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Exam Feedback | Synapses, Neurons and Brains
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You submitted this exam on Fri 7 Jun 2013 7:47 PM IST (UTC +0530). You got a
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Question 1
AIS – Axon Initial Segment,Myelin,The soma,Node of
Ranvier,Axonal boutons,Dendrite
Choose the correct order of numbers that match to the section list as they appear in the figure
above
6,1,3,2,5,4
6,1,3,4,5,2
2,3,1,5,4,6
4,5,2,3,1,6
6,2,3,1,4,5
Question 2
Optogenetics is a new scientific method allowing:
Change of the genetic code in neurons
Simulating neuronal networks of 104 cells in the eye
Activation (or inactivation) of specific cells (that were manipulated genetically) using light
Coloring of different cell types with different colors
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Question 3
Select the answer with the correct order of terms that match the spaces in the sentence below:
The _____ connects the ____ of a pre-synaptic neuron
with the _____ of the post-synaptic neuron.
An action potential in the pre-synaptic cell triggers
release of _____ containing ______ that spreads into the
synaptic gap.
______ in the post-synaptic cell recognize transmitter
molecules and this may results in voltage change (the
post synaptic potential).
synapse,dendrite,axon,receptors,vesicles,neurotransmitters
dendrite,vesicles,receptors,synapse,axon,neurotransmitters
synapse,axon,dendrite,vesicles,neurotransmitters,receptors
synapse,receptors,dendrite,vesicles,neurotransmitters,axon
Question 4
Injection of a constant positive current into a neuron will:
Select all the correct answers
Result with less negative membrane potential (depolarization)
Lead to a more negative membrane potential (hyperpolarization)
Charge the internal side of the membrane capacitance with positive ions
Will not change the membrane voltage since the cell’s capacitor is sensitive only to the
change in voltage (CdV/dt) rather to a constant current
Question 5
Mark the correct sentences about the following equation:
V (t) = I ∗ R ∗ (1 − e
−t/RC
)
The equation describes the development of membrane voltage responding to a step
current injection to a passive isopotential cell.
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V = I ∗ R
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We can extract from the equation the maximal voltage (V
= I ∗ R)
that may be attained
during the injection of a step current I.
The equation describes the decay of membrane voltage in a passive isopotential cell
following the ending of the injected step current.
We can extract from the equation the minimal voltage (V
t/RC
= (1 − e
))
that may be
attained during the injection of a step current I.
Question 6
Mark the correct sentences about the membrane time
constant - τ m :
τ m = RC
τm
is the time that it takes for the membrane potential to rise to about 63% of its steady
state value following a long step current pulse.
τm = V R
τm = IR
Question 7
What is a typical resting potential of a neuron?
−70mV
−70μV
0mV
−20mV
+70mV
−70V
Question 8
Potassium (K+) concentration is higher inside the
neuron than in the outside. The opening of potassium
ion channels in the cell’s membrane will result in:
Select all the correct answers
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Hyper-polarization of the cell’s membrane
Depolarization of the cell’s membrane
A flow of K+ ions into the cell
Flow of K+ ions outside of the cell
Question 9
Mark the correct sentences regarding the EPSP
(Excitatory Post Synaptic Potential)
Opening of transmitter-gated potassium channels will result with an EPSP
The EPSP results from the opening of synaptic (transmitter-gated) membrane ion channels
associated with a positive battery
The opening of transmitter-gated sodium channels will result with an EPSP
EPSP results from the opening of synaptic channels associated with a (inward directed)
negative battery
Question 10
Mark the correct sentences regarding the IPSP
(Inhibitory Post Synaptic Potential)
The opening of transmitter-gated sodium channels will result with an IPSP
The IPSP results from the opening of synaptic (transmitter-gated) membrane ion channels
associated with a positive battery
IPSP results from the opening of synaptic channels associated with a (inward directed)
negative battery
Opening of transmitter-gated potassium channels will result with an IPSP
Question 11
Activation of an EPSP at t=0 and then an IPSPs at t =
τ m will result with:
Select all the correct answers:
A PSP- post synaptic potential that is smaller (less depolarized) than the EPSP alone
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First depolarization then hyperpolarization
No change in membrane voltage as I (inhibition) exactly vetoes E (excitation)
A PSP - post synaptic potential- that is larger than the EPSP alone
Question 12
What is typical amplitude of a spike? (from the cell’s
resting potential to the peak of the spike)
10mV
1V
100mV
200mV
Question 13
What is a normal duration of a spike? (the width at its
half amplitude)
1-2 msec
100-200 msec
0.1-0.2 msec
10-20 msec
Question 14
With the voltage clamp (VC) technique:
Select all the correct answers (could be more than one)
The experimenter may fix the membrane voltage at different pre-determined values.
