Implicit learning in patients with probable Alzheimer's disease

Neural Underpinnings of Learning in Dementia Populations: A Review of Motor Learning Studies Combined with Neuroimaging

The intent of this review article is to serve as an overview of current research regarding the neural characteristics of motor learning in Alzheimer disease (AD) as well as prodromal phases of AD: at-risk populations, and mild cognitive impairment. This review seeks to provide a cognitive framework to compare various motor tasks. We will highlight the neural characteristics related to cognitive domains that, through imaging, display functional or structural changes because of AD progression. In turn, this motivates the use of motor learning paradigms as possible screening techniques for AD and will build upon our current understanding of learning abilities in AD populations.

Autistic Adults Show Intact Learning on a Visuospatial Serial Reaction Time Task

Some theories have proposed that autistic individuals have difficulty learning predictive relationships. We tested this hypothesis using a serial reaction time task in which participants learned to predict the locations of a repeating sequence of target locations. We conducted a large-sample online study with 61 autistic and 71 neurotypical adults. The autistic group had slower overall reaction times, but demonstrated sequence-specific learning equivalent to the neurotypical group, consistent with other findings of typical procedural memory in autism. The neurotypical group, however, made significantly more prediction-related errors early in the experiment when the stimuli changed from repeated sequences to random locations, suggesting certain limited behavioural differences in the learning or utilization of predictive relationships for autistic adults.

Performance Differences of a Touch-Based Serial Reaction Time Task in Healthy Older Participants and Older Participants With Cognitive Impairment on a Tablet: Experimental Study

BACKGROUND

Digital neuropsychological tools for diagnosing neurodegenerative diseases in the older population are becoming more relevant and widely adopted because of their diagnostic capabilities. In this context, explicit memory is mainly examined. The assessment of implicit memory occurs to a lesser extent. A common measure for this assessment is the serial reaction time task (SRTT).

OBJECTIVE

This study aims to develop and empirically test a digital tablet-based SRTT in older participants with cognitive impairment (CoI) and healthy control (HC) participants. On the basis of the parameters of response accuracy, reaction time, and learning curve, we measure implicit learning and compare the HC and CoI groups.

METHODS

A total of 45 individuals (n=27, 60% HCs and n=18, 40% participants with CoI-diagnosed by an interdisciplinary team) completed a tablet-based SRTT. They were presented with 4 blocks of stimuli in sequence and a fifth block that consisted of stimuli appearing in random order. Statistical and machine learning modeling approaches were used to investigate how healthy individuals and individuals with CoI differed in their task performance and implicit learning.

RESULTS

Linear mixed-effects models showed that individuals with CoI had significantly higher error rates (b=-3.64, SE 0.86; z=-4.25; P<.001); higher reaction times (F1,41=22.32; P<.001); and lower implicit learning, measured via the response increase between sequence blocks and the random block (β=-0.34; SE 0.12; t=-2.81; P=.007). Furthermore, machine learning models based on these findings were able to reliably and accurately predict whether an individual was in the HC or CoI group, with an average prediction accuracy of 77.13% (95% CI 74.67%-81.33%).

CONCLUSIONS

Our results showed that the HC and CoI groups differed substantially in their performance in the SRTT. This highlights the promising potential of implicit learning paradigms in the detection of CoI. The short testing paradigm based on these results is easy to use in clinical practice.

What neurological diseases tell us about procedural perceptual-motor learning? A systematic review of the literature

INTRODUCTION

Procedural perceptual-motor learning of sequences (PPMLS) provides perceptual-motor skills in many activities of daily living. Based on behavioral and neuroimaging results, theoretical models of PPMLS postulate that the cortico-striatal loop, the cortico-cerebellar loop and the hippocampus are specifically involved in the early stage of PPMLS while the cortico-striatal loop would be specifically involved in the late stage of PPMLS. Hence, current models predict that the early stage of PPMLS should be impaired in Parkinson's disease (PD: lesion of the cortico-striatal loop), in cerebellar disease (CD: lesion of the cortico-cerebellar loop) and in Alzheimer's disease (AD: lesion of the hippocampus), whereas the late stage of PPMLS should be specifically impaired in PD.

OBJECTIVE

The aim of the study is (1) to draw a complete picture of experimental results on PPMLS in PD, CD and AD (2) to understand heterogeneity of results as regard to participant and task characteristics.

