- Email: [email protected]
Negative priming in aphasia
Brain and Language 103 (2007) 8–249 www.elsevier.com/locate/b&l
Negative priming in aphasia Lori R. Bartels-Tobin *, Jacqueline J. Hinckley The University of South Florida, Department of Communication Sciences and Disorders, USA
According to Anderson (1994), the presentation of a stimulus, such as a picture, activates the semantic representation of that stimulus in long-term memory. When the stimulus is a lexical representation such as a word, the activation of that word spreads throughout a connected network such that all concepts related to that word are also activated according to how strongly the concepts are associated to the stimulus. This spreading activation (Collins & Loftus, 1975) to associated lexical representations is excitatory and facilitates retrieval of related concepts. If several related concepts are highly activated due to a strong relationship with the target representation, competition can occur amongst them for the most highly activated, producing interference. Interference is disruptive to processing because it can cause bottlenecks so that production is temporarily limited (Harnishfeger, 1995). When interference occurs, inhibition can be recruited (Anderson, 1994). Inhibition is important because it reduces the activation level of competing responses that may be irrelevant or inappropriate for the context. If inhibitory mechanisms are slowed or intermittently active, the retrieved lexical representation may not always be the most highly activated. This could occur because unresolved interference between competitors may lead to selection of an incorrect word, the inability to retrieve a word, or intermittent target word retrieval. Persons with aphasia often exhibit difficulty with producing the desired response, which could be the result of inadequate inhibitory processes to overcome response competition. The purpose of this study was to determine if persons with aphasia would exhibit inhibition as measured by a negative priming paradigm. Materials and methods Twenty participants with aphasia, 20 age-matched aphasic group controls and 27 young participants were recruited for this study. Young participants were necessary to ensure the stimuli would invoke negative priming. Participants with aphasia completed a picture-naming task, two written lexical decision tasks, subtests of an aphasia assessment, and a negative priming lexical decision task. Control groups completed only the negative priming task. This task consisted of 4 blocks of 72 trials
*
Corresponding author. Fax: +1 813 974 0822. E-mail address: [email protected] (L.R. Bartels-Tobin).
doi:10.1016/j.bandl.2007.07.091
each in which target words were related associates (RA), related distractors (RD), unrelated words (UN), or pseudowords. Prime and probe displays consisted of a black screen with white stimuli, as well as a target presentation flanked above and below by identical lexical distractors. Prime displays remained on the screen until a response was made, followed by a 300 ms ISI before the probe display appeared. The ITI was 1000 ms. Results Error rates were higher in the aphasia group, although the distribution of errors was significantly different. In both the aphasia and the aphasiacontrol groups, errors were higher for related conditions. It would seem as if the related words ‘‘surprised’’ participants, causing more mistakes in lexical judgment. A repeated measures ANOVA analyzed the difference in performances between the two groups. As Table 1 show, the young control group was the only group to exhibit significant negative priming. While the aphasic group produced slower RTs than the aphasia-control group, there was no overall RT difference between the three conditions. Activation-based inhibition would predict that the RD condition would have slower RTs than the UN condition and that RTs in the UN condition would be slower than in the RA condition. This was not evidenced by either group. While the aphasic group showed a trend towards this effect (RA fastest, UN slow, RD slowest), this trend was not significant. The aphasia-control group did show significantly slower RTs to the UN condition than the RD condition. Traditional NP literature with older participants would seem to fall in line with this result. Multiple regression analysis was also utilized to determine if any extraneous variables in the aphasia group were contributing to the RT results. These analyses determined that time post-onset, age, education, and classification of anomia were not significant predictors of these results in the aphasia group. One interesting comparison was between the participants with fluent (8) vs. non-fluent aphasia (12). A marginally significant interaction was found between group and condition. To explore this possibly significant interaction, two participants whose aphasia was difficult to classify were eliminated from the analysis. A significant interaction was found after this elimination. While there were no group differences for the UN condition, the fluent group was significantly slower than the non-fluent group for both the RA and RD conditions. In the fluent group, RD was slower than UN, while the non-fluent participants performed similarly to the control group (UN slower than RD). If the RA condition is put aside, the partic-
Abstract / Brain and Language 103 (2007) 8–249 Table 1 Means and standard deviations (in ms) of median reaction times for all groups to the probe display for all conditions Group
Condition RD
UN
Priming difference RA
(UN RD)
(UN RA) 3
Young SD
626 73
615 72
618 80
11*
Aphasia controls SD
717 162
755 188
727 159
38*
28
Aphasia SD
950 228
933 189
924 235
17
9
Note. RD, related distractor; UN, unrelated pairs; RA, related targets. *p < .05.
