Clinical language performance and neurophysiological correlates of language
processing were measured before and after intensive language therapy in
patients with chronic (time post stroke >1 year) post stroke aphasia (PSA). As
event-related potential (ERP) measure, the mismatch negativity (MMN) was
recorded in a distracted oddball paradigm to short spoken sentences. Critical
‘deviant’ sentence stimuli where either well-formed and meaningful, or
syntactically, or lexico-semantically incorrect. After 4 weeks of speech-
language therapy (SLT) delivered with high intensity (10.5 h per week),
clinical language assessment with the Aachen Aphasia Test battery demonstrated
significant linguistic improvements, which were accompanied by enhanced MMN
responses. More specifically, MMN amplitudes to grammatically correct and
meaningful mini-constructions and to ‘jabberwocky’ sentences containing a
pseudoword significantly increased after therapy. However, no therapy-related
changes in MMN responses to syntactically incorrect strings including
agreement violations were observed. While MMN increases to well-formed
meaningful strings can be explained both at the word and construction levels,
the neuroplastic change seen for ‘jabberwocky’ sentences suggests an
explanation in terms of constructions. The results confirm previous reports
that intensive SLT leads to improvements of linguistic skills in chronic
aphasia patients and now demonstrate that this clinical improvement is
associated with enhanced automatic brain indexes of construction processing,
although no comparable change is present for ungrammatical strings.
Furthermore, the data confirm that the language-induced MMN is a useful tool
to map functional language recovery in PSA