METHOD

This review is based on the guideline proposed by the PRISMA statement.

RESULTS

Our review reveals (1) that the experimental results clarify the theoretical models and (2) that the impairment of PPMLS depends on both the personal characteristics of the participants and the characteristics of the task to-be-learnt rather than on the disease itself.

CONCLUSION

Our results highlight that these characteristics should be more carefully considered to understand the heterogeneity of results across studies on PPMLS and the effects of rehabilitation programs.

Feasibility of personalized visual mapping assistive technology to improve functional ability in persons with dementia

Background

Mobile health (mHealth) apps using novel visual mapping assistive technology can allow users to develop personalized maps that aid people living with cognitive impairment in the recall of steps needed to independently complete activities of daily living (ADLs), such as bathing, toileting, and dressing.

Objective

This study aims to determine the feasibility and preliminary impact of an mHealth assistive technology app providing guidance to aid individuals living with cognitive impairment in the recall of steps to independently complete ADLs.

Methods

A total of 14 Veterans (mean age 65 SD 9.5 years; 14/14, 100% male; 10/14, 71.4% Black) and 8 non-Veterans (mean age 78, SD 10.3 years; 5/8, 62.5% male; 8/8, 100% Black) were recruited and enrolled from the Department of Veterans Affairs (VA) and non-VA cognitive care clinics. A visual mapping software program, MapHabit, was used to generate a series of personalized visual map templates focused on ADLs created within the MapHabit app. The visual maps were accessed through a tablet device. A 19-item exit questionnaire was administered to the participants to assess perceived improvement in their functional ability after using the MapHabit system for 3 months.

Results

A total of 13 (93%) VA clinic participants and 8 (100%) non-VA clinic participants completed the 3-month study. Baseline cognitive testing indicated impaired to significantly impaired cognitive function. After 3 months of using the MapHabit system, VA clinic participants reported perceived improvement in social engagement (P=.01) and performance of ADLs (P=.05) compared to the baseline, whereas non-VA clinic participants reported improvements in the performance of ADLs (P=.02), mood (P=.04), social engagement (P=.02), and memory (P=.02). All study participants reported they would recommend the MapHabit system to a colleague, and 85% (11/14) of VA and 100% (8/8) of non-VA clinic participants reported a willingness to participate in a future study.

Conclusions

Older VA and non-VA clinic participants with cognitive impairment were willing to use an mHealth app to assist with the completion of ADLs, and they reported positive preliminary effects. A larger study is warranted to assess the efficacy in the setting of a randomized controlled trial.

Serial Reaction Time Task Performance in Older Adults with Neuropsychologically Defined Mild Cognitive Impairment

BACKGROUND

Studies have found that individuals with mild cognitive impairment (MCI) exhibit a range of deficits outside the realm of primary explicit memory, yet the role of response speed and implicit learning in older adults with MCI have not been established.

OBJECTIVE

The current study aims to explore and document response speed and implicit learning in older adults with neuropsychologically defined MCI using a simple serial reaction (SRT) task. In addition, the study aims to explore the feasibility of a novel utilization of the simple cognitive task using machine learning procedures as a proof of concept.

METHOD

Participants were 22 cognitively healthy older adults and 20 older adults with MCI confirmed through comprehensive neuropsychological evaluation. Two-sample t-test, multivariate regression, and mixed-effect models were used to investigate group difference in response speed and implicit learning on the SRT task. We also explored the potential utility of SRT feature analysis through random forest classification.

RESULTS

With demographic variables controlled, the MCI group showed overall slower reaction time and higher error rate compared to the cognitively healthy volunteers. Both groups showed significant simple motor learning and implicit learning. The learning patterns were not statistically different between the two groups. Random forest classification achieved overall accuracy of 80.9%.

CONCLUSIONS

Individuals with MCI demonstrated slower reaction time and higher error rate compared to cognitively healthy volunteers but demonstrated largely preserved motor learning and implicit sequence learning. Preliminary results from random forest classification using features from SRT performance supported further research in this area.

