Hoorcollege 7 – Memory: Varieties & Mechanisms
An important concept in cognitive neuroscience is that of Representations. Somehow the
world is represented in the mind and the brain.
Churchland & Sejnowki: The defining function of nervous systems is representational.
Brain states represent states of some other system – the outside world or the body itself.
“Representations that are happening now are patterns of activation across the units in a
neural net”
Stored representation, by contrast, are believed to depend on the configuration of weights
between units (neurons). In neural terms, these weights are the strength of synaptic
connections between neurons.
What is happening in the brain? How does the weights between units work?
- Tanzi (1893) and Hebb (1949): an alteration in the effectiveness of existing
connections.
- Cajal (1894) formation of new connections between neurons.
Both Hebb and Cajal agree that there are structural changes in neuronal connectivity, at the
level of the synapse.
Human Amnesia = memory loss
Some memory functions are intact in amnesic patients:
- Declarative memory impaired (specific events)
- Procedural memory often intact (“skills”, simple forms of classical conditioning,
priming)
Trace conditioning vs delay conditioning. Amnesia patients have difficulties with trace
conditioning, because it is involved with declarative memory.
The hippocampus (in the medial temporal lobe, MTL)
,Non-declarative (implicit) memory -> memory without awareness
Classical conditioning
- The conditioned stimulus is a neutral stimulus, such as a light or a tone.
- The unconditioned stimulus is a ‘motivationally relevant’ stimulus, such as food,
juice, or an electric shock.
Before conditioning, the animal responds to the US, but not to the CS. At this stage, this
called the ‘unconditioned response’.
During conditioning the CS and the US are paired repeatedly.
Conditioning leads to a Conditioned Response -> behavior towards the formerly neutral
stimulus.
Forms of Amnesia:
- Anterograde amnesia: amnesia for events after surgery/trauma
- Retrograde amnesia: amnesia for events before surgery/trauma
,Neural plasticity: When do changes occur?
- Hebb (1949): Simultaneous activity in two neurons
Hebb’s principle / The Hebb synapse:
Changes in the effectiveness of synaptic transmission take place as a result of simultaneous
pre- (incoming action potential) and postsynaptic activity (depolarization).
Cells that fire together, wire together.
Neurobiology of learning and memory, two research strategies:
- Top-Down: presupposing a certain principle
- Bottom-Up: No presuppositions about the mechanism, but attempts at localization:
Where in the brain do these changes happen?
Bottom-Up: imprinting
Filial imprinting = the formation, through learning, of an early social preference for the
mother or another stimulus.
Neural mechanisms of imprinting
- Memory formation involves structural changes in the connections between neurons
(synapses)
- Such structural changes involve protein synthesis
Hoorcollege 8 – Declarative memory
Declarative memory can be divided into events (episodic) and facts (semantic). Both episodic
and semantic memory contribute to people’s memories of their own lives, or
autobiographical memory. Episodic memory can be further subdivided into recollection and
familiarity.
Although familiarity is usually classified as a form of episodic memory, its mechanisms are
also related to those of semantic memory and priming. Priming = het verschijnsel dat een
stimulus een snellere of sterkere respons in het brein oproept als die stimulus eerder
waargenomen is.
, Developmental amnesia = occurs in children, is a result of hypoxia (a temporal loss of oxygen
in the brain).
A simple model of episodic memory (p.283 -285)
- Medial temporal lobe lesions lead to severe amnesia
- MTL (the hippocampus lays in the medial temporal lobe) lesions lead to global
amnesia
- Remote memories spared after MTL lesions
Which parts of the medial temporal lobe are part of memory?
Theories of hippocampal memory function:
1. Cognitive map theory
2. Relational memory theory
3. Episodic memory theory
Recollection = you can remember the previously event.
Familiarity = when you see the stimulus again, you can say “yes I saw this before”
Roles of subdivisions of MTL:
- Two-process theory: Recollection (HPC) vs familiarity (perirhinal cortex)
An important concept in cognitive neuroscience is that of Representations. Somehow the
world is represented in the mind and the brain.
