Lecture 4 - Neuroscience Basics Flashcards
What is Neuroscience?
What is Neuroscience?
Researchers in the field of neuroscience—the study of the brain and the rest of the nervous system—overwhelmingly believe that the brain is the seat of learning and memory.
Historically, most early studies of learning and memory focused on observable behavior rather than on the brain and how it functions. (in more modern times as teqnies for studying the brain have developed people have put a neuroscience lense to the study of memory )
Last class we looked at some of the early approaches to thinking about the relationship between brain and cognition or brain and behavior.
Localization of function versus equipotentiality: where do we stand?
We stand somewhere in the middle
- we do think there is some spealization in the brain but we have also come to understand that the brain works as a network
Do researchers make a distinction between cognitive neuroscience and neuroscience?
FYI: Researchers make a distinction between cognitive neuroscience and behavioural neuroscience, the former focusing on research in humans and the latter focusing on research in non-human animals.
The reason I am telling you this is because it is confusing, especially for some of you who may apply to graduate school! You might ask yourself why the difference in names?
DO THE 15 Minute TAKE A TOUR OF THE BRAIN ACTIVITY
What is the corpus collosum? What is the cerebullum?
White matter bundle that connects the two hemispheres called the ‘corpus collosum
Cerebellum is associated with many kinds of motor movements
What is the orientation of the human brain?
Superior is the top
of the bran
Posterior is the back of the brain
Inferior is
the bottom of
the brain
When we are talking about the front of the
brain we are using the term anterior
These are other terms for
the brain
- they are different terms but they are
reffering to the same thing
Dorsal (superior)
Caudal (posterior)
Ventral (inferior)
Rostral (anterior)
LOOK AT DIAGRAM ON SLIDE 8
What is the cortex?
Cortex: brain tissue covering the top and sides of the brain, involved in many functions
What is the brainstem?
Brainstem: connects the rest of the brain to the spinal cord and plays critical roles in regulating automatic functions (e.g., breathing and body temperature).
(Brain stem connects
the brain to the rest of
the body)
What is the cerebellum?
Cerebellum: regulation and coordination of complex voluntary muscular movement
How is the brain divided?
The brain is devided into two hemispheres
the left hemisphere and the right hemisphere
LOOK AT SLIDE 12 TO UNDERSTAND CORONAL HORIZONTAL and SAGGITAL SLICES OF THE BRAIN
What is the benefit of a coronal slice?
The coronal slice gives
you a nice look at the
hippocampus
What are the 4 lobes of the brain?
Frontal
Temporal
Parietal
Occipital
What is the frontal lobe responsible for?
Frontal lobe: plan and perform actions, among other things
What is the temporal lobe responsible for?
Temporal lobe: language and auditory processing and learning and memory, among other things
What is the parietal lobe responsible for?
Parietal lobe: processing somatosensory (touch) inputs, among other things
What is the occipital lobe responsible for?
Occipital lobe: important for visual processing
What is a good way to memorize the 4 lobes of the brain?
○ Frontal is Front
○ Parietal is at the Peak
○ Temporal is behind the Temples
○ Occipital lobe is Out back
What do we know about comparative neuroanatomy?
Humans have a disproportionately
large cerebral cortex.
Larger cortical proportion in other animals considered clever, such as dolphins and chimps.
Brains vary both in overall size, and in relative proportions.
May related to specialization. Birds have bigger proportioned cerebellums than humans. This may relate to the motor coordination necessary for flight. (- size of different regions has to do with specialization that is
necessary for survival)
Bigger isn’t necessarily better.
Elephant brain is bigger ~5 kg Human brain ~1.4 kg (but we would not trade a brain with
an elephant)
We can look at the brain in different species and notice some
interesting differences
- the size and the proportion of regions differ
Explain what you know about Incoming Stimuli: Sensory Pathways into the Brain. How do we distinguish the cortical regions?
Incoming Stimuli: Sensory Pathways into the Brain
Regions of the cerebral cortex are specialized for processing difference sensory info: light (primary visual cortex), sound (primary auditory cortex), and sensation (primary somatosensory cortex).
Other regions are specialized for generating movements (primary motor cortex).
