Changes in neural activation patterns and brain anatomy as a function of non-pathological first language attrition

In recent years the Critical Period Hypothesis of language acquisition has come under close scrutiny. The premise that native-like language proficiency can only be attained if the language is learned early in life seems difficult to maintain, as neuroimaging data have revealed a greater plasticity of the human brain to master new languages than has previously been assumed. The field of non-pathological first language (L1) attrition has not contributed much to this debate. Adding attrition perspectives, however, can inform the field of language learning and the critical period in general: learning a language early in life should leave long-lasting traces in the neural circuit. But investigations of this nature would also directly benefit the field of L1 attrition itself. Attrition theories have largely built on behavioral paradigms, and two pivotal questions remain unanswered but could be addressed using neuroimaging techniques: 1) is the cause of L1 attrition mainly L1 non-use or rather the introduction and mastery of a second language (L2)? 2) is L1 attrition an irreversible, permanent phenomenon or does it merely reflect a temporary inaccessibility of the L1 system? This paper aims to review the scantly available evidence for functional and/or anatomical brain changes as a function of non-pathological L1 attrition, specifically focusing on the two outstanding questions above. Building on previous insights, this paper theorizes about L1 attrition-induced neurological changes that have not been addressed in previous work and formulates goals and avenues for future studies