آغازگر متن در نام پریشی معنایی: مطالعه موردی

The present case continues the series of anomia treatment studies with contextual priming (CP), being the second in-depth treatment study conducted for an individual suffering from semantically based anomia. Our aim was to acquire further evidence of the facilitation and interference effects of the CP treatment on semantic anomia. Based on the results of the study of Martin, Fink, and Laine (2004a), our hypothesis before the treatment was that our participant would show short-term interference and at most modest and short-term benefit from treatment. To acquire such evidence would not only be important for the choice of anomia treatment methods in individual patients, but would also prompt further development of the CP method. The CP technique used for our participant included cycles of repeating and naming items in three contextual conditions (semantic, phonological, and unrelated). As predicted, the overall improvement of naming was modest and short-term. Interestingly, the contextual condition that corresponded with the nature of our patient’s underlying naming deficit (semantic) elicited immediate interference in the form of contextual naming errors, as well as short-term improvement of naming. Based on this and a recent study by Martin et al. (2004a), it appears that despite short-term positive effects, in its current form the CP treatment is not sufficient for those aphasics who have a semantic deficit underlying their anomia. The possible mechanism and directions for future research are discussed.

Contextual priming (CP) is a theoretically motivated and relatively simple naming treatment technique that was originally developed to test predictions of different word-production models (Laine & Martin, 1996). It has since proved to have potential as a technique to be used in anomia treatment (see Martin, Fink, & Laine, 2004a; Martin et al., 2004b, Martin and Laine, 2000 and Renvall et al., 2003). The CP technique includes cycles of repeating and naming items in different contextual conditions, including semantic condition in which items are only semantically related, phonological condition in which items are only phonologically related, and an unrelated (baseline) condition in which items are neither semantically nor phonologically related to each other. The first two relatedness conditions are aiming at the main stages of word production. One of the aims of the present and the other recent CP studies is to determine whether it is better to treat a deficit directly or to use preserved abilities to improve lexical access. This issue has gained much interest in the field of anomia treatment (see e.g., Nickels, 1997, Nickels, 2002 and Nickels and Best, 1996) and has sparked a growing body of carefully designed treatment studies targeting this question (e.g., Bastiaanse et al., 1996, Drew and Thompson, 1999, Hickin et al., 2002, Hillis and Caramazza, 1994, Marshall et al., 1998 and Nettleton and Lesser, 1991). However, there is yet no conclusive evidence of interactions between the nature of the naming deficits (semantically or phonologically based) and the effects of treatments that target specifically semantic or phonological processing. Sometimes it is difficult to ascertain the precise mechanisms by which the observed effects of a treatment have been achieved (Nickels & Best, 1996). Here, we report a study that is part of an ongoing investigation of possible treatment–deficit interactions. We will use the CP technique of priming by repeating a group of target words, but varying the relationship among the words (semantic, phonological, and no relation). This feature of the technique, along with use of a well-defined model as a framework allows us to draw conclusions about why and at which level observed effects occur. Employment of repetition and semantic/phonological contexts in the CP technique is by no means a totally new approach. Repetition is widely used in almost all speech therapy tasks, and it has been studied by Weigl (1961), who used the so called ‘de-blocking’ technique, and more recently by Nettleton and Lesser (1991) and Miceli, Amitrano, Capasso, and Caramazza (1996). In these and other studies, repetition has been combined with other phonologically based methods of stimulating word retrieval, such as phonological cueing and reading aloud, as well as semantically based methods such as word-to-picture matching and producing semantic features and synonyms (e.g., Basso et al., 2001, Best et al., 1997, Greenwald et al., 1995, Hillis, 1991, Hillis, 1998, Hillis and Caramazza, 1994 and Raymer et al., 1993). Other studies have concentrated on tasks tapping primarily the semantic level processing (e.g., Coelho et al., 2000, Kiran and Thompson, 2003 and Visch-Brink et al., 1997). The CP technique combines repetition and naming contexts in a way that each participant gets both semantic and phonological level treatment in a more or less implicit fashion. Still, as we will argue later in this section, it is possible to detect the separate effects of the semantic and phonological priming as they are contrasted to the condition in which there is no relation among words being trained. The locally interactive models such as that of Dell, 1986, Dell and O’Seaghdha, 1992, Martin et al., 1994, Dell et al., 1997 and Foygel and Dell, 2000 serve as a framework for the CP technique. According to these models, lexical retrieval is expected to involve two steps (lexical-semantic and lexical-phonological) in a network consisting of three