Only $2.99/month

Biological Level of Analysis

Terms in this set (54)

-Aim: To better understand the effects that the surgery had on patient HM

-Method: A longitudinal case study was performed on HM. He was hit by a cyclist while crossing the road when he was 7 and sustained a serious head injury. When he was 10, he began receiving epileptic attacks. At 27 he became so incapacitated due to the seizures that he could not lead a normal life and medication did not help him. With approval from HM and his family, William Scoville performed an experimental surgery where he removed tissue from the medial temporal lobe (including the hippocampus) on both side of HM's brain. Brenda Miler studies HM until he died in 2008. The first time Milner visited HM after the operation she observed that he forgot daily events nearly as fast as they occurred. After the operation HM remembered his childhood well. He later experienced retrograde amnesia and had a difficult time remembering the period about a year prior to the operation. He primarily suffered from anterograde amnesia (can not create new memories). Milner used method triangulation to carry out her studies. She used: psychometric testing(IQ testing), direct observation, interviews, cognitive testing (memory recall tests, like reverse mirror testing), and later an MRI.

-Results:
-HM could not acquire new episodic (memory for events) or semantic (general knowledge about the world) knowledge. This suggests that the brain structures that were removed from his brain are important for the transfer of information from short term to long term memory.
-HM was able to remember his house and could draw a picture of the floor plan of his new home. This indicates that he was able to form a cognitive map of the spatial layout of his house. This may mean that this type of memory is not encoded in the same way as semantic or episodic memories.
-HM had a capacity for working memory, since he was able to carry on a normal conversation. This requires a minimal level of retention of what has just been heard and said. On being asked to recall the number 584, HM was able to do so even 15 minutes later, apparently by means of constant rehearsal. However, after the task was over, HM would not be able to recall the number
-Memories in the form of motor skills, i.e. procedural memories, were well maintained; for example, he knew how to mow a lawn. He also showed improvements on the performance of new skills such as reverse mirror-drawing in which he had to acquire new eye-hand coordination (Milner, 1966). Although he showed improvement on the skill over time, he never remembered learning the skill. Every time Milner asked him to do it, he would say that he had never tried it before
-In 1992 and then 2003, Corkin carried out an MRI scan of HM's brain to see the extent of the damage. It was possible to see that parts of HM's temporal lobe including the hippocampus had the most damage. However, the damage was less extensive than originally estimated by Scoville. Damage to the hippocampus explains the problem of transferring short-term memory to long term memory as this is the area where the neurotransmitter acetylcholine is believed to play an important role in learning and formation of memories.
-The memory systems in the brain constitute a highly specialized and complex system.
-The hippocampus plays a critical role in converting memories of experiences from short-term memory to long-term memory.
-However, researchers found that short-term memory is not stored in the hippocampus as HM was able to retain information for a while if he rehearsed it.
-Since HM was able to retain some memories for events that happened long before his surgery it indicates that the medial temporal region is not the site of permanent storage but rather plays a role in the organization and permanent storage of memories elsewhere in the brain.
-Implicit memory contains several stores - for example, procedural memory, emotional memory and skills and habits. Each of these areas is related to different brain areas.

-Evaluation: (Pros)
-Longitudinal case study
-Method Triangulation
-High ecological validity
(Cons)
-Cannot easily be replicated
-Retrospective in nature
-Ethics - confidentiality (name was found out after his death), consent (HM was incapacitated and could not remember things
-Aim: To investigate the extent of the hippocampal and medial temporal lobe damage to HM's brain and to determine whether this could be sufficient to have resulted in the drastic memory loss suffered by HM.

-Method: HM was hit by a cyclist while crossing the road when he was 7 and sustained a serious head injury. When he was 10, he began receiving epileptic attacks. At 27 he became so incapacitated due to the seizures that he could not lead a normal life and medication did not help him. With approval from HM and his family, William Scoville performed an experimental surgery where he removed tissue from the medial temporal lobe (including the hippocampus) on both side of HM's brain. Corkin had known HM since 1962, during with time he had never recognized her from one visit to another. Corkin and her colleagues used MRI scanning in 1992 and 1993 to determine if Scoville's estimated lesioning of HM's temporal medial lobe atea had been as he stated, and whether this could be sufficient to have resulted in the drastic memory loss suffered by HM. Before the 1992 MRI scan, HM completed an IQ test and a memory test. The IQ test showed that he had normal intelligence, but the memory test showed that he had a memory quotient that was 37 points lower than his IQ and showed that he had severe amnesia.

