Paradoxical Long-term Memory Augmentation following Temporal Pairing between "Limited" and "Extensive" Motor Sequence Training Experiences.

Consecutive training on two movement sequences often leads to retroactive interference-obstructing memory for the initially trained sequence but not for the second. However, in the context of hippocampal-system dependent memories, a poor learning experience, memory for which would soon decay, can be enhanced if temporally paired with a "strong," memory triggering experience. The synaptic tagging and capture hypothesis explains this paradoxical enhancement by suggesting that only strong experiences generate cellular resources necessary for synaptic remodeling. However, synapses engaged in a "weak" learning experience can capture and utilize plasticity-related resources generated for a subsequent strong learning experience. Here, we tested whether such "paradoxical" outcome would result in the context of motor (procedural) memory, if two movement sequences are unequally trained, consecutively. We show, in young adults (n = 100), that limited practice on a novel sequence of finger-to-thumb opposition movements led to different long-term outcomes, depending on whether and when (5 min, 5 hr) it was followed by extensive training on a different sequence. Five-minute pairing, only, resulted in overnight gains for the limited-trained sequence that were well-retained a week later; the overnight gains for the extensively trained sequence were compromised. Thus, consecutive training on different motor tasks can result in mnemonic interactions other than interference. We propose that the newly discovered mnemonic interaction provides the first-tier behavioral evidence in support of the possible applicability of notions stemming from the synaptic tagging and capture hypothesis in relation to human motor memory generation, specifically in relation to the practice-dependent consolidation of novel explicitly instructed movement sequences.

Sequence-specific delayed gains in motor fluency evolve after movement observation training in the absence of early sleep.

Following physical practice, delayed, consolidation-phase, gains in the performance of the trained finger-to-thumb opposition sequence (FOS) can be expressed, in young adults, only after a sleep interval is afforded. These delayed gains are order-of-movements specific. However, in several perceptual learning tasks, time post-learning, rather than an interval of sleep, may suffice for the expression of delayed performance gains. Here we tested whether the affordance of a sleep interval is necessary for the expression of delayed performance gains after FOS training by repeated observation. Participants were trained by observing videos displaying a left hand repeatedly performing a 5-element FOS. To assess post-session observation-related learning and delayed gains participants were tested in performing the observed (trained) and an unobserved (new, the 5-elements mirror-reversed) FOS sequences. Repeated observation of a FOS conferred no advantage to its performance, compared to the unobserved FOS, immediately after practice. However, a clear advantage for the observed FOS emerged by 12 h post-training, irrespective of whether this interval included sleep or not; the largest gains appeared by 24 h post-training. These results indicate that time-dependent, offline consolidation processes take place after observation training even in the absence of sleep; akin to perceptual learning rather than physical FOS practice.

Improving old tricks as new: Young adults learn from repeating everyday activities.

The notion that young healthy adults can substantially improve in activities that are part of their daily routine is often overlooked because it is assumed that such activities have come to be fully mastered. We followed, in young healthy adults, the effects of repeated executions of the Timed-Up-and-Go (TUG) task, a clinical test that assesses the ability to execute motor activities relevant to daily function-rising from a seated position, walking, turning and returning to a seated position. The participants (N = 15) performed 18 consecutive trials of the TUG in one session, and were retested on the following day and a week later. The participants were video recorded and wore inertial measurement units. Task execution times improved robustly; performance was well fitted by a power function, with large gains at the beginning of the session and nearing plateau in later trials, as one would expect in the learning of a novel task. Moreover, these gains were well retained overnight and a week later, with further gains accruing in the subsequent test-sessions. Significant intra-session and inter-session changes occurred in step kinematics as well; some aspects underwent inter-sessions recalibrations, but other aspects showed delayed inter-session changes, suggesting post-practice memory consolidation processes. Even common everyday tasks can be improved upon by practice; a small number of consecutive task repetitions can trigger lasting gains in young healthy individuals performing highly practiced routine tasks. This new learning in highly familiar tasks proceeded in a time-course characteristic of the acquisition of novel 'how to' (procedural) knowledge.

Memory for incidentally learned categories evolves in the post-learning interval.

