Editing Hebbian theory (section)

{{short description|Neuroscientific theory}}
'''Hebbian theory''' is a [[neuropsychological]] theory claiming that an increase in [[synapse|synaptic]] efficacy arises from a [[presynaptic cell]]'s repeated and persistent stimulation of a postsynaptic cell. It is an attempt to explain [[synaptic plasticity]], the adaptation of [[neuron]]s during the learning process. Hebbian theory was introduced by [[Donald Hebb]] in his 1949 book ''[[The Organization of Behavior]].''<ref name="Hebb 1949">{{Cite book |last=Hebb |first=D.O. |title=The Organization of Behavior |publisher=Wiley & Sons |year=1949 |location=New York}}</ref> The theory is also called '''Hebb's rule''', '''Hebb's postulate''', and '''cell assembly theory'''. Hebb states it as follows:

<blockquote>Let us assume that the persistence or repetition of a reverberatory activity (or "trace") tends to induce lasting cellular changes that add to its stability. ... When an [[axon]] of cell ''A'' is near enough to excite a cell ''B'' and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that ''A''’s efficiency, as one of the cells firing ''B'', is increased.<ref name="Hebb 1949"/>{{rp|62}}</blockquote>

The theory is often summarized as "'''Neurons that fire together, wire together'''."<ref>[[Siegrid Löwel]], Göttingen University; The exact sentence is: "neurons wire together if they fire together" (Löwel, S. and Singer, W. (1992) Science 255 (published January 10, 1992) {{cite journal |last1=Löwel |first1=Siegrid |last2=Singer |first2=Wolf |date=1992 |title=Selection of Intrinsic Horizontal Connections in the Visual Cortex by Correlated Neuronal Activity |url=https://www.science.org/doi/10.1126/science.1372754 |journal=Science Magazine |location=United States |publisher=American Association for the Advancement of Science |volume=255 |issue=5041 |pages=209–212 |bibcode=1992Sci...255..209L |doi=10.1126/science.1372754 |issn=0036-8075 |pmid=1372754|url-access=subscription }}</ref> However, Hebb emphasized that cell ''A'' needs to "take part in firing" cell ''B'', and such causality can occur only if cell ''A'' fires just before, not at the same time as, cell ''B''. This aspect of causation in Hebb's work foreshadowed what is now known about [[spike-timing-dependent plasticity]], which requires temporal precedence.<ref name=":2">{{cite journal |last1=Caporale |first1=Natalia |last2=Dan |first2=Yang |date=2008 |title=Spike timing-dependent plasticity: a Hebbian learning rule |journal=Annual Review of Neuroscience |volume=31 |pages=25–46 |doi=10.1146/annurev.neuro.31.060407.125639 |pmid=18275283}}</ref>

Hebbian theory attempts to explain [[associative learning|associative]] or ''Hebbian learning'', in which simultaneous activation of cells leads to pronounced increases in [[synaptic strength]] between those cells. It also provides a biological basis for [[errorless learning]] methods for education and memory rehabilitation. In the study of [[Artificial neural network|neural networks]] in cognitive function, it is often regarded as the neuronal basis of [[unsupervised learning]].<ref>{{Cite journal |last=Sanger |first=Terence D. |date=1989-01-01 |title=Optimal unsupervised learning in a single-layer linear feedforward neural network |url=https://www.sciencedirect.com/science/article/abs/pii/0893608089900440 |journal=Neural Networks |volume=2 |issue=6 |pages=459–473 |doi=10.1016/0893-6080(89)90044-0 |issn=0893-6080|url-access=subscription }}</ref>