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| Reference | Nature of task
(lexical/phonological/syntactical) | Group differences
(age of acquisition/language proficiency/task performance) | Methodology and structural/functional effects on the brain | Details |
|
| Mechelli et al., 2004, Nature [83] | — | L2 proficiency (indexed by neuropsychological tests of reading, writing, speech comprehension, and production)
AoA (monolinguals versus early bilinguals versus late bilinguals) | Structure: VBM (grey matter density) | L2 proficiency was positively related to grey matter density in L inferior parietal cortex (and negatively related to AoA)
L2 AoA was negatively related to grey matter density in L and R inferior parietal cortex |
|
| Klein et al., 2014, Brain and Language [123] | — | AoA (simultaneous versus sequential early versus sequential late bilinguals) | Structure: MRI (cortical thickness) | L2 AoA was associated with cortical thickness; positive relationship for L inferior frontal gyrus and L superior parietal lobe, negative relationship for R inferior frontal gyrus
The researchers argued that the positive relationship could reflect the growth of new cortical tissue as demanded by the new learning in adolescence/adulthood and the ensuing cortical folding to accommodate new tissue |
|
| Mohades et al., 2012, Brain Research [180] | — | AoA (simultaneous bilinguals versus sequential bilinguals versus monolinguals) | Structure: MRI DTI (white matter) | L2 AoA was negatively associated with mean fractional anisotropy values for inferior occipitofrontal fasciculus (IIFOF) tracts negatively associated with AoA
L2 AoA was positively associated with mean fractional anisotropy values for the bundle of white matter fibres arising from the anterior part of the corpus callosum projecting to the orbital lobe (AC-OL) |
|
| Grogan et al., 2012, Neuropsychologia [139] | Lexical (efficiency) | Task performance (speed and accuracy of lexical decisions, and lexical fluency)
AoA | Structure: MRI/VBM | L2 task performance was negatively related to grey matter in the L pars opercularis
L2 AoA was negatively related to grey matter in the L pars opercularis |
|
| Pliatsikas et al., 2014, Cerebellum [148] | Lexical (grammar) | Task performance (speed of processing regular inflections)
Years of naturalistic exposure (number of years living in UK) | Structure: VBM | L2 task performance was positively associated with grey matter volume in the cerebellum
Years of naturalistic exposure to L2 were positively correlated with grey matter volume in the posterior bilateral putamen |
|
| Das et al., 2011, Neuroimage [57] | Lexical (reading proficiency) | Task performance
AoA (simultaneous versus sequential bilinguals) | Function: fMRI | L2 task performance (English reading proficiency) was positively related to L inferior temporal gyrus activity
L2 AoA was negatively related to left inferior parietal lobe activity |
|
| Cummine and Boliek, 2013, Brain Structure and Function [31] | Lexical (reading) | Task performance (response time for a complex reading task) for sequential bilinguals versus monolinguals | Structure: DTI
(white matter) | L2 task performance was positively associated with mean fractional anisotropy values in the parietal-occipital sulcus
The researchers contended that the parietal-occipital sulcus could be a possible gating system for modulating the contribution of sublexical and lexical stream processes |
|
| Grogan et al., 2009, Cerebral Cortex [33] | Lexical + phonological | Task performance (semantic and phonemic fluency scores) | Structure: MRI, VBM | Task performance (phonemic fluency) in L1 and L2 was associated with grey matter in the presupplementary motor area and the head of caudate
Task performance (semantic fluency) in L1 and L2 was positively associated with grey matter density in the L inferior temporal cortex |
|
| Krizman et al., 2015, Neuroscience Letters [182] | Phonological (listening to syllables) | AoA, matched for proficiency (simultaneous versus sequential) | Function: EEG | L2 AoA was negatively associated with amplitude of fundamental frequency response in the auditory brainstem to syllables like “ba” and “ga”
L2 AoA was negatively associated with neural consistency of responses to syllable “ba”
The researchers argued that bilingualism enhances subcortical auditory processing |
|
| Archila-Suerte et al., 2015, Brain and Language [183] | Phonological (processing L2 speech sounds) | AoA (early versus late), matched for proficiency and SES | Function: fMRI | L2 AoA was positively associated with neural activity in the bilateral superior temporal gyrus and the Rolandic operculum
The researchers posited that late bilinguals recruit this premotor area to support subvocal rehearsal of L2 sounds learned late in development
L2 AoA negatively associated with neural activity in the R middle frontal gyrus |
|
| Golestani et al., 2006, Neuropsychologia [163] | Syntax | L2 grammatical (syntactic) proficiency as assessed with TOEFL in late bilinguals | Function: fMRI | L2 task proficiency was positively associated with neural activity in the basal ganglia (particularly left caudate nucleus/putamen)
During syntactical production, language proficiency was positively related to the closeness of L1 and L2 activity peaks in L inferior frontal gyrus |
|
| Jasinska and Petitto, 2013, Developmental Cognitive Neuroscience [181] | Syntactical (sentence judgment task) | AoA (early versus late) | Function: fNIRS | In children, L2 AoA was positively associated with neural activity in the classic language neural areas (bilateral superior temporal gyrus, Broca’s area) and negatively associated with neural activity in domain-general areas (dorsolateral prefrontal cortex, frontopolar cortex) |
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