Lecture 17 - The Role of the Temporal Lobe Memory Function

Question 1

Who is Henry Malaison?

Answer 1

Had debilitating epilepsy. Had surgery in 1953 to remove areas of the temporal lobe to reduce seizures.
This surgery resulted in profound memory loss. This case study heralded research and understanding of the modularity of memory.
One of the main areas of the cortex that was removed was most of the hippocampi.

HM is one of the most studied individual’s in psychology/psychiatry.

Question 2

The fact that HM did not have impaired cognitive functions, other than memory, suggested that memory was largely encoded in a modular way and that the area of this encoding was what was removed in the HM surgery, i.e the hippocampi.
True or false.

Answer 2

True.

Question 3

What were the impacts of the surgery on HM?

Answer 3

Initially had retrograde amnesia, but over time largely resolved his retrograde amnesia, i.e. recovered memories from his life before the surgery.

Had complete anterograde amnesia, but with differences with declarative memory and procedural memory.

Question 4

What is declarative memory and procedural memory.

Question 5

Declarative memory is divided into episodic and semantic memory. Define these.

Answer 5

Episodic memory refers to the recall of contextual personal memories.
Semantic memory refers to the recall of facts.

Question 6

Did HM maintain procedural memory?

Answer 6

Yes, however, he had no memory of this learning (declarative memory).

Question 7

Were the hippocampi the only parts of the cortex removed in HM’s surgery.

Answer 7

No. Part of the hippocampi were removed, as well as the amygdala, and connections between frontal and temporal lobes were damage/severed. The hippocampi and amygdala are part of the mesial/medial temporal lobe.

Question 8

What is one of the main functions/responsibilities of the temporal lobes?

Answer 8

Memory.

Question 9

Are the hippocampus and hippocampal formation the same thing?

Answer 9

No. The hippocampus is one of a collection of brain areas known as the hippocampal formation.

Question 10

The medial temporal lobe/temporal neocortex is the main area of longterm memory.
The hippocampal formation is part of the medial temporal lobe. In what direction do the structures of the temporal neocortex communicate to generate and maintain longterm memory?

Answer 10

The areas of the temporal neocortex communicate and interlink with each other in a complex network that allows for the generation and maintenance of longterm memory.

Question 11

What areas make up the hippocampal formation?

Answer 11

The hippocampus (CA1,CA2,CA3), the dentate gyrus (which includes CA4), and the subiculum

Question 12

What is the role of the hippocampal formation?

Answer 12

The hippocampal formation is involved in learning and consolidating novel information.

Question 13

What is Papez’s circuit?

Answer 13

Papez’s circuit refers to a selection of modules within the brain thought to be significantly involved in emotional experience and expression and includes the hippocampus.

Question 14

Declarative memory loss is most frequent when damage is done to what brain structures?

Answer 14

The hippocampus, and anterior thalamic nuclei.

Question 15

What role does the amygdala play in memory formation?

Answer 15

The amygdala plays a key role in memory of emotionally arousing experiences, e.g fear conditioning.

Question 16

Areas in the frontal lobes play what role in memory?

Answer 16

Certain areas of the frontal lobes play a key role in memory encoding and retrieval, including chronological order of memories.

Question 17

What is confabulation?

Answer 17

Confabulation refers to the recalling of memories in a bizzare and inaccurate way.

Question 18

There are extensive connection between neurons in the hippocampus and temporal neocortex with certain areas of the frontal lobe, all of which contribute to the rich and complex encoding of memory into a wide network of neurons.

True or false?

Answer 18

True.

Question 19

What structures are part of the diencephalon and what is their main function?

Answer 19

The diencephalon is made up of the thalamus and the hypothalamus. These areas are the primary relay station for sensory information from the body to the rest of the brain and play a key role in controlling autonomic functions.

Question 20

Does the thalamus play a role in memory?

Answer 20

There are no specific area that is solely engaged in memory formation or maintenance, however, there is an interconnection of areas that do contribute to these cognitive tasks.

Question 21

What ions are responsible for the propagation of an action potential?

Answer 21

Sodium (Na+) and Potassium (K+).

Question 22

What ions are responsible for the propagation of an action potential?