Humans generate categories from complex regularities evolving across even imperfect sensory input. Here, we examined the possibility that incidental experiences can generate lasting category knowledge. Adults practiced a simple visuomotor task not dependent on acoustic input. Novel categories of acoustically complex sounds were not necessary for task success but aligned incidentally with distinct visuomotor responses in the task. Incidental sound category learning emerged robustly when within-category sound exemplar variability was closely yoked to visuomotor task demands and was not apparent in the initial session when this coupling was less robust. Nonetheless, incidentally acquired sound category knowledge was evident in both cases one day later, indicative of offline learning gains and, nine days later, learning in both cases supported explicit category labeling of novel sounds. Thus, a relatively brief incidental experience with multi-dimensional sound patterns aligned with behaviorally relevant actions and events can generate new sound categories, immediately after the learning experience or a day later. These categories undergo consolidation into long-term memory to support robust generalization of learning, rather than simply reflecting recall of specific sound-pattern exemplars previously encountered. Humans thus forage for information to acquire and consolidate new knowledge that may incidentally support behavior, even when learning is not strictly necessary for performance.

Skill-learning by observation-training with patients after traumatic brain injury.

Traumatic brain injury (TBI) is a major cause of death and disability in Western society, and often results in functional and neuropsychological abnormalities. Memory impairment is one of the most significant cognitive implications after TBI. In the current study we investigated procedural memory acquisition by observational training in TBI patients. It was previously found that while practicing a new motor skill, patients engage in all three phases of skill learning-fast acquisition, between-session consolidation, and long-term retention, though their pattern of learning is atypical compared to healthy participants. A different set of studies showed that training by observing a motor task, generally prompted effective acquisition and consolidation of procedural knowledge in healthy participants. The aim of our study was to (i) evaluate the potential benefit of action observation in TBI patients. (ii) Examine the possibility of general improvement in performance between the first (24 h post-training) and second (2 weeks post-training) stage of the study. (iii) Investigate the link between patients' ability to benefit from observational learning (via performance gains-speed and accuracy) and common measures of injury (such as severity of injury, functional and cognitive measures). Materials and methods: Patients hospitalized after moderate to severe TBI, were trained by observation for the finger opposition sequence (FOS) motor task. They were then tested for the observation-trained sequence (A) and a similar control sequence (B), at two different time-points (24 h post-training and 2 weeks later). Results revealed: (i) a significant difference in performance between the trained (A) and untrained (B) sequences, in favor of the trained sequence. (ii) An increase in performance for both sequences A and B toward the second (retention) session. (iii) The advantage for sequence A was stable and preserved also in the second session. (iv) Participants with lower moderate Functional Independence Measure (FIM) scores gained more from observational-procedural learning, compared with patients with higher functional abilities. Conclusion: Overall, these findings support the notion that TBI patients may achieve procedural memory consolidation and retention through observational learning. Moreover, different functional traits may predict the outcomes of observational training in different patients. These findings may have significant practical implications in the future, regarding skill acquisition methods in TBI patients.

Practice schedule and testing per se affect children's transfer abilities in a grapho-motor task.

Children's ability to transfer the gains of a motor experience, such as learning to write a letter, to novel conditions, such as cursive writing of the same letter, are affected by the way in which the learning experience is parsed. Parsing may have limitations because a short session may hamper the engagement of procedural memory consolidation processes. Here, we compared the effects of two practice schedules with the total amount of practice identical training provided in a single-session practice versus multi-session practice, wherein each session on its own was insufficient for generating long-term gains. A total of 40 7- and 8-year-old children practiced the production of a novel letter form by connecting dots, namely, the Invented Letter Task (ILT). Multiple ILT-related transfer tasks were assessed at 24 h post-training and again at 4-5 weeks post-training. Although by the end of training the single-session practice group outperformed the multi-session practice group in speed and accuracy, at 24 h post-training both groups showed comparable gains. However, after multi-session practice, children were as fast or faster and more accurate in the transfer tasks. By 4-5 weeks post-training, the multi-session practice group showed larger gains in the trained condition, a speed advantage in the transfer tasks, and a significant improvement on the transfer tasks. The results suggest that parsing training over several brief sessions may lead to long-term gains in children's grapho-motor skills. Moreover, multi-session practice protocols may contribute to the potential for transfer and to more effective learning from experiences such as transfer tasks.

