Success modulates consolidation of a visuomotor adaptation task

Consolidation is a time-dependent process that is responsible for the storage of information in long-term memory. As such, it plays a crucial role in motor learning. Prior research suggests that some consolidation processes are triggered only when the learner experiences some success during practice. In the present study, we tested whether consolidation processes depend on the objective performance of the learner or on the learner's subjective evaluation of his or her own performance (i.e., how successful the learner believes he or she is). Four groups of participants performed 2 sessions of a visuomotor adaptation task for which they had to learn a new internal model of limb kinematics; these sessions were either 5 min or 24 hr apart. The task was identical for all participants, but each group was given a difficult or an easy objective that affected the participants' evaluation of their own performance during the initial practice session. All groups adapted their movements similarly to the rotation of the visual feedback during the first session. However, when retested the following day, participants who had a 24-hr rest interval and had initially experienced success performed significantly better than those who did not feel successful or who were given a 5-min rest interval. Our results indicate that a certain level of subjective success must be experienced to trigger certain consolidation processes.     

Experience-dependent alterations in conscious resting state activity following perceptuomotor learning

In monkeys and rats, neural activity patterns during learning are reactivated during subsequent periods of rest or sleep. According to the reactivation–consolidation account, this process underlies the consolidation of memories. Brain imaging studies have extended these findings to humans during sleep, but not yet, during rest. Here, we show that learning-related reactivation also occurs in humans during rest. During functional MRI-scanning, participants trained on a perceptuomotor task flanked by rest periods. During training, we found robust activity in the superior parietal cortex. During post-training rest, this same area reactivated. We also found a link between parietal reactivation and learning. Activity in superior parietal cortex was associated with learning during training, and a control group that did not train on the perceptuomotor task did not show any difference between the pre- and post-training rest blocks in this region. These findings indicate that, during rest, reactivation also occurs in humans. This process may contribute to consolidation of perceptuomotor memories.     

Striatal activity in concept learning

Striatal learning systems have been implicated in learning relationships between visual stimuli and outcomes. In the present study, the activity of the striatum during visual concept learning in humans was examined by using functional magnetic resonance imaging (fMRI). Participants performed three concept-learning tasks and a baseline task. The participants were trained to criterion before fMRI scanning on two tasks, verbal and implicit. In the verbal task, classification could be performed on the basis of a simple verbal rule, but in the implicit task, there was no simple verbal rule. The novel-implicit learning task, in which an implicit structure was used, was not encountered by the participants before scanning. Across all three concept-learning tasks, there was significant activation in the striatum, in comparison with the baseline task. The striatum was recruited similarly in classification when the participants had different levels of expertise (novel-implicit vs. verbal and implicit) and were able to verbalize their learning to different degrees (verbal vs. implicit and novel-implicit). There was left lateral occipital activation when learning was implicit (implicit and novel-implicit), but not when learning was easily verbalized (verbal).     

睡眠对知觉与动作序列内隐学习离线巩固效应的影响

离线阶段发生的学习被称为离线巩固, 即在最初获得知识之后, 即使没有额外的练习, 其记忆痕迹也会保持稳定或提高。有研究初步探究了睡眠对知觉和动作序列内隐学习离线巩固的影响, 然而, 这些研究未能实现知觉序列与动作序列的完全分离, 序列类型是否调节睡眠对内隐序列学习离线巩固的影响仍需进一步探讨。此外, 既往外显学习的研究发现相对于简单的序列, 复杂的序列更容易从睡眠中获益, 表现出基于睡眠的离线巩固效应。睡眠对知觉序列与动作序列内隐学习离线巩固的影响是否会受到序列复杂程度的调节尚不明确。为此, 本研究在完全分离知觉序列和动作序列的情况下, 通过3个实验操纵序列的长度及结构, 设置3种不同复杂程度的序列规则, 考察了这一问题。结果发现, 对于动作序列, 序列规则复杂程度较低时, 无论是否经过睡眠都会发生离线巩固效应, 而当动作序列规则较为复杂时, 只有经历睡眠才会引起离线巩固效应; 对于知觉序列, 无论何种难易程度的规则, 均未发生离线巩固效应。上述结果表明内隐序列知识基于睡眠的离线巩固会受到序列类型及序列复杂程度的调节, 这为内隐学习的离线巩固争论提供了新的视角。     

Perceived racism and cardiovascular reactivity and recovery to personally relevant stress.

