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Learning and maintenance in aphasia rehabilitation
Brain and Language 87 (2003) 181–182 www.elsevier.com/locate/b&l
Learning and maintenance in aphasia rehabilitationq Rhonda B. Friedman,a,b Elizabeth H. Lacey,a and Susan Nitzberg Lotta a Department of Neurology, Georgetown University, Washington, DC, USA MedStar Research Institute/National Rehabilitation Hospital, Washington, DC, USA
b
An important issue in rehabilitation research is maintenance or retention of that which is learned during treatment. Studies that have measured maintenance rarely report 100% retention over time. That is, even if accuracy levels remain above baseline levels weeks or months after cessation of treatment, accuracy rarely remains at the level that had been reached by the end of treatment; some items are invariably lost. Understanding which items are likely to be lost, and why, would contribute to improvements in the design and implementation of treatment paradigms. In one common aphasia rehabilitation paradigm, a group of items are trained together until accurate performance is achieved on a predetermined percentage of the items. Training then proceeds to the next set of items. As a set is being trained to criterion, accurate performance is achieved for some of the individual items before others. One question that can be asked is whether the number of trials required to learn a word predicts the degree to which that word will be retained after treatment ceases. Three possibilities present themselves. One is that words that take longer to learn are more likely to be lost, perhaps because they are inherently more difficult. A second possibility is that words that take longer to learn are likely to be more tenacious; the hard work involved in learning helps to create a stronger representation. The third possibility is that this variable is not relevant to maintenance; once an item is learned, it is just as likely to be retained as any other learned items. To explore these alternatives, we compared number of errors on training with number of errors at maintenance for two patients who had successfully completed treatment for phonologic alexia.
Subjects Patient HN had a left hemisphere stroke four years prior to her participation in the study. She had a fluent aphasia and phonologic alexia. Patient DN had a left hemisphere stroke two years prior to his participation in the study. He had a severe nonfluent aphasia and phonologic alexia. Both patients’ reading of PWs were impaired relative to real words, and their reading of words exhibited part of speech and concreteness effects; words with greater semantic value were read better than functor words. HN participated in two experimental treatments aimed at improving her reading of words that are low in semantic value. The treatments, semantic mediation, and expanded semantic mediation, have been described elsewhere (Friedman,
q
Supported by NIH Grant HD36019.
Sample, & Lott, 2002; Friedman, Sample, Lott, & Oliver, 2001). DN participated in the semantic mediation treatment.
Procedure HN learned three sets of 20 words in the semantic mediation treatment and four sets of 15 words in the expanded semantic mediation treatment. DN was trained on three sets of words, but because he took an 8 month hiatus from treatment due to illness during training of set 3, we report only errors recorded for training and maintenance during sets 1 and 2. HN and DN were trained to criterion (90% accuracy for two consecutive sessions) on each set before moving on to the next set. Maintenance was assessed from one to seven months after criterion was reached in the learning trials for the semantic mediation treatment words and from 2 weeks to 3.5 months after criterion was reached on the expanded semantic mediation words. For the anlaysis, we compare the number of errors made on individual words during the learning stage of treatment with the number of errors made on those same words when they were later tested for maintenance. The errors were produced on bi-weekly probe tests given during training of the words, and on the maintenance probes.
Results Fig. 1 shows the relationship between number of errors made by HN during learning and number of errors made during maintenance testing, for the semantic mediation treatment. HN tended to produce more errors during maintenance testing on words that she took longer to learn. This trend was demonstrated in both the semantic mediation treatment (r = .61) (see Fig. 1) and the expanded semantic mediation treatment (r = .56). DNs data for semantic mediation showed a similar trend (r = .52).
Discussion The results of this analysis are consistent with the first alternative described above: greater ease in learning the words predicted a greater likelihood of maintaining those words following treatment. Why might this be the case? The most obvious explanation is that the words that are learned first are easier words to learn, and words that are easier to learn are more likely to be retained over time. This may indicate that
0093-934X/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0093-934X(03)00260-8
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Abstract / Brain and Language 87 (2003) 181–182 9
Errors Produced During Maintenance Testing
8
r = 0.612
7 6 5 4 3 2 1 0 0
5
10
15
20
25
30
Total Errors Produced During Training
items should continue even after they are learned, to further strengthen the underlying representations. An alternative explanation is that during training, the words that took many trials to learn were repeatedly being paired with incorrect responses. That is, the target words were being paired with incorrect responses produced by the patient, thereby causing interference with the correct response. In contrast, items that were learned early on in the treatment were being produced correctly on subsequent trials, further reinforcing the correct response. If this explanation is correct, one means of improving maintenance would be to create treatment paradigms that minimize the production of errors during training. Further studies are being designed to test these explanations of our results.
Fig. 1 References the representations of those words were fairly strong to start with, although below the threshold needed to produce the correct response. Words that are more difficult to train are those that have a lower initial resting state. Over time, as the trained information is degraded, the more difficult items will fall more rapidly towards their original resting state, resulting in incorrect responses. If this explanation is correct, it might suggest that the training and reinforcement of slowly learned
Friedman, R. B., Sample, D., & Lott, S. N. (2002). The role of level of representation in the use of paried associate learning for rehabilitation of alexia. Neuropsychologia, 40, 223–234. Friedman, R. B., Sample, D. M., Lott, S. N., & Oliver, R. T. (2001). Can a phonologic alexic learn to read ‘‘much’’ from ‘‘mud pies’’? Brain and Language, 79(1), 132–134.