Long-term benefits after a rhyme-repetition based intervention program for kindergarteners: Better reading and spelling in the first grade.

Oral language proficiency in kindergarten can facilitate the acquisition of reading and writing. However, in diglossic languages, like Arabic, the large gap between the spoken and the formal, modern standard (MSA) varieties of the language may restrict the benefits of oral language proficiency to subsequent literacy skills. Here, we tested, in a randomized controlled study, whether an intervention program, implemented in kindergarten, that familiarized the children with rhymes presented in MSA through recitation, facilitated reading and spelling in first grade. We also tested whether engaging the children in recitation affords an advantage over repeated listening by itself and whether rhymes directly referring to the alphabet impart additional advantages. The children were assigned to one of four intervention conditions (10 sessions, 2 months) wherein they either recited or repeatedly listened to nursery rhymes that were either related or unrelated to the alphabet, or engaged in nonlinguistic activities (control). A year later, all intervention groups read faster compared to a control group (nonlinguistic activity). The two recitation groups gained in reading accuracy, reading efficiency, and spelling; spelling gains were found also in children who only listened to alphabet-related rhymes. The reciting groups were superior to the listening groups in all study measures (reading and spelling). The results suggest long-term contributions from structured interventions based on oral rhyme repetition, in kindergarten, to reading and spelling in first grade. Vocal recitations in kindergarten can benefit the mastering of literacy skills even in a language that differs from the one spoken in the child's home. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Motor sequence learning in patients with ideomotor apraxia: Effects of long-term training.

Recent studies show that limb apraxia is a quite frequent, yet often underdiagnosed, higher motor impairment following stroke. Because it adversely affects every-day life and personal independence, successful rehabilitation of apraxia is essential for personal well-being. Nevertheless, evidence of long-term efficacy of training schemes and generalization to untrained actions is still scarce. One possible reason for the tendency of this neurological disorder to persist may be a deficit in planning, conceptualisation and storage of complex motor acts. This pilot study aims at investigating explicit motor learning in apractic stroke patients. In particular, we addressed the ability of apractic patients to learn and to retain new explicit sequential finger movements across 10 training sessions over a 3-week interval. Nine stroke patients with ideomotor apraxia in its chronic stage participated in a multi-session training regimen and were included in data analyses. Patients performed an explicit finger sequence learning task (MSLT - motor sequence learning task), which is a well-established paradigm to investigate motor learning and memory processes. Patients improved task performance in terms of speed and accuracy across sessions. Specifically, they showed a noticeable reduction in the mean time needed to perform a correct sequence and the number of erroneous sequences. We found also a trend for improved performance at the Goldenberg apraxia test protocol: "imitation of meaningless hand and finger gestures" relative to when assessed before the MSLT training. Patients with ideomotor apraxia demonstrated the ability to acquire and maintain a novel sequence of movements; and, this training was associated with hints towards improvement of apraxia symptoms.

Better later: evening practice is advantageous for motor skill consolidation in the elderly.

How does the time of day of a practice session affect learning of a new motor sequence in the elderly? Participants practiced a given finger tapping sequence either during morning or evening hours. All participants robustly improved performance speed within the session concurrent with a reorganization of the tapping pattern of the sequence. However, evening-trained participants showed additional gains overnight and at 1 wk posttraining; moreover, evening training led to a further reorganization of the tapping pattern offline. A learning experience preceding nocturnal sleep can lead to a task-specific movement routine as an expression of novel "how to" knowledge in the elderly.

Recitation as a structured intervention to enhance the long-term verbatim retention and gist recall of complex texts in kindergarteners.

