Lecture 7- Memory and the Temporal Lobe Flashcards
What was Karl Lashley’s proposition for where memory was stored?
Came up with the principle of mass action where memories were stored/ distributed throughout the cortex. He didn’t think memories was located in a particular place.
Which famous patient of psychology proved Lashley’s hypothesis for memory storage wrong?
H.M. :
Had a history of seizures suffering from age 10-16. He did not respond to medication so at age 27 he underwent temporal lobectomy removing the temporal lobe, hippocampus and surrounding cortex like the parahippocampal gyrus (as this is the part of the brain the seizures started at). The result was severe anterograde amnesia (unable to form new memories) and retrograde amnesia for 2 years prior to the surgery. His short term memory and remote memory was intact. This shows that in fact the temporal lobe is invovled in storing certain types of memory (it is localised in this way).
For patient H.M. what was surprising about the acquisition of certain types of new information?
In mirror drawing task (i.e. procedural memory) H.M. improved with each consecutive day despite not having source memory/ episodic memory for having done the learning.
What part of the brain does procedural memory (such as that displayed in the mirror drawing task) involve?
Striatum
What part of the brain does priming memory involve?
Neocortex
What are the different types of declarative or explicit memory, what area of the brain do they invovle and what was damaged for H.M.?
- Declarative (explicit) memory is spilt into facts (semantic) and events (episodic). Both of these are stored in the medial temporal lobe + diencephalon.
- Interestingly for H.M. only event/ episodic memory was damaged, semantic memory/ general logical sense of how the world worked stayed intact.
What do H.M. deficits show?
- Dissociation of intelligence and memory (H.M.’s IQ score actually improved, you can still be intelligent and have poor memory).
- Dissociation of declarative memory from working and procedural memory
- The hippocampus is invovled in memory consolidation (this was removed bilaterally in patient H.M. leading to deficits).
What happens when you disrupt the hippocampal circuit? What patient (not H.M.) shows this?
- Hippocampal circuit goes from the dentate gyrus to CA3 neurons to CA1 neurons
- For Patient R.B. an ischemic episode (problem with blood flow to the brain) after open heart surgery resulted in selective, marked anterograde amnesia and very minor retrograde amnesia
- Patient R.B. died shortly after and the brain was examined to show that the hippocampus had been compressed down a lot (loss of neurons). It’s the damage to the CA1 neurons in the hippocampal circuit particularly that leads to memory problems.
What did damage to a small section of the hippocampus cause in the Rey-Osterreith figure test?
- Produced memory deficits
- The Rey-Osterreith figure test is where you show an image and the patient has to draw it first by copying and then from memory. Patient RB was fairly good at copying but way worse than controls when had to draw from memory.
In Patient H.M. what other regions of the brain where damaged?
The cortical regions around the hippocampus, this is known as the rhinal cortex
What was seen in the Rey-Osterreith figure test when the rhinal cortex was damaged as well as the hippocampus?
- Patients couldn’t remember anything! 1 drew nothing, 1 drew a horse
- When it was just hippocampal damage patients were not as good as those with hippocampus intact but generally got some of the elements or the outline of the shape correct.
What did patient N.A. have?
- Diencephalic amnesia
- Damage to the mediodorsal thalamus and mammillary bodies
What is Wernicke-Korsakoff Syndrome?
This syndrome, which occurs in heavy drinkers, produces similar
memory deficits to those that result from temporal lobe damage
Wernicke-Korsakoff syndrome is caused by lack of thiamine (vitamin
B1) which affects the brain and nervous system, rather than by
alcohol directly.
Lack of thiamine can occur because:
Many heavy drinkers have poor eating habits. Their nutrition is inadequate and will not contain essential vitamins.
Alcohol can inflame the stomach lining and impede the body’s ability to absorb the key vitamins it receives.
The syndrome is also known as ‘wet brain’ or ‘Beriberi’
What regions of the brain are damaged in Wernicke-Korsakoff Syndrome? Therefore what type of amnesia is it an example of?
- Dorsomedial nucleus of the thalamus
- Mammillary bodies
- An example of diencephalic amnesia
How were IQ scores and memory scores effected in patients with Wernicke-Korsakoff Syndrome?
- IQ scores were not overly effected
- Memory scores were however, a lot lower even compared to those with temporal lobe amnesia
How did performance on a pair-associates memory task and story recall task compare across different groups of participants with memory conditions and to alcoholics?
- Low across all the memory conditions tested (lowest in KORS). Some groups didn’t remember anything (particularly in recall test)
- Alcoholics could still perform well although slightly less than the controls
What is the hippocampal-diencephalon memory system?
- Spatial information goes to the parahippocampal gyrus, object information goes to the perirhinal cortex
- This information then integrates in the entorhinal cortex then via binding memories are stored in the hippocampus travelling up the fornix to the mamillary body and then into the thalamus
- From here memories are then linked to associations in the neocortex
- These associations can consolidation/ strengthen over time
Why would it have initially been hard for researchers like Lashley to discover the hippocampal- dicephalic memory system?
Because the tasks they gave participants could be solved in many different ways
What does the limbic system consist of?
- Cingulate gyrus
- Hippocampus
- Amygdala
- Fornix
- Parts of the thalamus
True or false: new and recent memories are dependent on the hippocampal-diencephalic memory system?
True
What does damage to the diencephalic-hippocampal memory system cause?
Both anterograde and retrograde amnesia
What is a common test used to discover the relationship between the hippocampus and spatial information?
-The Morris water maze test (rats without a hippocampus struggle to remember where the platform is- don’t retain spatial information).
What are the two ways we can represent our location in space?
Difference is in the reference frame:
Egocentric: the frame of reference is the individual
e.g. left/right, in front of me
Ego: Latin for “I” or “self“
Allocentric: the frame of reference is the external world
e.g. north, south, to the east of the tree.
between the tree and the house
How do you manipulate the Morris water maze task to either be egocentric or allocentric? How did rats with hippocampal damage compare to controls in each of these two conditions?
- Constant start (egocentric): rats know they just have to perform a certain pattern of movement to reach the platform. Rats with lesion were nearly as good at this as controls (saw same rapid decrease in time to find the platform)
- Variable start (allocentric): means rats would have to use cues in room. Rats with lesions were far worse than controls (time remain consistently high indicating not much retention of the spatial information).
