11.1 Neuroplasticity and Synaptic Changes
4 min read•august 7, 2024
is the brain's ability to change and adapt. This section explores how synapses strengthen or weaken over time, and the molecular mechanisms behind these changes. It also covers structural changes in neurons and the formation of new brain cells.
shows how our brains change based on what we learn and do. This part also looks at , which helps us recover from injuries, and , which can lead to problems like chronic pain or addiction.
Synaptic Plasticity Mechanisms
Long-Term Synaptic Changes
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- refers to the ability of synapses to strengthen or weaken over time in response to increases or decreases in their activity
- (LTP) is a persistent strengthening of synapses based on recent patterns of activity resulting in a long-lasting increase in signal transmission between neurons
- (LTD) is an activity-dependent reduction in the efficacy of neuronal synapses lasting hours or longer following a long patterned stimulus (low-frequency stimulation)
- suggests that an increase in synaptic efficacy arises from the presynaptic cell's repeated and persistent stimulation of the postsynaptic cell meaning neurons that fire together, wire together
Molecular Mechanisms of Synaptic Plasticity
- LTP is induced by high-frequency stimulation and involves the activation of NMDA receptors, calcium influx, and subsequent activation of kinases (CaMKII, PKC) leading to increased AMPA receptor insertion and enhanced synaptic strength
- LTD is induced by low-frequency stimulation and involves the activation of phosphatases (calcineurin, PP1) resulting in AMPA receptor endocytosis and decreased synaptic strength
- Hebbian plasticity involves the coincident activation of pre- and postsynaptic neurons causing NMDA receptor activation, calcium influx, and CaMKII activation leading to increased AMPA receptor trafficking and enhanced synaptic efficacy (spike-timing-dependent plasticity)
- Synaptic plasticity is also regulated by (dopamine, norepinephrine) and (BDNF) that can modulate the induction and maintenance of LTP and LTD
Structural Changes in Neuroplasticity
Dendritic and Axonal Remodeling
- Dendritic spine remodeling involves changes in the shape, size, and number of dendritic spines in response to synaptic activity and is associated with synaptic plasticity and memory formation
- Axonal sprouting refers to the growth of new axonal branches from existing axons allowing neurons to form new synaptic connections and reorganize neural circuits in response to experience or injury
- is the formation of new synapses between neurons and is important for learning, memory, and recovery from brain injury
- is the selective elimination of synapses and neurons during development and throughout life to refine neural circuits and optimize brain function
Neurogenesis and Gliogenesis
- is the birth of new neurons from neural stem cells and occurs primarily in the hippocampus and subventricular zone of the adult brain contributing to learning, memory, and mood regulation
- is the formation of new glial cells (astrocytes, oligodendrocytes) from glial progenitor cells and is important for supporting neuronal function, myelination, and brain repair after injury
- Experience and environmental factors (enriched environment, exercise, stress) can modulate the rate of neurogenesis and gliogenesis in the adult brain impacting brain plasticity and behavior
- Neurotrophic factors (BDNF, NGF) and transcription factors (CREB, NeuroD) regulate the proliferation, differentiation, and survival of new neurons and glial cells in the adult brain
Types of Neuroplasticity
Experience-Dependent Plasticity
- Neuroplasticity refers to the brain's ability to change and adapt in response to experience, learning, and environmental stimuli throughout life
- Experience-dependent plasticity is the modification of neural circuits and synapses in response to specific experiences or sensory inputs leading to the acquisition of new skills, knowledge, and behaviors
- Examples of experience-dependent plasticity include:
- Learning a new language or musical instrument
- Acquiring motor skills through practice (juggling, dancing)
- Developing enhanced sensory perception in specific domains (visual acuity in artists, auditory discrimination in musicians)
- are windows of heightened plasticity during development when the brain is particularly sensitive to specific experiences and environmental inputs (language acquisition, visual development)
Adaptive and Maladaptive Plasticity
- Adaptive plasticity refers to beneficial changes in neural circuits and behavior that promote learning, memory, and functional recovery after brain injury or disease
- Examples of adaptive plasticity include:
- , which is the brain's ability to maintain function despite age-related changes or pathology due to a lifetime of learning and experiences
- , where the loss of one sensory modality (vision) leads to the enhanced processing of other senses (hearing, touch) in the deprived cortical areas
- Maladaptive plasticity refers to detrimental changes in neural circuits and behavior that contribute to the development or maintenance of neurological and psychiatric disorders
- Examples of maladaptive plasticity include:
- Chronic pain, where persistent nociceptive input leads to the sensitization of pain pathways and the expansion of pain-responsive cortical areas
- Addiction, where repeated drug use induces long-lasting changes in reward circuits and decision-making processes leading to compulsive drug-seeking behavior
Key Terms to Review (30)
Adaptive Plasticity: Adaptive plasticity refers to the brain's ability to change and reorganize itself in response to new experiences, environmental changes, or injury. This dynamic process allows the nervous system to adjust its functions and connections, enhancing survival and learning capabilities. By reshaping neural pathways, adaptive plasticity supports learning, memory formation, and recovery from trauma.
