Memory and the Hippocampus

H.M was the first clear insight that the medial temporal lobe of the human brian was a _______ of anatomically connected structures that were organized into a memory system

system

H.M. underwent experimental surgery to remove the source of his seizures, the _______________

Medial Temporal Lobe

H.M. suffered __________ memory impairment after removal of his medial temporal lobes.

Declarative

Although H.M lost declarative memory almost entirely, his ____ declarative memories were intact

Early

Which two episodic memory tasks was H.M not able to perform because of loss of his declarative memory?

1. Recall of stories

2. Paired-associate learning

Which two semantic memory tasks was H.M not able to do because of loss of his declarative memory?

1. Remember words entered in the dictionary after his surgery

2. Remember names of people who became famous after his surgery

Beth, Jon, and Kate experienced damage to the _________ only which gave them amnesia for personal events and on labtests of episodic memory

Hippocampus

Beth, Jon, and Kate all had good _______ memory abilities but not _________ memory abilities

Semantic, Episodic

________ recall was slow for Beth, Jon, and Kate but ______ recall was average compared to people with no damage to the hippocampus.

Delayed, immediate

Hippocampus is important for ________ memories and the other structures besides the hippocampus in the medial temporal lobe are important for _______ memories

Episodic, Semantic

Task requires (at least some) episodic-like memory

• Sample Phase: sample object presented

• Test Phase: After delay, choice between sample object and new object

• Choosing the new object is rewarded

• New pairs on each trial

If the monkey chooses the new object, must remember __________ recently so they know which one will be rewarded.

seeing the sample object

Task requires (at least some) episodic-like memory

• Sample Phase: sample object presented

• Test Phase: After delay, choice between sample object and new object

• Choosing the new object is rewarded

• New pairs on each trial

Results: If the monkey chooses the new object, must remember seeing the sample object recently so they know which one will be rewarded.

Which is this experiment a model of?

Human Amnesia

Task requires (at least some) episodic-like memory

• Sample Phase: sample object presented

• Test Phase: After delay, choice between sample object and new object

• Choosing the new object is rewarded

• New pairs on each trial

Results: If the monkey chooses the new object, must remember seeing the sample object recently so they know which one will be rewarded.

As delay extended normal control performance goes down but then there is a quick decline in performance in monkeys with ______ than a __________________

greater, hippocampus-only lesion

Task requires (at least some) episodic-like memory

• Sample Phase: sample object presented

• Test Phase: After delay, choice between sample object and new object

• Choosing the new object is rewarded

• New pairs on each trial

Results: If the monkey chooses the new object, must remember seeing the sample object recently so they know which one will be rewarded.

Results: As delay extended normal control performance goes down but then there is a quick decline in performance in monkeys with greater than a hippocampus-only lesion

The results held true _____ years after lesion

1-2

Hippocampal memories are stored (at least initially) by the same neurons that were activated by _______

learning

Context A: Context paired with footshock and mice display fear response to context

• Hippocampal neurons activated

Context B: Neurons that have been activated in Context A were __________ reactivated

artificially

Context A: Context paired with footshock and mice display fear response to context

• Hippocampal neurons activated

Context B: Neurons that have been activated in Context A were artificially reactivated

• Fear response by mice, as if they were remembering Context A

This experiment supports which theory?

Hippocampal Engrams

Hippocampal memories are stored (at least initially) by the same neurons that were activated by learning

Hippocampal Engrams

Tom Cruise Neuron

• Patients with untreatable epilepsy implanted with electrodes in the hippocampus to localize the focus of seizure onset; neuronal activity recorded from electrode tips

• Viewed a series of short clips while neurons recorded from hippocampus

• A few minutes later, asked to recall clip and report when they remembered a specific clip (“Tom Cruise Clip”)

What were the results?

Hippocampus neurons began firing before verbal report of the clip