Brain Structures involved in Learning and Memory
- Plays a central role in the process of learning
- Learning new info that will become declarative memory typically involves an interaction between the hippocampus (for consolidation) and relevant areas of the cortex that specialise in storing declarative-type info, such as the Occipital Lobe for visual memory of written words.
- Higher order animals & humans with damaged Hippocampi on both lobes, can feel emotions of fear when experiencing pain from a stimulus (electric shock). But are unable to learn or remember to be fearful next time a similar situation is experienced (declarative memory)
- With a damaged hippocampus, it is unable to learn and remember declarative information
- Has a role in emotional memory - in learning to associate fear with a new unpleasant stimuli (essential for survival)
- Humans with damaged Amygdala's cannot be classically conditioned (to learn) to fear a dangerous object (stimulus), even if they know that every time a bell sounds, they'll receive a shock.
g. Not displaying any physical sign of fear to a bee (such as raised GSR, increased heart rate) when confronted by one
- Also has role in learning - can strengthen the learning of information that will become declarative memory if that memory is associated with positive or negative emotions
- Stimulation of the Amygdala activates the Hippocampus
- Learning and memory for pleasant/unpleasant emotional info is linked to the amount of activity in the Amygdala when learning occurs
CEREBRAL CORTEX -
One key area of the Cerebral cortex involved in learning and memory is the Basal Ganglia
- Located in the frontal lobes
- Uses info from the Primary and Secondary motor areas of the frontal lobes, as well as from the Somatosensory cortex, to integrate and smooth bodily movements
- People who suffer diseases that damage the Basal Ganglia, (Parkinson's or Huntington's disease), have great difficulty learning to do tasks that result in non-declarative memories, such as learning skills that result in procedural memory.
- Located in the Hind brain
- Plays a role in the order of muscular movement, balance and posture
- Also necessary for learning motor skills and contributes to non-motor learning
- The cerebellum and the Basal Ganglia work together in learning movement sequences so that movements can be carried out together
VENTRAL TEGMENTAL AREA -
- Located in the mid brain
- Has a role in learning through operant conditioning, particularly plays a role in the rewarding effects of primary reinforcers e.g.
food or sex
The Development of Neural path-ways including the role of axons, dendrites, synapses and neurotransmitters
SYNAPSE FORMATION IN LEARNING -
When we learn, synapse formation involves either
- The creation of new neural pathways
- The strengthening of existing neural pathways
- A neural pathway is a bundle of myelin covered neurons that provide a connection between one part of the N.S and another
When learning takes place (depending on the type of learning), existing synapses are sometimes moulded or new synapses are formed between neurons (Synaptogenesis)
- Synaptogenesis is more evident in early childhood but is evident in parts of an adults brain
The process of Synaptogenesis involves the zone that acts as a junction between two neurons; the synapse
- Comprised of the axon terminal of the presynaptic neuron, the synaptic gap, and the dendrite of the postsynaptic neuron
- During learning, the axon terminals (terminal buttons) of the presynaptic neuron release a neurotransmitter called Glutamate into the synaptic gap between the presynaptic neuron and the dendrites of a neighbouring postsynaptic neuron
When we acquire new info or skills from learning, neurons form new connections with each other - new sprouts called filigree appendages begin to grow from the axon terminal towards the dendrites of neighbouring postsynaptic neurons so more neurotransmitters can be released
- As a result of learning, neural pathways are strengthened between neurons -enables newly learnt info to be transferred from one neuron to the next more efficiently
- If a neural pathway is frequently used or activated during learning it's more likely to be strengthened and less forgotten
- When particular neural pathways are not activated, learning may be forgotten if the synapses become weakened through infrequent use
DEVELOPMENT OF NEURAL PATHWAYS INVOLVED IN LEARNING (Dendrites and Neurotransmitters) -
- Neurons excite one another when learning takes place. They do this by releasing neurotransmitters
- In this process, glutamate is released by the presynaptic neurons
- It's the main excitatory neurotransmitter in the brain for learning
- When released by the P.S.
