3 lecture 6

Question 1

how do Neurons send signals

Answer 1

using the highly controlled movement of ions along their concentration and electrical gradients

ions pass through specialized channels in the membrane
channels are proteins that open and close based on the voltage

Energy used to return the system back to where it started

Question 2

what does action potential read as

Answer 2

The action potential will read as 0 until the cell that it is measuring has a voltage which at that point it will read as 1, then when it passes it will reach 0 again

Question 3

what s the synapse

Answer 3

The connection between the terminal of one cell and the dendrite on the next cell is known as the synapse

Question 4

what happens at the synapse

Answer 4

At the synapse, the electrochemical wave or action potential is converted into a chemical signal

This chemical signal is released by the terminal of the sending cell (the pre-synaptic cell) and taken up by the receiving cell (post-synaptic cell)

Question 5

what are the steps of synapse

Answer 5

1) Voltage gated calcium channels in the terminal open
2) Calcium helps release neurotransmitters from the cell
3) Transmitter diffuses across the space between cells, then binds to receptors on the dendrites of a nearby cell
4) This binding to receptors does ALL KINDS OF THINGS

Question 6

There are many (many) kinds of neurotransmitters and neuroactive substances, what do they do

Answer 6

These all modulate a cell’s activity
They can affect the probability and timing of action potentials
–how much input will be needed to fire
–when the cell will fire relative to that input
–how many action potentials will be produced And so on

Question 7

what are the types of neurotransmitters

Answer 7

excitatory
inhibitory
modulatory

Question 8

what are 2 things to keep in mind about neurotransmitters

Answer 8

There are many (many) kinds of neurotransmitters and neuroactive substances
There are receptors for all of these different kinds of substances

Question 9

what is the neurotransmitter we will be focusing on

Answer 9

GABA

Question 10

what are EXCITATORY transmitters

Answer 10

We’ve talked about action potentials or spikes as being the currency of the brain –and there are lots of chemicals that can result in more spikes being produced (these chemicals are EXCITATORY transmitters)

Question 11

must a spike always be produced?

Answer 11

But it turns out that it can be just as important to not produce a spike as to produce one

INHIBITION is really important too

Question 12

what is a seizure

Answer 12

For example, seizures are just one consequence of a burst of too much excitatory activity

Question 13

what does GABA do

Answer 13

GABA is the main neurotransmitter ensuring that there isn’t just an action potential free-for-all going on in the brain

Rather than exciting a cell to produce a spike, GABA inhibits a cell and prevents a spike (or makes a spike harder to produce)
Often it does so by making the inside of the cell MORE negative
–e.g. instead of -70mV, it might lower it to -90mV

This means that instead of just needing a little nudge to get an action potential started, a cell might need a shove –i.e. the cell will need more or stronger input

Question 14

how does GABA do it

Answer 14

GABA receptors are chloride channels, the let chloride flow into the cell
Chloride is negative (Cl-)
When chloride enters the cell because of its concentration gradient, it lowers the resting potential

Question 15

what is Multisensory integration

Answer 15

This is the ability to pull together information from more than one sense at the same time
We actually do this all the time, without really thinking about it
But you can see the evidence of it when we do something called the McGurk Effect

Question 16

what animal uses a lot of Multisensory integration

Answer 16

the owl– for hunting
They are very good at localizing prey based on sound
They then orient to the prey (with their eyes) and swoop in to catch it

Question 17

how do owls do it

Answer 17

To do this, they have to have two maps in their brain, each recreating the world around them –one is a map based on the auditory or sound information
–one is a map based on the visual information

Not only do they have to have these maps, but they have to be in register
–a location in the auditory map should correspond to the same location in the visual map

This takes a lot of practice to get the maps to line up properly
but eventually they do and owls become amazing hunters

Question 18

what happens if we mess up one of the maps

Answer 18

Work by Eric Knudsen at Stanford has looked in detail at these maps
How do they get set up, that is, how does the brain not only create the maps but get them to correspond to each other
He also studies what happens if you alter the sensory input or the maps
For example, by putting prism goggles on the owls
The prisms shift where the target appears to be
Thus, if there’s a mouse straight ahead, it will look like it’s a few degrees to the right or left, depending on which glasses the owl is wearing
This means that the auditory and visual maps are not longer in register
So the owl has to learn (again) how to relate the sound and the visual signal
–it turns out that they can do this too, even if they are learning to do so as adults

Question 19

why is GABA critical for owls

Answer 19

GABA is critical for how the brain can create that second map

Question 20

how does GABA inhibit the maps

Answer 20

It turns out that the brain doesn’t write over or erase the old maps
The old ones are there, they are just silent, inhibited, while the new map is formed That inhibition is done by GABA
If you block GABA, both the old and new maps are present at the same time
When the prisms are taken off, GABA inhibits the new maps and the old ones are active again

Question 21

sum u p the information thus far

Answer 21

We have an all-or-none action potential that arrives at a terminal
That electrochemical signal gets turned into a chemical signal that can be more graded and complex than just all-or-none
–you can think of it as an analog rather than a digital signal