-Results:
-Both scans showed that the lesioning (also called ablation or cutting) of HM's brain was 3 cm less than Scoville had estimated. It therefore did not extend as far into the posterior hippocampal region as he thought, although there was surrounding damage, as stated, to the uncus and the amygdala. Approximately 50% of the posterior hippocampus on each side remained, but this had shrunk considerably on the right side. Corkin believed that this could be due to both the removal of the rest of the hippocampus, and also to the druge and continuing (much reduced) epileptic seizures.
-The small amount of normal hippocampus remaining in the left temporal lobe was not sufficient to support normal memory. Therefore, this study demonstrates the importance of the hippocampus and the temporal medial lobe area for memory.

-Evaluation: (Pros)
-Longitudinal
-Used MRI
(Cons)
-Ethics: Milner gave permission for Corkin to scan HM's brain. It is not clear if she was the appointed responsible adult legally able to do this. HM, even if he gave permission himself, would not have remembered it, so there are issues with informed consent and right to withdraw.
-Ethics: Anonymity was maintained until his death.
-Aim: To investigate whether large lesions on the medial temporal lobe is responsible for the formation of long term memory

-Method: In 1992, Larry Squire and his team were introduced to one of the most interesting cases of amnesia since the famous HM study. At the age of 70, Eugene Pauly was diagnosed with viral encephalitis. His physical recovery was amazing, but his cognitive impairment was very significant. He had large lesions on his medial temporal lobe, the part of the brain responsible for the formation of long-term memory. Both the amygdala and the hippocampus were completely destroyed. When he returned home with his wife, the results of this cognitive impairment began to show. He couldn't remember the day of the week, the names of nurses or doctors or friends. He had trouble following a conversation but could talk about topics that interested him. Often he would repeat the same story or comment several times in a single afternoon. He would often forget what he had already done and as a result he would eat breakfast several times in a single day. Although he could not form new declarative memories, he could recall and discuss most of the events of his life that happened prior to 1960. - three decades earlier. Unlike HM, he was still socially functional. Whenever someone walked in the room, he would introduce himself and ask them about their day. Squire carried out a series of interviews with EP at his home. During one interview he asked EP to draw a map of his home. He was not able to do it. However, EP excused himself and got up to go to the toilet. How could a man that could not draw a map of his home find the bathroom on his own? When sitting in the living room, he could not identify which door led to the kitchen. But if Squire asked him to get him something to eat, he immediately got up and headed for the kitchen. This was a behavior not seen in HM. It led Squire and his team to carry out a case study that would deepen our understanding of how memory works. In this case study, Squire and his team used several different methods: interviews, psychometric testing, observations, and MRI's. One of the important tests done was the Autobiographical Memory Interview. The AMI is a structured interview that asks for detailed information about three periods of life: childhood, early adult life, and recent life. Within each of these periods EP's memory was tested for both personal semantic knowledge and autobiographical memory. The accuracy of all his responses was verified by at least two family members. For the recent time period, EP performed extremely poorly. He did better at answering questions about his early adult life, but his scores were still below the control scores. In contrast, EP performed normally when answering questions about his childhood, scoring nearly as high as the highest-scoring control subjects. Another important finding was an experiment in which Squire took 16 different objects and glued them on cardboard rectangles. He then organized the objects in 8 pairs. On the bottom of one of the objects in each pair was written the word "correct." EP had to choose between the two with the goal that with rehearsal, he would be able to consistently choose the "correct" object. However, he couldn't remember which objects were correct. The experiment was repeated twice a week for months. On each day that the experiment was repeated, there were 40 pairings. The findings were surprising. After 28 days he was choosing the correct object 85% of the time; after 36 days he was right 95% of the time. He would even turn the objects over on his own, even though he didn't remember that there would be a sticker there, as he could not recall ever doing the task. Squire wanted to see if this was true learning - that is, that Pauly actually remembered the objects, or whether there was something else happening. He then asked EP to put all the "correct" objects in a pile. He was unable to do so. He could only select the correct object from the consistent pairings.

