Flashcards
Spatial Cognition
Flashcards do conjunto (13)
- 1What evidence suggests the hippocampus's involvement in spatial memory?Clarke's nutcrackers, a type of bird, have the 5th largest hippocampus with respect to body size of any bird, reflecting their ability to remember the locations of thousands of seeds in the Grand Canyon.
Studies also found that black capped chickadees with lesions to the hippocampus retrieved less food.
In both birds, the hippocampus is largest in October, when the birds are storing the most food. - 2What is the significance of each side of the hippocampus?The left side is responsible for declarative memory (e.g. lists, verbalisable information), and the right side is responsible for spatial cognition.
A patient with damage restricted to the right side was only able to find his room in the hospital by counting the doors from the end of the hall. Because his left side was in tact, his declarative memory of the number of doors was unaffected. - 3How is spatial behaviour tested?In the Morris Water Maze, a rat is placed in a pool filled with water. Under the water (and not visible to the rat), there are barriers. There are four images on the walls, which serve as cues to guide spatial memory. The rat searches the maze for a platform, which it then stands on.
- 4What is the difference between allocentric and egocentric navigation?Allocentric navigation requires the hippocampus, and involves the memory of a target's position, rather than the route used to find it. If a rat uses allocentric memory to find the platform within the Morris Water Maze, it is able to find the platform regardless of the starting position.
Egocentric navigation requires use of the entorhinal cortex, and involves memory of the route to the target, rather than the target's position. If a rat uses egocentric navigation within the Morris Water Maze, it will always take the same route, and thus will not find the platform unless starting from a particular position. - 5What human experiments show the significance of the hippocampus in spatial skills?In an experiment, participants navigated a virtual town, having to pick people up at a cinema and take them to a library. They showed activation in the right hippocampus.
Taxi drivers have also been shown to have a larger right hippocampus than controls. No correlation between hippocampal volume and navigational skills was found in a control, non-taxi driver population. It was also seen that, after passing The Knowledge, taxi drivers showed significantly greater hippocampal volume than they did three years prior, before passing.
A study also found that taxi drivers had a larger hippocampus than bus drivers, showing the significance of increased spatial skills, rather than simple driving experience. - 6What are place cells?These cells are active depending on where you are in the environment, according to the external cues. Experiments have found that place cells in rats always respond to being in a branch of an apparatus specific to the surrounding external cues, not to the branch itself - so when the apparatus is rotated, the branch which a particular place cell responds to changes, so that its firing is consistent with the external cues.
- 7What do we know about entraining place cells?They take about 10 minutes worth of exploration for their firing to become stable. Landmarks which are farther away are also more salient cues than closer landmarks, since our relationship with distal ones is more stable.
- 8What evidence suggests that place cells predict where an animal will co?The place cells' activation correlates with where the animal will be in about 120 milliseconds.
The cells fire differently depending on whether the animal will turn left or right at a T maze. While deciding, place cells associated with each side fire sequentially, suggesting that place cells indicate navigational planning.
In a double Y maze, rats were trained to run right or left in alternating trials, and again, the place cell activation indicated which way the animal would turn.
The cells also fire based on the animal's final destination. - 9Describe evidence of 'tricking' place cells.The activation of place cells reflects where the animal thinks it is, rather than where it actually is.
In an apparatus where to rooms are connected by a hallway, a rat is consistently placed in the same chamber, and its place cells develop different patterns depending on which chamber it's in. However, when the rat is placed in the other chamber, its place cells fire as if it was in the original chamber, reflecting the rat's belief that it is in the original chamber. When the rat leaves, and sees that it must turn the opposite direction, it realises its mistake, and the place cells begin to fire appropriately. - 10What is the significance of motion and visual information over the activation of place cells?In a study, rats were trained to operate a VR system using an air-cushioned ball, which worked as a treadmill, allowing the rat to move within the VR. In one stage, the rat had to reach a white disk without any visual cues, including no texturing on the walls to indicate contours, and no white disk visible. This disrupted 81% of place cells, showing the significance of visual cues.
In another stage, the ball was deflated so the rat was unable to move with the VR, thus eliminating motion cues. This disrupted 75% of place cells.
This shows that both types of cues are combined to produce appropriate firing.
During a conflict stage, the rat was required to take twice as many steps to have traveled the same distance in the VR. Thus, a target which was typically 50 steps away was now 100 steps away. The place cells associated with the target location began firing not at 50 steps (using motion cues) nor at 100 steps (using visual cues), but at about 70 steps. This shows the required interaction of these cues to build up place field stability hippocampal spatial representations. - 11Temporal lobe epilepsy, as well as the surgery used to treat, both cause damage to the hippocampus. What research shows the effect of these on spatial cognition?In a study, participants were first taught to find a platform, then to find the location of the platform when it is not visible. Then, after a delay of two weeks, they were tested on their ability to find the position of the platform when it was not visible.
Both participants who had already undergone surgery and the patients waiting for surgery showed similar times for finding the platform. Both took significantly longer than the control group.
Probe 1 shows the effect on acquisition, which uses working memory. This trial showed a lesser deficit than Probe 2, which showed the effect on maintenance. All patients performed at about chance level, showing accelerating forgetting, or the inability to retain learned memories over long periods.
This shows that both short-term memory and long term reference memory can be impaired by hippocampal damage. - 12Describe neurogenesis in the hippocampus.Stem cells start off in the subgarnular zone, and as they develop, they move into the granule layer, by which point they become grunule, or pyramidal, cells. They then integrate with the neural network and become active. These new cells have lower activation thresholds, and thus receive preferential recruitment. Within the first month of their development, over 50% of these new cells die, but are more likely to survive while the person is learning.
Temporal lobe epilepsy causes a reduction in neurogenesis. Scans show that new neurons are often oriented incorrectly and thus aren't integrated into neural networks, and also have shorter dendrites. - 13What research has investigated the effect of neurogenesis on spatial learning in cases of temporal lobe epilepsy?Studies with rats using the Morris Water Maxe have shown that animals with induced seizures are slower to perform the task both in the acquisition and maintenance phases. Those with induced seizures also showed far fewer cells being integrated in the granule layer of the dentate gyrus, with many oriented incorrectly. When given fluoxetine (a powerful stimulant of hippocampal neurogenesis), they showed normal performance in the acquisition phase, including normal dendrite length and orientation. However, the effect did not carry over to probe 2, as they spent the same proportion of time in the platform zone as the seizure-induced rats which did not receive fluoxetine.
It's unknown if there is a deficit of consolidation (movement of the information to LTM) or recall (retrieving the info to LTM) which is caused by the seizures, and not aided by fluoxetine.
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- Cognitive Neuroscience FlashCards sobre Spatial Cognition, criado por Jamie Otten em 23-04-2019.
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- Jamie Otten
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