This study evaluated cardiovascular responses (CVR) to an active speech task with blatantly discriminatory (BRC) versus neutral (NRC) stimuli and an anger recall task in a sample of Black men (N = 73; age 18 to 47). Diastolic blood pressure scores were higher for NRC versus BRC stimuli during anger recall (p = .05). Moreover, persons in the NRC group who perceived high levels of racism (vs. no racism or BRC group) during active speech showed larger increases in blood pressure across postspeech rest, anger recall, and subsequent rest (p = .03). The notable elevation in CVR in response to an ambiguous event extends current models of racism suggesting that subtle racism is a psychosocial stressor that erodes health through chronically elevated CVR.     

Rest improves performance,nature improves happiness: Assessment of break periods on the abbreviated vigilance task

The abbreviated vigilance task can quickly generate vigilance decrements, which has been argued is due to depletion of cognitive resources needed to sustain performance. Researchers suggest inclusion of rest breaks within vigilance tasks improve overall performance (Helton & Russell, 2015; Ross, Russell, & Helton, 2014), while different types of breaks demonstrate different effects. Some literature suggests exposure to natural movements/stimuli helps restore attention (Herzog, Black, Fountaine, & Knotts, 1997; Kaplan, 1995). Participants were randomly assigned to one experimental condition: dog video breaks, robot video breaks, countdown breaks or continuous vigilance. We assessed task performance and subjective reports of stress/workload. The continuous group displayed worst performance, suggesting breaks help restore attention. The dog videos did not affect performance, however, decreased reports of distress. These results support the importance of rest breaks and acknowledge the benefit of natural stimuli for promoting wellbeing/stress relief, overall suggesting performance and wellbeing may be independent, which warrants future studies.     

Interaction between stimulus-driven orienting and top-down modulation in attentional capture

The present study investigated whether visual and kinesthetic stimuli are stored as multisensory or modality-specific representations in unimodal and crossmodal working memory tasks. To this end, angle-shaped movement trajectories were presented to 16 subjects in delayed matching-to-sample tasks either visually or kinesthetically during encoding and recognition. During the retention interval, a secondary visual or kinesthetic interference task was inserted either immediately or with a delay after encoding. The modality of the interference task interacted significantly with the encoding modality. After visual encoding, memory was more impaired by a visual than by a kinesthetic secondary task, while after kinesthetic encoding the pattern was reversed. The time when the secondary task had to be performed interacted with the encoding modality as well. For visual encoding, memory was more impaired, when the secondary task had to be performed at the beginning of the retention interval. In contrast, memory after kinesthetic encoding was more affected, when the secondary task was introduced later in the retention interval. The findings suggest that working memory traces are maintained in a modality-specific format characterized by distinct consolidation processes that take longer after kinesthetic than after visual encoding.     

Decision-making and associative color learning in harnessed bumblebees (Bombus impatiens)

In honeybees, the conditioning of the proboscis extension response (PER) has provided a powerful tool to explore the mechanisms underlying olfactory learning and memory. Unfortunately, PER conditioning does not work well for visual stimuli in intact honeybees, and performance is improved only after antennal amputation, thus limiting the analysis of visual learning and multimodal integration. Here, we study visual learning using the PER protocol in harnessed bumblebees, which exhibit high levels of odor learning under restrained conditions. We trained bumblebees in a differential task in which two colors differed in their rewarding values. We recorded learning performance as well as response latency and accuracy. Bumblebees rapidly learned the task and discriminated the colors within the first two trials. However, performance varied between combinations of colors and was higher when blue or violet was associated with a high reward. Overall, accuracy and speed were negatively associated, but both components increased during acquisition. We conclude that PER conditioning is a good tool to study visual learning, using Bombus impatiens as a model, opening new possibilities to analyze the proximate mechanisms of visual learning and memory, as well as the process of multimodal integration and decision-making.     