-Results:
-MRI indicated that EP's basal ganglia were undamaged. This explains why EP could find the kitchen and the bathroom. It also explained why he was able to make breakfast and other tasks that were "routine." Of course, this also explains Squires experiment with the pairing of objects.It also explains another phenomenon which EP's wife reported. EP was able to take a walk around the block by himself, since his wife had taken him on a daily walk around the block after his surgery. She would even follow him around the block to make sure that he was ok, but he was able to find his way home without any problems. When he was asked from any point on his walk where he lived, he would say he didn't know, but since the task was associative - or a habit - he was able to simply walk home. However, occasionally there was a problem. If the sidewalk was being repaired and he had to leave his familiar path, EP would get lost. Returning to our example of driving a car - even when we drive a long time, bad weather or heavy traffic forces us to concentrate more. The task reverts from associative to cognitive. When this happened to EP, he did not have the capacity to solve the problem as his memory was only procedural. Once the familiar pattern was changed - as when Squire asked him to put the objects in piles - he was unable to complete the task.
-The conclusions of this case study show us that memory is more complex than initially believed and that the creation of memories is not solely dependent on the hippocampus. Even with hippocampal damage, tasks may be learned - even though the individual may not remember learning the task. In the case of HM, he was taught to draw using a mirror, but he never remembered learning this. This was the result of the role of the basal ganglia.
-The research also showed that habits need to be triggered. A cue leads to a routine. When EP was cued to play the object identification game, the routine was triggered, telling the brain to go into automatic mode.

-Evaluation: (Pros)
-Method triangulation was used
-In depth study
-Qualitative research
(Cons)
-Case study - unable to be replicated
-Ethics - anonymity (EP, aka Eugene Pauly's, name was found out), perhaps consent because EP had a bad memory
-Aim: To search for localization memory trace or engram

-Method: In a typical study he would train a rat to run through a maze without errors in search of food. After learning occurred, he would remove an area of the cortex, then place the rat back at the start of the maze and register the change in behavior. He removed varying portions of the cortex in different rats ranging from 10% to 50%. The idea was that if memory of the maze is localized somewhere, you will finally be able to pinpoint the specific region in the cortex responsible for it.

-Results:
-Although it took the rats longer, they were still able to get through the maze.
-The search turned out to be a failure and Lashley abandoned his initial hypothesis, concluding that memory was distributed rather than localized.
-His conclusion is supported by two observations: The principle of mass action (based upon a correlation observed between the percentage of cortex removed and learning abilities. The less cortex, the slower and more inefficient the learning. The key idea here is that the performance deterioration depends on the percentage of cortex destroyed but not on the location of the destroyed cells) and equipotentiality (this refers to the ability of one part of the cortex to take over the functions of another part of the cortex)
-These observations led Lashley to believe that memory is widely distributed across the cortex

-Evaluation: (Pros)
-Procedure is replicable
-Showed evidence to oppose localization of function
-Relative localization is still supported today
(Cons)
-Ethics - rats were harmed
-Aim: To investigate whether environmental factors such as a rich or an impoverished environment would affect the development of neurons in the cerebral cortex

-Method: Three male rats from a common litter were randomly allocated to one of three environments. In the control condition [CC] there were three rats in the cage. In the impoverished condition [IC], the researchers placed each rat in individual cages. The individual cages lacked the toys and the maze which were in the enriched environment. For the enriched condition [EC], the researchers placed 10 - 12 rats in a cage containing different stimulus objects to explore and play with. All groups had free and adequate access to food and water. The rats typically spent 30 to 60 days in their respective environments before they were killed in order for the researchers to study changes in the brain's anatomy.

-Results:
-The anatomy of the brain was different in the EC and the IC. There was an increased thickness and higher weight of the cortex in EC rats compared to that of IC rats. The researchers also noted that rats in the EC condition had developed significantly greater activity in the neurons in the cerebral cortex associated with transmission of acetylcholine, which is an important neurotransmitter for learning and memory
-It appears that the thickness of the cortex and the overall weight of the brain increased as a result of the enriched environment. A follow-up to this research indicated that just 30 minutes a day in an enriched environment produced the same changes in the brain in rats as had been observed in the original experiment where rats were exposed to the EC condition for a much longer period of time.
-One variable that was not clear in the enriched environment is whether it was the environment (the toys) or the social activity. Putting rats alone in large cages with toys for two hours a day showed no effect. The single rat tended not to play with the objects and instead rested and groomed himself. The enriched environment produced cerebral changes in a single rat only if the rat was stimulated to interact with the objects
-Since brain plasticity is assumed to follow the same pattern in both animals and humans, the implications of the study are that the human brain should also be affected by environmental factors such as intellectual and social stimulation. It is now known that poverty is a major risk factor in children's cognitive development as poverty is related to a number of risk factors such as poor nutrition, lack of access to good education and poor health

