In order to investigate the causal mechanisms of brain function and behavior we need to:
Correlate the activity of specific cells with behavior
Perturb the activity of specific cells during behavior
Quantitatively model the causal interactions driving brain function and behavior
All of the above steps are essential for linking brain function and behavior
Question 6.1.2
What methods investigate cellular mechanisms of brain function?
Electroencephalography (EEG) and magnetoencephalography (MEG)
Whole-cell electrophysiology and high-resolution optical imaging
Positron emission tomography (PET)
functional magnetic resonance imaging (BOLD fMRI)
Question 6.1.3
An observer measures the neuronal activity of a number of neurons and finds that some specific neurons reliably fire action potentials just before a mouse licks a water spout during task performance. The observer concludes that these neurons might contribute to driving licking behavior. What further experiments are necessary to test whether the activity of these specific neurons is necessary and sufficient?
Stimulation of the specific cells to test for necessity, and inactivation of the specific cells to test for sufficiency
Stimulation of the specific cells to test for necessity and sufficiency
Inactivation of the specific cells to test for necessity, and stimulation of the specific cells to test for sufficiency
Inactivation of the specific cells to test for necessity and sufficiency
Question 6.1.4
Why did Karl Popper propose that scientific hypotheses can only be falsified and they can never be proved correct?
Some experimental data might be consistent with a hypothesis, but perhaps further experiments will contradict the hypothesis
Experimental data are always inconsistent
Experiments are carried out by experimentalists
Hypotheses are always wrong
Question 6.2.1
Which statement about the relation between man and mouse is correct?
There is little genetic similarity between man and mouse
Reptiles are genetically closer to man than mouse
The human genome has approximately ten times more genes than the mouse genome
Approximately 99% of genes coding for proteins have homologs comparing man and mouse
Question 6.2.2
Size is the most obvious difference between the brain of a mouse and that of a man. What are their relative sizes?
Mouse: length ~1 cm, volume ~1 ml; Man: length ~100 cm, volume ~1000 l
Mouse: length ~1 cm, volume ~1 ml; Man: length ~10 cm, volume ~1 l
Mouse: length ~0.1 cm, volume ~0.001 ml; Man: length ~10 cm, volume ~1 l
Mouse: length ~0.1 cm, volume ~0.001 ml; Man: length ~100 cm, volume ~1000 l
Question 6.2.3
What would be a very rough estimate for the total number of neurons in man and mouse?
100 thousand for mouse and 100 million for man
100 million for mouse and 100 billion for man
100 thousand for mouse and 1 million for man
100 thousand for mouse and 100 billion for man
Question 6.2.4
Imagine that each neuron in the brain synaptically connects to 1,000 other neurons. Using the rough numbers of neurons from the question above, what would be the ratio of the numbers of synapses comparing man and mouse?
Man would have 1 million times more synapses than a mouse
Man would have 1 thousand times more synapses than a mouse
Man would have 1 billion times more synapses than a mouse
Man and mouse would have the same number of synapses
Question 6.2.5
Which neural circuits are similar in man and mouse?
Visual, tactile, gustatory and auditory information flow through the thalamus to the neocortex
Neocortex sends long-range excitatory glutamatergic signals to other brain areas
Cerebellar circuits help fine-scale sensorimotor coordination.
All of the above.
Question 6.3.1
Approximately how deep in the living brain is it possible to optically image with cellular resolution in a non-invasive manner?
~1 um
~30 um
~1 mm
~3 cm
Question 6.3.2
If a fluorescent voltage sensor was present on all neuronal membranes, what spatiotemporal resolution of cortical neuronal activity might one hope to achieve through wide-field epifluorescence imaging in vivo?
~100 um and ~1 ms
~10 um and ~100 ms
~1 um and ~10 us
Only depends on your camera resolution
Question 6.3.3
Which of the following statements about two-photon excitation is not correct?