A latent consolidation phase in auditory identification learning: time in the awake state is sufficient

Large gains in performance, evolving hours after practice has terminated, were reported in a number of visual and some motor learning tasks, as well as recently in an auditory nonverbal discrimination task. It was proposed that these gains reflect a latent phase of experience-triggered memory consolidation in human skill learning. It is not clear, however, whether and when delayed gains in performance evolve following training in an auditory verbal identification task. Here we show that normal-hearing young adults trained to identify consonant-vowel stimuli in increasing levels of background noise showed significant, robust, delayed gains in performance that became effective not earlier than 4 h post-training, with most participants improving at more than 6 h post-training. These gains were retained for over 6 mo. Moreover, although it has been recently argued that time including sleep, rather than time per se, is necessary for the evolution of delayed gains in human perceptual learning, our results show that 12 h post-training in the waking state were as effective as 12 h, including no less than 6 h night's sleep. Altogether, the results indicate, for the first time, the existence of a latent, hours-long, consolidation phase in a human auditory verbal learning task, which occurs even during the awake state.     

Offline Improvement during Motor Sequence Learning Is Not Restricted to Developing Motor Chunks

Robust offline performance gains, beyond those that would be anticipated by being exposed to additional physical practice, have been reported during procedural learning and have been attributed to enhancement consolidation, a process by which memory is transformed in such a way that it is not only more resistant to forgetting but may also involve a reorganization of information that supports superior task execution. The authors assessed the impact of increasing within-session practice extent on the emergence of offline performance gains. Practice-dependent improvements occurred across 12 and 24 30-s practice trials of a 5-element motor sequencing task. Offline improvements were observed following both 12 and 24 trials. The improvement following 12 trials was associated with the formation of motor chunks important for establishing movement sequence structure. In contrast, the offline improvement after 24 trials was not related to further changes in movement structure beyond those that had emerged during practice. These data suggest that additional memory operations, beyond those needed to amalgamate subsequences of the SRT task, are susceptible to enhancement consolidation.     

A cross‐syndrome study of the differential effects of sleep on declarative memory consolidation in children with neurodevelopmental disorders

Sleep plays an active role in memory consolidation. Because children with Down syndrome (DS) and Williams syndrome (WS) experience significant problems with sleep and also with learning, we predicted that sleep‐dependent memory consolidation would be impaired in these children when compared to typically developing (TD) children. This is the first study to provide a cross‐syndrome comparison of sleep‐dependent learning in school‐aged children. Children with DS (n = 20) and WS (n = 22) and TD children (n = 33) were trained on the novel Animal Names task where they were taught pseudo‐words as the personal names of ten farm and domestic animals, e.g. Basco the cat, with the aid of animal picture flashcards. They were retested following counterbalanced retention intervals of wake and sleep. Overall, TD children remembered significantly more words than both the DS and WS groups. In addition, their performance improved following night‐time sleep, whereas performance over the wake retention interval remained stable, indicating an active role of sleep for memory consolidation. Task performance of children with DS did not significantly change following wake or sleep periods. However, children with DS who were initially trained in the morning continued to improve on the task at the following retests, so that performance on the final test was greater for children who had initially trained in the morning than those who trained in the evening. Children with WS improved on the task between training and the first retest, regardless of whether sleep or wake occurred during the retention interval. This suggests time‐dependent rather than sleep‐dependent learning in children with WS, or tiredness at the end of the first session and better performance once refreshed at the start of the second session, irrespective of the time of day. Contrary to expectations, sleep‐dependent learning was not related to baseline level of performance. The findings have significant implications for educational strategies, and suggest that children with DS should be taught more important or difficult information in the morning when they are better able to learn, whilst children with WS should be allowed a time delay between learning phases to allow for time‐dependent memory consolidation, and frequent breaks from learning so that they are refreshed and able to perform at their best.     

