Chpt 2 - Cognitive Neuroscience

Question 1

What is cognitive neuroscience?

Answer 1

The study of the PHYSIOLOGICAL basis of cognition

Question 2

Why are both behavioral and physiological experiments necessary when studying the mind?

Answer 2

We need to use different LEVELS OF ANALYSIS to study the mind.

Question 3

Levels of analysis

Answer 3

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.

Question 4

Neurons

Answer 4

Small units in the brain that create and transmit information about what we experience and know.

Question 5

Nerve net theory

Answer 5

• Conceptualized that the microstructure of the brain was a continuously interconnected network
• Signals could be conducted uninterrupted through the network.

Question 6

Neuron doctrine

Answer 6

• 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)

Question 7

Name the basic parts of a neuron.

Answer 7

1. Cell body: Metabolic center of the neuron, contains mechanisms to keep the cell alive.
2. Dendrites: Branch out from the cell body to RECEIVE signals from other neurons.
3. Axons (nerve fibers): Long processes that TRANSMIT signals to other neurons.

Question 8

Synapse

Answer 8

Gap between the end of a neuron’s axon and the dendrites or cell body of another neuron.

Question 9

Neural circuits

Answer 9

Groups of interconnected neurons (for specific functions)

Question 10

Receptors

Answer 10

Specialized neurons that pick up information from the environment (e.g. Neurons in the eye, ear, skin)

Question 11

How are action potentials recorded?

Answer 11

• 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.

Question 12

Resting potential

Answer 12

• 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.

Question 13

What happens when a neuron’s receptor is stimulated? What is an action potential?

Answer 13

• 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.

Question 14

Do action potentials change in height/shape when they travel down the axon? (Hint: It needs to travel across a distance)

Answer 14

• 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!

Question 15

How does the intensity of a stimulus affect the action potential?

Answer 15

• 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)

Question 16

The principle of neural representation

Answer 16

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.

Question 17

How are images represented/how do we see?

Answer 17

1. Light is reflected off the object
2. The image of the object is focused on your retina (layer of neurons that line the back of your eye)
3. Receptors in the retina transform the image into electrical signals
4. These signals travel through the retina and leave the back of the eye in the optic nerve.
5. The signal eventually reach the visual cortex (the area in the back of the brain that receives signals from the eye).

Question 18

If all nerve impulses/action potentials are the same height and shape, how can these impulses stand for different qualities?

Answer 18

1. Representation by single neurons - feature detectors and neurons that respond to complex stimuli
2. Sensory coding - population coding and sparse coding by groups of neurons

Question 19

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?”

Answer 19

1. 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!
2. 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.

Question 20

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?”

Answer 20

“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

-

Question 21

Specificity coding

Answer 21

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!

Question 22

Population coding

Answer 22

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!

Question 23

Sparse coding

Answer 23

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.

Question 24

What is the localization of function?

Answer 24

Specific functions are served by certain areas of the brain.

Question 25

How did neuropsychology demonstrate localization of function?

Answer 25

Neuropsychology - the study of behavior of people with brain damage

• Studying what these people can or cannot do sheds light on whether a particular brain part is specialized to serve a particular function.

Question 26

How does demonstrating a DOUBLE DISSOCIATION help researchers reach more definite conclusions about brain functions?

Answer 26

Double dissociation: Method of proving the function of specific brain regions (Must show that damage to part A of brain causes function A to be absent while function B is present, and that damage to part B of brain causes function B to be absent while function A is present)

Significance:
- Shows that functions A and B are served by different mechanisms/parts of the brain, and that they operate independently of each other.

Example:
- Finding a patient who can recognize faces, but not objects, and another patient who can recognize objects but not faces.

Question 27

How does recording from single neurons demonstrate localization of function?

Answer 27

Measuring the response of neurons in different brain areas to different stimuli.

• Usually conducted on animals.

Question 28

Magnetic resonance imaging (MRI)

Answer 28

• Creates images of brain structures

- BUT doesn’t show neural activity

Question 29

Functional magnetic resonance imaging (fMRI)

Answer 29

• Measures blood flow (how strongly hemoglobin responds to a magnetic field) as an indicator of brain activity.
• Allowed researchers to determine how various types of cognition activate different brain areas.
• Activity is recorded in the unit voxels (small units of analysis created by the fMRI scanner)

Question 30

How have brain imaging experiments supported the theory of “localization of function”?

Answer 30

• Used still pictures to measure brain areas that best respond to faces, places and bodies.
• Measured brain responses to movies (many different stimuli) in order to create a brain map indicating the stimuli that activate different brain areas

Question 31

Distributed representation

Answer 31

Specific cognitive functions activate many areas of the brain.

• This principle applies to perception, memory and other cognitive processes –> shows the GENERALITY of cognitive mechanisms –> Different cognitive functions often involve similar mechanisms.
• Cognitive processes are created by many specialized brain areas that work together to create a distributed pattern of activity, in order to create the different components of a particular cognition (i.e. Coordinate recognition, response, action etc.)

Question 32

How does the “localization of function” theory complement the “distributed representation” theory?

Answer 32

• Localization of function theory suggests that there are certain areas of the brain that serve specialized functions (e.g. The fusiform face area is responsible for perceiving faces)
• However, other brain areas are also activated when you perceive the face (e.g. To evaluate the attractiveness) and when you RESPOND to the face (e.g. I recognize this person, I should say hi!)

Question 33

Neural networks

Answer 33

Groups of neurons or structures that are connected together.

• Reinforces the idea that different brain areas work together to create different cognitions.

Example: The pain matrix
- A number of connected structures that are involved with the different parts of the pain experience –> sensory aspects, emotional aspects, evaluation of the significance of pain for ongoing behavior.

Question 34

How has neuroscience contributed to the understanding of the mind?

Answer 34

1. Determining WHERE different capacities occur in the brain (studying the “geography of the brain.”)
2. Showing that proposals based on behavioral research can be supported by the findings of physiological research.

Question 35

Broca’s area

Answer 35

Area in the left frontal lobe specialized for SPEECH (producing language)

Question 36

Wernicke’s area

Answer 36

Area in the temporal lobe responsible for COMPREHENDING language

Question 37

Temporal lobe

Answer 37

Hearing

Question 38

Parietal lobe

Answer 38

Perceptions of touch, pressure and pain

Question 39

Frontal lobe

Answer 39

Receives signals from all senses

Responsible for coordination of the senses, and higher cognitive functions (thinking, problem-solving)

Question 40

Occipital lobe

Answer 40

Vision