COMPLETED Sensation and perception chapter 2

Elaborate how one may measure an action potential

Electrical signals are recorded from the axons (or nerve fibers) of neurons using 2 small electrodes (a recording electrode and a reference electrode) to pick up the signals. They are connected to a meter that records the difference in charge between the tips of the two electrodes. The difference is then displayed on a computer screen.

Describe the three basic principles underlying action potentials

1. It is a propagated response. Once the response is triggered, it travels all the way down the axon without decreasing in size. Important because it enables neurons to transmit signals over long distances.

2. Remains the same size regardless of the intensity of the stimulus.

3. Action potentials that occur in the absence of stimuli from the environment are called spontaneous activity. It establishes a baseline level of firing for the neuron.

Describe the step by step process of how an action potential leads to the action potential of neurotransmitters into the synaptic cleft.

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Intracellular

Inside the neuron

Extracellular

Outside of the neuron

Differentiate between the different notions of sensory coding

1. Specificity coding: involves a specific stimulus responding to a specific stimulus in the environment 

2. Sparse coding: involves small number of specific neurons responding to a specific stimulus in the environment

3. Population coding: involves a larger number of neurons firing in specific ways (patterns) to represent an environmental stimulus.

Discuss the notion of localization of function  and contrast it with distributed representation

Localization of function means certain brain areas are mainly responsible for certain jobs. Distributed representation means most complex abilities use many brain areas working together, not just one area.

So:

• Localization = one area has a specific main function.

• Distributed representation = several areas work together as a network.

How can scientists determine the different locations associated with a perceptual experience if they are distributed?

Scientists use fMRI to see which brain areas are active at the same time. If several areas show similar activity patterns, scientists assume those areas are working together to process the same experience.

Neurons

cells specialized to transmit electrochemical signals in the body

What are the key components of the neuron?

Cell body, dendrites and axon.

What does the cell body do?

Contains mechanisms to keep the cell alive

What do the dendrites do?

Branch out from the cell body to receive electrical signals from other neurons

What does the axon do?

It is filled with fluid to conduct electrical signals

What are sensory receptors?

Neurons specialized to respond to environmental stimuli

What is happening inside and outside the neuron during AP? What’s happening

As the AP travels down the axon, K+ is more inside the cell than sodium is, as the AP reaches the site on the axon, you see the NA+ channels open causing the sodium to rush into the cell. as that happens there is depolarization. then the potassium channels open which accesses the potassium to escape. The sodium potassium pump then helps return the cell back to its resting state. As we reach the end of the axon at the terminals, the calcium channels open which causes calcium to rush into the terminals. Then the synaptic vesticles move towards the terminals and fuse to the terminal membrane. Then the vesticles release NTs into the synaptic cleft.

What happens at the postsynaptic neuron?

NTs attach to the postsynaptic neuron

What happens at the synaptic cleft?

NTs cross the synaptic cleft to pass signals from one nerve cell to the next

What happens at the axon terminal?

An electrical nerve signal is changed into a NT and is passed on to the next cell

What are some mechanisms of the action of drugs on neural processes?

1. alter the synthesis of NTs.

2. reduce/increase the release of NTs (ex. Alcohol with Glutamate and GABA)

3. prevent storage of NTs in synaptic vesicles.

4. block the reuptake (or the degradation of them; ex. Cocaine with Dopamine) of NTs from the synaptic cleft.

5. Mimic NTs (agonists; ex. Marijuana with Cannabinoids) or prevent NTs from binding (receptor antagonists; ex. antipsychotics).

What is the stimulus-physiology method?

Recording how a neuron responds to a stimulus.

How is electrical activity in an axon measured?

One electrode is placed inside the axon and another outside, and the difference in charge is recorded.

What is the resting potential of a neuron?

-70 mV

What ions are mainly inside the neuron?

K+ and Cl-

What ions are mainly outside the neuron?

Na+

What is an action potential?

A rapid electrical signal that travels down the axon

How long does an action potential last?

1 milisecond

What is a propagated response?

An action potential does not lose strength as it travels down the axon.

What happens during depolarization?

Sodium channels open and Na+ enters the neuron, making it more positive.

What happens to the voltage during depolarization?

It changes from about -70 mV to +40 mV

What happens during depolarization/hyperpolarization?

Sodium channels close, potassium channels open, and K+ leaves the neuron

What does the sodium potassium pump do?

Pumps sodium out of the neuron and potassium into the neuron.

Are some action potentials stronger than others?