We distinguish cortical regions as primary and secoundary
- We will only look at the primary ones
1) Primary Autiory cortext
- sits in the temporal lobe
2) Primary motor cortext
- responsible for generating motor movements
3) Primary somatosensory cortext
- responsible for sensation
4) Primary visual cortext
- responsible for processing incoming visual information
UNDERSTAND THE DIAGRAM ON Slide 16
What is the difference between Gray matter and white matter?
people also distinguish between grey and white matter
- if we take under a microscope we would see that the brain
is filled with cells called neurons but their location differs
across different parts of the brain
- we have axons in our neurons that have this white seath
on them, these make up the white matter because it is a fatty
substance and it appears whiter. This is one part of the brain.
Then we have the cell bodies which we would call the grey matter
of the brain because it looks darker
We have axons that fill the brain and they give
rise to different colours of tissue
UNDERSTAND THE DIAGRAM ON SLIDE 17
What do you know about the white matter paths?
How do we image the white axons in the brain
- if we wanted to image the corpus collusum which connects
the two hemispheres. This is what it would look like. It is coloured in
this way because we have a special mathimatical alghrotims that
can label the white matter tracks depending on which direction
they are going in
Daniela’s Favorite White Matter Path?
Certain white matter pathway that connects
the frontal lobes to the temporal lobes
There are white matter tracks in the brain and we can image them
in different ways
what are some brain regions involved in memory?
basal ganglia
amygdala
thalamus
hippocampus
Many of these are “subcortical”
This image makes it hard to see; go back to your 3D anatomy!
If we were to peel away the cortext and look under the hood we would see
the regions we commonly refer to as subcortical
- For example the basal ganglie which is a collection of nuclei
- these are the regions you would be able to see if you were to peel off the outer
layer of the brain (we would see the basal ganglia, thalamus, amygdala,
hippocampus)
TRY THE LABELLING REGIONS EXERCISE ON SLIDE 20
What makes up the central nervous system?
Brain and spinal cord make up the “central nervous system”
Brains are also connected to the rest of the body
- the brain and spinal cord make up the central
nervous system
How are the brain and body connected?
The “central nervous system” connects to the body (organs, muscles) (peripheral nervous system) Organs and mussles of the body
Central nervous system is the brain
and spinal cord and it is connected to the rest
of the body (organs and muscles) which is
the peripheral nervous system
What is the human brain made of?
What is it made of?
○ (1) Close to 100 billion neurons (We have LOTS of different neurons in the
brain)
○ (2) Other types of cells (numerous) (The brain is made of other types of cells)
○ (3) Blood vessels (brain has blood vessles
- so it is not just neurons, lots of other stuff)
Know what a textbook neuron looks like?
Neurons are split into different parts:
- dendrites
- cell body
- axon
Explain what we know about the prototypical neuron.
The prototypical neuron has three main parts:
- Dendrites are input areas that receive signals from other neurons
- The cell body integrates signals from the dendrites
- One or more axons, which transmit signals to other neurons
(the reason axons can transmit signals very quickly is because they are covered in this fatty substance called mylien seath)
What are the other cells in the brain called?
Glia: cells of various types. They provide functional or structural support to neurons. Some contribute to changes in connections between neurons
○ Astrocytes line the outer surface of blood vessels (in the brain)
○ Oligodendrocytes wrap the axons in myelin, a fatty substance that insulates electrical signals transmitted by neurons (they have a different name outside of the brain)
○ Does glia have other functions? More evidence is needed.
What do we know about blood vessels?
Blood vessels are like spider webs wrapped around the brain and is in the inner parts of the brain
- we have the outer surface
- blood vessles continue through the inner portions of the brain. This is because blood vessels
are very important in suppyling nutrients to different parts of the brain. And when there is blockage
of blood flow there can be catatrophic concequences
How do neurons communicate?
Neurons communicate in the synapse
There is some input from the environmet (such as seeing a flickering light on the screen, hearing your
professor speak) this will lead to the firing of neurons and there will be a signal that transmits across
those neruons, but how does that happen?
If you zoom in on the neurons you will see that there is a space
between a presynapatic neuron and post synaptic neuron
- the space is called the synapse (the neurons do not actually
touch each other)
- this is important for understanding how neurons are actually
commincating with one another
What do you know about the synapse?
Synapse –specialized for chemical communication between axon and dendrite, where the two cells draw very close but do not quite touch (The presynaptic and post synatic neurons are very close to one another but they do not touch)
● Presynaptic side – The axon has vesicles loaded with neurotransmitters. (The presynaptic side is the axon that has vesicles that are loaded with neurotransmitters)
● Postsynaptic side – The dendrite is lined with receptors to detect the neurotransmitter. (The postsynpatic side is the dendrite which is lined with
recptors that are waiting to reicve neurotransmitters )
The presynpatic neuron is going to release neurotransmitters (we call this
chemical transmission because it is a chemical being released) and that is
going to bind to the posysyaptic neuron aand that is how the neurons are going
to talk to one another
Who is important for pointing out that neurons don’t touch?
