krCognitive Neuro

Question 1

Pros and Cons of EEG

Answer 1

Amazing temporal resolution but horrible spatial resolution

Question 2

Pros and Cons of fMRI

Answer 2

low spatial resolution (relatively) but bad temporal resolution. very human-friendly.

Question 3

PET

Answer 3

horrible spatial and temporal resolution (worse than fMRI)

Question 4

single-unit recordings

Answer 4

great spatial and temporal resolution but poor brain coverage since you can only record from a given brain region.

Question 5

Difference between extracellular and intracellular single-neuron recording

Answer 5

microelectrode is placed outside, somewhere in the vicinity of a neuron in extracellular. micro electrode is inserted into axon and can directly record in intracellular, but will damage the cell.

Question 6

Difference between aspiration and excitotoxic lesion

Answer 6

Aspiration Lesions removes whole tissues. Strength of this is that it is a complete removal, but con is it may damage fibers of passage, affecting other brain functions.

Excitotoxic lesions selectively kills cells and spare fibers of passage.

Question 7

Difference between Ventral and Dorsal Stream

Answer 7

Ventral: the “what.” object recognition pathway and visual perception. Involved in the identification and recognition of objects and shapes.

Dorsal: the “where and how” pathway. responsible for spatial awareness, motion perception, and coordination and guiding motor actions.

Question 8

Explain the Middle Temporal Area’s role in motion perception and how it is organized.

Answer 8

MT has columnar organization for motion direction and depth. MT is part of dorsal stream.MT neurons have direction selectivity, meaning they are particularly responsive to motino in specific directions (preferred direction). The neurons are organized in columns, where each column corresponds to a particular direction of motion. The columnar structure shows clusters of neighboring neurons sharing receptive fields with a similar preferred direction motion.

Question 9

What is the task design for the random dot motion discrimination task?

Answer 9

Monkeys are first required to maintain fixation on a small spot of light. Then, a motion stimulus turned on (different correlations of where dots were moving towards neuron’s preferred direction). Next, two saccade targets appeared and monkeys had to make an eye movement to where they think the direction of motion was.

Question 10

What does the psychometric curve tell us in the random dot discrimination task?

Answer 10

The X axis measures the correlation (how easy it was to detect motion direction of stimuli) and then Y axis shows us the proportion of correct decisions. The graph makes sense as the higher correlation (more dots are obviously going towards one direction), the easier it is to make a saccade to the correct target.

Question 11

What is the ROC curve and how is it connect to a neurometric function? What do these two tell us about the random dot discrimination task?

Answer 11

The ROC represents the relationship between correctly identifying preferred direction trials (hit rate) and incorrectly identifying anti-preferred direction trials (false alarm rate), measuring the rate at which the monkey actually guesses correctly.

By taking the area of the curse of each ROC curve (the proportion correct), we can get the dots for the neurometric function. Comparing this to the psychometric (behavioral) graph lets us know how good that singular neuron is at predicting perceived motion (if psychometric and neurometric graphs match up, very good)

Question 12

Understand how the evidence leads to the abstract concept-like representation of the human MTL cells.

Answer 12

The Medial Temporal Lobe is associated with memory and recognition of certain objects. In a specific study, neurons only fired to specific celebrity faces (even in different backgrounds), suggesting we have a concept of specific individuals and places. Neurons in the MTL respond selectively to these faces and places.

We also found invariant face neurons that responded to an identify of different faces, which suggest some neurons encode a more abstract representation of facial identity.

Question 13

how do we perceive faces?

Answer 13

In this study, shows monkeys many images of faces missing different attributes and measured how face cells in the inferior temporal cortex (IT) fired. Tells us that face cells encode combination of dimensions relevant to perceiving face and different groups of neurons were selective for specific facial features.

Question 14

The inherent confounders of stimuli for numerical cognition study

Answer 14

Issues such as space, density, and size make it difficult to accurately measure numeric abilities.

Say you want the stimuli to be same size and you’re testing 4 and 8, the problem then becomes you’re stimulating a lot more visual processing in the 8 condition than the 4 condition (8 takes up more area). But if you want to match the same cumulative area, there is still a different overall-area in the 8 because otherwise, the stimuli will be clustered together. if you want the same overall stimulation area for 4 and 8, but you have to make the area for 8 much smaller .. now results in different density

Question 15

Numerical cognition: How the number was dissociated from other quantity specificity and what was the result?

Answer 15

In a study looking at the Intraparietal Sulcus (IPS) and numerical cognition, they tested different modalities (presenting visual, auditory, etc. stimuli) to make sure the brain was responding to just number-based stimuli.

Results showed that activation of areas were most pronounced for numbers, no matter the modality (as compared to colors and letters). This lets us conclude that IPS is strongly connected to number cognition!