Answer 22

Sodium (Na+) and Potassium (K+).

Question 23

Neurons communicate via electrical and chemical signals. From the axon terminal, to the synaptic cleft to the dentrite the signal goes from electrical to chemical to electrical.

True or false?

Answer 23

True.

Question 24

What is synaptic plasticity?

Answer 24

Synaptic plasticity refers to the ability of neural connections (i.e. synapses) to increase in strength and efficiency with use or decrease in strength and efficiency when not used.
It also refers to habituation and sensitisation.

Question 25

What is Hebb’s Rule?

Answer 25

Hebb’s Rule states that the more neuron A excites neuron B the more changes will occur which allow for the more efficient excitation of neuron B by neuron A. These changes occur in both neuron A and B.

Question 26

What does Long-Term Potentiation (LTP) mean?

Answer 26

LTP refers to the strengthening of the synaptic connection between neurons the more one neuron excites another.

Question 27

What is the main excitatory neurotransmitter?

Answer 27

Glutamate

Question 28

What is Long-Term Depression?

Answer 28

LTP refers to the decrease in connectivity, strength and efficiency of neural connections/synapses with the decreased use of these connections/synapses.

Question 29

What is the role of the entorhinal cortex?

Hint: memory

Answer 29

The entorhinal cortex is part of the hippocampal formation and plays a key role in memory, although, the specifics of this role are still unclear.
It is thought the EC plays a key role in mediating the transfer of information into and out of the hippocampus proper.

Question 30

What were the effects of the infamous surgery HM went through when he was 27?

Answer 30

Normal attention span.
General intelligence maintained.
Anterograde amnesia.
Procedural memory.
Declarative memory lost.

Question 31

What makes up the hippocampal formation?

Answer 31

Dentate gyrus.
Hippocampus (C1 TO C3).
Subiculum.

Question 32

What is the role of the Hippocampal Formation?

Answer 32

Important for learning and consolidating novel information.
Unclear what role it plays in memory retrieval.

Question 33

What is Papez’s circuit?

Answer 33

Papez’s circuit refers to the modules of the brain, including the hippocampus, which are thought to be involved in emotional expression and experience. Damage to areas of Papez’s circuit, especially hippocampus, results in the loss or impairment of declarative memory.

Question 34

The amygdala is responsible for the fear response and therefore is essential for fear learning and and memory of emotionally laden experiences.
What happens if the amygdala is damaged?

Answer 34

Damage to the amygdala can lead to the loss of declarative memories and emotionally laden memories, as well as an impairment in the ability to acquire new fear learning.

Question 35

Damage to what part of the brain can lead to confabulation?

Answer 35

Damage to the frontal lobes.

Question 36

Frontal lobes are thought to be responsible for encoding memories, chronological ordering of memories and contextualising memories.
What is one key aspect of how the frontal lobes are able to encode memories?

Answer 36

The frontal lobes, like most of the cortex, are highly interconnected with other areas of the cortex and brain. This interconnection allows for encoding of memory based on the experience of the event, including the senses and associations of the event.

Question 37

What structures make up the diencephalon?

Answer 37

The paired thalamus and hypothalamus.

Question 38

The thalamus is important to memory, however, exact function of the thalamus in memory formation and retrieval is unclear.
Different areas of the thalamus play different roles in memory formation and retrieval.

Answer 38

Yes.

Question 39

All learning involves change at what level?

Answer 39

The synaptic level.

Question 40

What is Hebb’s Rule?

Hint: neural plasticity

Answer 40

Hebb’s Rule states that if neuron A repeatedly excites neuron B, changes will occur in both neuron A and B,
such that neuron B is more easily excited by neuron A.

Question 41

What is Long Term Potentiation?

Answer 41

LTP refers to the strengthening of neural connections and efficacy of these neural connections. It involves the increased connection of dendrites/synapses, the increased production of neurotransmitters, the increased production/expression of receptors.

Question 42

What role does LTP play in memory formation?

Answer 42

LTP is one of the key mechanisms behind memory formation.
LTP has been shown to occur in the hippocampus when learning takes place.

Question 43

What other mechanisms are involved in synaptic plasticity?

Answer 43

LTD.
Habituation.
Sensitisation.