Editing Learning (section)

===Epigenetic factors===
{{Further|Epigenetics in learning and memory}}
The underlying molecular basis of learning appears to be dynamic changes in [[gene expression]] occurring in [[brain]] [[neuron]]s that are introduced by [[epigenetic]] mechanisms.  Epigenetic regulation of gene expression involves, most notably, chemical modification of [[DNA]] or DNA-associated [[histone]] proteins.  These chemical modifications can cause long-lasting changes in gene expression. Epigenetic mechanisms involved in learning include the [[DNA methylation|methylation]] and [[DNA demethylation|demethylation]] of neuronal DNA as well as [[histone methylation|methylation]], [[histone acetylation and deacetylation|acetylation and deacetylation of neuronal histone proteins]].

During learning, information processing in the brain involves induction of [[DNA oxidation|oxidative modification in neuronal DNA]] followed by the employment of [[DNA repair]] processes that introduce epigenetic alterations.  In particular, the DNA repair processes of [[non-homologous end joining]] and [[base excision repair]] are employed in learning and memory formation.<ref>{{cite journal | last1 = Li | first1 = X | last2 = Marshall | first2 = PR | last3 = Leighton | first3 = LJ | last4 = Zajaczkowski | first4 = EL | last5 = Wang | first5 = Z | last6 = Madugalle | first6 = SU | last7 = Yin | first7 = J | last8 = Bredy | first8 = TW | last9 = Wei | first9 = W | year = 2019 | title = The DNA Repair-Associated Protein Gadd45γ Regulates the Temporal Coding of Immediate Early Gene Expression within the Prelimbic Prefrontal Cortex and Is Required for the Consolidation of Associative Fear Memory | journal = J Neurosci | volume = 39 | issue = 6| pages = 970–983 | doi = 10.1523/JNEUROSCI.2024-18.2018 | pmid = 30545945 | pmc = 6363930 }} Erratum in: {{cite journal | pmid = 30545945 | doi=10.1523/JNEUROSCI.2024-18.2018 | volume=39 | title=The DNA Repair-Associated Protein Gadd45γ Regulates the Temporal Coding of Immediate Early Gene Expression within the Prelimbic Prefrontal Cortex and Is Required for the Consolidation of Associative Fear Memory | pmc=6363930 | year=2019 | journal=J Neurosci | pages=970–983 | last1 = Li | first1 = X | last2 = Marshall | first2 = PR | last3 = Leighton | first3 = LJ | last4 = Zajaczkowski | first4 = EL | last5 = Wang | first5 = Z | last6 = Madugalle | first6 = SU | last7 = Yin | first7 = J | last8 = Bredy | first8 = TW | last9 = Wei | first9 = W| issue=6 }}</ref><ref>{{cite journal | last1 = Brito | first1 = David V.C. | last2 = Kupke | first2 = Janina | last3 = Gulmez Karaca | first3 = Kubra | last4 = Zeuch | first4 = Benjamin | last5 = Oliveira | first5 = Ana M.M. | year = 2020| title = Mimicking Age-Associated Gadd45γ Dysregulation Results in Memory Impairments in Young Adult Mice | journal = J Neurosci | volume = 40 | issue = 6| pages = 1197–1210 | doi = 10.1523/JNEUROSCI.1621-19.2019 | pmid = 31826946 | pmc = 7002144 }}</ref>