ipants with fluent aphasia exhibited the expected NP effect since the RD condition was significantly slower than the UN condition (51 ms). This seems to imply that the participants with fluent aphasia were successfully able to inhibit the distractors in the RD condition, in direct contrast to the conclusions of Wiener, Connor, and Obler (2004) for Wernicke’s participants.
153
Discussion It is argued that these results are not strategically induced. Using a prospective or a retrospective strategy would be useless since only a small portion of the prime–probe pairs are directly related. The results of the aphasia group and the aphasia-control group are similar to those found in the aging negative priming literature, but it is unclear if this should be interpreted as degraded inhibitory processes. Studies of negative priming may be useful clinically in the future for naming and semantic association treatments. Planned future studies to further explore negative priming in aphasia are discussed. References Anderson, M. C. (1994). Rethinking interference theory: Executive control and the mechanisms of forgetting. Journal of Memory and Language, 49, 415–445. Collins, A. M., & Loftus, E. F. (1975). A spreading activation theory of semantic processing. Psychological Review, 85, 407–428. Harnishfeger, K. K. (1995). Development of cognitive inhibition. In F. Dempster & C. Brainerd (Eds.), Interference and inhibition in cognition (pp. 176–204). San Diego, CA: Academic Press. Wiener, D. A., Connor, L. T., & Obler, L. K. (2004). Inhibition and auditory comprehension in Wernicke’s aphasia. Aphasiology, 18, 599–609.
Negative priming in aphasia Lori R. Bartels-Tobin *, Jacqueline J. Hinckley The University of South Florida, Department of Communication Sciences and Disorders, USA
According to Anderson (1994), the presentation of a stimulus, such as a picture, activates the semantic representation of that stimulus in long-term memory. When the stimulus is a lexical representation such as a word, the activation of that word spreads throughout a connected network such that all concepts related to that word are also activated according to how strongly the concepts are associated to the stimulus. This spreading activation (Collins & Loftus, 1975) to associated lexical representations is excitatory and facilitates retrieval of related concepts. If several related concepts are highly activated due to a strong relationship with the target representation, competition can occur amongst them for the most highly activated, producing interference. Interference is disruptive to processing because it can cause bottlenecks so that production is temporarily limited (Harnishfeger, 1995). When interference occurs, inhibition can be recruited (Anderson, 1994). Inhibition is important because it reduces the activation level of competing responses that may be irrelevant or inappropriate for the context. If inhibitory mechanisms are slowed or intermittently active, the retrieved lexical representation may not always be the most highly activated. This could occur because unresolved interference between competitors may lead to selection of an incorrect word, the inability to retrieve a word, or intermittent target word retrieval. Persons with aphasia often exhibit difficulty with producing the desired response, which could be the result of inadequate inhibitory processes to overcome response competition. The purpose of this study was to determine if persons with aphasia would exhibit inhibition as measured by a negative priming paradigm. Materials and methods Twenty participants with aphasia, 20 age-matched aphasic group controls and 27 young participants were recruited for this study. Young participants were necessary to ensure the stimuli would invoke negative priming. Participants with aphasia completed a picture-naming task, two written lexical decision tasks, subtests of an aphasia assessment, and a negative priming lexical decision task. Control groups completed only the negative priming task. This task consisted of 4 blocks of 72 trials
*
Corresponding author. Fax: +1 813 974 0822. E-mail address: [email protected] (L.R. Bartels-Tobin).
