Quizlet Questions Flashcards
What are types of brain lesions?
Aspiration lesion - literally take out/suck out parts of the brain (vacuum cleaner).
Excitotoxic lesion - using drugs to either inhibit or activate parts of the brain.
Directed lesions
Naturally occurring lesions
- UPSIDES: can strongly implicate a region as being essential for a task, occur naturally
- DOWNSIDES: Need double dissociation to strongly confirm selectivity, no temporal resolution, and relatively few subjects
Intracranial stimulation
- Can provide specific neural perturbation, BUT limited to animals
What is an antagonist, or agonist drug?
An antagonist drug: bind to and block receptors
An agonist drug: bind to and activate receptors, mimicking neurotransmitter (more reuptake)
What is temporal and spatial resolution?
Temporal resolution refers to how closely the measured activity corresponds to the timing of the actual neuronal activity. The temporal resolution with PET is poor compared to both fMRI, EEG and MEG,
Spatial resolution refers to how accurately the measured activity is localised within the brain.
What are types of single-neuron electrical recordings?
Extracellular: information about small groups of nerve cells
Intracellular - how single cells behave during cognitive functions.
What is fMRI?
Functional magnetic resonance imaging. It is an indirect measure of brain activity. It measures BOLD signals (Blood Oxygen Level Dependent). It is low temporal (2-6 seconds) and spatial resolution, but most human friendly. It divides the brain into voxels (1-5 mm), each voxel has millions of neurons and tens of billions of synapses.
fMRI is good for analyzing activation patterns within a brain area. It can also look at coactivation, in which two or more brain regions change similarly in response to an experimental condition.
What is a PSTH?
Peri-stimulus time histogram. It counts the spikes after aligning the spikes, temporally, relative to an event of interest. This measures the change in activity over time, at a marked moment of external stimulus/interest.
Where is the perception of motion? How are those neurons specialized?
In the middle temporal (MT), V5 - middle temporal visual area specifically.
It is an area known to be best driven by visual motion stimulus
MT neurons are specialized for receptive field (which is anchored to the retina - each neuron is mapped onto the retina!) and direction of motion (cells have preferred motion direction)
What is the ventral stream, what is the dorsal stream, and what do those relate to?
This is how our brain processes visual information. Ventral stream (to temporal lobes - asks WHAT); dorsal stream (parietal lobes - asks WHERE + HOW (action oriented))
Random dot motion correlogram?
Discrimination with correlation/coherence - dots moving all in the same direction, or some random. This is a good task for testing visual information processing.
What is a psychometric curve?
A psychometric curve measures behavior.
What is a neurometric function? What are the key assumptions with a neurometric function? (include essential vocab)
A neurometric function measures the firing rates of a single neuron - it reflects what the neuron itself is “perceiving.”
The firing rate is essential:
- assume this neuron has all the information in its firing rate, that this neuron is “the ideal observer”
- Assume the neuron votes ‘yes’ when monkeys perceived motion stimuli in the preferred direction of this neuron, it votes ‘yes’ by increasing its firing rate
How do you make a neurometric function?
We measure Hit rate vs. False Alarm rate.
The criterion is the specific firing rate - at which this neuron votes ‘yes’
Question is - how clear/unambiguous is the information that the neuron is passing along?
If the criterion is set too low, this neuron does poorly, since the two distributions (the firing rate distribution for the preferred motion and the firing rate distribution for the anti-preferred motion direction) are largely overlapping.
As the criterion is set higher, this neuron does better since the two distributions start to separate more.
If the criterion is very high, this neuron does very well since the two distributions don’t overlap much.
The method: change the criterion (spike/s) to get Hit rate and False Alarm rate. Plot Hit vs. False Alarm rate, to make the ROC (receiver operating characteristic curve)
Then, from there, you make a neurometric function, mapping it onto the x = correlation/y = proportion correct graph space. Here, each dot represents the area under the curve from the ROC.
The goal is to directly compare the psychometric (behavior) and neurometric (neuron’s view) functions directly.
What is the relationship between a psychometric curve and a neurometric function? What is the purpose of mapping those onto the same space?
This is to compare whether a single neuron can do a sufficient job at describing the perceived motion (or worse? Or better?) The result - some neurons are more, or less, or about the same sensitivity as the overall perception of the monkey.
Puts the behavior and neuronal activity in the same space, to figure out whether the neuron is the ideal observer.
can assess how closely neural activity correlates with behavioral outcomes. A strong correlation suggests that the neural activity is relevant to the behavioral task.
How would you design a study to ask the central question - does MT cells reflect perceived motion, beyond just visually-driven motion? Can neurons tell us what subjects perceived in motion direction? What do you expect to find?
Need to create a graphing space upon which you can map the subject’s/animal’s behavior onto the same space as a neuron’s firing rate. So, create a psychometric function and a neurometric function.
Experiment: use random dot motion correlogram.
Result: some neurons are more, or less, or about the same sensitivity as the overall perception of the monkey.
