Learning and the Brain Flashcards
Understanding the mechanisms of learning and the neuroscience of it
What is Learning?
Learning is the process where we develop new behaviours or change existing ones in response to new experiences or situations. This process isn’t due to our natural instincts, growth over time, or temporary conditions like being tired or influenced by drugs. Instead, it involves actively adapting and reacting to the things we encounter. - Learning changes our brain
Why are we interested in the relationship between two Neurons? And what are the basic mechanisms?
One Neuron connects to another neuron by connecting its axon terminals to the dendrites of the next.
- We’re interested in what’s happening when these 2 neurons interact ( they do this at the synapse) as their interaction (neural communication) is crucial for learning. Synaptic connections and their strength change when we learn new information or skills. These changes, known as synaptic plasticity, are the basis for memory formation and the ability to adapt and acquire new knowledge.
How do 2 neurons communicate?
They communicate via an action potential that travels from one neuron - down the axon - to the axon terminals - and that electric signal gets transferred into a neuro-chemical signal.
- The chemicals involved are neurotransmitters.
- Some neurotransmitters help with communication between neurons, which also results in changes in your brain as you learn new things, interact with the environment, and go about life.
These changes occur because neurotransmitters strengthen or weaken synaptic connections, which is the basis for learning and memory formation.
What is neural communication and when is it happening?
Neural communication is always happening.
It happens due to electrical signals travelling down the neuron. These axons go from the tip of our brain to all the way down our spinal cord.
The release of electrical signals through our axon terminals, and onto the next neuron is determined by the activity and charge. It exits the synaptic cleft, meeting the post-synaptic membrane, causing things to change in consequence.
What are the basic principles of Synaptic Transmission? Explain Calcium channel processes.
-We have 2 neurons, interacting between their synapses.
- We have the pre-synaptic nerve terminal: the axon terminals, and the Post-synaptic cell/membrane which receives electrical signals.
-The pre-synaptic action potential: travels through the nodes of Ranvier which are located along the axon - if there is enough of it then it will fire- sending the signal out. Changes occur:
- When an action potential reaches the presynaptic terminal, it opens calcium channels.
- Calcium ions (Ca²⁺) rush into the presynaptic terminal.
- The influx/flow of calcium ions triggers vesicles containing neurotransmitters to move to and fuse with the presynaptic membrane.
-Neurotransmitters are released into the synaptic cleft.
-Some neurotransmitters bind to receptor channels on the postsynaptic membrane (the dendrites of the second neuron).
-Calcium channels close.
-If enough neurotransmitters bind to the receptors, it will allow the transmission to happen.
-The transmitter molecules bind to excitatory receptors, which open channels allowing sodium ions to enter the postsynaptic cell, continuing the signal transmission. - The time during up to 2-3 weeks after this occurrence, depending on which neurotransmitters were involved, things will change in the synapse as a consequence.
- Some of the receptors and connections will reduce and some will grow
What are the basic elements of the taxonomy of Memory/ Learning?
Memory is divided into 2 main parts in this taxonomy.
- Long-term memory which splits off into Declarative Memory (explicit memory) and Nondeclaritive memory (implicit memory).
and - Short-term memory (sensory, short-term/ working memory).
LTM splits off into many other forms of memory.
What is Nondeclarative Memory?
Implicit memories that are just happening because we’re interacting with our environment. i.e. convos with friends, getting up early/late, going to a lecture or staying home etc.
- Our brain changes from these experiences, this is called NON ASSOCIATIVE LEARNING (habituation, sensitisation to your environment).
- Nondeclarative memories are a heterogeneous collection of learning and memory capabilities. They all acquire info implicitly.
-Over time we become less sensitised to things and more habituated. eg: the feeling of our clothes 1 hr after putting them on.
How does Nondeclarative Memory work? What’s the basic format?
Discovered by Eric Kandel, through observing the learning process of a snail.
- As we learn, we have chemical signals that change the structure of the connections between cells/neurons.
- Between the pre-synaptic axon terminal - through the synapse, the signals are sent to the dendrites of interconnecting neurons.
- Kandel showed that at the synapses- where signals are sent and received, things change as a consequence of that in terms of short-term and long-term memory.
What is Habitution? And what memory is this a part of?
Habituation is the simplest case of Nondeclarative memory.
- We can use this for animals and babies because it’s unlikely to get them to understand/ give feedback on other memory assessment tasks.
THE IDEA: - we can learn to ignore a large number of innocuous stimuli. i.e putting on clothes, the lighting in the room
- The client is shown an Innocuous stimulus on a repetitive trial, - recording their physiological responses by measuring their visual fixation.
- eventually after looking, the client becomes habituated to the stimulus/gets bored over time.
- When the client is shown a slightly different stimulus - on the 6th round of trials, its physiological responses are heightened again
What are the basic principles that cause Habituation? and why?
- The reaction/ attention changes as a result of the brain changing to stimuli.
- Our minds want to conserve energy, therefore it’s the survival of the fittest- the stimulus most important for our attention. Our brains can’t be excited about everything at once.
How do they identify/record the physiological changes of habituation?
They record this info from 6 specific identical neurons to identify how each contributes to the habituated behaviour
- stimulating the snail, and then recording from the motor neuron, asking: how does it respond in consequence of the sensory neuron
Which main neurons are involved in Habituation?
Sensory Neuron
Motor Neuron
Interneuron
How can learning and Memory be stored in a pre-wired circuit?
Depend on the strength, modification of the connections.
With the snail: They stimulate the snail’s siphon.
- This Siphon stimulation is happening on the Sensory Neuron which excites the snails Gill and Siphon via the Interneuron and Motor Neuron both working strongly together
- and then these converging inputs from the Interneuron and Sensory Neuron ON the Motor Neuron result in Fast withdrawal
With repeated Siphon Stimulation + there is the habituation of withdrawal - ‘getting used to it’. EVEN THOUGH the amount of stimulation is the same - but it’s observed at a weaker level, causing a ‘synaptic depression’
What are the mechanisms of short-term and long-term habituation? (In sea snail)
Much of the habituation is due to the modification of the presynaptic terminal.
- Fewer amounts of the vesicle packets are being released with those action potentials - this is due to fewer transmitters docking at the release sight of the pre-synaptic membrane, and also fewer fusing with the post-synaptic membrane
- This effect can last several seconds or minutes - following a single stimulation
- It can last for 10-15 minutes if there’s more stimulation received
- It can last upto a week, with multiple sessions of this happening
Long term Habituation is causing an inactivation of connection, and also structural changes - in terms of the amount of connectivity from the sensory neuron linking with the motor neuron
- In order for things to keep that homeostasis (because we can’t keep building inside a limited skull) we have reduction and inactivation of connections
- This is called synaptic pruning
What is sensitisation?
It is a more complex form of nondeclarative memory.
It happens at the pre-synaptic and post-synaptic membrane.
- It’s where an organism becomes more responsive to a stimulus after being exposed to a strong noxious stimulus.
-For example, if a snail receives a strong shock, it will respond more strongly to a light touch afterwards. This increased response happens because the nervous system amplifies its reaction to the stimulus, making the organism more alert and reactive to potential threats.
A single shock to the snail (noxious stimuli) caused short-term memory for 5 mins.
Multiple shocks = long-term memory change - can last up to weeks, or for a human: a lifetime
When we’re sensitised to a stimulant, that’s because we need to know it’s there - we don’t want to get another shock/ we change our engagement with our environment.