Axon remodeling: Axon remodeling is the process by which neurons adjust and reorganize their axonal structures in response to changes in activity, injury, or developmental cues. This dynamic process can involve the pruning of unnecessary axon branches, the growth of new branches, or changes in axon diameter, ultimately influencing how signals are transmitted within neural networks. Axon remodeling is a crucial aspect of neuroplasticity, enabling the nervous system to adapt to new information and experiences.
Cognitive Rehabilitation: Cognitive rehabilitation refers to a set of therapeutic strategies designed to help individuals regain cognitive functions that may have been lost or impaired due to injury, illness, or developmental issues. This approach leverages the brain's ability to adapt and reorganize itself, known as neuroplasticity, to enhance learning and memory capabilities, ultimately improving everyday functioning.
Cognitive reserve: Cognitive reserve refers to the brain's ability to improvise and find alternative ways of getting a job done, which can help mitigate the effects of aging or brain damage. It is a concept that suggests that individuals with higher levels of education, engaging jobs, and mentally stimulating activities develop a greater reserve of cognitive resources, allowing them to better cope with neurological decline.
Consolidation: Consolidation is the process through which newly acquired information is transformed into a stable and enduring memory, allowing it to be stored and retrieved later. This mechanism is essential in the journey from short-term memory, where information is temporarily held, to long-term memory, where it becomes more resistant to forgetting. It plays a crucial role in ensuring that experiences and knowledge are integrated into an individual's existing memory framework.
Critical Periods: Critical periods refer to specific windows of time during development when the brain is particularly sensitive to certain types of environmental stimuli, which can significantly influence learning and behavioral outcomes. These periods are crucial for the development of various cognitive and sensory functions, as well as social behaviors, highlighting the interplay between biological processes and experiential factors in shaping learning.
Cross-modal plasticity: Cross-modal plasticity is the brain's ability to adapt and reorganize itself by transferring functions from one sensory modality to another, especially after injury or sensory deprivation. This phenomenon highlights the brain's remarkable flexibility and capacity for change, enabling it to compensate for lost functions by enhancing the processing capabilities of remaining senses, often seen in individuals who lose one sense and experience heightened sensitivity in others.
Dendritic branching: Dendritic branching refers to the process by which dendrites, the tree-like structures of neurons, extend and form new branches. This phenomenon is crucial for neuroplasticity, allowing neurons to create new synaptic connections and strengthen existing ones in response to experience, learning, and environmental changes.
Developmental plasticity: Developmental plasticity refers to the ability of an organism's brain to change and adapt during its early stages of growth in response to experiences, environmental factors, and learning. This concept highlights how neural connections are formed, strengthened, or weakened based on interactions with the environment, which is crucial for cognitive and motor development.
Electrophysiology: Electrophysiology is the branch of physiology that studies the electrical properties of biological cells and tissues. This field is crucial for understanding how neurons communicate with each other through electrical signals, which plays a significant role in neuroplasticity and synaptic changes. By examining the electrical activities in nerve cells, scientists can better grasp how experiences and environmental factors influence brain functions and adaptations.
Encoding: Encoding is the process of converting information into a format that can be stored and later retrieved by the brain. This process plays a crucial role in how we learn and remember information, as it transforms sensory input into a meaningful representation that can be held in memory. Encoding involves various techniques and strategies that enhance memory retention and retrieval, which are interconnected with how we think, adapt, and utilize our brain structures.
Experience-dependent plasticity: Experience-dependent plasticity refers to the brain's ability to change and adapt its structure and function based on individual experiences throughout life. This type of neuroplasticity is driven by learning, memory, and sensory input, resulting in alterations in synaptic strength and neural pathways. It emphasizes that the brain is not static; rather, it is constantly reshaping itself based on how we interact with our environment.
Functional MRI: Functional MRI (fMRI) is a neuroimaging technique that measures brain activity by detecting changes in blood flow and oxygenation. It allows researchers to observe which areas of the brain are engaged during specific tasks or in response to stimuli, making it a powerful tool for understanding neuroplasticity and synaptic changes as the brain adapts and reorganizes itself based on experience and learning.
GABA: GABA, or gamma-aminobutyric acid, is the primary inhibitory neurotransmitter in the brain, crucial for reducing neuronal excitability throughout the nervous system. This neurotransmitter plays a key role in balancing excitation and inhibition in the brain, which is essential for maintaining proper brain function and supporting learning processes. The modulation of GABAergic activity is linked to neuroplasticity and synaptic changes, affecting how we learn and adapt to new information.
Gliogenesis: Gliogenesis is the process of forming glial cells, which are non-neuronal cells in the nervous system that support and protect neurons. This process is essential for maintaining homeostasis, providing support, and facilitating communication between neurons. Glial cells, including astrocytes, oligodendrocytes, and microglia, play critical roles in brain function and are involved in neuroplasticity, influencing how neural circuits adapt and change over time.
Glutamate: Glutamate is a key neurotransmitter in the brain that primarily acts as an excitatory signal, promoting communication between neurons. It plays a vital role in various brain functions, including learning and memory, by facilitating synaptic plasticity and neuroplasticity, which are essential for adapting and reorganizing neural connections in response to experiences.
