4.3 Flashcards
Neuroplasticity
the ability of the brain to form and reorganize synaptic connections, especially in response to learning or experience or following injury
When does neuroplasticity occur?
during development and throughout life and can lead to lasting changes in the structure and function of brain circuitry underlying behavior
Steps of neuroplasticity
- Induction of cell differentiation
- Neuron generation and apoptosis
- Neuronal guidance (how neurons hit targets)
- Synapse formation
Neuroplasticity during early development
As the brain and spinal cord develop, neurons are generated at an astounding rate = neurogenesis
Neurons grow as the growth cone of an axon is attracted or repelled and new synapses form.
The fetal brain grows and synapses proliferate. After the baby is born and begins to grow, some of the synapses are no longer needed.
Synaptic pruning
the removal of extra synapses
Neuroplasticity beyond early development is called
Synapse modification
Types of synapse modification
Long term potentation
Long term depression
Long term potentation
Results in well-established connections
- repeated exposure to a stimulus results in increased level of activity at that synapse
- example: improved speed in motor learning
Receptors moved from within the cell to synaptic surface - stronger signal
Long term depression
Results in poor connectivity, potentially cell death
- repeated or lack of exposure to a stimulus results in decreased level of activity at that synapse
- example: motor learning of the cerebellum, suppressing unwanted movement
Receptors endocytosed - weaker signal
Neuroplasticity in the mature brain: healing and learning
Both require a change in neural connections
Neurogenesis is rare and early childhood, but gliogenesis persists throughout the lifespan
Neuroplasticity in the mature brain: healing after CNS injury
Often mediated by glial cells
- salvage and strengthen surviving neurons
Facilitate new axon: dendritic connections
Spontaneous recovery involves:
- neurite regrowth
- angiogenesis
- synaptogenesis
Learning and neuroplasticity: experience dependent platicity
Maladaptive prevents recovery
- learned nonuse
Adaptive promotes recovery
- focused training to regain use of hand and maintain control in the proper cerebral hemisphere
Adaptive therapy
increases activity in brain tissue surrounding damaged area, results in decreased activity in the opposite hemisphere
How does the brain adapt and reorganize in response to activity?
- Synaptogenesis
- White matter changes (tracks of new synapses)
- Altered gene expression
LTP is associated with skill acquisition. LDT can lead to microglial synaptic pruning.
4 components of memory
- Acquisition
- Consolidation
- Storage
- Retrieval (recall)
Sensory or immediate memory
Lasts no mare than a few seconds
Modality specific and not dependent on attention.
However, attention is required to encode sensory memories into short term memories.
Attention
Moves sensory input to short term memory as memories are encoded
- stimulus and goal driven
Involves frontal lobe for sustained attention.
Also involves parietal lobe, thalamus, and visual areas.
Short term memory
Lasts seconds to minutes; 4-7 pieces of info
Attention to sensory input –> short term memory
Enhanced with effort
- chunking
- rehearsing
* repeat, organize, contextualize
Working memory
Short term memories are dynamically organized and manipulated.
Long term memories are retrieved.
Two subsystems: visual and auditory
Prefrontal cortex
Long term memory
Permanent
Large amounts of information stored for prolonged periods
- requires time to encode short term memories into long term memories
Consolidation often occurs during REM sleep
LTP: the process of rehearsing as memories move from short to long term memory, new synapses are formed.
Synaptic consolidation –> systemic consolidation
Types of long term memory
Declarative/explicit
- facts and events
Nondeclarative/implicit
- procedures and responses
Declarative/explicit memory
To form long term declarative memories, the hippocampus must be intact.
Damage to the medial temporal lobe results in the inability to form long term memories.
Semantic (facts) and episodic (events)
Loss of declarative memory = amnesia
Semantic: lateral and anterior temporal cortex, prefrontal cortex
Episodic: hippocampus, medial temporal lobe, neocortex
Nondeclarative/implicit
Procedures and responses
Do not require conscious thought
Basal ganglia and cerebellum
Reinforced by
- procedures
- priming
- associative memory: direct associations are made between two events
* classical and operant learning
- nonassociative learning
* habituation: learn to ignore
* sensitization: increased response following repeated stimulus
Forgetting
Retrograde amnesia: before injury
Anterograde: after injury
Anterograde amnesia
Typical of MTL lesions
Can be seen in concussion
Passive and active forgetting
Passive:
- loss of context cues
- similar memories interfere
- trace decay
Active:
- interference based
- motivation based
- retrieval induced
- intrinsic
3 subcategories of nondeclarative memory
Task performance
Behavior
Response
Priming
Perceptual ID of words, objects, and other stimuli
Nonassociative learning
Involves a change in the strength of a response to a single stimulus, resulting from repeated exposure to that stimulus
Habituation
Occurs after repeated exposure to ignore a stimulus that is neither beneficial nor harmful in its environment
Sensitization
Progressive increase of a response following repeated administrations of a stimulus
Compare working and short term memory
Working memory handles information that enters from sensory memory and recently recalled long-term stores. Working memory is bidirectional, serving as an input and output device, for holding and processing of new and already stored information.
