THE NEURAL BASIS OF MEMORY

Memories are stored throughout our brains, and

linked together through neural pathways.

Different brain areas are involved in different memory

types and stages.

Kandel’s Research Into the Role of the Neuron in Memory Formation

Eric Kandel – Austrian Psychiatrist

Identified changes in the structure & function of neurons in the brain when learning (a new memory) occurs.

KANDEL - CONTINUED

Worked with large seaweed eating slugs called Aplysia californica.

KANDEL - CONTINUED

It has a relatively simple nervous system – only 20,000 neurons, compared to trillions in humans.

The neurons can be seen by the naked eye, so can be observed, stimulated or removed .

KANDEL - CONTINUED

Kandel used a thin electrode to stimulate the siphon (like a tail). This caused the siphon to contract.

Read the second column on Pgs 335 of your text and summarise Kandel’s experiment.

CHANGES TO THE NEURON

Kandel observed that, after learning, the slugs neurons functioned differently

More neurotransmitter produced & released

More dendrites developed and made more connections with other neurons

Synaptic connections form – neurotransmitter passes more easily next time this pathway is used

These changes are collectively called: LONG-TERM POTENTIATION

KANDEL - CONTINUED

With Short-Term memory storage, there is only an increase in the release of the neurotransmitter

With Long-Term memory storage, all the 3 changes mentioned on the previous slide occur.

Each time the memory is recalled, the communication links in the memory circuit are strengthened.

Difficult to generalise to humans, but similar changes have been found in fish, chicks and mammals.

HIPPOCAMPUS & TEMPORAL LOBE

Thalamus

Amygdala

The hippocampus is just above each ear and 4cm straight into the brain, 3.5 cm long.

Shaped like a sea-horse??, wrapped around the thalamus, extending into the temporal lobes.

HIPPOCAMPUS & TEMPORAL LOBE The hippocampus and the medial temporal

lobe are involved in the formation of new long-term memories (not storage)

The Hippocampus is specifically involved in:

- Deciding if the info received by the sense is worth remembering

- Mapping & organising memories before sending them to other parts of the brain for storage – maybe several sections at once.

- Seems to provide a cross referencing system for memories – draws all the different aspects of a memory from parts of the brain.

HIPPOCAMPUS

Important in recalling spatial relationships in the world around us. (Damage results in disorientation & impaired ability to navigate in familiar surroundings).

Helps process sense of smell Left hippocampus – verbal memory Eg word lists &

digit span Right hippocampus – spatial & visual memory Eg

facial recognition, visual directions

Mainly involved in declarative memories (about facts or events) – not procedural (how to do things)

HIPPOCAMPUS & TEMPORAL LOBE Case Study – HM (Henry Molaison)

- Severe epileptic – medial temporal lobes removed to try to stop seizures

- Most areas of functioning unaffected – except memory

- He couldn't remember things he experienced after surgery; couldn’t form new memories of personal events or general knowledge

- ST memory worked as long as he didn’t get distracted