Oculomotor anticipation reveals a multitude of learning processes underlying the serial reaction time task

Sequence learning is the cognitive faculty enabling everyday skill acquisition. In the lab, it is typically measured in speed of response to sequential stimuli, whereby faster responses are taken to indicate improved anticipation. However, response speed is an indirect measure of anticipation, that can provide only limited information on underlying processes. As a result, little is known about what is learned during sequence learning, and how that unfolds over time. In this work, eye movements that occurred before targets appeared on screen in an ocular serial reaction time (O-SRT) task provided an online indication of where participants anticipated upcoming targets. When analyzed in the context of the stimuli preceding them, oculomotor anticipations revealed several simultaneous learning processes. These processes influenced each other, as learning the task grammar facilitated acquisition of the target sequence. However, they were dissociable, as the grammar was similarly learned whether a repeating sequence inhabited the task or not. Individual differences were found in how the different learning processes progressed, allowing for similar performance to be produced for different latent reasons. This study provides new insights into the processes subserving sequence learning, and a new method for high-resolution study of it.

Procedural Learning in Individuals with Amnestic Mild Cognitive Impairment and Alzheimer's Dementia: a Systematic Review and Meta-analysis

The notion that procedural learning and memory is spared in Alzheimer's disease (AD) has important implications for interventions aiming to build on intact cognitive functions. However, despite these clinical implications, there are mixed findings in the literature about whether or not procedural learning remains intact. This meta-analysis examines the standard mean difference of all published studies regarding procedural learning in AD dementia or amnestic Mild Cognitive Impairment (aMCI) compared to cognitively healthy older adults. Additionally, we conducted statistical equivalence analyses. Our systematic review showed that only a limited number of studies (k = 17) have compared procedural learning between individuals with aMCI or AD dementia and healthy controls. Our meta-analysis, which synthesized these studies, demonstrated that while procedural learning performance was not statistically equivalent between individuals with aMCI or AD dementia, and healthy older adults, the difference was clinically and statistically trivial. Although larger studies are needed, the present findings suggest that procedural learning does appear to remain spared in aMCI and AD dementia.

Resistance, vulnerability and resilience: A review of the cognitive cerebellum in aging and neurodegenerative diseases

In the context of neurodegeneration and aging, the cerebellum is an enigma. Genetic markers of cellular aging in cerebellum accumulate more slowly than in the rest of the brain, and it generates unknown factors that may slow or even reverse neurodegenerative pathology in animal models of Alzheimer's Disease (AD). Cerebellum shows increased activity in early AD and Parkinson's disease (PD), suggesting a compensatory function that may mitigate early symptoms of neurodegenerative pathophysiology. Perhaps most notably, different parts of the brain accumulate neuropathological markers of AD in a recognized progression and generally, cerebellum is the last brain region to do so. Taken together, these data suggest that cerebellum may be resistant to certain neurodegenerative mechanisms. On the other hand, in some contexts of accelerated neurodegeneration, such as that seen in chronic traumatic encephalopathy (CTE) following repeated traumatic brain injury (TBI), the cerebellum appears to be one of the most susceptible brain regions to injury and one of the first to exhibit signs of pathology. Cerebellar pathology in neurodegenerative disorders is strongly associated with cognitive dysfunction. In neurodegenerative or neurological disorders associated with cerebellar pathology, such as spinocerebellar ataxia, cerebellar cortical atrophy, and essential tremor, rates of cognitive dysfunction, dementia and neuropsychiatric symptoms increase. When the cerebellum shows AD pathology, such as in familial AD, it is associated with earlier onset and greater severity of disease. These data suggest that when neurodegenerative processes are active in the cerebellum, it may contribute to pathological behavioral outcomes. The cerebellum is well known for comparing internal representations of information with observed outcomes and providing real-time feedback to cortical regions, a critical function that is disturbed in neuropsychiatric disorders such as intellectual disability, schizophrenia, dementia, and autism, and required for cognitive domains such as working memory. While cerebellum has reciprocal connections with non-motor brain regions and likely plays a role in complex, goal-directed behaviors, it has proven difficult to establish what it does mechanistically to modulate these behaviors. Due to this lack of understanding, it's not surprising to see the cerebellum reflexively dismissed or even ignored in basic and translational neuropsychiatric literature. The overarching goals of this review are to answer the following questions from primary literature: When the cerebellum is affected by pathology, is it associated with decreased cognitive function? When it is intact, does it play a compensatory or protective role in maintaining cognitive function? Are there theoretical frameworks for understanding the role of cerebellum in cognition, and perhaps, illnesses characterized by cognitive dysfunction? Understanding the role of the cognitive cerebellum in neurodegenerative diseases has the potential to offer insight into origins of cognitive deficits in other neuropsychiatric disorders, which are often underappreciated, poorly understood, and not often treated.