doi:10.1016/j.bandl.2007.07.091
each in which target words were related associates (RA), related distractors (RD), unrelated words (UN), or pseudowords. Prime and probe displays consisted of a black screen with white stimuli, as well as a target presentation flanked above and below by identical lexical distractors. Prime displays remained on the screen until a response was made, followed by a 300 ms ISI before the probe display appeared. The ITI was 1000 ms. Results Error rates were higher in the aphasia group, although the distribution of errors was significantly different. In both the aphasia and the aphasiacontrol groups, errors were higher for related conditions. It would seem as if the related words ‘‘surprised’’ participants, causing more mistakes in lexical judgment. A repeated measures ANOVA analyzed the difference in performances between the two groups. As Table 1 show, the young control group was the only group to exhibit significant negative priming. While the aphasic group produced slower RTs than the aphasia-control group, there was no overall RT difference between the three conditions. Activation-based inhibition would predict that the RD condition would have slower RTs than the UN condition and that RTs in the UN condition would be slower than in the RA condition. This was not evidenced by either group. While the aphasic group showed a trend towards this effect (RA fastest, UN slow, RD slowest), this trend was not significant. The aphasia-control group did show significantly slower RTs to the UN condition than the RD condition. Traditional NP literature with older participants would seem to fall in line with this result. Multiple regression analysis was also utilized to determine if any extraneous variables in the aphasia group were contributing to the RT results. These analyses determined that time post-onset, age, education, and classification of anomia were not significant predictors of these results in the aphasia group. One interesting comparison was between the participants with fluent (8) vs. non-fluent aphasia (12). A marginally significant interaction was found between group and condition. To explore this possibly significant interaction, two participants whose aphasia was difficult to classify were eliminated from the analysis. A significant interaction was found after this elimination. While there were no group differences for the UN condition, the fluent group was significantly slower than the non-fluent group for both the RA and RD conditions. In the fluent group, RD was slower than UN, while the non-fluent participants performed similarly to the control group (UN slower than RD). If the RA condition is put aside, the partic-
Abstract / Brain and Language 103 (2007) 8–249 Table 1 Means and standard deviations (in ms) of median reaction times for all groups to the probe display for all conditions Group
Condition RD
UN
Priming difference RA
(UN RD)
(UN RA) 3
Young SD
626 73
615 72
618 80
11*
Aphasia controls SD
717 162
755 188
727 159
38*
28
Aphasia SD
950 228
933 189
924 235
17
9
Note. RD, related distractor; UN, unrelated pairs; RA, related targets. *p < .05.
ipants with fluent aphasia exhibited the expected NP effect since the RD condition was significantly slower than the UN condition (51 ms). This seems to imply that the participants with fluent aphasia were successfully able to inhibit the distractors in the RD condition, in direct contrast to the conclusions of Wiener, Connor, and Obler (2004) for Wernicke’s participants.
153
Discussion It is argued that these results are not strategically induced. Using a prospective or a retrospective strategy would be useless since only a small portion of the prime–probe pairs are directly related. The results of the aphasia group and the aphasia-control group are similar to those found in the aging negative priming literature, but it is unclear if this should be interpreted as degraded inhibitory processes. Studies of negative priming may be useful clinically in the future for naming and semantic association treatments. Planned future studies to further explore negative priming in aphasia are discussed. References Anderson, M. C. (1994). Rethinking interference theory: Executive control and the mechanisms of forgetting. Journal of Memory and Language, 49, 415–445. Collins, A. M., & Loftus, E. F. (1975). A spreading activation theory of semantic processing. Psychological Review, 85, 407–428. Harnishfeger, K. K. (1995). Development of cognitive inhibition. In F. Dempster & C. Brainerd (Eds.), Interference and inhibition in cognition (pp. 176–204). San Diego, CA: Academic Press. Wiener, D. A., Connor, L. T., & Obler, L. K. (2004). Inhibition and auditory comprehension in Wernicke’s aphasia. Aphasiology, 18, 599–609.