Schmidt hippocampus 1

Question 1

Who was patient H.M?

Answer 1

Had bilateral removal of medial temporal lobes and hippocampus to cure his epilepsy
Resulted in anterograde amnesia and partial retrograde amnesia
Huge impact on memory research
Highlighted clear connection of brain regions to memory

Question 2

What is the controversy of hippocampal function?

Answer 2

Originally thought to be involved with anxiety due to pharmacological studies but is no longer a dominant theory
Believed to be more involved with memory and spatial navigation

Question 3

What is one problem with studies looking at hippocampus function?

Answer 3

A lot are based on lesion studies so it is difficult to be so specific and also use the right behavioural testing
Meaning there are sometimes issues with interpretation

Question 4

Which type of memory is related to the medial temporal lobe?

Answer 4

Declarative memory, episodic memory

Question 5

Why do we use animals in cognitive research?

Answer 5

There is limited ethics with human studies and are therefore more techniques available in animal studies

Question 6

But can you measure cognitive abilities in animals?

Answer 6

Relates to the argument that cortex is special and has special organisation that allows for higher cognitive function
Mammals have cortex but birds don’t
But may not be the only way higher cognitive functioning is achieved
Can look at studies with birds

Question 7

What did the studies of birds and theory of mind show?

Answer 7

A study of magpies and a mirror showed that some displayed aggressive behaviour indicating that they think their mirror image is a rival
BUT depends on the bird as some behaved differently e.g. looking behind the mirror and checking whats happening in the mirror with their own actions (contingency learning)
Indicating that they knew something was different

Question 8

What did studies of crows show?

Answer 8

Crows in a lab setting use a metal rod to get food out of a tube demonstrating causal reasoning

Question 9

After investigating animal studies can you study cognitive abilities in animals?

Answer 9

Yes they also have impressive cognitive abilities
Even animals without cortex (birds) show evidence for insight-related cognition
But there might be simpler ‘pre-cursors’ for cognitive abilities in some animals, so don’t have episodic memory but have something similar
Provides interesting insights for research

Question 10

What is the hippocampus?

Answer 10

A banana-like shaped region going from the central part of the brain to the more lateral part.
Described as a tri-synaptic pathway because there are 3 main processing steps that reflect the flow of information through the hippocampus

Question 11

What are the 3 main processing steps?

Answer 11

1. The pathway is mediated by the perforant pathway as the input to the hippocampus, which leads to the dentate gyrus
2. Mossy fibres then project from the DG to the CA3
3. The Schaffer collaterals connect the CA3 to the CA1

These steps are simplified as there are a lot of processes going on within this flow of information

Question 12

What are the subregions of the hippocampus?

Answer 12

Dentate Gyrus
CA3
CA1
Subiculum
(there is a CA2 subregion but it isn't as prominent and not been studied as much)

Question 13

What are the two types of neurons within the regions of the hippocampus?

Answer 13

1. Projection neurons i.e. across subregions

2. Inhibitory interneurons i.e. within subregions

Question 14

What is the Dentate Gyrus?

Answer 14

The input region of the hippocampus with densely packed granule cells. Also lots of different inhibitory interneurons
Found to have high rates of neurogenesis which is the formation of new neurons - thought to be related to memory

Question 15

What are granule cells?

Answer 15

Excitatory projection neurons

Question 16

What are the CA3 and CA1 subregions?

Answer 16

They mostly consist of pyramidal projection neurons
But also have a lot of inhibitory interneurons
CA3 has a dense recurrent network such that the pyramidal neurons are also connected to each other - this provoked ideas about formation of memories

Question 17

What is the CA3 and CA1 network like?

Answer 17

A complex network of pyramidal neurons and interneurons

Cannabinoids act on these microcircuits through cannabinoid receptors

Question 18

What is the Subiculum?

Answer 18

The output region of the hippocampus, has 2 types of principal neurons:
- regular firing neurons
- bursting neurons
These are to do with the patterns of action potentials
Overall less well studied area of the hippocampus

Question 19

What is the hippocampal formation?

Answer 19

Part of the limbic system and also has connection with the entorhinal cortex and other structures
Has significant projections from the entorhinal cortex (which has 6 layers) to the hippocampus
But the connections are very complex

Question 20

What are the projections between the entorhinal cortex and the hippocampus?

Answer 20

• perforant pathway: layer II of the EHC to CA3 in the hippocampus
• tempero-ammonic pathway: layer III of the EHC to CA1 of the hippocampus

Question 21

How does the neural activity in the hippocampus relate to learning and memory?

Answer 21

Have to look at it in the context of firing patterns of the hippocampal neurons

Question 22

What causes action potentials?

Answer 22

Primarily caused by the flux of sodium and potassium ions due to the opening and closing of ion channels

Question 23

How do we measure the flow of ions in the brain?

Answer 23

Using electrodes.
From the recorded signal we can determine the time when a certain neuron fired an action potential
The resulting spike trains are key in relating neuronal activity with behaviour