-Evaluation: (Pros)
-Highly controlled lab experiment
-Has been replicated several times
(Cons)
-Used animals, so it may not be able to be generalized to humans
-In the enriched environment, it could have been exercise that made a difference, rather than "stimulation." It is still not clear from the enriched environment how the variables of social interaction, environmental stimulation and exercise may interact
-There is the ethical consideration of undue stress or harm to the animals in the study. Not only were some rats isolated and put into an impoverished environment, but they were killed at the end of the study. A cost-benefit analysis should demonstrate that the goals of the study are worth the harm done to the animals.
-Aim: To find out whether the human brain can really change structure in response to environmental demands

-Method: Researchers used a random sampling design and a self-selected sample. They randomly allocated volunteers into one of two groups: jugglers and non-jugglers. They made sure that the groups had no experience of juggling before the start of the experiment. Whole brain MRI scans were performed before the start of the experiment. Participants in the juggler group then spent 3 months learning a classic juggling routine with 3 balls. Another brain MRI was performed. Participants spent another 3 months where they were instructed not to practice juggling. A third MRI scan was completed. The control group (non-jugglers) just lived their daily lives and had their brains scanned 3 times on the same schedule as the jugglers.

-Results:
-Comparison of the brain scans in the 2 groups prior to the start of the experiment showed no differences in the brain structure.
-Comparison of the second scans showed the juggler group had significantly more greymatter in some areas of the cortex - most notably the mid-temporal area in both hemispheres (areas associated with coordination and movement)
-The third scan showed a decrease in the differences between the two groups, but the amount of grey matter in these areas in jugglers was still greater than at the time of the first scan.
-Also there was a correlation between juggling performance and the amount of change: brain changes in participants who trained better were more pronounced.

-Evaluation: (Pros)
-Random sampling
-Random allocation of groups
(Cons)
-Low ecological validity
-Lacks internal validity (no changes in the coordination part of the brain)
-Lack of generalizability due to the small population and only the effect of learning juggling was measured.
-Aim: To see whether the brains of London taxi drivers would be somehow different as a result of the exceptional training they have to do to be certified.

-Method: The participants of the study were 16 right handed male London taxi drives. The taxi drivers were compared with the MRI scans of 50 right handed males who did not drive taxis. In order to take part in the study, the participants had to have completed the "Knowledge" test and have their license for at least 1.5 years. The controls were taken from an MRI database. The sample included a range of ages so that age would not be a confounding variable. The study is correlational in nature as the IV is not manipulated by the researcher. The researchers were looking to see if there was a relationship between the number of years of driving a taxii and the anatomy of one's brain. It was also a single blind study(the researcher did not know whether she was looking at the scan of a taxi-driver or a control. The data from the MRI was measured using two different techniques: vowel-based morphometry (VMB) and pixel counting. Voxel-based morphology (VMB) was used in this study to measure the density of grey matter in the brain. Pixel-counting consists of counting the pixels in the images provided by the MRI scans in order to calculate the area of the hippocampus.

-Results:
-Pixel counting revealed that the posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects and the anterior hippocampus were significantly smaller. VBM showed that the volume of the right posterior hippocampus correlated with the amount of time spent as a taxi driver. No differences were observed in other parts of the brain. Maguire argues that this demonstrates that the hippocampus may change in response to environmental demands.
-How does this relate to localization of function? It appears that the posterior hippocampus is involved when previously learned spatial information is used, whereas the anterior hippocampal region may be more involved during the encoding of new environmental layouts.

-Evaluation: (Pros)
-A single blind control was used to avoid researcher bias
-Ethics (no health risks to the participants and all gave consent)
-You cannot argue that the MRI has low ecological validity because the participants were not asked to do anything while in the scanner. They simply had their brain anatomy measured
(Cons)
-Quasi experiment (No cause and effect relationship can be established)
-May not be able to be generalized because only males were used