Neural correlates of late talking: A systematic review of electrophysiological and neuroimaging studies.

BACKGROUND

Late talking (LT), a delay in expressive vocabulary in early childhood, affects a significant minority of toddlers and can be a precursor to persistent language and literacy impairments. While behavioral profiles are well-documented, a systematic synthesis of its underlying neurobiology is lacking. This systematic review aimed to identify, evaluate, and synthesize evidence from electrophysiological (EEG) and neuroimaging (MRI) studies on the neural correlates of late talking in children.

METHODS

We conducted a systematic search of Scopus, Web of Science, and PubMed from inception to September 2025, following PRISMA guidelines. Studies investigating children formally identified as late talkers without comorbid neurological or global developmental conditions, using EEG/ERP or MRI modalities, were included. Risk of bias was assessed using the Joanna Briggs Institute (JBI) critical appraisal tool.

RESULTS

Sixteen studies (8 EEG, 8 neuroimaging) comprising 231 LT children in EEG studies and 315 in neuroimaging studies were included. EEG studies revealed a neurodevelopmental cascade, beginning with atypical oscillatory activity (increased frontal gamma power) and deficits in auditory discrimination (reduced Mismatch Negativity), progressing to higher-order impairments in phonological (absent PMN) and lexical-semantic (altered N400) processing. Neuroimaging studies consistently identified structural and functional anomalies within a distributed perisylvian network, including reduced gray matter in left temporal regions, atypical right-hemispheric lateralization, reduced activation in cortical-subcortical circuits, and altered white matter connectivity. These neural markers demonstrated significant predictive value for later language outcomes.

CONCLUSION

Late talking is a clear neurodevelopmental disorder with a cascading pattern of neural dysfunction. The identified neural signatures are not just findings but have strong clinical potential as biomarkers for early identification and prognosis. This evidence advocates for a shift to a precision medicine approach, opening the door to novel, neurobiologically-informed interventions like neuromodulation that target the underlying brain circuits.