Ramón y Cajal is important for pointing out that neurons do not touch; neurons are individual units
Explain how neurons connect in the synapse?
● Neurons contain neurotransmitters, chemical substances that can cross a synapse to affect the activity of a nearby (postsynaptic) neuron
● Several different chemicals act as neurotransmitters
○ Glutamate, gamma-aminobutyric acid (GABA), acetylcholine, dopamine,
norepinephrine, epinephrine, and serotonin
● Receptors are molecules embedded in the surface of the postsynaptic neuron. They are specialized to bind with and respond to certain neurotransmitters (like a lock and key)
Receptors are only senstitive to certain neurotransmitters
- only certain keys are going to open up the lock
Which neurons are excitatory? Which neurons are inhibitory?
● Some neurotransmitters—glutamate, for example—are excitatory. They activate receptors that tend to increase the likelihood of the postsynaptic neuron firing.
● Other neurotransmitters— such as GABA—are inhibitory. They activate receptors that tend to decrease the likelihood of the postsynaptic neuron firing.
What is a neuromodulator?
● Neuromodulator: a neurotransmitter that modulates activity in a large number of neurons rather than at a single synapse.
○ Example: Dopamine
Some neurotransmitters are reffered to as Neuromodulators
- instead of acting on one postsynpatic neuron they actually mogulate
the activity of a large number of neurons. So rather than one single
synapse multiple synapses
- Ex: Dopamine.
What else is there to know about what happens when an action potential occurs?
● When an action potential occurs, there is a lot of stuff happening
○ Calcium enters the cell and that triggers neurotransmission
○ Neurotransmission, in turn, can spur an action potential
● Neuronal communication is electrical AND chemical!
(When we talk about action potentials and neurons firing we are talking about
something that is electrical in nature. The eletrcial signal is something that is
being probegated down those axons. What is happening at the synpase is chemical)
How does everything we talked about in relation to the neuroscience basics relate to learning and memory?
● Learning and memory researchers have focused almost exclusively on understanding the the ability of synapses to change as a result of experience (synaptic plasticity)
(Learning and memory researchers have focused a lot at what happens at the place of the synapse. Is there something that changes about the way
neurons are talking to each other (this is often referred to as synaptic plasticity))
● “Hebbian learning”: any physical change in neurons can affect neural communication, that is, the connections between neurons
(Hebbian learning
- any physical change that happens at the level of the neuron can affect the way that
the neurons are talking to each other)
○ Learning that involves strengthening connections between neurons that work together
(Hebbian learning referrs to learning invovles the strengthening of connects between neurons together
- somethinng about their relationship strengthens)
● These ideas were more hypothetical at the time of Donald Hebb (strong evidence came later)
● “Neurons that fire together wire together”
(important thing you need to remember from Donald Hebb is “neurons that fire together wire together”
- something about the wiring of the nervous system changes as a result of expirence)
How do we Measure Neural Patterns Due to Learning?
Measuring Neural Patterns Due to Learning
● Long-term potentiation (LTP): a process in which synaptic transmission (between neurons) becomes more effective as a result of recent, repeated activity
(The instation of the idea that neurons that fire together wire together)
● LTP is believed to represent a type of synaptic plasticity, which could be a neural mechanism for learning
What are the original studies on longterm potentiation?
(In this picture we have a presyanaptic and postsynpatic neuron with a synpase between them. It has a stimulating electrode that is going to stimulate that presynpatic neuron and a recording electrode that is going to record activity of that post synpatic neuron
- you are stimulating the axon and then you are recording from the dendrite)
(A) Researchers used an electrode to stimulate the axons of presynaptic neurons. A second electrode was used to record the activity of postsynaptic neurons.
(B) Initially, weak stimulation caused only a mild response in the postsynaptic neuron. But after a burst of high-frequency stimulation, the postsynaptic neuron responded more strongly to the weaker stimulation and this persisted.
(This is the key part
- you weakly stimulate the neuron you get a weak response
- you follow that with a high frequency stimulation and then
after when you stimulate that neuron again but only weakly
as you did initally you aare going to get a higher resonse
^- the neuron has been petentuated, it is more senstitive to a
weak stimulation after it has been stimulated very heavily)