Targeted Memory Reactivation During Sleep,But Not Wake,Enhances Sensorimotor Skill Performance: A Pilot Study

The benefits of sleep on memory consolidation have been enhanced for declarative and motor sequence learning through replaying classically conditioned auditory stimuli during sleep, known as targeted memory reactivation (TMR). However, it is unknown if TMR can influence performance of a sensorimotor skill, in the absence of the cognitive requirements of sequence learning. Here, young adults performed a nondominant arm throwing task separated by a full night of sleep or a full day of wake, with half of all participants receiving TMR between sessions. Participants who received TMR during sleep demonstrated enhanced sensorimotor performance relative to all other groups. In conclusion, this pilot study indicates that it is feasible to influence sensorimotor skill performance through TMR during sleep and may serve as a future adjunct to physical rehabilitation. Future studies will aim to confirm the present results with a larger sample size as well as investigate the effects of TMR during sleep on older adults both with and without a history of stroke.     

‘Sleep-dependent’ memory consolidation? Brief periods of post-training rest and sleep provide an equivalent benefit for both declarative and procedural memory

Sleep following learning facilitates the consolidation of memories. This effect has often been attributed to sleep-specific factors, such as the presence of sleep spindles or slow waves in the electroencephalogram (EEG). However, recent studies suggest that simply resting quietly while awake could confer a similar memory benefit. In the current study, we examined the effects of sleep, quiet rest, and active wakefulness on the consolidation of declarative and procedural memory. We hypothesized that sleep and eyes-closed quiet rest would both benefit memory compared with a period of active wakefulness. After completing a declarative and a procedural memory task, participants began a 30-min retention period with PSG (polysomnographic) monitoring, in which they either slept (n = 24), quietly rested with their eyes closed (n = 22), or completed a distractor task (n = 29). Following the retention period, participants were again tested on their memory for the two learning tasks. As hypothesized, sleep and quiet rest both led to better performance on the declarative and procedural memory tasks than did the distractor task. Moreover, the performance advantages conferred by rest were indistinguishable from those of sleep. These data suggest that neurobiology specific to sleep might not be necessary to induce the consolidation of memory, at least across very short retention intervals. Instead, offline memory consolidation may function opportunistically, occurring during either sleep or stimulus-free rest, provided a favorable neurobiological milieu and sufficient reduction of new encoding.