Recitation is an effective way for children to become familiar with basic blocks of knowledge. It is not clear, however, whether repeated structured exposure to complex texts via listening or active reciting benefits the ability of kindergarteners to retain verbal material in long-term memory verbatim and as content. Here, we tested the effectiveness of teaching longer texts to kindergarteners by repeated exposure in terms of long-term retention (6 months). A set of 28 rhyming sentences (224 words) were introduced, 3 in each session, and the increasingly longer text was practiced by either voiced recitation or listening. The rhymes were in a literary language, and word meaning in each new rhyme was elaborated when first introduced. Both groups (recitation and listening) showed good long-term retention, but the recitation group outperformed the listening group when assessed at 24 h, 1 month, and 6 months postintervention in terms of the recall rate, error rate, number of prompts required, and sequence fidelity. In the later assessments, the reciting group was the more fluent group in producing the rhymes. Moreover, at 6 months postintervention, the gist (content) of the rhymes and the meaning of vocabulary items from the texts were robustly retained, with an advantage for the recitation group. Thus, practice in affording multiple repetitions, specifically active recitation, resulted in fluent, effortless, and accurate recall of statements and their content. We propose that these results support the notion that repetition-based practice may promote the mastery of complex verbal material by enabling better engagement of procedural memory, that is, by promoting "proceduralization" processes.

Practice Makes Transfer Imperfect: Evidence From Auditory Learning.

BACKGROUND: Evidence from motor and visual studies suggests that the ability to generalize learning gains to untrained conditions decreases as the training progresses. This decrease in generalization was suggested to reflect a shift from higher to lower levels of neuronal representations of the task following prolonged training. In the auditory modality, however, the few studies that tested the influence of prolonging training on generalization ability showed no decrease and sometimes even an increase in generalization. OBJECTIVE: To test the impact of extending training in a basic psychoacoustic task on the ability to generalize the gains attained in training to untrained conditions. DESIGN: Eighty-two young adults participated in two experiments that differed in the specific training regimen. In both experiments, training was conducted using a difference limen for frequency (DLF) task with an adaptive forced-choice procedure, for either a single- or nine-session training. Following training, generalization to the untrained ear and to an untrained frequency was assessed. RESULTS: (a) Training induced significant learning (i.e., smaller DLF thresholds) following a single session of training, and more so following nine training sessions; (b) results from the combined data from both experiments showed that the ability to generalize the learning gains to the untrained ear and frequency was limited after the extended DLF training; (c) larger improvements under the trained condition resulted in smaller generalization to the untrained conditions. CONCLUSIONS: The findings of increased specificity with training in the auditory modality support the notion that gradual changes, both quantitative and qualitative, occur in the neural representations of an auditory task during its acquisition. These findings suggest common underlying mechanisms in basic skill learning across different modalities.

Recitation and listening to nursery rhymes in the familiarization with a literacy language in kindergarteners: Not kids' stuff.

A large linguistic distance exists between spoken Arabic and the Modern Standard Arabic (MSA) the literary language (a diglosia). Novice readers, therefore, struggle with the complex orthography of Arabic as well as the mastering of MSA. Here, we tested whether structured activities in MSA would advance kindergarteners' MSA aptitude by the end of the school year. We examined two issues: (a) whether reciting nursery rhymes in MSA would be more effective in promoting language and preliteracy skills in kindergarteners compared to listening to the same texts, and (b) whether there are additional advantages for using texts directly referring to the alphabet. Thus, 136 kindergarteners (Mage = 5:6; 61 girls), all native speakers of Arabic and with middle-low socioeconomic background, were assigned to a 10-session (2 months) program in 1 of 4 intervention conditions wherein nursery rhymes related/not related to the alphabet, were either repeatedly recited or listened to. The achievements of children in the intervention conditions were compared to those of peers that were given nonlinguistic activity of similar length (control). The four intervention groups improved their performance at the postintervention assessment in all tests of MSA aptitude and outperformed the control group in receptive and expressive vocabulary and listening comprehension. Also, the reciting groups were better than the control and listening groups in tests assessing vocabulary and morpho-syntactic sensitivity. Our results highlight the contribution of structured interventions based on rhyme repetition to MSA proficiency of kindergarteners. Moreover, the results suggest that reciting may be superior to listening in advancing language proficiency in preschoolers. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

A Delayed Advantage: Multi-Session Training at Evening Hours Leads to Better Long-Term Retention of Motor Skill in the Elderly.

