یادگیری مهارت توالی گفتار در بزرگسالان که لکنت زبان دارند
|کد مقاله||سال انتشار||مقاله انگلیسی||ترجمه فارسی||تعداد کلمات|
|33536||2011||12 صفحه PDF||سفارش دهید||7563 کلمه|
Publisher : Elsevier - Science Direct (الزویر - ساینس دایرکت)
Journal : Journal of Fluency Disorders, Volume 36, Issue 4, December 2011, Pages 349–360
The present study compared the ability of 12 people who stutter (PWS) and 12 people who do not stutter (PNS) to consolidate a novel sequential speech task. Participants practiced 100 repetitions of a single, monosyllabic, nonsense word sequence during an initial practice session and returned 24-h later to perform an additional 50 repetitions. Results showed significantly slower sequence durations in the PWS compared to PNS following extensive practice and consolidation. However, the hypothesis that poor performance gains in PWS compared to PNS during practice would be maintained following a 24-h consolidation period was not supported. Further descriptive analysis revealed large within group differences in PWS which to some extent were attributed to a subgroup of PWS who failed to show any improvements in performance following practice or consolidation. The results and the possible presence of subgroups of PWS are discussed with regard to their limitations in motor learning abilities.
Learning of complex motor skills such as speaking may be affected in people who stutter (PWS) (De Nil, 1999b) as evidenced by studies showing that PWS do not benefit to the same extent from practicing speech and nonspeech sequence skill tasks as people who do not stutter (PNS; Ludlow et al., 1997, Neilson and Neilson, 1991, Smits-Bandstra et al., 2006a and Smits-Bandstra et al., 2006b). Based on recent findings of poor motor practice effects in PWS (Smits-Bandstra, De Nil, & Saint-Cyr, 2006), it has been suggested that these findings may have potential clinical implications regarding the long-term effectiveness of fluency intervention strategies that involve acquiring a novel speech movement pattern such as forming light articulatory contacts or prolonging speech with a high degree of automaticity (Bloodstein & Bernstein-Ratner, 2008). One of the main limitations to stuttering treatment programs in general is the high incidence of relapse, ranging anywhere from 14% to 70% of participants within a year following treatment (Bloodstein & Bernstein-Ratner, 2008). Although there is now some evidence to suggest that a deficiency in motor learning may play a role (Smits-Bandstra et al., 2006a and Smits-Bandstra et al., 2006b) almost all behavioral studies with people who stutter have measured learning-related changes exclusively during single practice sessions. Little is known whether the observed group differences continue following a period of rest or consolidation. It they do, this could point to a deficit in learning rather than just practice-related effects. 1.1. Sequence skill learning Motor learning involves the interaction between the pre-existing capacities of an individual and the to-be-learned movement pattern (Kelso, 1995). It refers to the ability to acquire the temporal and spatial characteristics of a movement pattern in order that, with practice, muscle execution becomes increasingly dependent on an internal representation rather than external sensory feedback (Schmidt, 2004). Such motor learning is accompanied by a decrease in sensory and attentional demands (Schmidt & Lee, 2005). Practice or repetition of a given movement pattern is an essential component of learning. Practice effects are traditionally measured using such variables as accuracy, reaction time and sequence duration. Upon practicing a motor task, an individual's performance is often characterized by shorter response times and sequence durations as well as more accurate responses. Practice effects are thought to represent the momentary changes in performance (Schmidt, 2004) and may be used to predict the relatively permanent consequences of practice (Schmidt & Lee, 2005). Learning, however, cannot be assumed to occur based on practice effects alone as variables in the environment such as fatigue may affect performance during a single practice session. As a result, learning is not directly observable and must be inferred from measured variables such as whether the improvements from practice transfer to a similar but novel task or whether the performance improvement is retained following a period of rest (Magill, 1998). 1.2. The role of consolidation in motor learning Memory consolidation refers to processes by which a motor memory that is initially encoded into a ‘fragile’ state (sensitive to interference) is transformed into a more stable state with the passage of time (Fischer et al., 2002 and Robertson, 2004). Memory consolidation does not stop when practice ends but has been shown to continue across hours, days and weeks following the termination of practice (Fischer et al., 2002 and Press et al., 2005). For instance, Karni et al. (1995) found that speed and accuracy of a sequential finger tapping task continued to improve after training had ended and that only a small number of repetitions on the following day were required to initiate further gains in performance. Although the time it takes a skill to stabilize is dependent on many factors (e.g. task difficulty and length of practice), several studies using simple, repetitive motor tasks have shown the stabilization of a motor memory following a relatively short 24-h rest period (Walker and Stickgold, 2004 and Press et al., 2005). 