brain?
- ~80-100 billion neurons
- over ten trillion connections
What part of the neuron is the receiving end and which one is the transmitting end?
- Receiving end: dendrite
- transmitting end: axon
Do neurons touch each other ?
no
- they have gaps between them called synapses
- the communicate using chemical signals called neurotransmitters
What role does dopamine play?
- reward processing and addiction
what role does glutamate play?
- learning
what role does GABA play?
- inhibition
Afferent versus Efferent
- afferent: sensory information, incoming information
- efferent: motor output
What is the membrane potential at resting potential?
(-70mV)
What happens during the depolarization phase of an action potential
- when a neurotransmitter excites the neuron it results in moving towards a positive charge
- if this excitation crosses a threshold level, it triggers a large depolarization called an action potential
- reaches +40mV
What happens during the repolarization phase of an action potential
- after a neuron fires a signal, the neuron returns to resting potential
What happens during the hyperpolarization phase of an action potential
- becomes more negative before returning to resting potential
- (-80mV)
- inhibitory , less likely to fire an action potential
How does an action potential work
- the AP propagates to the end of the neuron and triggers the release of a NT which will affect other neurons
- the signal switches from electrical to chemical at terminal
- the prescence of myelination (glial cells) speeds up neural transmissions
Do Action Potentials vary in strength?
no they do not (this means they are binary)
- this means that every action potential Is the same height and shape
- what does change is the frequency of an action potential
What are the characteristics of strong stimuli regarding action potentials
- stronger stimuli are represented by a higher rate of firing
for example, stronger pressures on skin versus light pressure on skin
How long does it take for one action potential
aprox. 1ms ( 1/1000ms)
What does it mean for Action Potentials to be an all or none response
- this means that if the excitation a neuron exceeds a threshold level (50mV), it will trigger an action potential, though if it does not reach the threshold potential than there will not be an action potential
- either fires or it doesn’t
- INTENSITY DOES NOT CHANGE, ONLY FREQUENCY!!!!
What is the Principle of Neuronal Representation?
- all experiences are based on representations in the nervous system
- ex. some neurons respond to specific inputs like vision or hearing
What network of regions does memory involve
- hippocampus, temporal lobe, memory coding areas (visual areas)
What are the 3 components of Neuronal Representation?
- feature detectors
- neurons for complex stimuli
- sensory coding
What are Feature Detectors?
- the visual cortex has neurons which respond to specific types of stimuli (simple and complex cells)
- this is best understood in the visual system
Neurons that respond to specific stimuli from the external word including ? (3)
- orientations
- movements
- lengths
EXAMPLE - when you look at a tree you have different neurons in the Primary Visual Cortex fire in response to vertical aspects (trunk), diagonal, colour, movements and so on.
What are end-stopped cells?
- a type of neuron that responds to more complex features like a stimulus of a specific length moving in a specific direction
What is Hierarchical Processing?
- after a neuron fires, they code for simple features and then send the info off to more complex areas
- neurons which code for simple features (size, shape, movement) send inputs to higher regions containing neurons which code for complex features
- ex. faces
- simple to complex processing
What does the Fusiform Face Area (FFA) do?
Where is it located?
- its located in the temporal lobe, and specializes in facial recognition of both humans and animals.
What is sensory coding?
- this is how neurons represent various characteristics of the environment (this involves groups of neurons)
What are the 3 different kinds of sensory coding?
- Specificity Coding- specific neurons that respond to one stimulus
- Population Coding- all neurons respond to one stimulus
- Sparse Coding - subset of neurons respond to stimuli
What is Specificity Coding?
- these are neurons that only respond to one object or entity
- grandmother cells: neurons that respond to only one individual like your grandmother
- other examples: Jennifer Aniston cells, face specific neurons
What are the limitations of specificity coding
- this would mean that we would need separate neurons for every variation of every object which is not realistic because there is way to many variations
- neurons die constantly which would result in random loss of memories , which doesn’t happen
What is Population Coding?
- each object is represented by the firing of ALL neurons in a network
- can represent many different orientations, colours and aspects
- pattern of activation stays the same, loss of neurons would not change the rate of firing.
What are the limitations of Population Coding?
