Modern neuroscience has increasingly noted the importance of neuroplasticity in nervous system development. In summary, neuroplasticity is defined as the brain's ability to adapt the structure and function of its own neurons to the external changes in the environment, supporting processes such as learning, memory creation, healing from injury, and overall development. Traditional Hebbian plasticity, which is the most well-studied form of neuroplasticity, states that repeated action and experiences strengthen synapses (long-term potentiation) and lack of action and experiences weaken or diminish synapses (long-term depression). However, this can lead to potential instability in the nervous system, where synapses and nerves can saturate to either extremes, either firing constantly or not firing at all. In response, the nervous system can also perform homeostatic plasticity. Being a subset of neuroplasticity, homeostatic plasticity specifically acts as the brain's "self-correcting" counterforce. It acts as the nervous system's "thermostat", bringing neural activity back to specific balanced set point when it becomes too high or too low in certain regions of the brain. Homeostatic plasticity is the capacity of neurons to regulate their own excitability relative to network activity. The term homeostatic plasticity derives from two opposing concepts: homeostatic (a product of the Greek words for "same" and "state" or "condition") and plasticity (or "change"), thus homeostatic plasticity means "staying the same through change". In the nervous system, the neural circuit has to remain stable in function through a variety of fluctuating changes that occur in the number and strength of synaptic connections. Thus, neurons must be able to keep track of and evolve with their changing environment while ensuring there is stability on the functional and structural level. Hebbian neuroplasticity (the neuroplasticity that causes long-term potentiation and long-term depression) creates changes that pushes neural circuits away from equilibrium, and it is important to ensure that stability is still maintained for neurons to maintain their activity and functionality. Neurons need to have flexibility to adapt to changes in the connectivity and synaptic strength during development and learning, but they must also have a system in place to keep them in check. This is the purpose of homeostatic plasticity: the neuronal networks use a complex set of regulatory mechanisms to achieve homeostasis over a wide range of temporal and spatial scales. Whenever there is a perturbation to the nervous system, such as a synaptic connection or neural circuit that is over-excited to the point of harm, homeostatic plasticity mechanisms are triggered and circuit functions are stabilized.
Homeostatic plasticity acts as a negative feedback mechanism. Since this mechanism is used to offset the excessive excitation or inhibition through adjusting the synaptic strength of the neurons, it maintains stability by reversing a change.
Homeostatic plasticity has its own mechanism, subtypes, and comparators. Additionally, homeostatic plasticity can be connected to the nervous system by exploring its general purpose and roles in the system, specifically with central pattern generators and in neurological disorders. The remainder of this article will cover all important facets needed for thorough understanding homeostatic plasticity and the implication it has on clinical diseases and future research, including the topics mentioned above.
Mechanisms
While the way that homeostatic plasticity is induced is still being studied, there are many ongoing research projects and past projects that have uncovered details on the mechanisms that allow the negative feedback loop of homeostatic plasticity to take place. Key findings suggest that two main mechanisms behind homeostatic plasticity are intrinsic excitability and synaptic efficacy.
Synaptic scaling has been labeled as a potential mechanism of homeostatic plasticity. Homeostatic plasticity is often used to describe a process that maintains stability of neuronal functions through a coordinated plasticity among subcellular compartments, such as the synapses versus the neurons and the cell bodies versus the axons. Synaptic scaling aids in that regulation of neurons as the role of synaptic scaling is to adjust the strength of neuron's excitatory synapses, helping to keep the neurons in check so homeostatic plasticity can achieve its function properly. In 2021, it was proposed that homeostatic synaptic scaling may play a role in establishing the specificity of an associative memory.
In 2025, it was found that the protein LARGE plays a significant role in homeostatic resetting of Hebbian plasticity through the downregulation of AMPA-receptor trafficking in the Golgi apparatus. Other studies have stated that phosphorylation is another method in which homeostatic plasticity can be stimulated.
Research has also shown that heterosynaptic plasticity can act as an underlying mechanism for homeostatic plasticity in undoing the positive-feedback loop effects of Hebbian plasiticity.
Homeostatic plasticity also uses a separate mechanism to help maintain neuronal excitability in a real-time manner through the coordinated plasticity of threshold and refractory period at voltage-gated sodium channels, keeping them balanced so the barrier remains constant for stable firing actions.
Homeostatic plasticity can also be mediated by extracellular signals such as BDNF or TNF-α. These factors are released in an activity-dependent manner and can regulate both excitatory and inhibitory synapses across neurons, contributing to circuit-wide homeostatic adjustments.
There is often an overlap between the mechanisms behind homeostatic plasticity and the sub-types of homeostatic plasticity, as the sub-types play an important role in ensuring that homeostasis is achieved within neural networks.