Procedural Learning Improves Cognition in Multiple Sclerosis

Background:

Multiple sclerosis (MS) is considered a neurodegenerative disease and an inflammatory demyelinating neuropathology in young population. Procedural memory has been poorly investigated in MS.

Objective:

We assessed whether the MS group was able to develop a motor-cognitive skill, using a procedural task (PLSC) developed in our laboratory, applying a manual and serial reaction time (RT) paradigm to semantic categorization.

Methods:

We evaluated 26 MS patients and 26 socio-demographic matched control participants using the PLSC task.

Results:

Using non-parametric statistical analyses, we observed a significant improvement of semantic categorization RTs with practice (p = 0.002), even with new verbal material to categorize in MS patients (p = 0.006), despite their motor and executive moderate deficits. This same profile of semantic procedural learning in MS was observed in previous studies carried out with Alzheimer’s and Parkinson’s diseases. Moreover, the visual-motor RTs remained stable or slightly improved over the five blocks in both groups, as well as in the AD groups of previous studies. The MS group showed longer visual-motor reaction times than those of the control group (p < 0.042), except in motor initiation aspect (p = 0.064). Both groups showed no significant differences for any type of error. Additionally, disability level and cognitive performances were not associated with the ratio of semantic procedural learning.

Conclusion:

The present results support the notion that MS patients may be capable of acquiring semantic skill, despite their motor disabilities and executive troubles. This work also addresses the possibilities to improve motor-cognitive skill RTs in neurodegenerative diseases.

Phases of procedural learning and memory: characterisation with perceptual-motor sequence tasks

Procedural learning and memory has been conceptualised as consisting of cognitive and autonomous phases. Although the Serial Reaction Time Task (SRTT) is a popular task used to study procedural memory (PM), it has not been used to explore the different phases of PM. The present study employed a modified SRTT and investigated whether it can distinguish phases of PM. Our results revealed that performance at the beginning of typing a repeating sequence was marked by a steep learning curve, followed by gradual improvements and ending in high performance levels without further improvement. Steep performance increases characterise the effortful learning of the cognitive phase, gradual increases at higher performances characterise emerging automatisation of the associative phase, and sustained highest performance characterises autonomous procedures when PM has formed. Our study presents an easy-to-use measure, capable of distinguishing phases of PM, and which can be useful to assess PM during brain development.

Implicit and Explicit Tests: Evidence for Dissociable Motor Skills in Probable Alzheimer's Dementia

Previous authors reported evidence for intact implicit memories (those retrieved without conscious effort) in a serial reaction time task for both Alzheimer's subjects and age-matched controls, although performance on an explicit memory task (requiring conscious effort for retrieval) was poor. The current study assessed latencies on a puzzle-assembly task to assess implicit (procedural) memory for 23 female volunteers. Nine participants suffered from probable Alzheimer's Disease and fourteen did not. Even when subjects had no explicit memory of practicing the task, they demonstrated savings upon relearning. Implications for research on memory dissociations in Alzheimer's Disease are discussed.

On the Role of Fragmentary Knowledge in a Sequence Learning Task

There has been considerable debate about whether or not we need to distinguish between the acquisition of implicit—and, independently thereof, the acquisition of explicit—knowledge in sequence learning tasks. Proponents of the view that a unitary knowledge base is formed assume (a) that the knowledge acquired is explicitly available, and (b) that information about sequence fragments forms the core of this explicit knowledge. Both of these issues are addressed empirically in the present article. In two experiments, an adapted process dissociation procedure and a suitable measurement model were used to separate recollective (explicit) and fluency-based (implicit) memory processes in a sequence learning task. Experiment 1 demonstrated that fluency-based processes came into play much later than recollective processes. Such recollective processes have been conceptualized as being based on simple knowledge about sequence fragments or chunks. Indeed, Experiment 2 showed that recollective processes are more likely to contribute to sequence judgements if chunks are readily available at test than if they are not. Together, these results are in line with the view that the learning of an event systematicity can be conceived of as the memorization of chunks of events that support both the speeding up of reaction times to systematic events and explicit, recollective memory processes even after relatively little training.