The acquisition and retention of motor skills is necessary for everyday functioning in the elderly and may be critical in the context of motor rehabilitation. Recent studies indicate that motor training closely followed by sleep may result in better engagement of procedural ("how to") memory consolidation processes in the elderly. Nevertheless, elderly individuals are mostly morning oriented and a common practice is to time rehabilitation programs to morning hours. Here, we tested whether the time-of-day wherein training is afforded (morning, 8-10:30 a.m., or evening, 6-9 p.m.) affects the long-term outcome of a multi-session motor practice program (10 sessions across 3-4 weeks) in healthy elderly participants. Twenty-nine (15 women) older adults (60-75 years) practiced an explicitly instructed five-element key-press sequence by repeatedly generating the sequence "as fast and accurately as possible." The groups did not differ in terms of sleep habits and quality (1-week long actigraphy); all were morning-oriented individuals. All participants gained robustly from the intervention, shortening sequence tapping duration and retaining the gains (> 90%) at 1-month post-intervention, irrespective of the time-of-day of training. However, retesting at 7-months post-intervention showed that the attrition of the training induced gains was more pronounced in the morning trained group compared to the evening group (76 and 56.5% loss in sequence tapping time; 7/14 and 3/14 participants showed a > 5% decline in accuracy relative to end of training, respectively). Altogether, the results show that morning-oriented older adults effectively acquired skill in the performance of a sequence of finger movements, in both morning and evening practice sessions. However, evening training leads to a significant advantage, over morning training, in the long-term retention of the skill. Evening training should be considered an appropriate time window for motor skill learning in older adults, even in individuals with morning chronotype. The results are in line with the notion that motor training preceding a sleep interval may be better consolidated into long-term memory in the elderly, and thus result in lower forgetting rates.

Deficits in Explicit Language Problem Solving Rather Than in Implicit Learning in Specific Language Impairment: Evidence From Learning an Artificial Morphological Rule.

Purpose The purpose of this study was to delineate differences between children with specific language impairment (SLI), typical age-matched (TAM) children, and typical younger (TY) children in learning and mastering an undisclosed artificial morphological rule (AMR) through exposure and usage. Method Twenty-six participants (eight 10-year-old children with SLI, 8 TAM children, and ten 8-year-old TY children) were trained to master an AMR across multiple training sessions. The AMR required a phonological transformation of verbs depending on a semantic distinction: whether the preceding noun was animate or inanimate. All participants practiced the application of the AMR to repeated and new (generalization) items, via judgment and production tasks. Results The children with SLI derived significantly less benefit from practice than their peers in learning most aspects of the AMR, even exhibiting smaller gains compared to the TY group in some aspects. Children with SLI benefited less than TAM and even TY children from training to judge and produce repeated items of the AMR. Nevertheless, despite a significant disadvantage in baseline performance, the rate at which they mastered the task-specific phonological regularities was as robust as that of their peers. On the other hand, like 8-year-olds, only half of the SLI group succeeded in uncovering the nature of the AMR and, consequently, in generalizing it to new items. Conclusions Children with SLI were able to learn language aspects that rely on implicit, procedural learning, but experienced difficulties in learning aspects that relied on the explicit uncovering of the semantic principle of the AMR. The results suggest that some of the difficulties experienced by children with SLI when learning a complex language regularity cannot be accounted for by a broad, language-related, procedural memory disability. Rather, a deficit-perhaps a developmental delay in the ability to recruit and solve language problems and establish explicit knowledge regarding a language task-can better explain their difficulties in language learning.

Subclinical Scores in Self-Report Based Screening Tools for Attention Deficits Correlate With Cognitive Traits in Typical Evening-Type Adults Tested in the Morning.

