Part 1 LECTURE 7; memory: varieties & mechanisms Chapter 8 book
Important questions
- What happens in the brain during learning and memory formation?
- Where does it occur?
Representations
- Important concept in cognitive neurosciences
- The world is represented in the mind and brain
- The defining function of nervous systems is representational
- Churchland & Sejnowski
- Nervous systems represent states of the world outside the brain
- Brain states represent states of other systems (outside world or the body itself)
- Two different representations:
1. “Representations that are happening now are patterns ofcr activation across
the units in a neural net (neurons)”
2. Stored representations, by contrast, are believed to depend on the
configuration of weights between units. These weights are the strength of
synaptic connections between neurons. So information is stored in the form of
changing strengths of connections between neurons. They can become stronger,
weaker or stay the same.
What is happening in the brain?
- Different ways of thinking:
1. Tanzi and Hebb
- An alteration in the effectiveness of existing connections
- We don’t need new connections, because there are already enough connections
2. Cajal
- Formation of new connections between neurons
- New synaptic connections will be formed
- They all concluded:
- Structural changes in neuronal connectivity, at the level of the synapse
Where in the brain do these changes occur?
- Lashley did a lot of experiments with rats which had to learn
there way through a maze
- He either made lesions to various parts of the cortex (took them
out for example) or he made knife cuts to isolate different parts
of the brain
- Quote: “I sometimes feel, in reviewing the evidence on the
localization of the memory trace, that the necessary conclusion is that learning just is not
possible”
- So how is learning even possible if I can’t find a trace of it in the brain? He was
disappointed in the results of his experiments
1
, - He did find that a lesion had a negative effect on memory but it didn’t really matter where
to put the lesion
Human amnesia
- Amnesia is memory loss
- A few clinical cases
1. Clive Wearing
- Most severe version of amnesia
- Medial temporal lobe is damaged
- Video about Clive Wearing
- He knows things and still has the skill to play the piano, but forgets everything
that just happened
- MRI scan; left is Clive Wearing, right is normal person
- There a huge holes in the medial temporal lobe, hippocampus and part of the
cortex of Clive Wearing
2. Patient H.M. (Henry Molaison)
- Suffered from a serious form of epilepsy
- He was operated when parts of his temporal lobes were removed
- Real brain of H.M. & reconstruction of lesion
2
,Left side view of real brain
The lobes are named after the bones that
are on top of them
Hippocampus
- Called after Latin name for seahorse ‘hippocampo’, because it looks like a seahorse
- Underneath the cortex in the medial temporal lobe
Retrograde amnesia
- Retrograde amnesia is a form of amnesia where someone is unable to recall events that
occurred before the development of the amnesia, even though they may be able to
encode and memorize new things that occur after the onset.
3
, Anterograde amnesia
- Anterograde amnesia refers to a decreased ability to retain new information. This can
affect your daily activities. It may also interfere with work and social activities because
you might have challenges creating new memories.
Memory functions intact in amnesic patients
- Declarative memory
- Impaired
- Specific events
- Explicit
- Procedural memory
- Skills
- Simple forms of classical conditioning
- Priming
Non-declarative → procedural memory
- When asked for the major division of the memory system → visions of memory systems
within long-term memory system
Non-declarative memory (implicit)
- Drawing pin (punaise) experiment
- No awareness of
4
Important questions
- What happens in the brain during learning and memory formation?
- Where does it occur?
Representations
- Important concept in cognitive neurosciences
- The world is represented in the mind and brain
- The defining function of nervous systems is representational
- Churchland & Sejnowski
- Nervous systems represent states of the world outside the brain
- Brain states represent states of other systems (outside world or the body itself)
- Two different representations:
1. “Representations that are happening now are patterns ofcr activation across
the units in a neural net (neurons)”
2. Stored representations, by contrast, are believed to depend on the
configuration of weights between units. These weights are the strength of
synaptic connections between neurons. So information is stored in the form of
changing strengths of connections between neurons. They can become stronger,
weaker or stay the same.
What is happening in the brain?
- Different ways of thinking:
1. Tanzi and Hebb
- An alteration in the effectiveness of existing connections
- We don’t need new connections, because there are already enough connections
2. Cajal
- Formation of new connections between neurons
- New synaptic connections will be formed
- They all concluded:
- Structural changes in neuronal connectivity, at the level of the synapse
Where in the brain do these changes occur?
- Lashley did a lot of experiments with rats which had to learn
there way through a maze
- He either made lesions to various parts of the cortex (took them
out for example) or he made knife cuts to isolate different parts
of the brain
- Quote: “I sometimes feel, in reviewing the evidence on the
localization of the memory trace, that the necessary conclusion is that learning just is not
possible”
- So how is learning even possible if I can’t find a trace of it in the brain? He was
disappointed in the results of his experiments
1
, - He did find that a lesion had a negative effect on memory but it didn’t really matter where
to put the lesion
Human amnesia
- Amnesia is memory loss
- A few clinical cases
1. Clive Wearing
- Most severe version of amnesia
- Medial temporal lobe is damaged
- Video about Clive Wearing
- He knows things and still has the skill to play the piano, but forgets everything
that just happened
- MRI scan; left is Clive Wearing, right is normal person
- There a huge holes in the medial temporal lobe, hippocampus and part of the
cortex of Clive Wearing
2. Patient H.M. (Henry Molaison)
- Suffered from a serious form of epilepsy
- He was operated when parts of his temporal lobes were removed
- Real brain of H.M. & reconstruction of lesion
2
,Left side view of real brain
The lobes are named after the bones that
are on top of them
Hippocampus
- Called after Latin name for seahorse ‘hippocampo’, because it looks like a seahorse
- Underneath the cortex in the medial temporal lobe
Retrograde amnesia
- Retrograde amnesia is a form of amnesia where someone is unable to recall events that
occurred before the development of the amnesia, even though they may be able to
encode and memorize new things that occur after the onset.
3
, Anterograde amnesia
- Anterograde amnesia refers to a decreased ability to retain new information. This can
affect your daily activities. It may also interfere with work and social activities because
you might have challenges creating new memories.
Memory functions intact in amnesic patients
- Declarative memory
- Impaired
- Specific events
- Explicit
- Procedural memory
- Skills
- Simple forms of classical conditioning
- Priming
Non-declarative → procedural memory
- When asked for the major division of the memory system → visions of memory systems
within long-term memory system
Non-declarative memory (implicit)
- Drawing pin (punaise) experiment
- No awareness of
4