Of the myriad new experiences we encode each day, only a fraction are remembered over the long-term. The formation of long-term memory is crucial for optimal functioning in our everyday lives and for building knowledge across days, weeks, and years. Such enduring memories require not only the effective encoding of new information, but also a set of postencoding processes, termed “consolidation,” that function to stabilize and transform new memory traces over time (McGaugh 2000; Frankland and Bontempi 2005; Genzel and Wixted 2017).Consolidation of memory is better supported by some states of consciousness than others. For example, sleep has long been known to optimize memory consolidation, purportedly due to specific neurobiology that actively promotes the consolidation process (Diekelmann and Born 2010). Numerous studies have demonstrated that sleep facilitates the consolidation of both declarative and procedural memories. Slow oscillations (Huber et al. 2004; Marshall et al. 2006) and slow wave sleep (SWS) (Alger et al. 2012; Diekelmann et al. 2012) are thought to especially benefit hippocampus-dependent, declarative memory. Meanwhile, various forms of implicit and procedural memory have been linked to rapid eye movement (REM) sleep (Plihal and Born 1997; Mednick et al. 2009) or non-REM stage 2 (N2) sleep (Walker et al. 2002; Tucker and Fishbein 2009).A potential mechanism of offline memory consolidation during sleep is memory “reactivation,” in which patterns of neural activity in the hippocampus and cortex associated with awake experience are reiterated after learning. For example, when rats sleep after being trained on a spatial learning task, hippocampal “place cells” fire again in the same order as when the animals were being trained on the task during wake (Lee and Wilson 2002; Ji and Wilson 2007). Such neural reactivation not only occurs in the hippocampus, but also concurrently in a variety of cortical areas (Ji and Wilson 2007; Peyrache et al. 2009; Kaefer et al. 2020). The recent advent of optogenetics has allowed experimental investigation of memory reactivation in animal models. Experimentally disrupting the hippocampal ripple oscillations during which reactivation occurs impairs memory (Girardeau et al. 2009; Ego-Stengel and Wilson 2010). Conversely, selectively reactivating neural ensembles related to a particular memory appears to induce consolidation, particularly when this manipulation is applied during sleep or light amnesia (de Sousa et al. 2019).But is sleep the only brain state that facilitates memory consolidation in this way? It has been argued that sleep-specific neurobiology, including sleep slow waves (Alger et al. 2012), sleep spindles (Wamsley et al. 2012; Mednick et al. 2013; Laventure et al. 2016), and/or REM sleep (Karni et al. 1994; Stickgold et al. 2000; McDevitt et al. 2015; Boyce et al. 2016), is required for offline memory reactivation and consolidation to occur, or at least to occur optimally. However, a growing body of literature indicates that stimulus-free waking rest can similarly facilitate consolidation (Wamsley 2019). In two influential experiments, Dewar et al. (2012) demonstrated that compared with participants who completed a nonverbal distractor task, those who rested quietly with their eyes closed in a darkened room for 10 min after learning showed better memory for short stories encoded prior to the retention period. The rest group significantly outperformed the wake group after 15 min, 30 min, and 7 d (experiment 1), even in the absence of retrieval practice during the 7-d period (experiment 2).This effect of post-training rest on memory retention has been reported in an increasing number of papers across the last decade (Gottselig et al. 2004; Mercer 2015; Martini et al. 2018; Wamsley 2019; Martini and Sachse 2020). Brokaw et al. (2016) replicated the behavioral observations of Dewar et al. (2012) and showed that this memory benefit was associated with EEG slow oscillation activity, which is thought to facilitate hippocampal–cortical communication and concomitant memory consolidation during sleep (Marshall et al. 2006; Mölle and Born 2011). A recent study by Sattari et al. (2019) also linked improved memory performance to waking EEG slow oscillations, suggesting that the memory-enhancing effects of rest and sleep may share a common mechanism.Of course, it has been known for decades that at least some consolidation must occur during wakefulness. Local, cellular level consolidation begins to stabilize memory immediately following encoding (Bailey and Kandel 2008; Redondo and Morris 2011), enabling us to recall the events of the previous hours in the absence of intervening sleep. The novel suggestion of these more recent studies is that consolidation does not occur equivalently during all types of wakefulness (Dewar et al. 2012; Brokaw et al. 2016). Instead, stimulus-free rest periods appear to have features that are especially suited to facilitate memory.Reduced sensory processing during eyes-closed rest may be one factor accounting for the memory facilitation effect. However, even internally generated stimuli can also function to block consolidation, as demonstrated by the fact that mental tasks such as retrieval of autobiographical memory and focused meditation are also associated with a reduction in rest''s memory benefit (Craig et al. 2014; Collins and Wamsley 2020). Similarly, we reported in two previous studies