CogNeuro 8-9 Flashcards
For what purpose would you want to test sea slug gill reflexes?
PURPOSE: studying memory at the neural level
STRUCTURE OF STUDY: When touched, the gill shows withdrawal reflex. After conditioning (direct tactile stimulus + tail shock), a memory is formed. They figure out that you can condition withdrawal by pairing tactile stimuli with a tail shock. The shocked group means the stimulus takes on (and maintains) a very different meaning in the slug’s brain.
RESULT: This is memory at the synaptic level. The pairing of the tactile touch to siphon with the shock to tail results in a facilitation of EPSP in the synapse between the sensory neuron and motor neuron, which lowers the threshold for action potential, gives a lower signal a higher ability to activate the neuron.
Why would you choose a sea slug?
You would choose to study a sea slug because it has a very very simple system: tactile stimulus -> sensory neuron -> motor neuron -> gill retracted. With sensitization, the stimulus also feeds into the motor neuron. It’s a question of what happens at this synapse, in terms of EPSP and IPSP.
what is the main region associated with memory?
medial temporal lobe
how did aspiration lesion studies help our understanding of what regions are responsible for memory?
Using aspiration lesions, lesioned off a bunch of different areas in brain and recorded memory performance.
Saw that the Rhinal cortex (Rh), a key node in the MTL, is important enough such that lesioning that region off caused severe issues, even without a hippocampus lesion, suggesting that memory isn’t just located within the hippocampus.
what was the issue in the aspiration studies that studied memory? How was this resolved with another study?
Because aspiration lesions were used, we can not specify the cause of the behavior – is it the neurons we took our or is it disrupting communication in a bigger network of the brain because of destroyed fiber connections?
To study this better however, we need to use Excitotoxic lesions.
Results: Selective lesions to hippocampus + amygdala (‘AH’) results in intact visual recognition memory, whereas lesions of the RH (rhinal cortex) led to a huge decrease in intact visual recognition memory (ability to recognize and remember visual stimuli). This suggests that the RH plays a more pivotal role than the hippocampus in terms of visual recognition. Moreover, it suggests that the previous results from the aspiration lesions are due to destroying connective fibers rather than the specific regions themselves.
How did we test if the hippocampus still played a role in spatial memory? What was the task and what were the results?
Morris Water Maze!
The goal of this task is to make the rats swim to a platform somewhere on the maze. However, the water is opaque and the rats cannot see the platform, meaning that they must find their way to it through random guessing, or through their memory. They made the rat do this test multiple times with various lesions (hippocampus, cortical, and control) and conditions, and we can see the following result:
(1) The rats tend to find the platform over time through repeated trials, suggesting spatial memory.
(2) Hippocampal lesions ruin this memory, causing the rat to take strange paths.
(3) This problem is unique to hippocampal lesions and not lesions in general, as cortical lesions don’t seem to have significant effects on spatial memory.
*Takeaway: evidence that you need the hippocampus for spatial memory.
What is long term potentiation? long term depression?
LTP - an increase in a cell’s firing potential after brief, rapid stimulation (delivering repetitive electrical stimulation, find that certain stimuli pattern create long term changes in synaptic potential, which changes threshold for action potential.
LTD - long-term decrease in the excitability of a neuron to a particular synaptic input.
Significance: Believed to be a neural basis for learning and memory. If you used an antagonist to block the NMDA receptors in mice, you’d see a lack of LTP, which then results in spatial memory deficits.
Place cells vs Grid cells
Place cells refer to cells that are activated at specific and distinct places, encoding locations at specific neurons. We can see that these neurons are replayed after activity in the right sequence, suggesting that it is important for the sake of encoding and storing information.
Grid cells encode a space-like, equal-distanced grid-like pattern in hexagonal lattice. These are thought to provide input to the hippocampus. There seem to be correlations between these cells and the place cells in the hippocampus. Grid cells provide a continuous representation of space, contributing to the brain’s ability to create comprehensive cognitive maps of the entire environment, while place cells contribute to the formation of specific spatial memories.
What is cognitive control?
a non-precise term since it is hard to know what’s executive versus non-executive control in the brain. Often used to refer to the mental processes and mechanisms that enable regulation of thoughts, actions, and emotions in order to achieve specific goals or tasks
What task was used to study the differentiated roles of ACC and dlPFC in cognitive control?
STROOP TASK
Kerns et. al studied the role of the anterior cingulate cortex (ACC) in conflict monitoring by using a Stroop task, which is displaying color words in a color that does not match that collor (ex: “Blue” in a Yellow font). Participants’ response time was recorded for congruent (word matches color) and incongruent (word does not match color).
What were the findings of the stroop task?
Findings: Response time was faster overall for congruent trials than incongruent (no surprise there). However, when measuring interaction with a previous trial type (C or I), there was a task switch effect). So, going from Congruent to Incongruent is especially hard, but this is not true for the reverse condition (going from Incongruent to Congruent).
Found that in incongruent trials, there is a focal activity in the ACC. Saw that the LPFC had greater activation for high-adjustment than low-adjustment trials (more engaged on trials that require more control). Concluded that ACC detects conflict whereas LPFC is involved with implementing adjustment.
What was the saccade countermanding task that looked at rule/strategy-based cognitive control?
In the saccade countermanding task, there is a no-stop trial where there is no conflict for the animal – they make an eye movement as soon as target comes up and there is a stop-signal trial where there is a go-or-no-go cue that tells the animal to make the eye movement or cancel the eye movement. This cancellation is the key component of the “countermading” in this task.
SEF contains neurons that signal error (15%), conflict (13%), and reinforcement (22%), suggesting that SEF is involved in performance monitoring.
After doing the same saccade countermanding task and measuring ACC , found that AAC did not have cells that signal conflict (unlike SEF) but had neurons that signal error (like SEF). This suggests that ACC may monitor the consequences of actions, whereas SEF is more actively determining them in the first place.