Furthermore, when participants were asked to do simply subtractions (compared to just naming numbers), they found activation in parietal areas and some in prefrontal areas.

Question 16

How is numbers-selectiveness represented in the curves of IPS and PFC neurons? What was the task?

Answer 16

Each plot on the left is an example of individual neuron’s responsiveness (tuning curve) to the 5 different numbers (represented by 5 diff colors) over time. Takeaway here is that each neuron in the Prefrontal Cortex has their preferred number (as shown by the spikes for specific numbers) which shows number-specific sensitivity. On the right is the turning curve averaged from all the neurons that are most responsive to that number. The takeaway here is ~30% of the recorded neurons in the PFC are number-selective (i.e. most responsive to specific numbers).

monkeys were tasked with matching the tests to a sample shown before the delay period based on the number of dots there were. Dots were presented in numerous ways for stimulus control, but the number of dots remained constant.

Question 17

Classical theory of attention vs pre-motor theory of attention

Answer 17

The classic theory of attention suggests that attention acts as a selective filter that helps process relevant information while filtering out irrelevant stimuli. It suggests there is a limited capacity for processing information, and attention helps manage this limited capacity.

The premotor theory of attention suggests that attention is linked to motor planning and action. It suggests that attention is not just a filter for perception but is also involved in preparing the motor system for an appropriate response to stimuli. According to the theory, attending to an object or location involves the activation of motor-related processes, preparing the observer for potential actions related to the attended stimulus.

Question 18

Tasks of Bisley 2003: Study supporting classic theory of attention.

Answer 18

In Bisley 2003, monkeys were trained to do simple detection tasks. They are given a target (but can not go yet). A delay period pops up and then a distractor period that shifts the monkey’s attention (monkey knows this will never be the target). The distractor is always task-irrelevant, but captures attention (this is relevant because if a monkey knows they will never go there but still tracks their location, knows it is not a motor plan/not supportive of premotor theory). There will be a probe trial (different circles presented, direction of where it is opened represented GO (make saccade to goal) or NOGO (cancel saccade)). Depending on the trial, the probe will either be at the location of the distractor or target.

Question 19

Results of Bisley 2003: Study supporting classic theory of attention.

Answer 19

At a short distractor-to-prove time, the probe distractor results in a better performance (attentional benefit of distractor). However, after a certain distractor-to-probe time, the distractor effect goes away and the probe at target will perform better. When doing this study, they could confirm that there was attention to the distractor as there were changes to performance based on delay period and the location of the distractor stimuli.

Distractor captures attention and LIP (lateral intraparietal cortex) responses reflect that (even though distractor is task-irrelevant) → support attention (opposed to intention) because it shows you can pay attention to something even without intention of moving there.

Question 20

which region of the brain was recorded in the distractor-to-probe study?

Answer 20

lateral intraparietal cortex (LIP)

Question 21

Task of Synder 1997: study supporting the pre-motor theory

Answer 21

Monkeys are then given a spatial target and a task cue (whether they will saccade or reach). After a delay period, they are to complete their motor effector instruction.

Question 22

Result of Synder 1997: study supporting the pre-motor theory

Answer 22

Looking at the LIP neurons in the saccade trials, there is encoding of information. When monkeys reach for it, there is no high sustained activity anymore. Just the fact there is eye movement attention (LIP) and arm movement attention (PRR) tells us how you are going to use that space matters (intention of space) and suggests monkeys were planning their movements.

Question 23

Task of Calton 2002: Third study that drives home the pre-motor theory of attention

Answer 23

Here, in the cue-delay-target, we only tell monkeys the color (whether to reach or to look) and we do not tell them the spatial target until AFTER the delay period. On the other hand, the target-delay-cue-task gives the monkey just the spatial target cue and then the task cue AFTER the delay period. This way, they dissociated space from the motor effect.

Question 24

Result of Calton 2002: Third study that drives home the pre-motor theory of attention

Answer 24

These trials allow us to isolate the motor plan (given through the cue) from attention (given through target). Because the same cell increases its firing in both trials even without spatial information in the cue-delay-target-trial, the cell was firing in preparation of movement even if it is not clear where that movement will be directed towards since this is during the delay period (gray box behind graph).

Question 25

How does the binocular rivalry paradigm dissociate “perception” from “just seeing”?

Answer 25

Chose faces and house because we can clearly track the parahippocampal place area (PPA) which fire when you see a house, and the fusiform face area which fire when you see a face.

The % signal of rivalry matches the non-rivalry. Based on this, the idea is that what you see and perceive may be influenced by your consciousness and other biases happening in your mind. Specifically, the study showed that while signals for both activate during the rivalry condition, exactly what you see is based on more personalized factors such as perceived duration. This entire experiment and idea suggests that your consciousness and your self reported perceptions affect perception rather than just “seeing” something.