Retention of Implicit Sequence Learning in Persons Who Stutter and Persons With Parkinson's Disease

Abstract

The authors investigated the retention of implicit sequence learning in 14 persons with Parkinson's disease (PPD), 14 persons who stutter (PWS), and 14 control participants. Participants completed a nonsense syllable serial reaction time task in a 120-min session. Participants named aloud 4 syllables in response to 4 visual stimuli. The syllables formed a repeating 8-item sequence not made known to participants. After 1 week, participants completed a 60-min retention session that included an explicit learning questionnaire and a sequence generation task. PPD showed retention of general learning equivalent to controls but PWS's reaction times were significantly slower on early trials of the retention test relative to other groups. Controls showed implicit learning during the initial session that was retained on the retention test. In contrast, PPD and PWS did not demonstrate significant implicit learning until the retention test suggesting intact, but delayed, learning and retention of implicit sequencing skills. All groups demonstrated similar limited explicit sequence knowledge. Performance differences between PWS and PPD relative to controls during the initial session and on early retention trials indicated possible dysfunction of the cortico-striato-thalamo-cortical loop. The etiological implications for stuttering, and clinical implications for both populations, of this dysfunction are discussed.

Finger Sequence Learning in Adults Who Stutter

“…In our study, apparently the amount of training, i.e., 160 repetitions of the sequence, was sufficient for AWS to catch up to ANS. This is in line with other studies that report that AWS can perform at a comparable level as ANS after a substantial amount of repetitions ( Smits-Bandstra and Gracco, 2013 , 2015 ). A larger number of repetitions is needed by AWS to catch up to the performance of ANS ( Cooper and Allen, 1977 cited in Smits-Bandstra et al, 2006b ).…”

“…Thus, limitations in the speech skill of stuttering individuals could emerge due to the limited ability to learn motor sequences. In line with this suggestion, studies have reported poorer speech sequence skill learning in adults who stutter (AWS) than in those who do not (ANS; Smits-Bandstra et al, 2006b ; Namasivayam and van Lieshout, 2008 ; Smits-Bandstra and De Nil, 2009 ; Smith et al, 2010 ; Bauerly and De Nil, 2011 ; Smits-Bandstra and Gracco, 2013 , 2015 ; Sasisekaran and Weisberg, 2014 ). Other studies have used finger tapping tasks to investigate if limitations in motor sequence learning or performance also affect non-speech movements in AWS ( Webster, 1986 ; Smits-Bandstra et al, 2006a , b ; Bauerly and De Nil, 2015 ).…”

Apathy and noradrenaline

“…Two more recent studies highlight differences in retention for Parkinson's disease patients. An initial test of sequence learning was not affected in Parkinson's disease, though patient retention a week later was [55]. Patients tested on an implicit learning sequence task performed as well as healthy controls in a first block, but not in a second block [56].…”

The Neuroscience of Implicit Learning

“…Of course, given that PD patients have obvious movement difficulties and tremors, one might not be surprised by an impairment in a task that involves rapid button pressing. Some studies have shown reduced learning in PD when a verbal response is required (see Clark et al., 2014), while others have shown intact learning (Smith et al., 2001), or even the emergence of learning in a second training session after a 1‐week interval (Smits‐Bandstra & Gracco, 2015). The reason for such discrepancies is not clear.…”