Specific language impairment is not specific to language: the procedural deficit hypothesis

Area of Science:

• Neuroscience
• Linguistics
• Developmental Psychology

Background:

• Specific Language Impairment (SLI) is often explained by grammar-specific deficits or non-linguistic processing impairments.
• The procedural memory system, involving frontal/basal-ganglia circuits, is crucial for skill learning and execution.
• Emerging evidence links procedural memory to grammatical functions.

Purpose of the Study:

• To propose the Procedural Deficit Hypothesis (PDH) as an alternative explanation for SLI.
• To investigate the role of procedural memory system abnormalities in SLI.
• To examine literature supporting the PDH's predictions regarding brain structures and cognitive functions.

Main Methods:

• Retrospective literature review.
• Analysis of evidence implicating procedural memory in language and non-linguistic skills.
• Examination of neuroimaging and behavioral data related to SLI.

Main Results:

• The literature supports the PDH, indicating abnormal development in the procedural memory network in individuals with SLI.
• Impairments in linguistic and non-linguistic functions dependent on this network are observed.
• Lexical and declarative memory functions, relying on different brain structures, are largely unaffected.

Conclusions:

• The PDH provides a unifying framework for understanding SLI, linking it to procedural memory system dysfunction.
• Specific brain regions like Broca's area and the caudate nucleus are implicated.
• The PDH offers a novel and potentially productive research direction for SLI.