How would you test if we can causally induce motion perception?
Microstimulate to MT neurons, to test whether these microstimulations can cause changes/biases in the subjective perception
- For instance, weaker motion becomes more sufficient to perceive the right direction
How/where does the brain perceive faces? Why is that so important?
Face cells (which are primarily excited when they perceive a combination of face feature dimensions) are in the inferior temporal cortex (IT).
Face perception is so important because evolutionarily, faces carry the most important social and emotional cues for guiding survival and reproduction. So, it makes sense that we have a specialized neural system!
What are face patches? What excites them?
Face patches are concentrated clusters of mostly face cells in the IT (inferior temporal). They are excited by a combination of critical features - a combination of two black circles and a horizontal line.
What is the fusiform face area? What happens if you stimulate the fusiform face area?
It is a small region found on the inferior surface of the temporal lobe, which is specialized for facial recognition. Stimulating the fusiform face area impairs ability to perform match-to-sample tasks with faces.
The first electrophysiology studies of face patches in the temporal cortex showed that neurons specifically fire when monkeys view faces. How would one test whether these neurons are causally involved in face recognition? Describe a simple experiment to test this idea (task, method, and results).
One way to test the causal role of these face patches is to microstimulate the face patches when animals are performing a face identify match-to-sample task. If a given face patch is causally involved in face perception, I would expect that the microstimulation applied either during the sample stimulus period or the test stimulus period would disrupt the processing of face. This disruption would be behaviorally reflected in a lower performance level of the animals in matching the identity.
What are Jennifer Aniston cells? Where are they found? Would a Jennifer Aniston cell always encode Jennifer Aniston (forever?) What is going on in these cells?
Jennifer Aniston cells are found in the human medial temporal lobe (MTL), found in the hippocampus. They record high spiking activity whenever presented with Jennifer Aniston (sketching, the name, a picture, a group of Friends). This is evidence of invariant (viewing angle and size) representation of person identity - it proves the existence of concept cells, with specific identities! Though it does not imply that the Jennifer Aniston cells will encode Jennifer Aniston forever - perhaps next week will encode something different.
Still a live question - how do these concept cells get formed?
What do concept cells tell us about the way the MTL encodes things?
The MTL has high-level, “concept”-like visual recognition. It has been associated with recognition of faces, objects, scenes, as well as various aspects of memory.
It shows us that the MTL may transform complex visual percepts into long-term and abstract concept-like representations.
What is numerical cognition? Where does numerical cognition take place? Why is it inherently challenging to study?
Numerical cognition is non-symbolic. It’s challenging because it is inherently confounded with sensory and spatial information - inherently intertwined, which means something for the brain’s way of doing this/processing information. (same size stimuli results in different cumulative area…same cumulative area results in different overall area, same overall area results in different density).
It takes place in the prefrontal and parietal cortices - specifically, intraparietal sulcus.
Studying the neural substrate of numerical cognition has been partially impeded by the presence of multiple confounds inherent to using numerical stimuli. Could you name one example of such confounds? Describe one stimulus design that could be used to eliminate at least one of these confounds.
Imagine using number of dots to indicate numerosity - one stimulus set with three dots, and another stimulus set with five dots. If you are using the same-sized dots, then the two stimulus sets would have different total surface areas of the dots, which can lead to confounding results when investigating neural representations in brain regions that are sensitive to visual input. To solve this issue, one can match the total surface area by making the dots in the stimulus set with five dots to be smaller.
Is numerical cognition sense-modality specific? (would it care if it’s auditory or visual?)
Sensory modality doesn’t matter! As numerosity is non-sensory dependent.
What is a delayed match-to-sample experiment?
a procedure in which the participant is shown a sample stimulus and then, after a variable time, a pair of test stimuli and is asked to select the test stimulus that matches the earlier sample stimulus. Correct selection of the matching stimulus is reinforced.
What is the attention vs. intention debate? What area was studied in this debate?
The question is whether motor-processing systems are distinct from circuits for controlling covert and overt attention. Do motor-planning (action) and attention processes overlap (or are the same) in the brain? This would redefine attention as motor planning. Attention = sheer motor processing. Intention = action-oriented (as affected by movement goal).
The posterior parietal cortex (implicated in spatial attention and eye movements) was studied to determine whether the signals in the posterior parietal cortex reflected attention or intention.
How would you test if LIP (lateral intraparietal area) neurons really track attention (vs. movement goal)?
Design a saccade-to-goal experiment. A target cue always tells where to go on Go trials. But, there is a task-irrelevant distractor (which only appears on 50% of trials), BUT captures the attention at a different location than the potential motor goal. Why use the distractor? It captures attention at a different location than the potential motor goal (testing motorindependent attention) (i.e., distractor captures attention when it’s not a target -> so the distractor-driven activity argues for nonmotor-related attention signal)
The result: attention is involuntarily drawn to a distractor early when planning a saccade elsewhere, but the attentional effect lasts a short time. LIP responses reflect that the attention is captured, although it shows greater response to target WHEN there is an attentional benefit. Activity of LIP neurons show similar response to target and distractor when there is no attentional benefit. So, LIP activity is nicely tracking where attention is captured with respect to behavioral aspects of attention-related task performance. LIP activity is tracking where the attention is beneficial for the task.
