Neuroscience of memory Flashcards
What is the difference between learning and memory?
Learning is the neural mechanism by which a person changes his or her behaviour as a result of experiences. It helps us acquire new skills like a new language or riding a bicycle.
Memory is the mechanism for storing what is learned.
What is the definition of learning?
Include Kandel and Kimble’s definitions.
Definition: Learning is the ability of previous experiences to modify the inborn reactions or create new ones.
Or It is the acquisition of knowledge or skills as a result of experiences and consequently it can alter behaviour on the basis of this experiences
- Learning is the process by which we acquire knowledge about the world (Eric Kandel, 2000)
- Learning refers to a more or less permanent change in behaviour which occurs as a result of practice (Kimble, 1961)
Overall, these definitions all have skill gain through exposure to experiences in common. It’s about changing behaviour through new skills or knowledge.
What are the two different types of learning?
Associative learning (Classic conditioning, Operant conditioning)
Non-Associative learning (Habituation, Sensitization)
What is non-associative learning? (give the two examples)
In this type of learning, the subject learns whether to ignore or react to a certain stimulus. It is a simple way of learning that does not need association between 2 stimuli
• Habituation – It is a gradual decrease in the response to stimulus when it is frequently repeated
• Sensitization – It is a potentiation (increase) in the response to stimulus (painful or pleasant) when it is frequently repeated
What is habituation and give an example?
- It is a gradual decrease in the response to stimulus when it is frequently repeated
- It is simple and widespread – doesn’t require our conscious effort
Examples:
• A loud and unexpected sound will produce a high response the first time someone hears it, they may look towards the source of sound, have a change in heart rate, and change in blood pressure…
…However, if the sound turns to be insignificant, its repetition results in little or no response
What was Kandel’s Aplysia research?
Kandel’s Aplysia research (e.g., Squire & Kandel, 1999)
Habituation of a gill withdrawal reflex
The animal has a siphon and a gill. If there is a stimulus on the siphon, the animal immediately contracts the gill. This is a simple reflex mediated by a sensory neuron and motor neuron, when there is a stimulus on the siphon, there is a contraction of the gill – it’s a very fast response. By looking at this model (the animal has very large neurons) Kandel has been able to identify the neural mechanisms for both habituation and sensitization.
Habituation has been largely studied with gill withdrawal reflex. Repeated stimulus results in long lasting habituation, even for several weeks.
Explain Kandel’s research on habituation of a gill withdrawal reflex.
The stimulus is placed on the siphon. The siphon is innervated with a sensory neuron which is immediately connected with the motor neuron. The motor neuron can change the motor response of the gill causing a retraction. The sensory neuron is also connected with interneurons that allow the modulation of the behaviour. These interneurons can be excitatory or inhibitory – the activation of the interneuron may change the response of the motor neuron. In function of the response, the motor neuron can enhance or diminish the response.
Each spike shows an action potential, the rounded shape shows the activity that is mediated by the interneuron. If there is a stimulus at the level of the siphon, the first action potential is at the level of the sensory neuron. If the activation of the interneuron is excitatory, it can increase the synaptic potential which triggers another action potential in the motor neuron which causes the retraction of the gill. (this is what happens under normal circumstances).
Under the habituation condition, there is still an action potential at the level of the sensory neuron which is transmitted to the interneuron. But because of the frequency of the stimulus, the modulation that occurs with the interneuron leads to a decrease in action potential and decrease in synaptic potential. There is no action potential at the level of the motor neuron. Therefore, the motor neuron is not activated and there’s no retraction of the gill.
Explain the features of sensitisation?
- It is a potentiation (increase) in the response to stimulus (painful or pleasant) when it is frequently repeated
- = heightened awareness/responsiveness to a stimulus or class of stimuli for a period of time.
- It is simple and widespread (widespread means it’s very common and we don’t have to put very much effort into it)
- Makes us aware and responsive to stimuli that are potentially dangerous. Prepares us to react to the external environment.
Give an example of sensitisation?
