Changes in Neural Activation Patterns and Brain Anatomy as a Function of Non-Pathological First Language Attrition

Merel Keijzer

doi:10.4172/2329-6895.1000171

Abstract

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.

Highlights

A prevalent view in the field of language acquisition, most notably second language (L2) acquisition, was that language had to be learned before a certain age in order for the speaker to function at a native-like level
Because of advances in neuroimaging techniques, such as the Event-related potential (ERP) technique and Magnetic Resonance Imaging ((f) MRI), it has been convincingly shown that even the brains of speakers who learn a second language (L2) later in life can resemble those of mother tongue speakers (L1) in their functional activation patterns, given sufficient, consistent and long-term exposure to the L2 [4]
In recent years the critical period of language acquisition has come under close scrutiny as a direct consequence of neuroimaging evidence revealing a greater plasticity of the human brain to master new languages than has previously been assumed, the field of non-pathological L1 attrition has not contributed much to this debate. Would this be informative for the field of language learning and the critical period in general, as learning a language early in life should leave long-lasting traces in the neural circuit, but investigations of this nature would directly benefit the field of L1 attrition

Summary

Introduction

A prevalent view in the field of language acquisition, most notably second language (L2) acquisition, was that language had to be learned before a certain age in order for the speaker to function at a native-like level. The theory has been modified and age bands extended to accommodate cases of people who attain native-like proficiency levels in their L2, despite learning it later in life Behavioral evidence of this kind has caused the critical period to come under scrutiny. Even more compelling evidence refuting the Critical Period Hypothesis comes from neurocognitive studies that have shown the language function of the human brain to be much more flexible than has previously been assumed. This is in line with what we know about neuroplasticity in other domains [4]. More converging evidence comes from structural MRI scans, which reveal that such long-term L2 activation can even lead to anatomical brain changes, most notably in the realms of increased gray matter density, white matter integrity and cortical thickness [(see [4] for an overview of previous work in this area)

Objectives

Conclusion