No. Action potentials are all approximately the same strength.

How does the brain represent stronger stimuli?

By changing the rate and pattern of neuron firing.

What happens to firing rate as stimulus intensity increases?

Firing generally becomes faster and more regular.

What is the refractory period?

The short recovery period after an action potential when the neuron cannot immediately fire again.

What are NTs?

Chemicals that carry signals from one neuron to another.

Where are NTs stored?

In synaptic vesicles.

What happens when the AP reaches the axon terminal?

Calcium channels open and calcium enters the terminal.

What does calcium cause at the axon terminal?

Synaptic vesicles release neurotransmitters.

What is the synapse?

The small gap between neurons.

What happens after NTs enter the synapse?

They bind to receptors on the postsynaptic neuron

What is an excitatory response?

A response that makes the postsynaptic neuron more positive and more likely to fire. Depolarization happens

What is an inhibitory response?

A response that makes the postsynaptic neuron more negative and less likely to fire. Hyperpolarization happens

What is an agonist?

A substance that mimics or increases the effect of a neurotransmitter.

What is an antagonist?

A substance that blocks a neurotransmitter from activating its receptor.

What is sensory coding?

How neurons represent information about the environment.

What is specificity coding?

One specific neuron responds to one specific stimulus.

What is sparse coding?

A small group of neurons represents a particular stimulus.

What is population coding?

A stimulus is represented by the firing pattern of many neurons.

What is localization of function?

The idea that certain brain areas are specialized for certain functions.

Who was Franz Joseph Gall?

An early researcher who believed different brain areas had different functions.

What was phrenology?

The false idea that personality could be determined from the shape of the skull.

What is modularity?

The idea that particular brain areas are specialized for processing certain kinds of information.

What is the parahippocampal place area?

A brain area that responds strongly to places and scenes.

What is the extrastriate body area?

A brain area that responds strongly to bodies and body parts.

What is the fusiform face area?

A brain area that responds strongly to faces

What can damage to the FFA cause?

Prosopagnosia, difficulty recognizing faces

What is neuropsychology?

Studying how brain damage affects behavior and mental abilities.

What is Broca’s aphasia?

Difficulty producing speech, usually associated with damage to the left frontal lobe.

What is wernicke’s aphasia?

Difficulty understanding speech, usually associated with damage to the left temporal lobe

What is an advantage of case studies involving brain damage?

They help identify brain areas important for specific mental abilities.

What is another advantage of case studies?

They show connections between brain function and behavior.

What is a disadvantage of brain-damage case studies?

Researchers cannot control where the damage occurs.

Why can brain damage be difficult to interpret?

Damage may affect several brain areas at once.

What other limitation do case studies have?

Researchers can only study the areas that happen to be damaged.

What is distributed processing?

Multiple brain areas working together to perform a function.

How can localization and distributed processing both be true?

Certain areas may specialize in particular jobs, but several specialized areas often work together.

What does fMRI research show about processing?

Many stimuli activate distributed networks across multiple brain areas.

What is the subtractive method in fMRI?

Comparing brain activity during a test condition with activity during a baseline condition.

What is fMRI?

A brain-imaging technique that uses magnetic fields to measure changes related to blood flow.

In an fMRI, what does greater blood flow in an area generally suggest?

greater brain activity in the area

What is PET?

A brain-imaging technique that uses a small amount of radioactive tracer to measure brain activity and blood flow.

What is structural connectivity?

The physical neural connections between different brain areas.

What does structural connectivity create?

A map of the brain's physical wiring.

How is structural connectivity commonly studied?

With MRI-based methods.

What is functional connectivity?

How activity in different brain areas is related or synchronized.

When might brain areas show functional connectivity?

During a behavior, while viewing a stimulus, or even while resting.

What methods are commonly used to measure functional connectivity?

Task-state fMRI and resting-state fMRI.

What is resting-state functional connectivity?

Using fMRI to see which brain areas show similar activity while a person is resting.

What is the goal of resting-state functional connectivity?

To identify brain areas that work together as a network.

What is a seed location?

A brain area chosen as the starting point for comparison.

What is a test location?

Another brain area whose activity is compared with the seed area.

What does a high correlation between the seed and test area mean?

The areas have a strong functional connection.

Broca's and Wernicke's areas provided early evidence for which concept?

Modularity

_______is the "road map" of fibers connecting different areas of the brain.

Structural connectivity

In sensory physiology, understanding how physical processes like nerve impulses become transformed into perceptual experiences is referred to as _____.

the mind–body problem