- One normally ignores dogs by habituation, but if he is bitten, he will become more attentive and develop aversion reaction to them for long time
- Stimulus specific: One who is bitten by dogs will not be afraid of cats!
Explain Kandel’s research on sensitization of a gill withdrawal reflex.
The stimulus is applied on the siphon is connected with a sensory neuron which is interconnected to a motor neuron which makes the retraction happen at the level of the gill.
Another stimulus is applied at the tail. The tail is connected with a sensory neuron which is interconnected with an interneuron which communicates with a motor neuron which plays a key role with the gill.
Before sensitization, there is a flow of information from the siphon and the first sensory neurons. This leads to action potentials, synaptic potentials, motor neuron potential and retraction. However, if there is an activation at the tail, the interneuron has a strong connection to the motor neuron which enhances the signal. The sensitized circuit shows a higher flow of information, an enhancement in the response and therefore an enhancement in the motor response. The retraction is more enhanced and faster.
What are the four key players in sensitization?
The four key players are the sensory neuron at the level of the siphon, the motor neuron (which connects the siphon to the gill). A sensory neuron from the tail and an interneuron that connects the sensory neuron of the tail and the motor neuron. The activity of this interneuron can shape the behaviour.
Explain the differences between habituation and sensitization?
Habituation:
• Specific to particular stimulus and response
• Results in decreased response magnitude
• Specific to a particular brain circuit
• Occurs after repetition of a variety of types of stimuli
• Exhibited in both short-term and long-term
Sensitization
• General to a variety of stimuli and responses
• Results in increased response magnitude
• Heightens responses responses in many circuits
• Occurs only after emotional stimuli (e.g., has to be painful/unpleasant)
• Normally lasts only for a short period
What is associative learning?
In this type of learning, the subject learns about the relationship that can associate one stimulus to another. It is a conditioned process which results in the formation of learned responses called conditioned reflexes.
Conditioned reflex is an automatic response to a stimulus (conditioned stimulus) which did not previously evoke response acquired by repeatedly associating this stimulus with another stimulus (unconditioned stimulus).
Explain how classic conditioning was discovered?
- This type of conditioned reflexes was 1st described by Pavlov (Russian Physiologist)
- He noticed that his experimental dogs salivate just on seeing the animal housekeeper who used to feed…
- Some sort of association had developed in the brains of these animals between visual stimuli related to seeing the housekeeper (conditioned stimulus) and food ingestion (unconditioned stimulus for salivation when food is placed in mouth)
Explain the four different phases in classic conditioning?
Four different phases: an unconditioned stimulus producing an unconditioned response (food causing saliva). A neutral stimulus which causes no response (sound produces no reaction from the dog). During conditioning the two stimuli are presented around the same time which leads to an unconditioned response (the sound and food are presented). Lastly, after the neutral stimulus is conditioned, it produces a response (sound leads to dog salivating).
Explain what happens in classic conditioning?
Usually, we have a direct connection from the unconditioned stimulus with the response (e.g., salivating after food). The neutral stimulus produces no reaction. But after conditioning, there is likely to be a change in the connectivity of the brain areas, creating a pattern of response. The change in the level of connectivity creates new associations.
What is operant conditioning?
This type of conditioning requires a reward or punishment.
- In this type of conditioning the subject is taught to perform some voluntary action in response to a particular stimulus (visual or sound stimulus) that alert him to perform the learned action in order to obtain reward to avoid punishment.
- Alerting signal acts as conditioned stimulus whereas pleasant or unpleasant event that follow performance of learned response represents unconditioned stimulus.
Explain an example of operant conditioning with a rat in a maze.
In this type of operant conditioning, the modulation of behaviour is driven by reinforcement or punishment. The animal is free to go around the maze, it can choose to go right or left. During the conditioning, there is either reinforcement (reward of food) or punishment (electric shock). The association between the reward/punishment can dramatically change behaviour. If the animal is rewarded, it will go in the same direction in order to get the same response. However, if the animal is punished with a shock, it will go in the other direction.