The probability of two-photon excitation depends on the square of the photon density
Two-photon excitation occurs equally within the entire excitation light cone
Emitted fluorescent photons mainly originate from the focal plane
Long wavelength light (near infrared) is used excite the fluorophore
Question 6.3.4
What is the approximate resolution of two-photon microscopy in the living brain?
About 1 um
About 30 nm
About 30 um
About 1 cm
Question 6.3.5
Typically pulsed femtosecond infrared lasers are used to excite two-photon fluorescence. What would be the expected increase in two-photon fluorescence if the same sample was excited by 100 MHz laser pulses each lasting 100 fs compared to a continuous emission laser with the same average power?
100,000,000
100
10^10
100,000
Question 6.4.1
Which signal can be observed with extracellular electrophysiological recordings in vivo?
Somatic membrane potential at the soma
Calcium dynamics in a single neuron
Action potential firing
Dendritic membrane potential
Question 6.4.2
What are the advantages of in vivo whole-cell recordings compared to typical extracellular recording methods?
Subthreshold membrane potential fluctuations can be recorded
Cells can be filled with dye through the recording pipette for anatomical identification
Membrane potential can be changed by injecting currents
All of the above
Question 6.4.3
What pattern of membrane potential fluctuations in excitatory layer 2/3 neurons dominates during the quiet resting state in mouse primary somatosensory cortex?
Slow fluctuations (0.1-0.5 Hz), with amplitude of ~50 mV, highly synchronised in nearby neurons
Slow fluctuations (1-5 Hz), with amplitude of ~10 mV, highly synchronised in nearby neurons
Fast fluctuations (10-50 Hz), with amplitude of ~10 mV, highly synchronised in nearby neurons
Fast fluctuations (10-50 Hz), with amplitude of ~2 mV, desynchronised in nearby neurons
Question 6.4.4
Which statement about combining electrophysiology and imaging is true ?
Combining electrophysiology with imaging allows recordings from genetically-defined neuron types
Electrophysiology needs the insertion of electrodes and this prevents optical imaging
Electrophysiology and imaging have different time scales and are thus incompatible
Imaging needs photons, and the photons interfere with and prohibit electrophysiogical measurements
Question 6.4.5
Layer 2/3 neocortical GABAergic neurons :
represent ~10% of the layer 2/3 neuronal population, and fire at ~10 times higher rates than excitatory pyramidal neurons
represent ~50% of the layer 2/3 neuronal population, and fire at similar rates to excitatory pyramidal neurons
represent ~90% of the layer 2/3 neuronal population, and fire ~10 times as infrequently as excitatory pyramidal neurons
represent ~10% of the layer 2/3 neuronal population, and fire ~10 times as infrequently as excitatory pyramidal neurons
Question 6.5.1
With what tool one can do cell-type specific, temporally-controlled brain stimulation?
Microstimulation
Optogenetics
Deep brain stimulation
Glutamate uncage
Question 6.5.2
What is channelrhodopsin-2 (ChR2)?
ChR2 is a light-sensitive G-protein coupled receptor
ChR2 is a light-sensitive cation channel
ChR2 is a light-sensitive anion channel
ChR2 is a light-sensitive tyrosine kinase
Question 6.5.3
What happens if we express channelrhodopsin-2 (ChR2) in excitatory neurons of mouse whisker motor cortex (wM1) and excite with blue light?
Mouse closes its eyes
Mouse starts rythmic exploratory whisking
Mouse begins grooming its whisker pad
Nothing happens
Question 6.5.4
Which approach fails to reversibly inhibit activity in a local region of the mouse brain?
Expressing channelrhodopsin-2 (ChR2) in inhibitory neurons and thereby driving local inhibition
Expressing halorhodopsin (NpHR) in excitatory neurons to optically hyperpolarise them
Expressing archaerhodopsin (Arch) in excitatory neurons to optically hyperpolarise them
Making a lesion in the brain
Question 6.5.5
Why might a light-gated anion channel be better at inhibiting neuronal activity than the light-driven transporters halorhodopsin (NpHR) or archaerhodopsin (Arch)?
Channels can move more ions per second than transporters