How would you design a study to test the difference between “space” and “motor effect,” in attention/intention debate?
Two tasks. First, a cue-delay-target task. In this task, the monkey knows from the beginning whether it’ll saccade or reach with its arm (motor effect). But, the information for where the intended motion will be cued is delayed (spatial target comes up afterwards)
Second, a target-delay-cue task. In this task, the monkey knows from the beginning where its spatial target will be. It finds out how it’ll gesture (saccade or reach) after a delay period.
By dividing it into two tasks with a delay period, you can measure the monkey’s brain activity, to understand how the monkeys response to intention (effector instruction) or spatial information (attention). Even without the spatial information, these cells respond to effector instruction. However, they still are spatially tuned. So, they’re responding to BOTH attention and intention.
How do you use visual awareness to study consciousness? How does the binocular rivalry paradigm relate to this?
Conscious perception, by testing how the same visual stimuli are “gated by” consciousness or “reach” consciousness.
The binocular rivalry paradigm - to study what’s reaching the brain/consciousness stream. Red/Green filter glasses (only house on Left eye and only face on Right eye), leads to alterations in subjective perceptions (don’t perceive both). However, the actual brain activity matches the non-rivalry condition.
This indicates the importance of “perception” rather than “just seeing.”
What is the premotor cortex? How would you test if the PM is the system that integrates information (e.g. - which arm for which target?)
PMd (dorsal) and PMv (ventral) represent movement direction at a higher level than the primary motor cortex. Neurons are tuned to a preferred direction (PD - when moving an arm to a specific location in space), movement field (activity only evoked with motion).
Setup: cue for which arm (left or right), then cue for direction of target (which target, left or right), then GO. The key here - sequential information allows to tease apart the processing.
Result: They have effector instruction selective cells, and target instructions elective cells (pure right arm instruction selective (before knowing which target), and pure right target instruction selective, (before knowing which arm)). And, there is action selective neuron (moving right arm to left target - integration order doesn’t matter as long as that’s the final action).
When measuring the effects of the premotor cortex in selecting motor decisions (attention vs. intention): What would you expect to see if a task has two possible targets, with a memory moment, and then the correct target later revealed? (versus the one target task, the target known the entire time)?
I would expect to see the build-up cell show activity for both directions, but activity for the undesired direction shuts down once target is given. The selected-response cell will have no activty until target is known, where activity shoots up for desired direction.
The immediate drop in cell activity (when revealed that that stored direction is no longer the target) shows that premotor cortex “selects” motor decisions.
What is mirroring in the premotor cortex? How would you design an experiment to record these neurons?
Mirror neurons are those neurons which light up for both the direct action, and seeing the action (monkey see, monkey do).
Method: Three tasks. First, experimenter and monkey do the same action (monkey seeing and monkey doing). Second, the experimenter and monkey do different actions (monkey doing, but not seeing). Finally, as a control, have the monkey grab the food in the darkness (ruling out simple visual feedback as driving these neurons).
The result - in all three cases, the same neuron lights up for the correct action (either perceived or done themselves). The neuron does not light up for the seeing the experimenter do a different action.
Significance: confirming that these mirror neurons in the premotor cortex really are responding to that action, independent of whether it’s perceived or done by the animal itself.
How would you design an experiment to see whether PMv mirror neurons take into account peri- vs. extra-personal space? What is the significance of this question?
What would you expect to happen with this same experiment, if an experimenter put up a panel in the peripersonal space - so that the object touched was now outside the workspace, but still inside peripersonal space?
The purpose of this is to test if the mirror neuron cares about intention; if it’s further away, you know that you cannot reach it and vice versa.
Experiment design: a monkey sitting on a table. An object is either placed inside or outside their peripersonal space. Three trials - an object inside the peripersonal space is grabbed by an experimenter, or it is grabbed by the monkey. Or, an object in the extra-personal space is grabbed by the experimenter.
Result: some neurons were turned to extrapersonal space (higher when farther) and some were turned to peripersonal space (higher when closer). Evidence that some mirror neurons change how they fire based on whether the monkey might interact with what’s happening.
How do human mirror neurons relate to action / intention?
Method: Manipulated video clips - picking up cup (context: before tea), versus picking up cup (context: after tea). The intention is inferred differently - before tea, the action is linked with the intention of drinking. With after tea, the action is linked with the intention of cleaning up.
Result: PMv related areas are active for intention (look at the overall activation patterns, subtract intention from action), processing intention and goal.
What are hypotheses about the function of mirror neurons?
Motor rehearsal: even if you’re not doing the action, you’re still practicing the circuite loop.
Simulating others? (figuring out the intention of others?)