Previous studies suggest that in adolescents and young adults, evening chronotype is a subclinical factor in physical, cognitive, and psychiatric fitness; poor sleep habits and larger misalignment with the social schedule constraints may exacerbate symptoms of inattention, impulsivity and the risks for detrimental behaviors. The influence of chronotype on neurocognitive performance during morning hours and scores in self-reports about attention deficit symptoms (ADS) and executive functioning, was explored in 42 healthy young university students (29 women), divided to evening type (ET) and combined morning/intermediate type (MT/IT) groups. Evening chronotypes scored significantly higher in the questionnaires of inattention Adult ADHD Self-Report Scale (ASRS-6) (MT/IT: 1.62 ± 1.59; ET: 2.71 ± 1.62, p < 0.05) and day-time sleepiness Epworth scale (MT/IT: 7.19 ± 5.17; ET: 11.48 ± 5.26, p < 0.01), reported lower subjective alertness (MT/IT: 63.02 ± 21.40; ET: 40.76 ± 17.43, p < 0.001), and had slower reaction times (MT/IT: 321.47 ± 76.81; ET: 358.94 ± 75.16, p < 0.05) during tests, compared to non-evening chronotypes. Nevertheless, ETs did not significantly differ in self-reports of executive functioning in the Behavioral Rating Inventory of Executive Functions-A (BRIEF-A) from non-ETs. The scores on standard self-report screening tools for ADS and executive functioning (ASRS-6, BRIEF-A-Metacognition) correlated with eveningness. We conclude that eveningness, subjective sleepiness and low arousal levels during morning can present as subclinical Attention Deficit and Hyperactivity Disorder (ADHD) symptoms in typical young adults with no evident sleep problems. Self-report based screening tools for ADS and executive functioning reflect chronotype-related traits in healthy young adults. Strong eveningness may bias the results of neurocognitive performance screening for ADHD when administered at morning hours.

Susceptibility of consolidated procedural memory to interference is independent of its active task-based retrieval.

Reconsolidation theory posits that upon retrieval, consolidated memories are destabilized and need to be restabilized in order to persist. It has been suggested that experience with a competitive task immediately after memory retrieval may interrupt these restabilization processes leading to memory loss. Indeed, using a motor sequence learning paradigm, we have recently shown that, in humans, interference training immediately after active task-based retrieval of the consolidated motor sequence knowledge may negatively affect its performance levels. Assessing changes in tapping pattern before and after interference training, we also demonstrated that this performance deficit more likely indicates a genuine memory loss rather than an initial failure of memory retrieval. Here, applying a similar approach, we tested the necessity of the hypothetical retrieval-induced destabilization of motor memory to allow its impairment. The impact of memory retrieval on performance of a new motor sequence knowledge acquired during the interference training was also evaluated. Similar to the immediate post-retrieval interference, interference training alone without the preceding active task-based memory retrieval was also associated with impairment of the pre-established motor sequence memory. Performance levels of the sequence trained during the interference training, on the other hand, were impaired only if this training was given immediately after memory retrieval. Noteworthy, an 8-hour interval between memory retrieval and interference allowed to express intact performance levels for both sequences. The current results suggest that susceptibility of the consolidated motor memory to behavioral interference is independent of its active task-based retrieval. Differential effects of memory retrieval on performance levels of the new motor sequence encoded during the interference training further suggests that memory retrieval may influence the way new information is stored by facilitating its integration within the retrieved memory trace. Thus, impairment of the pre-established motor memory may reflect interference from a competing memory trace rather than involve interruption of reconsolidation.

Learning to decipher time-compressed speech: Robust acquisition with a slight difficulty in generalization among young adults with developmental dyslexia.

Learning to decipher acoustically distorted speech serves as a test case for the study of language-related skill acquisition in persons with developmental dyslexia (DD). Deciphering this type of input is rarely learned explicitly and does not yield conscious insights. Problems in implicit and procedural skill learning have been proposed as possible causes of DD. Here we examined the learning of time-compressed (accelerated) speech and its generalization to novel materials among young adults with DD compared to typical readers (TD). All participants completed a training session that involved judging the semantic plausibility of sentences, during which the level of time-compression was changed using an adaptive (staircase) procedure according to each participant's performance. In the test, phase learning (test on same items) and generalization (test on new items and same items spoken by a new speaker) were assessed. Both groups showed robust gains after training. Moreover, after training, the initial disadvantage of the DD group was no longer significant. After training, both groups experienced relative difficulties in deciphering learned tokens spoken by a different voice, though participants with DD were less able to generalize the gains to deciphering new tokens. Thus, DD individuals benefited from repeated experience with time-compressed speech no less than typical readers, but their evolving skill was apparently more dependent on the specific characteristics of the tokens. Atypical generalization, which indicates that perceptual learning is contingent on lower-level features of the input though does not necessarily point to impaired learning potential per se, may explain some of the contradictory findings in published studies of speech perception in DD.