The VC system injects current to counter balance the membrane currents
The voltage-gated ion channels in the axon open or close in response to the assigned
membrane potential
The experimenter measures the voltage change in response to the opening of the voltage
gated channels
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Question 15
Mark the correct sentence for the squid giant axon
membrane:
Sodium current is a slow inward inactivated current
Sodium current is a fast non-inactivating inward current
Sodium current is a slow outward inactivated current
Sodium current is a fast outward inactivated current
Sodium current is a fast inward inactivated current
Question 16
Mark the correct sentence for the squid giant axon
membrane:
Potassium current is a fast inward inactivated current
Potassium current is a slow inward inactivated current
Potassium current is a slow outward non-inactivated current
Potassium current is a fast outward inactivated current
Potassium current is a fast non-inactivating inward current
Question 17
Mark the correct sentences about the potassium
conductance (gk ) according to the H&H model:
We may interpret the potassium ion channel as having 4 identical gates
Depolarizing the membrane will increase n
We may interpret the potassium ion channel as having 3 activated gates and one
inactivated gate
gk
depends on the maximal potassium conductance and on n raised to the power of 4
Depolarizing the membrane will decrease n
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Question 18
According to H&H model, what are the reasons for the
termination (repolarization) of the spike?
Select all the correct answers (could be more than one)
The fast opening of the m-gate
The opening of passive leakage channels
Opening of the outward K-conductance
Inactivation of the sodium current due to the closing of the h-gate
Question 19
In the Held and Hein experiment (the two kittens
experiment) only the active kitten could functionally see.
Why?
Select all the correct answers (could be more than one)
Only the active cat developed operational motor system; a functional motor system is the
foundation for the development of all other systems in their brain, including vision.
Building an internal (brain) model of the visual world requires, early on, to generate visual
predictions via self-movement
Vision is possible only when the brain successfully links between the movement it generates
and the visual input it receives (the perception-action cycle)
Being passively moved by someone else confuses (at any developmental stage) the visual
system. Consequently, the visual system cannot distinguish between self-movement and
external movement.
Question 20
Sensory substitution implies that:
Merging several senses to improve performance
Enhancing a particular sense (e.g., vision) with a device (such as a binocular)
Substitution of a lost sense with mechanical devices (e.g., artificial retina)
Utilizing a healthy sense for a lost sense (e.g., the somatosensory/tactile sense for vision in
Braille reading)
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Question 21
What is the Hebb hypothesis?
The connection between the cells will strengthen if cell A is repetitively involved as one of
the cells that activate Cell B
Cell B fire consistently before cell A then their connection will be weakened
That the synapse between cell A and B is strengthened if cell A is sufficiently active
That some metabolic change is involved in learning
Question 22
The term synaptic plasticity describes:
The addition of new dendritic spines during learning and memory processes
That existing synapses change their efficacy
The ability of a synapse to switch from excitatory and inhibitory
The capability of the synapse to release a neurotransmitter as result of the pre-synaptic
spike
Question 23
Biophysical experiments show that excitatory synapses
strengthens/weakens as a function of the timing of prevs. postsynaptic spikes (STDP).
Mark the correct sentences.
When the pre synaptic cell fires a spike immediately after the post synaptic cell – no change
in the synaptic strength
When the postsynaptic spike fires before the pre-synaptic spike, the EPSP’s amplitude
(recorded at the post synaptic cell following presynaptic activation) is reduced.
In cortical/hippocampal pyramidal cells, when the pre synaptic cell fires a spike before the
post synaptic cell – the excitatory synapses between these cells is strengthened (LTP) and
vice-versa for synaptic weakening (LTD)
When the pre synaptic cell fires before the post synaptic cell – the spike in the post
synaptic cell is reduced in amplitude (LTD)
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Question 24
What is the time-scale for long term potentiation (LTP)
and depression (LTD)?
Tens of milliseconds
Seconds
Minutes
Hours
Question 25
Is it feasible to copy memories from one brain to another
(“disc on key”)?
Select all the correct answers
Yes, because eventually memories are stored in all brains using the same synaptic
mechanisms.
Yes, if we could read out all spikes/cells involved in a particular memory
No as each of us stores/represents (codes for) memories in an individual way (different
cells/different spike patterns in different brains)
No, because when forming a memory the particular activity in the respective neural network
should be correlated with a particular physical item/event to be remembered.
Question 26
Is it possible in principle to physically erase memories?
Yes, because when forming a memory the particular activity in the respective neural
network could be monitored and then suppressed (memory will then be lost)
Yes, because eventually memories are stored in all brains using the same synaptic
mechanisms; destroying these synapses will erase the memory embedded.
