Final long answer Flashcards
Morris Water Maze Task
The Morris Water Maze Task is a behavioural test used to assess rodents’ spatial learning and memory, particularly concerning the hippocampus. The task involves placing a rodent in a pool of opaque water and training it to find a hidden platform using spatial environmental cues. The rodent is given several trials over some days to learn the platform’s location, and its performance is measured by how quickly it can find the platform on subsequent trials when the water is opaque; therefore must rely on memory instead of visual cues.
- Train with clear water and a platform slightly above the water surface (typically do three training trials)
- Make water opaque for testing and lower the pedestal below the surface level
In the image:
B: intact hippocampus - can do in clear and opaque
C: hippocampus lesion - can do in clear but not opaque – cannot form spatial memory for external cues
Evidence for Hippocampal Place Fields
Referencing the left image: the rats are placed in this circular environment and are allowed to explore; the longer the rats are in the environment, we begin to see the “place neurons” fire very specifically when the rat is in a certain location in the environment.
- Single-cell recording in rats, over several trials that allow it to get familiar
Hippocampal place cells are neurons in the hippocampus that selectively fire when an animal is in a specific location within its environment. In other words, these cells represent the animal’s cognitive map of its environment. The discovery of place cells and their role in spatial navigation was made possible through single-cell recordings in rats.
In these experiments, researchers implanted electrodes in the brains of rats and recorded the activity of individual neurons while the rats were allowed to explore a novel environment. They found that the place neurons in the hippocampus fired selectively when the rat was in a particular location. These neurons were dubbed place cells and provided strong evidence for cognitive maps in the brain.
- when rats were placed in a larger environment with the same “floor plan,” they still saw the same firing in the place neurons in the same portion of the circle
- the initial development of the spatial specificity in the hippocampus that occurred in the smaller region was maintained, but it expanded to fit the larger circular environment
Image C, left) Fire for the left side of L/R field
Image C, right ) Area expands to a new environment
We see this in Image A and B as well
Korsakoff’s Syndrome Study
Task: recognizing faces of individuals who were present across different decades; Ronald Reagan was used in this study.
- Nonalcoholic controls do well across all decades
- Alcoholic controls develop a trend with impairments in the more current decades, suggesting some in antegrade amnesia while also seeing some impairment in the older information (i.e., retrograde)
- Korsakoffs have antegrade and retrograde amnesia; you can stop the damage from continuing, but you cannot full recover (i.e., the damage has been done)
Extended digit span
- 7+ n task (1634589 + 8; + 2; ….)
Extended digit span (HM cannot do this, this requires long-term explicit storage): this one uses the same base and adds a new number onto the end; therefore, the person needs to remember the base and continue to remember the additions
- 7+ n task (1634589 + 8; + 2; ….)
- involves the long-term memory store (the more you repeat the base, you encode and consolidate the base number)
- HM cannot do this because he cannot put the base into the LTM storage
- recall that HM has trouble with the hippocampus
The extended digit span task is a variation of the digit span task. In this task, the participant is initially presented with a sequence of seven digits to remember, just like in the standard digit span task. Afterward, the participant is asked to recall the sequence in the correct order. If the participant succeeds, the task continues with a new sequence of eight digits to be remembered and recalled in the correct order. If the participant is successful again, the sequence increases to nine digits, and so on.
- involves the long-term memory store (the more you repeat the base, you encode and consolidate the base number)
In this task, the digit sequence length starts at seven and increases by one digit on each subsequent trial. The participant’s score is the highest number of digits recalled in the correct order across all the trials. This task is used to assess the individual’s working memory capacity, as it measures the maximum number of digits that an individual can hold in working memory at any given time.
Case DF - Occiptial Damage and Visual Agnosia
- Bilateral damage to LO region & tissue between the parietal & occipital lobes
- Visual form agnosia - inability to recognize line drawings of objects
- Can use visual information to guide movements but not to recognize objects
- carbon monoxide damage
- double dissociation with VK
- Damage to the ventral stream
Tower of London Task
The Tower of London task is a neuropsychological test of planning and problem-solving skills. It requires the participant to rearrange a set of coloured balls or disks on three pegs to match a goal configuration, with specific rules for how many moves are allowed and how the pieces can be moved. The task is timed and becomes progressively more difficult with each new problem. The Tower of London task is often used to assess frontal lobe function and executive functioning in clinical and research settings.
- Three pegs; 3, 2, 1 ball
- Assess strategies used to sequence action
- Left Hemisphere-PFC damage has trouble: LH is involved in goal-directed planning and strategy (imaging data – activation in PFC in NI)
Novelty & Prefrontal Regions: Oddball Task
Frontal Lobe:
- Important for detecting and focusing on novel items in the environment
- Damage can impair this ability to focus on extremely novel items
- Novel elicits P3a. The frontal lobe has a higher activation of this in the brain, and we need to adjust our attention to these things.
- P3a decreases after prefrontal cortex damage
Experiment:
Frequent = high pitch 78% of the time
Rare = low pitch 20% of the time
Novel = car horn, sneeze, etc. 2% of the time, very unique
The P3a is most strongly elicited by rare or unexpected stimuli that require attentional processing and orienting responses. The exact characteristics of the stimuli can vary depending on the experimental paradigm and task used to elicit the ERP.
- you do not see p3a activate for the frequent condition
ERPs and PFC:
- ERPs (event-related potentials) can measure brain responses to novel stimuli
- P3a is an ERP component typically elicited by novel or unexpected stimuli that require attentional processing and orienting responses; we see activation after they see something novel
- PFC (prefrontal cortex) is involved in attentional processing and orienting responses
Examples of stimuli that can activate P3a:
- Sudden or unexpected changes in the environment
- Novel or unfamiliar stimuli
- Emotionally salient stimuli
- Stimuli that require a shift in attention or a response
Wisconsin Card Sorting Test (WCST)
The Wisconsin Card Sorting Test (WCST) is a neuropsychological test that measures a person’s ability to switch their attention from one rule to another and their capacity for abstract reasoning. In this test, the participant is presented with cards and asked to sort them based on different rules such as colour, shape, or number. After a certain number of correct responses, the rule is changed without warning, and the participant must deduce the new rule and start sorting according to it.
- initially shown the row of cards
- given a card, and must sort it by a specific rule
- receive feedback “correct” or “incorrect”
- after 10 rounds, the rule will change
- frontal lobe damage results in the inability for them to change the rule and inhibit their behaviour (i.e., response inhibition, perseverating)
- similar to Stroop task
Individuals with frontal lobe damage or dysfunction, including those with certain types of dementia, schizophrenia, or traumatic brain injury, may have difficulty with the WCST. One of the most significant difficulties observed in this population is perseveration, which is the tendency to continue using the old rule even after being told that the rule has changed. Perseveration is seen as a disconnection between a person’s thoughts and actions, where the individual cannot adjust their behaviour in response to changing circumstances. The WCST is used clinically to diagnose frontal lobe damage and assess cognitive flexibility, a component of executive function.
- After 10 correct trials: change the rule
- Patients who perseverate cannot switch behaviour to fit with new rules.
- Even continue when they “know” they are not following the new rule.
- Disconnection between thought and action.