- this would take up way to much energy
- expensive
- prone to errors
What is Sparse Coding?
- an object is represented by pattern of firing of a subset of neurons while other remain silent
- used to represent information in visual, auditory and olfactory systems (eg. pitch of sound)
- most popular coding theory
What are population and sparse coding involved in? Explain how specific memories are stored in neuronal representation.
- perception
- representation of memory and higher cognitive functions like reasoning
- specific memories are stored as patterns of neuronal activations which are re-activated during retrieval.
Do we know how activation of neurons can result in a unified perception of an object or entity?
- no it is not fully understood.
- it is a combination of all types of coding
- there are no grandmother cells or conscious centre where all the neurons merge to create a unified perception for something
What Is Localized Representation
- the localization of function
- specific areas are served by specific areas of the brain
What does Broca’s Area specialize in?
Where is it located?
Whats another name for it?
- language production
- also called Brodmans Area 44 (BA44)
- located in the frontal lobe
What is Broca’s Aphasia?
- slow, laboured, ungrammatical speech due to damage in Broca’s area due to stroke or injury.
- results in choppy speech
- they are not able to make grammatically correct speech production but they do still make sense when they talk.
What does Wernicke’s Area specialize in?
Where is it located?
Whats another name for it?
- language comprehension
- Brodmans Area 22 in temporal area
Whats is Wernicke’s Aphasia
- Fluent and grammatically correct but incoherent
- these patients are unable to understand other peoples speech, match words with meanings or use the rules of grammar
- the intended speech of these patients is not what they say
What is the evidence for localization in the brain ?
- brocas and wernicke’s areas
- damage to occipital lobe can cause cortical blindness
- auditory cortex and hearing
- primary somatosensory cortex (perception of touch, pressure, pain)
- frontal lobes (thinking, problem solving, language production)
What Is prosopagnosia?
- the inability to recognize faces
- results from damage to the fusiform face area
How do fMRI’s work
- neural activation associated with oxygen and blood flow to brain areas
- our blood contains iron in our hemoglobin, de-oxygenated blood responds more strongly to magnetic fields than oxygenated blood
Parahippocampal Place Area shows fMRI activation with what?
- shows activation when viewing spatial layout
- for example: indoor and outdoor scenes, not objects
What is Distributed Representation
- involves several areas in the brain being involved in a specific task.
- even the simplest tasks are multidimensional
Evidence for Distributed Representation
- FFA
- Amygdala
- Temporal lobe
- Prefrontal Cortex
(for example, looking at a face involves identifying )
- the presences of a face: fusiform facial area
- emotions: amygdala
- intent/focus: temporal lobe
- attractiveness: prefrontal cortex
- familiarity: movement of facial parts
- memory
What is you Episodic Memory
- memory for personal events
What is your Semantic Memory
- memory for general knowledge
Does memory involve one or more brain areas?
- multiple brain regions activating together
What is Arcuate Fasciculus?
- brocas area and wernickes areas connecting together for language
What is Conduction Aphasia?
- patient has the inability to link speech comprehension and production even tho they can use both separately, but not together
- they are not able to answer a question or repeat
What are the Four principles of Neural Networks
- Structural Connectivity
- Functional Connectivity
- Dynamics of cognition
- Default mode network
What is Structural Connectivity
- the complex structural pathways that form the brains information highway
- the wiring diagram of the brain
- white matter connections connect brain regions to different brain regions
What is Functional Connectivity?
- how structural networks create functional pathways that serve different functions
- the extent to which neural activity in 2 brain regions are connected
How do you know if 2 areas are functionally connected
- when both are structurally connected information is passed from the first to the second (primary - secondary)
- when both are receiving inputs from another area (third?)
- they do not have to be structurally connected
What are the Dynamics of Cognition
- the pattern of activity across functional networks change in response to conditions
- eg. coffee- visual networks, attentional networks., motor networks, visuo-motor coordination
What is the Default Mode Network?
Does the DMN increase or decrease when a person is engaged in a task?
When is the DMN active
- some parts of the brain are active all of the time
- fMRI shows brain activity when at rest
- activity in DMN decreases when a person is engaged in a specific task
- DMN active during mind wandering
- DMN is vital for sleep, memory and creativity
