neuroscience Neuroscience is the science, scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a Multidisciplinary approach, multidisciplinary science that combines physiology, an ...

, homeostatic plasticity refers to the capacity of

neurons A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...

to regulate their own excitability relative to network activity. The term homeostatic plasticity derives from two opposing concepts: '

homeostatic In biology, homeostasis ( British also homoeostasis) (/hɒmɪə(ʊ)ˈsteɪsɪs/) is the state of steady internal, physical, and chemical conditions maintained by living systems. This is the condition of optimal functioning for the organism and ...

' (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".

Comparison with Hebbian plasticity

Homeostatic synaptic plasticity is a means of maintaining the synaptic basis for learning, respiration, and locomotion, in contrast to the Hebbian plasticity associated with learning and memory. Although Hebbian forms of plasticity, such as

long-term potentiation In neuroscience, long-term potentiation (LTP) is a persistent strengthening of synapses based on recent patterns of activity. These are patterns of synaptic activity that produce a long-lasting increase in signal transmission between two neurons ...

and

long-term depression In neurophysiology, long-term depression (LTD) is an activity-dependent reduction in the efficacy of neuronal synapses lasting hours or longer following a long patterned stimulus. LTD occurs in many areas of the CNS with varying mechanisms dependi ...

occur rapidly, homeostatic plasticity (which relies on protein synthesis) can take hours or days.

TNF-α Tumor necrosis factor (TNF, cachexin, or cachectin; formerly known as tumor necrosis factor alpha or TNF-α) is an adipokine and a cytokine. TNF is a member of the TNF superfamily, which consists of various transmembrane proteins with a homolo ...

and

microRNA MicroRNA (miRNA) are small, single-stranded, non-coding RNA molecules containing 21 to 23 nucleotides. Found in plants, animals and some viruses, miRNAs are involved in RNA silencing and post-transcriptional regulation of gene expression. m ...

s are important mediators of homeostatic synaptic plasticity. Homeostatic plasticity is thought to balance Hebbian plasticity by modulating the activity of the

synapse In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or to the target effector cell. Synapses are essential to the transmission of nervous impulses fr ...

or the properties of ion channels. Homeostatic plasticity in neocortical circuits has been studied in depth by Gina G. Turrigiano and Sacha Nelson of

Brandeis University Brandeis University is a Private university, private research university in Waltham, Massachusetts. Founded in 1948 as a nonsectarian, non-sectarian, coeducational institution sponsored by the Jews, Jewish community, Brandeis was established on t ...

, who first observed compensatory changes in excitatory postsynaptic currents (mEPSCs) after chronic activity manipulations.

Mechanism

Synaptic scaling has been proposed as a potential mechanism of homeostatic plasticity. Homeostatic plasticity can be used to describe a process that maintains the 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. Recently, it was proposed that homeostatic synaptic scaling may play a role in establishing the specificity of an associative memory. Homeostatic plasticity also maintains neuronal excitability in a real-time manner through the coordinated plasticity of threshold and refractory period at

voltage-gated sodium channels Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels and can be classified according to the trigger that opens the channel ...

Role in central pattern generators

Homeostatic plasticity is also very important in the context of

central pattern generators Central pattern generators (CPGs) are self-organizing biological neural circuits that produce rhythmic outputs in the absence of rhythmic input. They are the source of the tightly-coupled patterns of neural activity that drive rhythmic and stereo ...

. In this context, neuronal properties are modulated in response to environmental changes in order to maintain an appropriate neural output.

References

External links

* {{scholarpedia, urlname=Homeostatic_Regulation_of_Neuronal_Excitability, title=Homeostatic Regulation of Neuronal Excitability Neuroplasticity