Longitudinal Assessment of Verbal Learning and Memory in Amnestic Mild Cognitive Impairment: Practice Effects and Meaningful Changes

Objectives: To identify learning effects and meaningful changes in amnestic mild cognitive impairment (aMCI) at a follow-up assessment.

Method: The Spanish version of the California Verbal Learning Test (CVLT) was administered to a sample of 274 adults of age over 50 years with subjective memory complains (SMC), including single and multiple domain aMCI groups and participants with SMC but without cognitive impairment (SMC group). The Wilcoxon test was used to compare results at baseline and after 18 months in short and long recall, and standardized regression-based (SRB) methods were used to study meaningful changes.

Results: Scores were significantly higher at follow-up for short and long-delayed recall in all groups indicating generalized practice effect. SRB scores indicated a significant decline in recall in a higher proportion of participants with aMCI than in SMC group.

Discussion: Patients with multiple and single domain aMCI benefit from practice in a verbal learning memory test. The SRB approach revealed a higher incidence of meaningful decline in short and long-delay recall and recognition in the aMCI groups than in the SMC group. Specifically, compared to SMC participants, single-domain aMCI individuals declined in a higher proportion in all measures, and multiple-domain aMCI individuals in long delay free recall.

Auditory access, language access, and implicit sequence learning in deaf children

Developmental psychology plays a central role in shaping evidence-based best practices for prelingually deaf children. The Auditory Scaffolding Hypothesis (Conway et al., 2009) asserts that a lack of auditory stimulation in deaf children leads to impoverished implicit sequence learning abilities, measured via an artificial grammar learning (AGL) task. However, prior research is confounded by a lack of both auditory and language input. The current study examines implicit learning in deaf children who were (Deaf native signers) or were not (oral cochlear implant users) exposed to language from birth, and in hearing children, using both AGL and Serial Reaction Time (SRT) tasks. Neither deaf nor hearing children across the three groups show evidence of implicit learning on the AGL task, but all three groups show robust implicit learning on the SRT task. These findings argue against the Auditory Scaffolding Hypothesis, and suggest that implicit sequence learning may be resilient to both auditory and language deprivation, within the tested limits. A video abstract of this article can be viewed at: https://youtu.be/EeqfQqlVHLI [Correction added on 07 August 2017, after first online publication: The video abstract link was added.].

Levodopa medication improves incidental sequence learning in Parkinson's disease

Empirical evidence suggests that levodopa medication used to treat the motor symptoms of Parkinson's disease (PD) may either improve, impair or not affect specific cognitive processes. This evidence led to the 'dopamine overdose' hypothesis that levodopa medication impairs performance on cognitive tasks if they recruit fronto-striatal circuits which are not yet dopamine-depleted in early PD and as a result the medication leads to an excess of dopamine. This hypothesis has been supported for various learning tasks including conditional associative learning, reversal learning, classification learning and intentional deterministic sequence learning, on all of which PD patients demonstrated significantly worse performance when tested on relative to off dopamine medication. Incidental sequence learning is impaired in PD, but how such learning is affected by dopaminergic therapy remains undetermined. The aim of the current study was to investigate the effect of dopaminergic medication on incidental sequence learning in PD. We used a probabilistic serial reaction time task (SRTT), a sequence learning paradigm considered to make the sequence less apparent and more likely to be learned incidentally rather than intentionally. We compared learning by the same group of PD patients (n=15) on two separate occasions following oral administration of levodopa medication (on state) and after overnight withdrawal of medication (off state). Our results demonstrate for the first time that levodopa medication enhances incidental learning of a probabilistic sequence on the serial reaction time task in PD. However, neither group significantly differed from performance of a control group without a neurological disease, which indicates the importance of within group comparisons for identifying deficits. Levodopa medication enhanced incidental learning by patients with PD on a probabilistic sequence learning paradigm even though the patients were not aware of the existence of the sequence or their acquired knowledge. The results suggest a role in acquiring incidental motor sequence learning for dorsal striatal areas strongly affected by dopamine depletion in early PD.

Age Effects in Adaptive Criterion Learning

OBJECTIVE

Although prior work has examined age-related changes to criterion placement and flexibility, no study tested these constructs through a paradigm that employs adaptive feedback to encourage specific criterion changes. The goal of this study was to assess age differences in how young and older adults adapt and shift criteria in recognition memory decisions based on trial-by-trial feedback.