layers of nodes (semantic features, words, and phonemes). These models assume that activation spreads among the related semantic and phonological nodes and that all more or less active lexical-semantic representations become also phonologically encoded. Moreover, the connections between the layers are not only one-way but bidirectional and excitatory. Based on these basic features of the models, it is possible to explain, for example, why normal adults make more mixed semantic-phonological errors than would occur by chance (see Martin, Weisberg, & Saffran, 1989). Similarly, as we will explain next, it can be understood why both semantic and phonological relatedness can have effects on aphasic speakers’ naming. The facilitation of naming in the CP treatment is expected to arise from two sources explained by the afore mentioned two-step interactive models (Dell, 1986, Dell and O’Seaghdha, 1992, Dell et al., 1997, Foygel and Dell, 2000 and Martin et al., 1994). The first source of facilitation is repetition priming which has been shown to have long-lasting effects in word production (for normal adults see, e.g., Cave, 1997, for anomic patients see, e.g., Davis and Pring, 1991 and Miceli et al., 1996). Repetition of words is assumed to increase the activation levels of the corresponding word forms and thus help in retrieving those items. The other sources of facilitation are the semantic and phonological priming effects. This facilitation mediates activation spreading amongst the related items in a picture set, and represents a fundamental feature of the interactive word-production models. Based on the models, the target items are assumed to activate several meaning-related items which share partly overlapping semantic features. The semantic activation in turn feeds forward to corresponding lexical nodes. Continuous feedforward–feedback activation between semantic and lexical nodes serves to strengthen the semantic relatedness effect so that the target and its semantic competitors have higher activation levels than items that are not semantically related to targets. This is why the items in the semantic contexts are assumed to become more available in the CP treatment. In the phonological contexts, the activation boost stems from shared sublexical representations which feed back activation to the corresponding lexical nodes. The repeated feedforward–feedback activation cycles increase activation levels of the target and its phonological competitors. Thus, the activation boost amongst related items via activation spreading may help an aphasic individual to name the pictures in both semantically and phonologically related sets better than those in an unrelated set. In addition to the direct facilitation effects, i.e., the increased number of correct naming responses, spreading activation also brings related nontarget representations closer to the selection threshold and can give rise to contextual errors (word substitution errors within a picture set) and noncontextual errors (semantically or phonologically related word errors from outside the target set). We have observed these errors in prior CP studies although in some patients they are very rare (Laine and Martin, 1996, Martin et al., 2004a, Martin et al., 2004b, Martin and Laine, 2000 and Renvall et al., 2003). The contextual errors reflect interference which seems to be short-lasting as these errors have mainly been observed in naming attempts that follow soon after the repetition priming of the same items (Martin et al., 2004a and Martin et al., 2004b). The interactive activation models predicts that the immediate interference, due to more available lexical competitors, shifts to short-term facilitation after some decay has occurred. The recent CP studies have indeed brought evidence of this shift in aphasic patients although the exact time intervals for the interference and facilitation effects are not yet known (Martin et al., 2004a and Martin et al., 2004b). The noncontextual word-errors that are either semantically or phonologically related to the target items but not within the target sets provide further evidence for activation spreading amongst multiple lexical candidates. In aphasic patients, the noncontextual related word errors are direct evidence for activation spreading within semantic or phonological lexical neighbourhood. Thus, both contextual and noncontextual errors can reveal important aspects of the mechanisms underlying the CP treatment. In the CP, specific effects of the repetition priming and spreading activation amongst related items can be distinguished by analyses of the patients’ responses in the different task conditions. This is important as most of the tasks employed in anomia therapy involve priming in some form but the effects of semantic and phonological priming as well as their efficacy for different aphasia types still remain unclear. Repetition priming should affect all picture sets, whereas semantic/phonological priming effects should be observed in the related picture sets only. A higher rate of correct responses and contextual errors in the semantic or phonological conditions as compared with the unrelated condition indicates that the contextual component (i.e., activation spreading amongst related items) is having an effect over and above that of repetition priming. The present case study continues the series of CP studies exploring the effects of this technique on the naming of aphasic individuals. Thus far, there are three smaller-scale facilitation studies (Laine and Martin, 