نرمالیزه کردن و افزایش غیر طبیعی الگوهای ERP همراه بازیابی از زبان پریشی در مرحله بعد از حاد
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|29995||2008||9 صفحه PDF||سفارش دهید||5680 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Neuropsychologia, Volume 46, Issue 8, July 2008, Pages 2265–2273
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.
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 measurements in patients before and after treatment (Belin et al., 1996, Leger et al., 2002 and Musso et al., 1999; Pulvermüller, Hauk, Zohsel, Neininger, & Mohr, 2005; Thompson, 2000). Several brain regions have been identified, including left perilesional areas (fMRI studies by Belin et al., 1996 and Leger et al., 2002; MEG study by Cornelissen et al., 2003) as well as right hemisphere regions (fMRI studies by Musso et al., 1999, Saur et al., 2006 and Thompson, 2000). In the longitudinal study by Saur et al. (2006) the right hemisphere activation 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 neuroimaging studies on recovery were carried out with PET or fMRI, thus limiting the description to spatial reorganization after brain damage, without information on the time course of the encoding or decoding processes. Magnetoencephalography (MEG) and electroencephalography (EEG) investigations on language recovery in aphasia are rare, especially when it comes to language production (Salmelin, 2007). Hensel, Rockstroh, Berg, and Schonle (2004) and Meinzer et al. (2004) have analysed the electrophysiological 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 aphasic 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 in the patients relative to the control group were observed starting at about 300 ms after stimulus presentation. With regard to therapy-induced changes in language production, Cornelissen et al. (2003) analysed spatio-temporal changes with MEG in three chronic anomic patients. Pre- and post-treatment differed in a time-window between 300 and 700 ms after picture onset in a naming task. This time-window has been estimated to correspond to post-lexical encoding during picture naming in healthy speakers (Indefrey & Levelt, 2004), which is compatible with the lexical–phonological impairment of the patients in that study. The electrophysiological processes underlying picture naming have been tracked with magnetoencephalographic investigations in healthy speakers (Salmelin et al., 1994, Levelt et al., 1998 and Vihla et al., 2006). The results suggested that activation during picture naming proceeds from occipital visual areas to bilateral parietal and left temporal areas, then to premotor frontal areas in the first 400–500 ms following picture presentation. Some studies tried to derive specific spatio-temporal correlates of the different processes during these first 500 ms, with tasks tapping into semantic or phonological encoding processes. For instance, Maess, Friederici, Damian, Meyer, and Levelt (2002) tracked semantic encoding with a semantic interference task in picture naming. Semantic processes linked to semantic interference were found to occur between 150 and 225 ms after picture presentation and were characterised by a left temporal source. Vihla et al. (2006) compared tasks requiring phonological processing (picture naming and phonological judgments from pictures) to a semantic categorization task. Differences in activation between tasks appeared at about 300 ms, suggesting that semantic processes, common to all these tasks, take place before 300 ms. Since the different processes involved in word production seem to be related to electrophysiological correlates in different time-windows, it is likely that electrophysiological changes linked to reorganisation of language after stroke occur in different time-windows in patients recovering from impairment at different levels of processing, for example patients with semantic impairment relative to patients with impaired phonological processes. In the present study we analysed the electrophysiological correlates of recovery from anomia in post-acute aphasic patients. ERPs were measured at baseline and after a period of therapy in four aphasic subjects and the data of each patient were compared to a healthy control group.
نتیجه گیری انگلیسی
3.1. Behavioral results The control subjects performed the naming task very easily (98% correct, S.D. = 3%). All the aphasic patients had very impaired naming performance at baseline and improved significantly (minimum McNemar's Chi-square = 20.632, p < .0001) after the treatment period (see Fig. 2), with no more significant improvement after treatment stop. Full-size image (28 K) Fig. 2. Percent correct naming at baseline and post-treatment assessments and after treatment stop for each patient. Figure options Despite similar severity among the four patients at baseline, the analysis of errors (see Table 1) showed that only P1 and P2 had a similar anomic pattern (mainly phonological paraphasias), while the other two patients had different error distribution: P3 produced mainly no responses and semantic errors and P4 produced mainly no responses and phonological errors. Table 1. Naming errors distribution at baseline and post-treatment assessment for each patient Semantic: semantic paraphasias; phonological: all phonological transformations including phonemic, conduites d’approche and neologisms; verbal: all word responses with no semantic o