Learning and maintenance in aphasia rehabilitationq Rhonda B. Friedman,a,b Elizabeth H. Lacey,a and Susan Nitzberg Lotta a Department of Neurology, Georgetown University, Washington, DC, USA MedStar Research Institute/National Rehabilitation Hospital, Washington, DC, USA
b
An important issue in rehabilitation research is maintenance or retention of that which is learned during treatment. Studies that have measured maintenance rarely report 100% retention over time. That is, even if accuracy levels remain above baseline levels weeks or months after cessation of treatment, accuracy rarely remains at the level that had been reached by the end of treatment; some items are invariably lost. Understanding which items are likely to be lost, and why, would contribute to improvements in the design and implementation of treatment paradigms. In one common aphasia rehabilitation paradigm, a group of items are trained together until accurate performance is achieved on a predetermined percentage of the items. Training then proceeds to the next set of items. As a set is being trained to criterion, accurate performance is achieved for some of the individual items before others. One question that can be asked is whether the number of trials required to learn a word predicts the degree to which that word will be retained after treatment ceases. Three possibilities present themselves. One is that words that take longer to learn are more likely to be lost, perhaps because they are inherently more difficult. A second possibility is that words that take longer to learn are likely to be more tenacious; the hard work involved in learning helps to create a stronger representation. The third possibility is that this variable is not relevant to maintenance; once an item is learned, it is just as likely to be retained as any other learned items. To explore these alternatives, we compared number of errors on training with number of errors at maintenance for two patients who had successfully completed treatment for phonologic alexia.
Subjects Patient HN had a left hemisphere stroke four years prior to her participation in the study. She had a fluent aphasia and phonologic alexia. Patient DN had a left hemisphere stroke two years prior to his participation in the study. He had a severe nonfluent aphasia and phonologic alexia. Both patients’ reading of PWs were impaired relative to real words, and their reading of words exhibited part of speech and concreteness effects; words with greater semantic value were read better than functor words. HN participated in two experimental treatments aimed at improving her reading of words that are low in semantic value. The treatments, semantic mediation, and expanded semantic mediation, have been described elsewhere (Friedman,
q
Supported by NIH Grant HD36019.
Sample, & Lott, 2002; Friedman, Sample, Lott, & Oliver, 2001). DN participated in the semantic mediation treatment.
Procedure HN learned three sets of 20 words in the semantic mediation treatment and four sets of 15 words in the expanded semantic mediation treatment. DN was trained on three sets of words, but because he took an 8 month hiatus from treatment due to illness during training of set 3, we report only errors recorded for training and maintenance during sets 1 and 2. HN and DN were trained to criterion (90% accuracy for two consecutive sessions) on each set before moving on to the next set. Maintenance was assessed from one to seven months after criterion was reached in the learning trials for the semantic mediation treatment words and from 2 weeks to 3.5 months after criterion was reached on the expanded semantic mediation words. For the anlaysis, we compare the number of errors made on individual words during the learning stage of treatment with the number of errors made on those same words when they were later tested for maintenance. The errors were produced on bi-weekly probe tests given during training of the words, and on the maintenance probes.
Results Fig. 1 shows the relationship between number of errors made by HN during learning and number of errors made during maintenance testing, for the semantic mediation treatment. HN tended to produce more errors during maintenance testing on words that she took longer to learn. This trend was demonstrated in both the semantic mediation treatment (r = .61) (see Fig. 1) and the expanded semantic mediation treatment (r = .56). DNs data for semantic mediation showed a similar trend (r = .52).
Discussion The results of this analysis are consistent with the first alternative described above: greater ease in learning the words predicted a greater likelihood of maintaining those words following treatment. Why might this be the case? The most obvious explanation is that the words that are learned first are easier words to learn, and words that are easier to learn are more likely to be retained over time. This may indicate that
0093-934X/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0093-934X(03)00260-8
182
Abstract / Brain and Language 87 (2003) 181–182 9
Errors Produced During Maintenance Testing
8
r = 0.612
7 6 5 4 3 2 1 0 0
5
10
15
20
25
30
Total Errors Produced During Training
items should continue even after they are learned, to further strengthen the underlying representations. An alternative explanation is that during training, the words that took many trials to learn were repeatedly being paired with incorrect responses. That is, the target words were being paired with incorrect responses produced by the patient, thereby causing interference with the correct response. In contrast, items that were learned early on in the treatment were being produced correctly on subsequent trials, further reinforcing the correct response. If this explanation is correct, one means of improving maintenance would be to create treatment paradigms that minimize the production of errors during training. Further studies are being designed to test these explanations of our results.
Fig. 1 References the representations of those words were fairly strong to start with, although below the threshold needed to produce the correct response. Words that are more difficult to train are those that have a lower initial resting state. Over time, as the trained information is degraded, the more difficult items will fall more rapidly towards their original resting state, resulting in incorrect responses. If this explanation is correct, it might suggest that the training and reinforcement of slowly learned
Friedman, R. B., Sample, D., & Lott, S. N. (2002). The role of level of representation in the use of paried associate learning for rehabilitation of alexia. Neuropsychologia, 40, 223–234. Friedman, R. B., Sample, D. M., Lott, S. N., & Oliver, R. T. (2001). Can a phonologic alexic learn to read ‘‘much’’ from ‘‘mud pies’’? Brain and Language, 79(1), 132–134.