that individuals with a high propensity for daydreaming show less memory benefit following a period of rest, presumably because intense internally generated mental activity inhibits consolidation (Humiston et al. 2019; Wamsley and Summer 2020).Together, these observations suggest that consolidation occurs during wakefulness when sensory processing is reduced, when low-frequency EEG oscillations are increased, and when internally generated cognition is at a minimum. Therefore, consolidation may not depend on neural mechanisms specific to sleep, instead opportunistically occurring across multiple states of consciousness whenever the correct conditions are met (Mednick et al. 2011). According to the opportunistic theory of memory consolidation, the processes of encoding and consolidation are mutually exclusive: During any brain state in which we are not currently encoding new information, existing memories consolidate as the neural milieu becomes favorable (Mednick et al. 2011; Wamsley 2019). Unoccupied quiet rest, like sleep, is a state in which the encoding of new stimuli is reduced. In addition, quiet rest and sleep also share a number of neurobiological features that are thought to actively promote memory consolidation, including overall slower EEG in comparison with active wakefulness, increased activation of default-mode network brain structures (Buckner and Vincent 2007), and decreased levels of acetylcholine in the brain (Hasselmo and McGaughy 2004). Additionally, the cellular-level offline reactivation of memory occurs not only during sleep, but also during quiet rest (Foster and Wilson 2006; Karlsson and Frank 2009; Carr et al. 2011; Staresina et al. 2013). At the same time, it must be noted that eyes-closed rest does not replicate all aspects of sleep neurobiology proposed to facilitate memory. For example, sleep spindle oscillations and sleep-specific neurohormonal changes are not present during eyes-closed rest.While sleep and rest both benefit memory in comparison with active wakefulness, it is not known whether they do so equivalently. With few studies directly comparing the size of rest''s memory benefit with that of sleep, it remains possible that sleep provides some benefit above and beyond that conferred by waking rest. The limited number of prior studies in this area have shown mixed results. As opposed to the type of truly task-free condition used in the waking rest studies reviewed above, most experiments comparing active wakefulness, rest, and sleep have used a “rest” condition in which participants are asked to complete an undemanding activity such as listening to music or books on tape. This approach sacrifices complete sensory restriction in return for allowing rest condition participants to maintain wakefulness for longer periods of time. For example, Mednick and colleagues have used quiet rest conditions in which participants listen to music or audiobooks, finding that this form of quiet rest facilitates memory equivalently to sleep for some forms of learning (Mednick et al. 2009; Sattari et al. 2019), but not for others (Mednick et al. 2002; McDevitt et al. 2014). Keeping rest participants awake via verbal instructions to alternately open and close their eyes, Simor et al. (2018) found no effect of post-training rest or sleep on performance of a serial reaction time task, relative to an active wake control. While these observations might indicate that only selected forms of memory can be consolidated during resting wakefulness, it is possible that the encoding of meaningful auditory stimuli during these rest conditions prevents optimal consolidation.Only a few prior studies have compared the memory effects of sleep with those of an equivalent duration of eyes-closed, entirely task-free rest. For example, Gottselig et al. (2004) successfully compared the effects of sleep, quiet rest, and active wakefulness on memory consolidation using a carefully controlled rest condition without any stimuli presented to the participants. Using a statistical auditory sequence learning task, they reported that both sleep and rest equivalently facilitated retention. In contrast, using a declarative memory task, Piosczyk et al. (2013) found that neither quiet rest nor sleep improved memory more than active wakefulness. A recent study from our own laboratory directly compared sleep, rest, and active wakefulness using declarative and procedural tasks commonly used in studies of sleep and memory (Tucker et al. 2020). However, high rates of attrition (due to rest participants inadvertently falling asleep and sleep participants failing to obtain sleep) prevented a robust test of our hypothesis that sleep and quiet rest would equivalently benefit memory, relative to active wakefulness.The goal of the current study was to directly compare the memory benefit of a brief nap (<30 min) with that of an equivalent duration of task-free quiet rest. We hypothesized that a brief period of sleep and quiet rest would have an equivalent effect on the consolidation of both declarative and procedural memories, significantly boosting memory retention compared with an equivalent duration of active wakefulness. Following our previous work, we expected that memory retention across sleep and quiet rest would be associated with slow oscillation EEG power in the <1-Hz range, but that participants with high trait daydreaming propensity would show less improvement across quiet rest.     