Churchland & Sejnowki: The defining function of nervous systems is representational.
Brain states represent states of some other system – the outside world or the body itself.
“Representations that are happening now are patterns of activation across the units in a
neural net”
Stored representation, by contrast, are believed to depend on the configuration of weights
between units (neurons). In neural terms, these weights are the strength of synaptic
connections between neurons.
What is happening in the brain? How does the weights between units work?
- Tanzi (1893) and Hebb (1949): an alteration in the effectiveness of existing
connections.
- Cajal (1894) formation of new connections between neurons.
Both Hebb and Cajal agree that there are structural changes in neuronal connectivity, at the
level of the synapse.
Human Amnesia = memory loss
Some memory functions are intact in amnesic patients:
- Declarative memory impaired (specific events)
- Procedural memory often intact (“skills”, simple forms of classical conditioning,
priming)
Trace conditioning vs delay conditioning. Amnesia patients have difficulties with trace
conditioning, because it is involved with declarative memory.
The hippocampus (in the medial temporal lobe, MTL)
,Non-declarative (implicit) memory -> memory without awareness
Classical conditioning
- The conditioned stimulus is a neutral stimulus, such as a light or a tone.
- The unconditioned stimulus is a ‘motivationally relevant’ stimulus, such as food,
juice, or an electric shock.
Before conditioning, the animal responds to the US, but not to the CS. At this stage, this
called the ‘unconditioned response’.
During conditioning the CS and the US are paired repeatedly.
Conditioning leads to a Conditioned Response -> behavior towards the formerly neutral
stimulus.
Forms of Amnesia:
- Anterograde amnesia: amnesia for events after surgery/trauma
- Retrograde amnesia: amnesia for events before surgery/trauma
,Neural plasticity: When do changes occur?
- Hebb (1949): Simultaneous activity in two neurons
Hebb’s principle / The Hebb synapse:
Changes in the effectiveness of synaptic transmission take place as a result of simultaneous
pre- (incoming action potential) and postsynaptic activity (depolarization).
Cells that fire together, wire together.
Neurobiology of learning and memory, two research strategies:
- Top-Down: presupposing a certain principle
- Bottom-Up: No presuppositions about the mechanism, but attempts at localization:
Where in the brain do these changes happen?
Bottom-Up: imprinting
Filial imprinting = the formation, through learning, of an early social preference for the
mother or another stimulus.
Neural mechanisms of imprinting
- Memory formation involves structural changes in the connections between neurons
(synapses)
- Such structural changes involve protein synthesis
Hoorcollege 8 – Declarative memory
Declarative memory can be divided into events (episodic) and facts (semantic). Both episodic
and semantic memory contribute to people’s memories of their own lives, or
autobiographical memory. Episodic memory can be further subdivided into recollection and
familiarity.
Although familiarity is usually classified as a form of episodic memory, its mechanisms are
also related to those of semantic memory and priming. Priming = het verschijnsel dat een
stimulus een snellere of sterkere respons in het brein oproept als die stimulus eerder
waargenomen is.
, Developmental amnesia = occurs in children, is a result of hypoxia (a temporal loss of oxygen
in the brain).
A simple model of episodic memory (p.283 -285)
- Medial temporal lobe lesions lead to severe amnesia
- MTL (the hippocampus lays in the medial temporal lobe) lesions lead to global
amnesia
- Remote memories spared after MTL lesions
Which parts of the medial temporal lobe are part of memory?
Theories of hippocampal memory function:
1. Cognitive map theory
2. Relational memory theory
3. Episodic memory theory
Recollection = you can remember the previously event.
Familiarity = when you see the stimulus again, you can say “yes I saw this before”
Roles of subdivisions of MTL:
- Two-process theory: Recollection (HPC) vs familiarity (perirhinal cortex)