Question 22

what are the reasons for the greater complexity

Answer 22

The diversity of things that can happen when a transmitter binds to a receptor
The post-synaptic cell is integrating inputs from many many cells

Question 23

Where does that “sprinkling” of Na+ that helps open the Na+ channels comes from

Answer 23

not all of these inputs will result in a spike, they may just alter the potential a little bit, i.e. they provide some or all of that initial “sprinkling” of Na+

Question 24

what happens when the post-synaptic cell sums up the inputs and determines a response

Answer 24

Once that post-synaptic cell sums up the inputs and determines a response, we’re back to the all-or-none, 1s and 0s, “digital” signal: the action potential

Question 25

in general, how does information flow through the brain

Answer 25

In general, information comes in the middle/bottom part of the brain (sub-cortical)
It goes through the thalamus, kind of a relay station
It then goes to higher or more dorsal and lateral brain areas like the cortex
And gets processed within the cortex
Then the output of the cortex goes back down to areas that will execute behaviors

Question 26

One of the first stops for incoming sensory input is the what

Answer 26

thalamus

Question 27

what is the thalamus

Answer 27

relay station for information coming in and going out

Question 28

what are the subdivisions of the thamalus

Answer 28

There are many subdivisions of the thalamus,

• -they connect to different parts of the brain
• -are involved in different functions

Question 29

From the thalamus, signals travel to what

Answer 29

the cortex

Question 30

what is the cortex

Answer 30

Cortex refers to the outermost part of the brain

In mammals it is a layered structure: the cells are highly organized into layers and columns

Question 31

what does the cortex do

Answer 31

The cortex does a lot of higher-level processing
In fact, a lot of what the cortex does is to integrate information from multiple sources
–it is where your brain recreates the sensory world –it is where your brain makes decisions and plans movements
Like the thalamus, there are many subdivisions –some are concerned with sensory input (figuring out what or where a stimulus is)
–some are concerned with memory or recognition or decisions, things that aren’t simply reconstructing a stimulus
–some are concerned with determining how to respond, assembling a behavior

Question 32

how deep does the cortex go

Answer 32

not very deep at all, under it is all grayish area is full of axons
We call it white matter because the myelin on it makes it appear white in sections
They are all of the axons going to and from the cortex –The cortex has lots of connections to other parts of cortex as well as to underlying structures

Question 33

how do Sensory systems process sensory input

Answer 33

Sensory receptors turn external information into action potentials
Information gets taken apart at the sensory receptors, then progressively assembled at higher stages in the brain (the thalamus and cortex)

Question 34

how does vision aid with inputs

Answer 34

Photoreceptors in your retina turn light into action potentials
–The pattern of action potentials in your visual cortex recreates the visual scene

Question 35

how does hearing aid with inputs

Answer 35

• -Hair cells in your cochlea turn sound waves into action potentials
• -The pattern of action potentials in your auditory cortex indicates what and where a sound is

Question 36

how does smell aid with inputs

Answer 36

–Olfactory receptors in your nose bind to odorants (different receptors for different odorants), generate action potentials –olfactory cortex, and other cortical and memory areas (hippocampus) identify smell

Question 37

what is processing

Answer 37

what you do with the information
Do you approach a stimulus? Attack it? Run from it? Have sex with it? Eat it? Nurture it? Speak to it? Remember it?Many sub-cortical regions monitor your current and previous internal state (hypothalamus, preoptic area, amygdala, nucleus accumbens, septum, ventral pallidum, hippocampus)

Question 38

what do Cortical regions do

Answer 38

Cortical regions provide top-down information on what you should or can do, decision-making

Question 39

what does the hypothalamus so

Answer 39

regulates body funtion

Question 40

what does amygdala do

Answer 40

emotion

Question 41

what does hippocampus do

Answer 41

memory

Question 42

what is behaviour

Answer 42

anything to do with your response

Question 43

what is included in processing (brain parts)

Answer 43

cerebral cortex
hypothalamus
amygdala
hipocampus
basal ganglia, ventral palidum, nucleus accumbens

Question 44

what is included in behaviour (brain parts)

Answer 44

motor cortex, basal gangliam, cereballum

they are important for learning and altering movements.
They assemble a motor plan to enable you to execute a behavior

Question 45

what is Electroencephalography EEG

Answer 45

Uses electrodes to measure electrical activity along the
scalp
Pros: Non-invasive
People can move around during recording (for example, there are studies of people playing the guitar)
Cons:
Poor spatial resolution:
activity happens, but hard to determine exactly where
can say when a change in
Also, because the electrodes are on the surface, it’s difficult to say what deeper structures are doing

Question 46

what is Positron Emission Tomography PET

Answer 46

How it works:
Person or animal eats radioactively labeled sugar (fluorodeoxyglucose or FDG)
Sugar gets picked up by active cells (because busy cells need energy to run that Na+/K+ pump!)
Cells release radioactivity (cells release positrons, which collide with electrons and emit a gamma ray or gamma photons)
Gamma photons are detected by the scanner Active regions will give off a lot of radiation and “light-up” on the scanner