Sub-types
Homeostatic plasticity serves to keep neuronal circuits in the appropriate range of activity for proper functioning. Homeostatic synaptic plasticity can be shown in presynaptic alterations, postsynaptic receptor expression, changes in intrinsic characteristics, synaptic scaling, structural homeostatic plasticity, and metaplasticity.
Homeostatic presynaptic plasticity Homeostatic presynaptic plasticity is the ability of neurons to regulate neurotransmitter release at presynaptic terminals, ensuring a steady range of brain activity. This process involves various mechanisms, such as quantal size adjustment, differential expression of presynaptic proteins, and modification of vesicle recycling. Quantal size adjustment helps maintain steady postsynaptic responses despite changes in synaptic strength. Differential expression of presynaptic proteins, such as calcium channels or synaptic vesicle proteins, can also be altered by neurons to affect neurotransmitter release rate.
Homeostatic postsynaptic plasticity Homeostatic postsynaptic plasticity is crucial for maintaining consistent levels of synaptic activity in neurons, which are formed at specific synapses in the brain. Homeostatic processes involve changes in the expression of receptors, changes in receptor sub-unit composition, and changes to intracellular signaling pathways. For example, the NMDA receptor can change its sub-unit composition to improve sensitivity to neurotransmitters. Additionally, changes in the expression and location of neurotransmitter receptors can impact synaptic transmission when specific signaling pathways are activated. Synaptic adhesion molecules can also be influenced by homeostatic processes. Overall, homeostatic postsynaptic plasticity contributes to the stability and proper functioning of neural circuits, allowing the brain to adapt to changing conditions without compromising the overall stability of neuronal activity.
Homeostatic intrinsic plasticity Homeostatic intrinsic plasticity refers to the ability of neurons to change their intrinsic electrical characteristics in response to changes in synaptic or network activity. This process involves alterations in the excitability or firing characteristics of individual neurons, rather than primarily adjusting synaptic strength. Intrinsic plasticity processes associated with homeostasis include ion channel expression alterations, membrane conductance modifications, action potential threshold alterations, and regulation of intrinsic excitability. Neurons can up-regulate the expression of sodium channels to maintain firing rates and increase excitability in case of a drop in synaptic activity. These changes impact the input-output link between neurons and the homeostatic control of neuronal activity.
Synaptic scaling Synaptic scaling is a homeostatic mechanism that allows neurons to modulate the strength of all synapses to maintain stable activity levels within a specific range. This process is characterized by changes in the quantity or sensitivity of neurotransmitter receptors on the postsynaptic membrane. Neurons can reduce the number of neurotransmitter receptors in response to network activity spikes, reducing synaptic strength, or increase the density in response to network activity drops, increasing sensitivity and boosting synaptic strength. This homeostatic regulation of brain circuits supports other types of synaptic plasticity, such as long-term depression and long-term potentiation.
Homeostatic structural plasticity Structural homeostatic plasticity is another subtype of homeostatic plasticity, and is a homeostatic mechanism that involves structurally remodeling neural circuits, such as forming, pruning, or altering synaptic size, in order to maintain stability within the network's activity. While it seems similar to synaptic scaling, it is different in the sense that synaptic scaling acts on the strength or weight of existing synapses, while homeostatic structural plasticity acts on the number of synapses. In a paper published in July 2025, it was found that synaptic scaling and structural homeostatic plasticity work hand-in-hand. In the study, mouse hippocampal tissue cultures were used to block AMPA receptors in two different doses. Results showed that a partial blockage of the AMPA receptors increased the spine density, whereas a complete blockage resulted in decreased spine density. This showed that there is not a linear relationship between neural activity and dendritic spine numbers; instead, it is biphasic (U-shaped) and dependent on the degree of inhibition. This biphasic result is related to structural homeostatic plasticity because it shows how the subtypes of homeostatic structural plasticity and synaptic scaling work together to govern the number of synapses and the strength of synapses to provide control over the homeostasis of neural circuits.
Metaplasticity Sometimes called the "plasticity of plasticity", metaplasticity is when a neuron or synapse's past activity changes the capacity it has for future plasticity. Instead of directly changing synaptic strength or working in the pre-synaptic or post-synaptic sense, it works on a higher level to shift the threshold at which future long-term potentiation of long-term depression can be triggered. Thus, it inhibits repeated excitability or degradation of synaptic connections through Hebbian neuroplasticity, and works as both a sub-type and mechanism of homeostatic plasticity.
Comparison to other types of plasticity At a high-level, homeostatic plasticity works to restore neural activity back towards a "set point" in order to promote stability of the nervous system and homeostasis, whereas more other forms of plasticity center around producing and promoting change and adaptability in the nervous system and synaptic connections.
Hebbian plasticity