METHOD

Young and older adults completed an adaptive criterion learning paradigm. Over 3 study/test cycles, a biased feedback technique at test encouraged more liberal or strict responding by false-positive feedback toward false alarms or misses.

RESULTS

Older adults were more conservative than young, even when feedback first encouraged a liberal response bias, and older adults adaptively placed criteria in response to biased feedback, much like young adults. After first being encouraged to respond conservatively, older adults shifted criteria less than young when feedback encouraged more lenient responding.

DISCUSSION

These findings evidence labile adaptive criteria placement and criteria shifting with age. However, age-related tendencies toward conservative response biases may limit the extent to which criteria can be shifted in a lenient direction.

Implicit perceptual-motor skill learning in mild cognitive impairment and Parkinson's disease

OBJECTIVE

Implicit skill learning is hypothesized to depend on nondeclarative memory that operates independent of the medial temporal lobe (MTL) memory system and instead depends on cortico striatal circuits between the basal ganglia and cortical areas supporting motor function and planning. Research with the Serial Reaction Time (SRT) task suggests that patients with memory disorders due to MTL damage exhibit normal implicit sequence learning. However, reports of intact learning rely on observations of no group differences, leading to speculation as to whether implicit sequence learning is fully intact in these patients. Patients with Parkinson's disease (PD) often exhibit impaired sequence learning, but this impairment is not universally observed.

METHOD

Implicit perceptual-motor sequence learning was examined using the Serial Interception Sequence Learning (SISL) task in patients with amnestic Mild Cognitive Impairment (MCI; n = 11) and patients with PD (n = 15). Sequence learning in SISL is resistant to explicit learning and individually adapted task difficulty controls for baseline performance differences.

RESULTS

Patients with MCI exhibited robust sequence learning, equivalent to healthy older adults (n = 20), supporting the hypothesis that the MTL does not contribute to learning in this task. In contrast, the majority of patients with PD exhibited no sequence-specific learning in spite of matched overall task performance. Two patients with PD exhibited performance indicative of an explicit compensatory strategy suggesting that impaired implicit learning may lead to greater reliance on explicit memory in some individuals.

CONCLUSION

The differences in learning between patient groups provides strong evidence in favor of implicit sequence learning depending solely on intact basal ganglia function with no contribution from the MTL memory system.

Frontostriatal and mediotemporal lobe contributions to implicit higher-order spatial sequence learning declines in aging and Parkinson's disease

Sequence learning depends on the striatal system, but recent findings also implicate the mediotemporal lobe (MTL) system. Schendan, Searl, Melrose, and Stern (2003) found higher-order associative, learning-related activation in the striatum, dorsolateral prefrontal cortex, and the MTL during the early acquisition phase of both implicit and explicit variants of a serial response time task. This functional MRI (fMRI) study capitalized on this task to determine how changes in MTL function observed in aging and compromised frontostriatal function characteristic of patients with Parkinson's disease (PD) impacts sequence learning and memory under implicit instructions. Brain activity was compared between "sequence" and "random" conditions in 12 nondemented patients with PD and education- and gender-matched healthy control participants of whom 12 were age matched (MC) and 14 were younger (YC). Behaviorally, sequence-specific learning of higher-order associations was reduced with aging and changed further with PD and resulted primarily in implicit knowledge in the older participants. fMRI revealed reduced intensity and extent of sequence learning-related activation in older relative to younger people in frontostriatal circuits and the MTL. This was because signal was greater for the sequence than random condition in younger people, whereas older people, especially those with PD, showed the opposite pattern. Both older groups also showed increased activation to the task itself relative to baseline fixation. In addition, right MTL showed hypoactivation and left MTL hyperactivation in PD relative to the MC group. The results suggest changes in frontostriatal and MTL activity occur during aging that affect task-related activity and the initial acquisition phase of implicit higher-order sequence learning. In addition, the results suggest that Parkinson's disease adversely affects processes in the MTL including sequence learning and memory.

Skill memory escaping from distraction by sleep--evidence from dual-task performance

BACKGROUND

Sleep facilitates off-line consolidation of memories, as shown for learning of motor skills in the absence of concomitant distractors. We often perform complex tasks focusing our attention mostly on one single part of them. However, we are equally able to skillfully perform other concurrent tasks. One may even improve performance on disregarded parts of complex tasks, which were learned implicitly. In the present study we investigated the role of sleep in the off-line consolidation of procedural skills when attention is diverted from the procedural task because of interference from a concurrent task.

