Chpt 2 - Cognitive Neuroscience Flashcards
(40 cards)
What is cognitive neuroscience?
The study of the PHYSIOLOGICAL basis of cognition
Why are both behavioral and physiological experiments necessary when studying the mind?
We need to use different LEVELS OF ANALYSIS to study the mind.
Levels of analysis
The idea that a topic can be studied in a number of different ways, with each approach contributing its own dimension to our understanding of the topic.
Neurons
Small units in the brain that create and transmit information about what we experience and know.
Nerve net theory
- Conceptualized that the microstructure of the brain was a continuously interconnected network
- Signals could be conducted uninterrupted through the network.
Neuron doctrine
- Individual units called neurons are the basic building blocks of the brain
- Each neuron transmits signals in the nervous system (and are NOT continuous with other cells, as proposed by nerve net theory)
Name the basic parts of a neuron.
- Cell body: Metabolic center of the neuron, contains mechanisms to keep the cell alive.
- Dendrites: Branch out from the cell body to RECEIVE signals from other neurons.
- Axons (nerve fibers): Long processes that TRANSMIT signals to other neurons.
Synapse
Gap between the end of a neuron’s axon and the dendrites or cell body of another neuron.
Neural circuits
Groups of interconnected neurons (for specific functions)
Receptors
Specialized neurons that pick up information from the environment (e.g. Neurons in the eye, ear, skin)
How are action potentials recorded?
- MICROELECTRODES pick up electrical signals at the electrode tip and conduct these signals back to a recording device.
- The tip of a RECORDING ELECTRODE is placed inside the neuron, and a REFERENCE ELECTRODE is put at some distance from it (so that it is not affected by the electrical signals).
- The difference in electrical charge between the two electrodes is fed into the computer.
Resting potential
- Difference between the recording and reference electrodes is -70 millivolts (one millivolt is 1/1000 of a volt) –> the inside of the neuron is 70 mV more negative than the outside.
- This value stays the same as long as there are no signals in the neuron.
What happens when a neuron’s receptor is stimulated? What is an action potential?
- When the neuron’s receptor is stimulated, an impulse passes through the recording electrode, and the the charge inside the axon rises to +40 mV.
- As the impulse moves past the recording electrode, the charge inside the axon starts to become negative again.
- This impulse is called the ACTION POTENTIAL,and lasts about 1 millisecond.
Do action potentials change in height/shape when they travel down the axon? (Hint: It needs to travel across a distance)
- NO, action potentials remain the same shape and height as they travel down the axon.
- This property makes action potentials GREAT FOR SENDING SIGNALS OVER A DISTANCE, because once it starts at one end of an axon, the signal will still be the same size when it reaches the other end of the axon!
How does the intensity of a stimulus affect the action potential?
- Shape and height of action potential remains the same
- RATE of nerve firing (number of action potentials that travel down the axon per second) is what changes! (i.e. Pressure that generates “crowded” electrical signals feels stronger - stronger pressure on skin, brighter lights)
The principle of neural representation
Everything that a person experiences is based on representations in the person’s nervous system (rather than direct contact with stimuli)
Example: John sees Mary because of the way that she is represented by action potentials in the brain, rather than because of direct contact with her.
How are images represented/how do we see?
- Light is reflected off the object
- The image of the object is focused on your retina (layer of neurons that line the back of your eye)
- Receptors in the retina transform the image into electrical signals
- These signals travel through the retina and leave the back of the eye in the optic nerve.
- The signal eventually reach the visual cortex (the area in the back of the brain that receives signals from the eye).
If all nerve impulses/action potentials are the same height and shape, how can these impulses stand for different qualities?
- Representation by single neurons - feature detectors and neurons that respond to complex stimuli
- Sensory coding - population coding and sparse coding by groups of neurons
How has research involving RECORDING FROM SINGLE NEURONS answered the question of, “How can we perceive different stimuli if all action potentials are the same shape and height?”
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Feature detectors: Neurons that respond to specific stimulus features, such as orientation, movement and length
(e. g. Some neurons fire specifically in response to straight lines) –> Therefore, many neurons work together to create a representation of a tree! - Neurons that respond to complex stimuli/hierarchical processing: Neurons in the visual cortex that process simple stimuli send their axons to increasingly high levels of the visual system in order to process increasingly complex visual stimuli.
How has research about SENSORY CODING answered the question of, “How can we perceive different stimuli if all action potentials are the same shape and height?”
“The problem of sensory coding” - How does neural representation work for our senses/how do neurons represent various aspects of our environment?
FINDINGS:
- The explanation is likely NOT specificity coding
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Specificity coding
An object is represented by the firing of a specialized neuron that only responds to that object
- This is an unlikely explanation because:
- Although there are neurons that respond specifically to faces, these neurons respond to many different faces, not just one particular one!
- There are too many faces and objects in this world to have one neuron dedicated to a specific face/object!
Population coding
Representation of a certain object due to a pattern of firing of a LARGE number of neurons
- Allows for a wide range of stimuli to be represented, as large groups of neurons can create a large number of different patterns!
Sparse coding
Representation of a certain object due to a pattern of firing of only a SMALL group of neurons, while the majority of neurons remain silent.
- Neurons can respond to more than one stimulus, but more strongly to some than others.
What is the localization of function?
Specific functions are served by certain areas of the brain.