Atypical Within-Session Motor Procedural Learning after Traumatic Brain Injury but Well-Preserved Between-Session Procedural Memory Consolidation.

Using the finger-to-thumb opposition sequence (FOS) learning task, we characterized motor skill learning in sub-acute patients hospitalized for rehabilitation following traumatic brain injury (TBI). Ten patients (Trained TBI) and 11 healthy participants (Trained Healthy) were trained using a multi-session protocol: a single session was afforded in the first week of the study, and four daily sessions were afforded during the second week. Intensity of practice was adapted to patients. Performance speed and accuracy were tested before and after each session. Retention was tested 1 month later. Ten patients (Control TBI) had no FOS training and were tested only at the beginning and the end of the 6 week period. Although baseline performance on the FOS was very slow, all three phases of skill learning found in healthy adults (acquisition, between-session consolidation gains, and long-term retention) could be identified in patients with TBI. However, their time-course of learning was atypical. The Trained TBI group improved in speed about double the spontaneous improvements observed in the Control TBI group, with no speed-accuracy tradeoff. Normalized to their initial performance on the FOS, the gains accrued by the Trained TBI group after a first training were comparable to those accrued by healthy adults. Only during the second week with daily training, the rate of improvement of the Trained TBI group lagged behind that of the Trained Healthy group, due to increasing within-sessions losses in performance speed; no such losses were found in healthy participants. The Functional Independence Measure scores at the start of the study correlated with the total gains attained at the end of the study; no correlations were found with severity of injury or explicit memory impairments. Despite within-sessions losses in performance, which we propose reflect cognitive fatigue, training resulted in robust overall learning and long-term retention in patients with moderate-severe TBI. Given that the gains in performance evolved mainly between sessions, as delayed, offline, gains, our results suggest that memory consolidation processes can be effectively engaged in patients with TBI. However, practice protocols and schedules may need to be optimized to better engage the potential for long-term plasticity in these patients.

Procedural Memory Consolidation in Attention-Deficit/Hyperactivity Disorder Is Promoted by Scheduling of Practice to Evening Hours.

In young adults without attention-deficit/hyperactivity disorder (ADHD) training on a novel movement sequence results not only in large within-session (online) gains in task performance but also in additional (delayed, off-line) gains in the performance, expressed after an interval of sleep. In contrast, young people with ADHD, given an identical practice, were shown to improve online but expressed much smaller delayed gains overnight. As delayed gains in performance are taken to reflect procedural ("how to") memory consolidation processes, this may explain skill learning deficits in persons with ADHD. However, motor training is usually provided in morning sessions, and, given that persons with ADHD are often evening types, chronobiological constraints may constitute a hidden factor. Here, we tested the hypothesis that evening training, compared to morning training, would result in larger overnight consolidation gains following practice on a novel motor task in young women with ADHD. Participants with (N = 25) and without (N = 24) ADHD were given training on a finger opposition sequence tapping task, either in the morning or at evening. Performance was assessed before and immediately after training, overnight, and at 2 weeks post-training. Individuals with ADHD reported a general preference for evening hours. Evening training was equally effective in participants with and without ADHD, both groups showing robust consolidation gains in task performance overnight. However, the ability to express delayed gains overnight was significantly reduced in participants with ADHD if trained in the morning. Typical peers were as effective in expressing overnight consolidation phase gains irrespective of the time-of-day wherein the training session was afforded. Nevertheless, even after morning training, participants with ADHD fully retained the gains acquired within the first 24 h over an interval of about 2 weeks. Our results suggest that procedural memory consolidation processes are extant and effective in ADHD, but require that specific biobehavioral conditions be met. The affordance of training in the evening hours can relax some of the constraints on these processes in ADHD. The current results are in line with the notion that the control of what is to be retained in procedural memory is atypical or more stringent in ADHD.