METHODOLOGY/PRINCIPAL FINDINGS

We used a dual-task paradigm containing (i) procedural serial reaction time task (SRTT), which was labeled as subordinate and unimportant and (ii) declarative word-pair association task (WPAT), performed concomitantly. The WPAT served as a masked distractor to SRTT and was strongly reinforced by the instructions. One experimental and three control groups were tested. The experimental group was re-tested after two nights of sleep (sleep group, SG). The first control group had sleep deprivation on the first post-learning night (nighttime-awake group, NA), the second control group was tested in the morning and then re-tested after 12-hours (daytime-awake group, DA); the third one had the same assignments as DA but with a subsequent, instead of a concomitant, WPAT (daytime-awake-subsequent-WPAT group, DAs). We found SRTT performance gains in SG but not in NA and DA groups. Furthermore, SG reached similar learning gains in SRTT as the DAs group, which gained in SRTT performance because of post-training interference from the declarative task.

CONCLUSIONS/SIGNIFICANCE

The results demonstrate that sleep allows off-line consolidation, which is resistant to deteriorating effects of a reinforced distractor on the implicit procedural learning and allowing for gains which are consistent with those produced when inhibited declarative memories of SRTT do not compete with procedural ones.

Dissociation between the procedural learning of letter names and motor sequences in developmental dyslexia

Motor sequence learning has been studied extensively in Developmental dyslexia (DD). The purpose of the present research was to examine procedural learning of letter names and motor sequences in individuals with DD and control groups. Both groups completed the Serial Search Task which enabled the assessment of learning of letter names and motor sequences independently of each other. Control participants learned both the letter names as well as the motor sequence. In contrast, individuals with DD were impaired in learning of the letter names sequence and showed a reliable transfer of the motor sequence. Previous studies proved that motor sequence learning is impaired in DD. The present study demonstrated that this deficit is more pronounced when the task to be learned involves linguistic units. This result implies that the procedural learning system of language is more deficient than the motor procedural learning system in individuals with DD. The dissociation between motor and letter names sequence learning in those with DD also implies that the systems underlying these two tasks are separable.

Spatial and nonspatial implicit motor learning in Korsakoff's amnesia: evidence for selective deficits

Patients with amnesia have deficits in declarative memory but intact memory for motor and perceptual skills, which suggests that explicit memory and implicit memory are distinct. However, the evidence that implicit motor learning is intact in amnesic patients is contradictory. This study investigated implicit sequence learning in amnesic patients with Korsakoff's syndrome (N = 20) and matched controls (N = 14), using the classical Serial Reaction Time Task and a newly developed Pattern Learning Task in which the planning and execution of the responses are more spatially demanding. Results showed that implicit motor learning occurred in both groups of participants; however, on the Pattern Learning Task, the percentage of errors did not increase in the Korsakoff group in the random test phase, which is indicative of less implicit learning. Thus, our findings show that the performance of patients with Korsakoff's syndrome is compromised on an implicit learning task with a strong spatial response component.

Is human information processing conscious?

Investigations of the function of consciousness in human information processing have focused mainly on two questions: (1) Where does consciousness enter into the information processing sequence, and (2) how does conscious processing differ from preconscious and unconscious processing? Input analysis is thought to be initially “preconscious” and “pre-attentive” - fast, involuntary, and automatic. This is followed by “conscious,” “focal-attentive” analysis, which is relatively slow, voluntary, and flexible. It is thought that simple, familiar stimuli can be identified preconsciously, but conscious processing is needed to identify complex, novel stimuli. Conscious processing has also been thought to be necessary for choice, learning and memory, and the organization of complex, novel responses, particularly those requiring planning, reflection, or creativity.

The present target article reviews evidence that consciousness performs none of these functions. Consciousness nearly alwaysresultsfrom focal-attentive processing (as a form of output) but does not itselfenter intothis or any other form of human information processing. This suggests that the term “conscious process” needs reexamination. Consciousnessappearsto be necessary in a variety of tasks because they require focal-attentive processing; if consciousness is absent, focal-attentive processing is absent. From afirst-person perspective, however, conscious statesarecausally effective. First-person accounts arecomplementaryto third-person accounts. Although they can be translated into third-person accounts, they cannot be reduced to them.