1.3. Motor practice effects in PWS Several studies have shown PWS to be slower and less accurate compared to PNS when performing speech-motor tasks. Adams and Hayden (1976) reported that PWS were slower at initiating and terminating phonation when cued by a tone and that this trend continued following practice. Cooper and Allen (1977) found that PWS required more repetitions than control subjects to increase their rate of speech when practicing a repetitive reading task. Similarly, in a study by Ludlow et al. (1997), PWS were slower to learn the correct productions of two, 4-syllable nonsense words and were overall less accurate compared to PNS. Similar trends in performance have been observed in studies employing nonspeech tasks (Neilson and Neilson, 1991, Smits-Bandstra et al., 2006b, Webster, 1986 and Weinstein et al., 1989), suggesting that group differences are not limited to the sensorimotor processes involved in speech production. For instance, Webster (1986) found that PWS were slower and less accurate than control participants when practicing a bimanual finger tapping task. Others have shown that group differences remain when stuttering speakers are given time to practice a motor skill (Neilson and Neilson, 1991 and Smits-Bandstra et al., 2006b). In a series of studies conducted by Smits-Bandstra et al., 2006a and Smits-Bandstra et al., 2006b, PWS's poor practice effects on both a syllable reading and finger tapping task were shown to have an effect on their ability to transition the skill to a more automatic level. Smits-Bandstra, De Nil, and Rochon (2006) found that PWS and PNS performed similarly during the initial sets of practice; however, as practice continued results indicated a trend for slower reaction times and longer sequence durations in the PWS. In addition, the PWS demonstrated poorer transfer and retention abilities. Although suggestive, these results should be taken with caution as the behavioral measures in this study were taken during a single practice session. This may not have provided sufficient time to allow the temporary influences on performance (e.g. fatigue) to dissipate (Schmidt & Lee, 2005), and the results may have reflected practice rather than learning effects. Dual task paradigms are commonly used in motor learning research in order to measure the level of automaticity achieved following practice (Magill, 1998 and Schmidt, 2004). It is assumed that repeated practice leads to a reduction in cognitive demands, leaving attentional resources available for a secondary task. Smits-Bandstra and De Nil (2009) found that the performance of PWS during a single speech and nonspeech task was as slow and inaccurate as the performance of the PNS during a dual task condition. Under such task conditions, the PNS showed a decrease in response time and accuracy rate on the primary task compared to the single task condition due to the added task complexity of the dual task. However, the response times remained consistently slow for the PWS regardless of whether they performed under either a single or dual task condition. These results suggest a relatively non-progressing performance pattern in stuttering speakers and may point to an impaired ability to reach automaticity. 1.4. Motor learning abilities in PWS One limitation to the studies described above is that performance gains were measured during a single practice session. Although practice effects can be observed in as little as ten repetitions (Schmidt, 1988), learning cannot be assumed to occur unless more permanent changes in the behavior take place. One of the few studies to date that sheds some light on the learning abilities of PWS has been reported by Namasivayam and van Lieshout (2008). In this study, the speed and coordination of lip movements were assessed as participants repeated a set of nonsense words at two different rates (normal and fast) across three test sessions, two on the same day and one at least a week later. Results were similar between PWS and PNS for movement amplitude and duration; however, during same day trials PWS showed less stability and strength in coordination patterns compared to PNS, a difference that remained a week later. PWS but not PNS also showed significant decreases in the strength of inter-gestural frequency coupling following retention at normal, habitual speaking rates. 1.5. Present investigation The studies reviewed so far suggest that PWS may have a limited ability to acquire a novel movement pattern as observed in same day practice performance. However, as discussed, such practice effects cannot be considered reliable indicators of learning. Therefore, the present study aimed to investigate directly whether differences in motor practice between stuttering and nonstuttering adults reflect practice effects or point to differences in motor learning capacity. Specifically, it was hypothesized that poor performance gains in PWS compared to PNS during practice would be maintained following a 24-h consolidation period.
نتیجه گیری انگلیسی
The results from the current study provide partial support for previous findings of performance differences between PWS and PNS when practicing a novel speech-motor task (Cooper and Allen, 1977, Ludlow et al., 1997 and Smits-Bandstra et al., 2006b). The present investigation extended these findings by demonstrating that some group differences remain following more extensive practice and after a 24-h consolidation period. Other hypothesis that motivated the present study, particularly the hypothesis that poor performance gains observed during practice for the PWS group would be maintained following a 24-h consolidation period, were not supported. While the findings of the present study need to be confirmed in future studies, preferably using larger sample sizes to confirm the presence of potential subgroups among adults who stutter, results may be indicative of the presence of difficulties in motor learning, at least in a subgroup of the stuttering population. Future research is also needed to determine whether the current findings are linked to age of onset, stuttering severity, or other factors. The conclusions from such research could have important clinical implications as it may contribute to the identification of potential risk factors or predictors of stuttering development. It also may shed further light on which factors affect relapse following fluency treatment.