ارتباطات عصبی درمان نام پریشی آواشناسی و مبتنی بر معناشناسی در زبان پریشی

Most naming treatments in aphasia either assume a phonological or semantic emphasis or a combination thereof. However, it is unclear whether semantic or phonological treatments recruit the same or different cortical areas in chronic aphasia. Employing three persons with aphasia, two of whom were non-fluent, the present study compared changes in neural recruitment associated with phonologic and semantic-based naming treatments. The participants with non-fluent aphasia were able to name more items following both treatment approaches. Although this was not the case for the participant who had fluent aphasia, her naming errors decreased considerably following treatment. Post-treatment fMRI revealed similar changes in neural activity bilaterally in the precuneus among the two non-fluent participants—increased activity was noted in the right entorhinal cortex and posterior thalamus on post-treatment scans for the third participant. These findings imply that cortical areas not traditionally related to language processing may support anomia recovery in some patients with chronic aphasia.

Although the ability to name common objects has limited ecological significance per se, it is commonly targeted in aphasia treatment based on the assumption that it ameliorates lexical-semantic processing deficits, which in turn would drive aphasia recovery. While the underlying cause of anomia varies significantly among patients, most treatment approaches either include a phonological or semantic focus (for a review see Maher & Raymer, 2004; Nickels, 2002). Previous research has suggested that to be optimally effective, anomia treatment should be tailored to the needs of each patient—for example, patients with primarily semantic deficits should be treated with regimens that emphasize semantic processing. However, other studies have shown that some patients who respond well to semantic-based anomia treatment also respond well to phonologically-based approaches (Fridriksson, Holland, Beeson, & Morrow, 2005; Wambaugh, Cameron, Kalinyak-Fliszar, Nessler, & Wright, 2004). While several cognitive models of lexical processing might explain this effect, a particularly influential ‘interactive activation model’ has been suggested by Dell and colleagues (Dell and O'Seaghdha, 1991 and Dell and O'Seaghdha, 1992; Gagnon, Schwartz, Martin, Dell, & Saffran, 1997; Martin, Dell, Saffran, and Schwartz, 1994; Schwartz, Dell, Martin, & Saffran, 1994). This account posits spreading activation within three processing levels with semantic-lexical information being processed at the first two levels and phonological constructions occurring at a third level. However, processing between levels is highly interactive as suggested by mixed semantic and phonological naming errors (as in “cow” for cat). Since this model is highly interactive, stimulation at one level (e.g., the phonological level) also stimulates processing at the other (semantic-lexical). This interactive stimulation has been shown in several anomia treatment studies of persons with aphasia ( Dell, Schwartz, Martin, Saffran, & Gagnon, 1997; Martin & Laine, 2000; Renvall, Laine, Laasko, & Martin, 2003). Some recent studies suggest aphasia recovery following stroke is dependent on left hemisphere reorganization while increased right neural activity following stroke represents maladaptive disinhibition (Martin et al., 2004). Perhaps even more convincingly, studies by Naeser and colleagues (Martin et al., 2004 and Naeser et al., 2005) have shown that repetitive transcranial magnetic stimulation (rTMS) of the pars triangularis in the right hemisphere in non-fluent aphasic patients’ results in improved naming. Since rTMS generally leads to tonic inhibition of the stimulated area, this finding suggests that right hemispheric activity is maladaptive, as its inhibition in this study ameliorated symptoms. It is possible that damage to the left pars triangularis leads to transcallosal disinhibition of the homologous area of the right hemisphere, with this activity decrementing performance and that rTMS to the right pars triangularis suppresses activity that normally would be inhibited by an intact Broca's area. The key question is why right hemisphere activity should be maladaptive, and why reduction of this activity should improve symptoms. Heiss and Thiel (2006) suggested that right hemispheric activity may itself suppress left hemisphere activity, and therefore that disrupting right hemisphere function allows the residual regions of the left hemisphere to become more active. Although this work provides substantial evidence suggesting a maladaptive role for the right hemisphere in inhibiting recovery, numerous studies have revealed right hemisphere recruitment associated with recovery of speech production (Crinion & Price, 2005; Crosson et al., 2005 and Meister et al., 2006). With regard to treatment-induced anomia recovery in aphasia, changes in neural activity have been reported in the left hemisphere (Cornelissen et al., 2003), right hemisphere (Peck et al., 2004), and both (Fridriksson, Morrow, Moser, Fridriksson, & Baylis, 2006). Employing two non-fluent and one fluent aphasic participant, the study by Cornelissen et al. (2003) used magnetoencephalography (MEG) to reveal anomia treatment-related changes in neural modulation in the left perilesional parietal lobe. In contrast, the results by Peck et al. (2004) showed primarily right hemisphere changes in the temporal aspects of the hemodynamic response (HDR) in three patients who underwent anomia treatment. More recently, Fridriksson et al. (2006) also employed three participants who received naming treatment and pre- and post-treatment fMRI. This study employed three fMRI scanning sessions before and after anomia treatment focused on errorless learning of a closed set of words. The results revealed a bilateral increase in neural activity associated with improved naming ability in two participants, while the third did not respond to treatment. These three studies included participants with a wide range of aphasia severity and type as well as different anomia treatment approaches; nevertheless, some gross similarities in treatment-related neural modulation were noted. For example, one of the fluent participants in the Fridriksson study also showed left parietal perilesional modulation associated with anomia recovery, much as the three participants studied by Cornelissen et al. (2003). The purpose of the present study was to investigate the neural correlates of phonological and semantic-based treatments of anomia in three persons with chronic aphasia. Each participant received five 2-hr treatment sessions with a phonological focus and five 2-hr sessions with a semantic focus. Treatment sessions for each of the two approaches were completed within a 1-week period and the order of approaches were counter-balanced, where two participants first received the phonological treatment and the third participant first received the semantic approach. Because only limited evidence exists to support the test-retest reliability of fMRI data in persons with aphasia (Kurland et al., 2004), two fMRI sessions testing picture naming were acquired before and after each treatment approach was completed. Thus, neurological activity associated with treatment was assessed in a higher-level fMRI analysis within each participant.

Following treatment utilizing either approach (semantic or phonological), NS was not able to name more treatment items during the fMRI sessions (Fig. 2). In fact, the number of her successful naming attempts remained remarkably stable (10 and 13 items in the two baseline sessions; 8 and 11 items in sessions three and four following completion of the phonological treatment approach; 11 and 13 items in sessions five and six at the end of the semantic treatment). This was also the case for her accuracy on the PNT across the six testing sessions (Fig. 3). However, the number of her errors on the PNT decreased as the study progressed; especially following completion of the phonological treatment approach. She made 66 and 64 errors during the two initial baseline PNT sessions; 29 and 33 errors in sessions three and four following the phonological treatment (p < .0001); 28 and 28 after completion of the semantic approach (p = ns). NS's baseline fMRI sessions revealed bilateral neural activation associated with naming common objects ( Fig. 4); local maxima were mainly noted in the frontal lobes including the spared section of Broca's area and its right hemisphere homologue ( Table 2). Although her successful naming attempts did not increase, the higher-level fMRI analysis revealed changes in cortical activity following administration of both treatment approaches. After completion of the phonological cueing hierarchy, increased neurological activity was noted in the right thalamus and left cerebellum. Increased neural modulation associated with the semantic approach was revealed in the right inferior temporal lobe specifically in the area of the entorhinal cortex.