Neuropsychologia 46 (2008) 2265–2273 Contents lists available at ScienceDirect Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia Normalisation and increase of abnormal ERP patterns accompany recovery from aphasia in the post-acute stage Marina Laganaro ∗ , St ´ ephanie Morand, Val ´ erie Schwitter, Carmel Zimmermann, Armin Schnider Laboratory of Cognitive Rehabilitation, Division of Rehabilitation, Geneva University Hospital and University of Geneva, Switzerland article info Article history: Received 28 August 2007 Received in revised form 27 December 2007 Accepted 7 February 2008 Available online 10 March 2008 Keywords: Aphasia Anomia ERP Recovery abstract Electrophysiological correlates of recovery from anomia were analysed in four aphasic patients in the post-acute stage. Event-related potentials (ERPs) were recorded during picture naming at baseline and after a period of therapy for anomia. All patients had severe anomia at baseline assessment and improved significantly in naming during the study period. Waveform analyses and temporal segmentation were carried out on the ERPs of each patient in comparison with 15 healthy control subjects. Normalisation as well as an increase of abnormal electrophysiological correlates accompanied recovery. An increase of abnormal amplitudes appeared in a patient with semantic impairment during the first 300 ms after picture onset, while only normalisation of amplitudes and topographic maps accompanied recovery in the three patients with lexical–phonological impairment in this early time-window. Abnormal amplitudes and topographic maps emerged during recovery in the patients with lexical–phonological impairment in later time-windows, starting between 250 and 300 ms. Follow-up ERP recordings carried out 6 months later in two of them showed normalisation of amplitudes and persistence of abnormal maps. The results suggest that electrophysiological changes accompanying recovery from anomia in the post-acute stage are observed in specific time-windows, probably corresponding to different encoding processes and that recovery correlates with normalisation of EEG patterns as well as with the emergence of abnormalities, which presumably indicates compensation mechanisms of specific encoding processes. © 2008 Elsevier Ltd. All rights reserved. 1. Introduction In the last 10 years there has been an increasing interest in the investigation of reorganization of language after stroke. Neuroimaging studies have first tracked the regions involved in reorganization of language through the analysis of patterns of activation in different language tasks in chronic aphasic speakers relative to control groups (Cappa et al., 1997; Heiss, Kessler, Karbe, Fink, & Pawlik, 1993; Karbe, Kessler, Herholz, Fink, & Heiss, 1995; Weiller et al., 1995). Afterwards, investigations have focused on therapy-induced changes in aphasia and performed repeated mea- surements in patients before and after treatment (Belin et al., 1996; Leger et al., 2002; Musso et al., 1999; Pulverm ¨ uller, Hauk, Zohsel, Neininger, & Mohr, 2005; Thompson, 2000). Several brain regions have been identified, including left perilesional areas (fMRI studies by Belin et al., 1996; Leger et al., 2002; MEG study by Cornelissen et al., 2003) as well as right hemisphere regions (fMRI studies ∗ Corresponding author at: Service de Neuro-R ´ e´ education, Geneva University Hospitals, Av. Beau-S´ ejour 26, CH-1211 Gen` eve 14, Switzerland. Tel.: +41 22 3823643; fax: +41 22 3828338. E-mail addresses: marina.laganaro@hcuge.ch, marina.laganaro@unine.ch (M. Laganaro). by Musso et al., 1999; Saur et al., 2006; Thompson, 2000). In the longitudinal study by Saur et al. (2006) the right hemisphere activa- tion was observed especially in the post-acute stage and activation shifted back to left hemisphere language areas in the chronic stage. Changes in temporal course of specific language processes may also accompany recovery from aphasia. Most neuroimag- ing studies on recovery were carried out with PET or fMRI, thus limiting the description to spatial reorganization after brain dam- age, without information on the time course of the encoding or decoding processes. Magnetoencephalography (MEG) and elec- troencephalography (EEG) investigations on language recovery in aphasia are rare, especially when it comes to language pro- duction (Salmelin, 2007). Hensel, Rockstroh, Berg, and Schonle (2004) and Meinzer et al. (2004) have analysed the electrophys- iological changes accompanying recovery from aphasia and only a few studies have investigated the temporal course of changes accompanying reorganization of language production after stroke. Event-related potential (ERP) patterns have been analysed with semantic and phonological categorization tasks in chronic apha- sic patients with partial recovery by Angrilli, Elbert, Cusumanu, Stegagno, and Rockstroh (2003) and Dobel et al. (2001). The mean amplitudes of five electrodes from four regions were compared to those of a healthy control group. Different activation patterns 0028-3932/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2008.02.013