N, it acts on two types of Glutamate receptors in the postsynaptic neuron: the AMPA receptor that activates the postsynaptic neuron and the NMDA receptor that produces long-lasting modifications to the synapse
- The repeated Glutamate release also stimulates the release of dopamine - which activates genes in the neuron
- This prompts growth in the postsynaptic neuron of an increased number of dendrite spines - outgrowth from from dendrites in synaptic gap so it can receive NT's faster
- These make the post synaptic neuron more sensitive to future firing by other neighbouring presynaptic neurons
E.g. A rat is given a pellet of food each time it presses a lever. It will press it repeatedly to get it. In the rat's brain, the learn behaviours (pressing the lever) to get the reward (food) causes the release of glutamate into the synaptic gap between the pre-synaptic and post-synaptic neurons. Glutamate will stimulate the growth of dendritic spites on the postsynaptic neuron (makes it more receptive for future bursts).
- the process results in long lasting structural changes to the glutamate receptors of the post-synaptic neurons
- The process also releases dopamine - interacts with genes in the neuron to generate new proteins in the neuron which also has a lasting structural change in the dendrites and increased efficiency of the neural pathways for the learnt beaviour
Development plasticity and adaptive plasticity
of the brain: changes to the brain in response
to learning and experience; timing of experiences
PLASTICITY OF THE BRAIN -
The brain is capable of learning throughout the lifespan because of its plasticity
- Plasticity of the brain refers to the way it changes in response to stimulation from the environment. Brain plasticity refers to the ability of the brain to modify its own structure and function following changes within the body or in the external environment.
- Process of plasticity occurs at the synaptic connections
- Plasticity is necessary for learning to take place and is present throughout a healthy life
DEVELOPMENTAL PLASTICITY -
- Generally, infants will have more plasticity than an adults brain - Developmental plasticity is the ability of synapses to be modified
- Although changes to the brain occur frequently in the foetal stage, babies, children and adolescents (developmental plasticity), these changes continue throughout life as learning takes place (Adaptive plasticity)
- Before birth, a child's neurons are flexible in terms of their functions
- Development of the N.S starts before birth
Development then goes through five stages:
- Proliferation - Migration - Circuit Information - Circuit Pruning - Myelination
Is the process whereby the unborn baby's cells that will become neurons divide and multiply, creating approximately 250,000 cells per minute
During this process, newly formed neurons move outward to their destined location
- The role of a particular neuron might have is determined by where it is located at its time of formation
- Different brain structures form during different stages of development
- Before/after the babies born, its neurons are flexible so brain tissue can be transplanted int an adult brain and the neurons will adapt, form synapses and take on the function of the brain area
Circuit Formation -
Occurs when the axons of new neurons grow out to target cells and form synapses with them e.g.
axons for motor neurons grow to the spinal cord where the neurons form synapses with other neurons on this location
Circuit Pruning -
Involves the elimination of excess neurons and synapses; those which have not established a connection with a target cell die.
- N.S also refine itself by eliminating excessive synapses. Also strengthening or weakening synapses according to whether the presynaptic and postsynaptic neurons fire together
- Neurons that does not fire fire at the same time as its neighbouring neurons is a neuron that's in an inappropriate area during circuit formation & might be part of Circuit pruning
- Pruning occurs in infancy and childhood - also a second wave of pruning in adolescence:
- Brain produces more neurons that will ever be used which will eventually be eliminated through pruning
- It does this to make up for errors - when some neurons fail to reach target cells
Is a process where the axons of the neurons in the child's brain become covered in myelin, is the final stage that needs to happen for a brain to become fully mature
- Myelin is a white, fatty, waxy substance that coats some axons and protects them from electrical interface from other neurons
- Process commence before a baby is born and doesn't finish till late adolescence or beyond
- Lower structures of the brain are myelinated first
- Followed by the Cerebral Hemispheres (Occipital Lobes first) - Temporal - Parietal - Frontal Lobes
- During early adolescence, there's a second burst of production of Cortical grey matter (Covering of the Cerebral hemispheres with no myelin covering)
- Pre-frontal cortex is the last to develop responsible for problem solving, planning, impulse control and critical thinking
Because A child's brain has greater plasticity than adults, it's able to use/utilise other parts of the brain to form alternative neural connections to compensate for missing or damaged part of the brain e.g.
can recover from damage to the part of the brain responsible for language.