Mask similarity impacts short-term consolidation in visual working memory

Short-term consolidation is the process by which perceptual representations are stabilized into visual working memory (VWM) representations to prevent interference from subsequent visual input. The present article reports how short-term consolidation is affected by the similarity of the subsequent visual items (i.e., visual masks) by using a color change detection task. In the task, masks were either similar or dissimilar to the memory stimuli and were displayed at varying intervals following the memory array. The similar masks were made up of the same colored squares as the to-be-remembered stimuli, whereas the dissimilar masks were black-and-white grids. The results showed more interference from similar than from dissimilar masks: Similar masks required more time to consolidate and elicited lower overall performance than did dissimilar masks. These results suggest that a simple overwriting process cannot fully account for the impact of mask type on short-term consolidation performance and that other cognitive mechanisms are involved (e.g., controlled attention).     

The effects of ageing and cognitive impairment on on‐line and off‐line motor learning

Skilled performance is a collective function of practice‐related experiences (online learning) and post‐practice memory consolidation during sleep (offline learning). This study examines the effects of ageing and cognitive impairment on the on‐ and offline learning of a point‐to‐point arm movement. In a 3‐day experiment, older adults (cognitively normal or impaired) and young adults (YAs) were randomly assigned to practice or no‐practice conditions. Changes in the dependent measures of movement time and timing error were analysed within and between conditions across days. The findings suggest that both age and cognitive function affect skill learning. YAs improved performance via both on‐ and offline learning whereas older adults with normal cognitive capacities appeared to learn the movement skill primarily in an online mode. Cognitive impairments were found to hinder both types of skill learning. Implications for motor skill acquisition and rehabilitation are briefly discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Tiger salamanders’ (<Emphasis Type="Italic">Ambystoma tigrinum</Emphasis>) response learning and usage of visual cues

We explored tiger salamanders’ (Ambystoma tigrinum) learning to execute a response within a maze as proximal visual cue conditions varied. In Experiment 1, salamanders learned to turn consistently in a T-maze for reinforcement before the maze was rotated. All learned the initial task and executed the trained turn during test, suggesting that they learned to demonstrate the reinforced response during training and continued to perform it during test. In a second experiment utilizing a similar procedure, two visual cues were placed consistently at the maze junction. Salamanders were reinforced for turning towards one cue. Cue placement was reversed during test. All learned the initial task, but executed the trained turn rather than turning towards the visual cue during test, evidencing response learning. In Experiment 3, we investigated whether a compound visual cue could control salamanders’ behaviour when it was the only cue predictive of reinforcement in a cross-maze by varying start position and cue placement. All learned to turn in the direction indicated by the compound visual cue, indicating that visual cues can come to control their behaviour. Following training, testing revealed that salamanders attended to stimuli foreground over background features. Overall, these results suggest that salamanders learn to execute responses over learning to use visual cues but can use visual cues if required. Our success with this paradigm offers the potential in future studies to explore salamanders’ cognition further, as well as to shed light on how features of the tiger salamanders’ life history (e.g. hibernation and metamorphosis) impact cognition.     

Influence of short-term memory codes on visual image processing: evidence from image transformation tasks.

Three experiments showed that phonological recording of visual stimuli in short-term memory (STM) affects coding in long-term memory (LTM) and therefore performance on tasks involving generation and manipulation of visual images of the stimuli. An image transformation task was devised. It consists of mentally subtracting a part of an image to discover in the remainder another object. In Experiment 1, Ss were required to learn a set of easily nameable visual stimuli and then perform the subtraction task on images retrieved from LTM. Performance was significantly better when initial learning was accompanied by articulatory suppression (AS). Experiment 2 confirmed that AS had no effect when the task was performed on an image of a just-presented stimulus. In Experiment 3, the nameability of the stimuli was manipulated. The results replicated the effect of AS for items that were easy to name but showed no effect of AS for stimuli that were difficult to name.     

Sequence learning at optimal stimulus-response mapping: evidence from a serial reaction time task

We propose a new version of the serial reaction time (SRT) task in which participants merely looked at the target instead of responding manually. As response locations were identical to target locations, stimulus-response compatibility was maximal in this task. We demonstrated that saccadic response times decreased during training and increased again when a new sequence was presented. It is unlikely that this effect was caused by stimulus-response (S-R) learning because bonds between (visual) stimuli and (oculomotor) responses were already well established before the experiment started. Thus, the finding shows that the building of S-R bonds is not essential for learning in the SRT task.     

The acquisition of morphological knowledge investigated through artificial language learning

Affix knowledge plays an important role in visual word recognition, but little is known about how it is acquired. The authors present a new method of investigating the acquisition of affixes in which participants are trained on novel affixes presented in novel word contexts (e.g., sleepnept). Experiment 1 investigated the role of semantic information on affix acquisition by comparing a form-learning condition with a condition in which participants also received definitions for each novel word. Experiment 2 investigated the role of long-term consolidation on affix acquisition by comparing knowledge of learned affixes two days and nearly two months after training. Results demonstrated that episodic knowledge of affixes can be acquired shortly after a single training session using either form or semantic learning, but suggested that the development of lexicalized representations of affixes requires the provision of semantic information during learning as well as a substantial period of offline consolidation.