For all of the following scenarios, answer the following questions:
- Is the proposed strategy reasonable?
- Why or why not?
- If not, what might be a better strategy and why?
1 - Dr. P. is interested in a behavior that can be observed in a variety of species, including humans. Nothing is currently known about how the behavior is controlled neurally. Dr. P. proposes to do some single-unit recordings to gain insight into the neural mechanism.
No, this is not a reasonable strategy.
Single unit recordings have very low coverage, and would likely be unsuccessful on shedding light on the neural mechanisms behind the behavior. Additionally, that technique is very invasive and is unsubstatiated for an exploratory study.
A better technique at this stage is fMRI. Non invasive, has large coverage, decent spatial resolution, and is more accessible than its alternative MEG.
2 - Perceptual decisions are usually made within approximately one second. Models of perceptual decision-making propose that a decision arises from integrating sensory evidence over time until
a decision threshold is reached. Decision-related neural activity is therefore expected to ramp up over the course of several hundred milliseconds. Dr. B. wants to perform an fMRI experiment
to demonstrate that this is indeed the case
No this is not a reasonable strategy.
fMRI has poor spatial resolution, and would not be adequate for helping measure decision activity in the scale of milliseconds.
A better alternative would be MEG if spatial resolution is critical, and potentially EEG if not.
The invasive option of VSD is also viable, if cortical substrates are known, and if not ECoG could be useful.
3 - Dr. S. believes that the primary visual cortical area of a particular species contains a map of colors. The preferred color is expected to be similar for nearby neurons over a range of approx. 200 microns. Dr. S. gets ready to set up an intrinsic optical imaging experiment to verify the color map
Yes, this is reasonable.
Optical imaging has resolution on the order of 100 microns, and would be appropriate for imaging the neural mapping of colors.
Additional potential techniques could be VSD/CaSD or potentially Utah arrays.
4 - Area PTF is known for its heterogeneity. Different neurons can have very different response properties, even when they are very close to each other. PTF neurons are generally known for their high spontaneous activity. A certain subpopulation of PTF neurons responds to auditory stimuli. Dr. G. would like to measure the tuning properties of these neurons and considers an MEG experiment.
No, not appropriate.
The heterogeneity would not generate a strong magnetic field, and would not be imaged well by MEG.
Alternatives to consider are extracellular recordings and microelectrode arrays.
5 - It has been suggested that the interaction between excitatory and inhibitory inputs to a particular class of neurons is critical for a particular neural function. To learn more about this interaction, Dr. N. decides to perform some single-unit recordings.
Likely inappropriate.
Single unit recordings measure outer membrane voltage, and would not be sensitive to excitatory and inhibitory inputs.
Although its difficult to do in vivo, intracellular recordings are the best technique for investigating the interaction between excitatory and ihibitory inputs.
6 - Dr. E. would like to demonstrate that cortical area X is critical for producing behavior Y. Luckily, the area is close to the surface of the brain, and Dr. E. decides to set up an optical imaging experiment.
No, not appropriate.
These recordings only measure correlation, not causation. In order to determine causation. It is necessary to use another technique.
Potential techniques need to control for cortical area X activation: including optogenetics, ablation, microstimulation, TMS, etc.
7 - Dr. K. is interested in how the brain processes complex visual stimuli. He used fMRI to identify several regions throughout inferior temporal cortex that became activated in response to the
stimuli. He concludes that the pyramidal cells, the large excitatory neurons that provide output to other areas, must have had a clearly elevated firing rate
No, not appropriate.
fMRI measures the BOLD response, nnot directly pyramidaly cell activation.
Better techniques are extracellular recording and calcium imaging.
8 - Dr. B. investigates how the brain discriminates between different directions of visual motion. She uses stimuli that allow her not only to specify the direction of motion, but also the strength
of the motion signal. She observes that her animal subjects make more accurate and faster discriminations when she provides a stronger motion stimulus. Her hypothesis is that neurons in
area MT, an extrastriate visual cortical area that is involved in motion processing, plays a role in motion direction discrimination. As a first step, she wants to demonstrate that the response of
MT neurons to a motion stimulus depends on its motion strength. She sets up a single-unit recording experiment.
Appropriate setup.
Single unit recordings would be great for determining the receptive field / selectivity of specific neurons in MT.
Potentially, microelectrode arrays could also be used to collect more data more quickly.
10 - Dr. C. studies how the brain processes color changes and is particularly interested in
a) how soon after a color change the brain can detect it and
b) what brain areas respond to the color change.
Dr. C. designs an ERP experiment given the technique’s good temporal resolution to address these questions
Good for detecting temporal onset, not good for determining brain areas responsible.
Consider MEG, ensemble fMRI/EEG, or VSD/CaSD if brain areas are somewhat known.