1996, Martin et al., 2004b and Martin and Laine, 2000) and two full-scale treatment studies (Martin et al., 2004a and Renvall et al., 2003) reported with the CP technique.1 In addition, CP with semantic contexts only has been used to treat the naming abilities of three chronic left-hemisphere-damaged aphasics in a functional brain imaging study (Cornelissen, Laine, Tarkiainen, Järvensivu, Martin, Salmelin, 2003). With regard to the efficacy of the CP treatment, the results of the prior studies have been promising as all of the patients who have participated in the CP facilitation studies or full-scale treatment programmes have shown at least short-term improvement on naming the trained items in one or more contextual conditions. In addition, long-term improvement has been observed in two of three patients of the treatment studies while all of the three patients have shown at least some evidence of generalisation of treatment to untrained words. While no consistent relationship between the primary source of naming impairments and the facilitating contexts has been observed, the recent results of Martin et al., 2004a and Martin et al., 2004b imply that the procedure itself could be most effective when semantic abilities are relatively spared. Another interesting phenomenon observed in the recent CP studies is that an immediate interference surfacing up as contextual word errors can turn into short-term facilitation of naming the same items (see Martin et al., 2004a and Martin et al., 2004b), as predicted by an interactive activation model of word retrieval (e.g., Dell & O’Seaghdha, 1992). Moreover, Martin et al. (2004b) suggest that more interference, i.e., increased rates of contextual and noncontextual errors, occurs when semantic context is used for semantically impaired persons and phonological context for phonologically impaired persons than when the treated context and the underlying impairment do not match. Here, we report the third full-scale treatment study conducted with the CP technique and the second one used with a patient suffering from semantically based anomia. Our aim was to acquire further evidence of the efficacy of the CP treatment when the patient suffers from a semantic deficit. We had four questions: (1) Does contextual priming facilitate or interfere with naming of hard-to-name targets in our semantic anomia case? (2) If there is facilitation and/or interference, do the effects differ between the different contextual conditions (semantic, phonological)? (3) If there is a facilitatory effect, is it enduring? (4) Does the treatment facilitate naming of the untrained control items? The first aphasic with a semantic deficit for whom a CP treatment with several contextual conditions was conducted, AS (Martin et al., 2004a), suffered also to some extent from a phonological deficit. For this reason, we were especially interested to carry out CP treatment with an aphasic having a more circumscribed semantic deficit. The participant in the present study, PH, had a more circumscribed semantic deficit. Before starting the treatment for PH, we predicted that he would still show a similar pattern of treatment effects as observed in the case of AS (Martin et al., 2004a) and those patients with semantic deficits in the earlier facilitation studies (Martin et al., 2004b and Martin and Laine, 2000). Thus, we expected to find an effect of immediate interference in the semantic condition in particular and at most modest and short-term improvement in the trained items. Whether we could get evidence of facilitation or lack of it was the most important goal in this study as a repeated negative finding of the CP treatment in semantic anomia would imply that CP treatment in its current form is not enough for this group of anomics. Since the participants of the prior CP studies have not shown consistent naming patterns in the different contexts after treatment, no predictions about the facilitation in the semantic vs phonological conditions were made. In theory, facilitation due to contextual effects could be possible in both semantic and phonological conditions, as explained above. If the improvement in the unrelated condition is comparable to that in the related context conditions, we would assume that the facilitatory effect is due to repetition priming.

The most important goal in this study was to explore whether treatment would have a facilitative effect on PH’s naming. The percent of totally correct responses in the six naming measurements before and after the treatment are shown in Fig. 1. To get an idea of PH’s performance during the treatment period, we have also included in the figure his performance on naming the trained items within the treatment sessions. As we did not administer separate naming measurements during the treatment period, we calculated the percent of correct naming responses each time a new picture set was displayed and PH was asked to name the pictures for the first time within each session. Thus, although the within-treatment results are not directly comparable to those of the pre- and post-naming measurements where pictures were presented in isolation, they provide an indication of the trajectory of PH’s response to the treatment over the course of intervention. The number of correct responses during treatment is further analysed in the light of context sensitivity (see below). We present nine within-treatment measurement points as each picture set was cycled and treated in nine sessions although the overall number of the treatment sessions was 12.