No, because we cannot detect the region/networks associated with a particular memory
No because each of us stores/represents (codes for) memories in an individual way
(different cells/different spike patterns in different brains)
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Question 27
The Hubel and Weisel experiment about the response
properties of cells in area V1 of the cat cortex showed:
V1 cells are sensitive to the color of the oriented line
Neurons in V1 of the cat are sensitive to moving spots of light
Neurons respond strongly (fire many spikes) to an oriented line moving in a specific
direction
Neurons in V1 recognize (respond strongly to) a particular face
Question 28
Rall argued against the “point neuron” model because:
Select all the correct answers (could be more than one)
Dendrites are non iso-potential electrical distributed devices
EPSP’s and IPSP’s cannot be explained under the “point neuron” assumption
A significant portion of the current injected to the soma flows to the dendrites and do not
remain in the soma
Inhibition does not always veto the excitation
Question 29
Comparing excitatory synaptic input triggered distally
with identical synapse triggered directly in the soma
Select all the correct answers (could be more than one)
At the synaptic input site itself, the amplitude of the distal EPSP will be smaller than the
EPSP originated at the soma
At the soma, the EPSP from the distal synapse will be narrower
At the soma the EPSP from the distal synapse will be broader
At the soma, the amplitude of the EPSP form the distal synapse will be smaller
At the soma, the time-to-peak is shorter for the distal synapse
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Question 30
Rall showed that:
Select all the correct answers (could be more than one)
Activation of excitatory synapses in the proximal-to-distal temporal order results in a
delayed and briefer EPSP in the soma
One could build a direction selective neuron using only passive dendrites and orderly
activated excitatory synapses
Activation of excitatory synapses in the proximal-to-distal temporal order results in a
delayed and broad EPSP at the soma
Activation of excitatory synapses in the distal-to-proximal temporal order results with a
larger voltage change in the soma
Activation of inhibitory synapses in the proximal-to-distal order will result with large
depolarization in the soma
Question 31
Enhanced optical resolution using two photon Ca+2imaging (the work of Arthur Konnerth and team) has
shown that:
Select all the correct answers (could be more than one)
That the orientation selectivity of an L2/3 cell may plastically change
A particular layer 2/3 pyramidal cell in mouse V1 interact synaptically only with cells having
the same orientation selectivity
In V1 of the mouse, L2/3 cell are orientation selective
The synaptic inputs to an orientation selective cell in mouse V1 are orientation selective,
with a variety of different orientation selective cells impinging of the post-synaptic L2/3
dendrites
Question 32
What is common to Parkinson, Alzheimer and Autism?
Mutations in the same gene are responsible for all the three diseases
All the three diseases emerge in adults
Electrical (deep brain) stimulation of the basal ganglia improves the patients' quality of life
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The electrical activity of the brain is different comparing with a non sick brain
Question 33
In a cubic mm of a mammalian cortex
There are ~ 30,000 neurons and ~10^8 synapses
There are ~ 300,000 neurons and ~10^8 synapses
There are ~ 3,000 neurons and ~10^10 synapses
There are ~ 3,000 neurons and ~10^6 synapses
Question 34
Different types of cells in the cortical column are
different from each other in:
Select all the correct answers (could be more than one)
Different cell types have a different DNA sequence
By their target output and by their synaptic effect (e.g., inhibitory/excitatory)
Different cells have significantly different spike shape
Their electrical characteristics
Their anatomy
Question 35
Mark the correct sentences:
The orientation of the column is defined by its physical orientation with respect to the skull
As in the mouse whisker system, cat V1 also consists of anatomically-identified columns
In cat V1 there are functional columns – most of the cells in the column respond to the
same orientation of the visual input
Cells in cat V1 are plastic – experience can change the orientation selectivity of the column
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Question 36
Simulation of a particular disease in the blue brain
project (BBP) means
Select all the correct answers (could be more than one)
That the spiking activity of different electrical-neuron types is replicated closely in the
simulations
That the dynamic properties of the simulated network replicate closely to that of the
corresponding disease
That the genes expressed in that disease are simulated in details
That we can repair the disease via interaction between the computer simulation and the
sick brain
That the simulation enables the identification of possible (synaptic, excitable or anatomical)
changes underlying the disease
Question 37
Mark the correct sentences about Functional Magnetic
Resonance Imaging (fMRI)
fMRI measures brain activity by directly detecting electrical activity (action potentials)
fMRI measures brain activity of different areas by detecting changes in blood flow.
Using fMRI we can detect the activity of a single neuron
A fMRI signal detects brain activity at a spatial resolution corresponding to the activity of
millions of cells.
Question 38
Mark the correct sentences:
Different brains detect faces in similar “object related” brain regions
We may learn what face is particularly represented in the brain using calibration and
repetitive fMRI
Specific faces are represented similarly between different persons
To date, it is impossible to write down an algorithm that outputs from a single fMRI or EEG
trial, what particular face is being processed
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Question 39
According to the (EEG) experiments of Benjamin Libet:
Select all the correct answers (could be more than one)
The movement-related brain activity starts seconds before we become aware that we
“decided” to move
That it is possible to read from brain activity at what time we decided to move (when we
became aware of our decision)
There is time gap between the awareness (the will to move) and the onset of the movement
That the reported time for the “will to move” coincides with the movement onset
Question 40
Using local stimulation in the brain:
Select all the correct answers (could be more than one)
We may trigger an action without the subject’s awareness to the action.
We can trigger the will to do an action but not the action itself.
We can trigger the subject’s action but we cannot trigger the subject’s will to do an action.
We can trigger the subject’s will to perform an action “conscious motor intention” and we
can also trigger illusory movement (subject feels he moved, but he did not).
We cannot trigger an action without the awareness of the subject to his own actions.
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