Hebb's Rule: Hebb's Rule is a fundamental principle in neuroscience that states 'cells that fire together, wire together.' This concept highlights how synaptic connections between neurons strengthen as they are activated simultaneously. It is crucial in understanding neuroplasticity, as it explains how learning and memory can lead to structural changes in the brain through the reinforcement of synaptic pathways.
Hebbian Learning: Hebbian learning is a principle in neuroscience that describes how synaptic connections between neurons strengthen when they are activated simultaneously. This concept is often summarized by the phrase 'cells that fire together, wire together', highlighting the relationship between neural activity and the formation of new connections. It emphasizes the role of experience in shaping neural pathways, contributing to neuroplasticity and synaptic changes in the brain.
Long-term depression: Long-term depression (LTD) is a lasting decrease in the strength of synaptic transmission that occurs after specific patterns of activity at the synapse. This process is crucial for various forms of neuroplasticity, allowing the brain to adjust synaptic strength based on experience and activity levels, which is essential for learning and memory. LTD helps in refining neural circuits by weakening less important or redundant synaptic connections, promoting more efficient communication within neural networks.
Long-term potentiation: Long-term potentiation (LTP) is a long-lasting enhancement in signal transmission between two neurons that results from their repeated stimulation. This process plays a critical role in synaptic plasticity, which is essential for learning and memory formation, and highlights the neurological mechanisms underlying various forms of learning.
Maladaptive plasticity: Maladaptive plasticity refers to the brain's ability to change and reorganize itself in ways that are harmful or counterproductive, often as a result of injury or chronic stress. While neuroplasticity is generally seen as a positive adaptation for learning and recovery, maladaptive plasticity can lead to negative outcomes such as chronic pain, mental health disorders, or impaired function following brain damage. Understanding this concept helps highlight the dual nature of neuroplastic changes.
Merzenich's Studies: Merzenich's studies refer to a series of groundbreaking research efforts led by neuroscientist Michael Merzenich, which focus on neuroplasticity, the brain's ability to reorganize itself by forming new neural connections throughout life. These studies demonstrate how experiences, training, and learning can reshape the brain's structure and function, particularly in areas related to sensory perception and motor skills. Merzenich's findings emphasize the importance of active engagement in learning as a key driver of synaptic changes and neural growth.
Neurofeedback: Neurofeedback is a type of biofeedback that uses real-time monitoring of brain activity to teach individuals how to self-regulate their brain function. It involves measuring brain waves using an electroencephalogram (EEG) and providing feedback to the individual, helping them learn to optimize their mental states and improve cognitive performance. This practice is often used in therapy to address various neurological and psychological issues, fostering neuroplasticity through targeted training.
Neurogenesis: Neurogenesis is the process by which new neurons are generated in the brain, primarily occurring during development but also continuing in certain regions throughout adulthood. This process is crucial for learning, memory, and overall brain health, illustrating the brain's ability to adapt and reorganize itself in response to experiences and environmental changes.
Neuromodulators: Neuromodulators are chemical substances in the brain that alter the activity of neurons and affect the strength of synaptic transmission. They play a critical role in regulating various functions like mood, pain perception, and learning by influencing the effectiveness of neurotransmitters at synapses. This makes them essential for neuroplasticity, as they can enhance or inhibit synaptic changes that are crucial for learning and memory.
Neuroplasticity: Neuroplasticity refers to the brain's ability to reorganize itself by forming new neural connections throughout life. This remarkable capacity allows the brain to adapt to new experiences, learn new information, and recover from injuries, emphasizing its dynamic nature and the importance of environmental interactions.
Neurotrophic factors: Neurotrophic factors are a group of proteins that play a vital role in the growth, survival, and differentiation of neurons. They help in the maintenance of neural connections and promote neuroplasticity by influencing synaptic changes, allowing the nervous system to adapt and reorganize in response to experiences and environmental changes.
Pruning: Pruning is a biological process that involves the selective removal of synapses or neural connections in the brain, which occurs during development and in response to experience. This process is crucial for optimizing brain function, as it helps to refine neural circuitry by eliminating excess or unused synapses, leading to more efficient communication between neurons. It plays a significant role in neuroplasticity, shaping how we learn and adapt over time.
Synaptic plasticity: Synaptic plasticity refers to the ability of synapses, the connections between neurons, to strengthen or weaken over time, in response to increases or decreases in their activity. This dynamic process is crucial for learning and memory as it enables the brain to adapt and reorganize itself based on experiences. Synaptic plasticity underlies various forms of neuroplasticity, allowing for both short-term and long-term changes in the efficiency of neurotransmission, which can be influenced by factors such as habituation, sensitization, and the presence of specific neurotransmitters.
Synaptogenesis: Synaptogenesis is the process by which new synapses are formed between neurons, crucial for the development and plasticity of the nervous system. This dynamic process allows the brain to adapt to experiences, learn new information, and recover from injuries. Synaptogenesis plays a fundamental role in shaping neural circuits during early brain development and throughout life as a response to learning and environmental changes.