This means that active regions will give off a lot of radiation and “light-up” on the scanner

Question 47

what are the pros of PET

Answer 47

Much better resolution than the EEG and can see deeper structures better

Question 48

what are the cons f PET

Answer 48

The part where you have to eat radioactive sugar
Also, you can’t move around much in the scanner
Lots of PET studies involve watching or listening to things

Question 49

what is Functional Magnetic Resonance Imaging fMRI

Answer 49

Also involves a scanner, but this time it uses magnets
Basically, the scanner applies magnetic fields to the brain, then measures the energy emitted by different brain areas as they return to their normal, unmagnetized states
Because deoxygenated blood is more magnetic than oxygenated blood, areas that are more metabolically active (areas using more oxygen) emit different signals than less active areas

Question 50

what are the pros and cons of fMRI

Answer 50

fMRI offers reasonable resolution (and you don’t have to eat radioactive sugar!) but once again, participants can’t move around much

Question 51

what is Electrophysiology

Answer 51

Uses electrodes to measure the activity (action potentials) of neurons Can measure one or hundreds at the same time
In humans, this is often done prior to brain surgery
–it can help the surgeon determine where speech and language areas are located and avoid them
but mostly it’s done in animals

Question 52

what are the pros of Electrophysiology

Answer 52

high resolution, you can find out what a single cell is doing during behavior

Question 53

what are the cons of Electrophysiology

Answer 53

Cons: difficult to follow networks of cells

Question 54

what is 2-photon imaging

Answer 54

Fusion of green fluorescent protein (GFP) and a calcium indicator (calmodulin and myosin light chain)
Cells light up, literally, when calcium in present –like when voltage gated calcium channels open

Question 55

wat are the pros of 2-photon imaging

Answer 55

Can look at many cells at the same time (easier than with electrophysiology)

Question 56

what are the cons of 2-photon imaging

Answer 56

time course for cells to light up is slightly slower than real action potentials
Also difficult to measure just one action potential

Question 57

How do we study the brain?

Answer 57

With these measures, can look at real-time changes in activity and relate them to behavior
They measure activity directly –electrophysiology and EEG directly measure action potentials
Or indirectly –PET and fMRI look at which areas use more energy or oxygen and are therefore more active

Question 58

wha is Gene and protein expression

Answer 58

Label mRNA with radioactivity or dye or
Label proteins with antibodies attached to fluorescent or other tags Look at the expression under the microscope

You can do this by making very thin brain slices and then reconstructing it
or, now, with the entire brain, all at once!

Question 59

what are the pros of Gene and protein expression

Answer 59

Can look at expression across a wide range of brain areas
(hard to do with electrophysiology) Can look at expression within single neurons
(can’t do with EEG, PET or fMRI)
Tells you about changes or differences in particular molecules or cell types

Question 60

what are the cons of Gene and protein expression

Answer 60

have to take the brain out to look at it

• -not a real-time measure of what’s going on
• -can only have one “treatment” per individual, compare expression between groups

Question 61

One type of protein that lets us get information about the activity of particular kinds of cells are those translated from immediate early genes, what is it

Answer 61

examples are EGR1 and cFOS

Question 62

what are Immediate early genes

Answer 62

These are genes that are rapidly transcribed when cells change their firing pattern

Question 63

how do Immediate early genes help us

Answer 63

By looking at immediate early gene expression, we can know –whether a cell was active at a particular time, during a behavior or in response to a stimulus
–if we label for other proteins, we can know what kind of cell it was
Here, green cells contain the protein of an immediate early gene called c-fos
–that means that these cells altered their pattern of action potentials in response to a particular stimulus
The red label of for a protein called parvalbumin
The merge is showing us that the c-fos and parvalbumin are expressed in the same cell

Question 64

How do you know what a brain area does?

Answer 64

Look at when it is active
Manipulate activity within the brain area itself
then look at effects on behavior
Increase the activity of cells

Decrease the activity of cells

Modulate the activity of cells

Question 65

how do you Increase the activity of cells

Answer 65

–stimulate cells using electricity
–stimulate cells using lights
(this is what we’ll talk about for false memories)

Question 66

how do you decrease the activity of cells

Answer 66

–lesion or kill the cells in that area
–block the activity of cells using different drugs
like adding GABA or tetrodotoxin
tetrodotoxin is a poison from pufferfish
it blocks sodium channels, which means it blocks action potentials

Question 67

how do you modulate the activity of cells

Answer 67

–you can change the activity of inputs or outputs to an area –you can change the pattern of action potentials
block or stimulate receptors for neuromodulators like serotonin, dopamine, norepinephrine

Question 68

give a sumar of thus far

Answer 68

Action potentials and how brain cells communicate Synapses, neurotransmitters and creating a graded signal
Summary so far
How does the brain work, inputs, processing and outputs
How do we study the brain? EEG, PET, fMRI, electrophysiology, gene and protein expression
Finding out what the brain does, ways to manipulate the brain