Towards a whole brain model of Perceptual Learning

Fast perceptual learning induces location-specific facilitation and suppression at early stages of visual cortical processing

Tens of minutes of training can significantly improve visual discriminability of human adults, and this fast perceptual learning (PL) effect is usually specific to the trained location, with little transfer to untrained locations. Although location specificity is generally considered as a hallmark of visual PL, it remains unclear whether it involves both facilitation of trained locations and suppression of untrained locations. Here we developed a novel experimental design to investigate the cognitive neural mechanism of location specificity of fast PL. Specifically, we manipulated attentional settings and recorded event-related potentials (ERPs) in both the training and tests. To get reliable location-specific PL effects on early ERPs, we adopted a new approach involving analysis of contralateral-minus-ipsilateral P1 (P1c-i). ERP results showed that tens of minutes of training not only increased the late P1c-i (~100-120 ms) evoked by targets at the trained location, but also decreased the early P1c-i (~75-95 ms) evoked by distractors at the untrained location, both of which were location specific. Moreover, comparison between the pretest and posttest revealed that the suppression effect of early P1c-i preserved even when the untrained location became target location, whereas the facilitation effect of late P1c-i appeared only when the trained location remained actively attended. These findings provide the first evidence that fast PL induces both location-specific facilitation and location-specific suppression at early stages of visual cortical processing. We speculate that while the facilitation effect indicates more efficient allocation of voluntary attention to the trained location induced by fast PL, the suppression effect may reflect learning-associated involuntary suppression of visual processing at the untrained location. Several confounding factors with regard to the early ERP effects of PL are discussed, and some important issues worth further investigation are proposed.

Dissociable components of visual perceptual learning characterized by non-invasive brain stimulation: Stage 1 Registered Report

Visual perceptual learning (VPL), the training-induced improvement in visual tasks, has long been considered the product of neural plasticity at early and local stages of signal processing. However, recent evidence suggests that multiple networks and mechanisms, including stimulus- and task-specific plasticity, concur in generating VPL. Accordingly, early models of VPL, which characterized learning as being local and mostly involving early sensory areas, such as V1, have been updated to embrace these newfound complexities, acknowledging the involvement on parietal (i.e. intra-parietal sulcus) and frontal (i.e. dorsolateral prefrontal cortex) areas, in aspects concerning decision-making, feedback integration and task structure. However, evidence of multiple brain regions differentially involved in different aspects of learning is thus far mostly correlational, emerging from electrophysiological and neuroimaging techniques. To directly address these multiple components of VPL, we propose to use a causal neuromodulation technique, namely transcranial random noise stimulation, to selectively modulate the activity of different brain regions suggested to be involved in various aspects of learning. Specifically, we will target a region in the occipital cortex, which has been associated with stimulus-specific plasticity, and one in the parietal cortex, which has been associated with task-specific plasticity, in a between-subject design. Measures of transfer of learning to untrained stimuli and tasks will be used to evaluate the role of different regions and test for double dissociations between learning effects and stimulated area, shedding lights on learning mechanisms in the visual system. Evidence of dissociable mechanisms of learning can help refine current models of VPL and may help develop more effective visual training and rehabilitation protocols.

Visual Perceptual Learning of Form-Motion Integration: Exploring the Involved Mechanisms with Transfer Effects and the Equivalent Noise Approach

Background: Visual perceptual learning plays a crucial role in shaping our understanding of how the human brain integrates visual cues to construct coherent perceptual experiences. The visual system is continually challenged to integrate a multitude of visual cues, including form and motion, to create a unified representation of the surrounding visual scene. This process involves both the processing of local signals and their integration into a coherent global percept. Over the past several decades, researchers have explored the mechanisms underlying this integration, focusing on concepts such as internal noise and sampling efficiency, which pertain to local and global processing, respectively. Objectives and Methods: In this study, we investigated the influence of visual perceptual learning on non-directional motion processing using dynamic Glass patterns (GPs) and modified Random-Dot Kinematograms (mRDKs). We also explored the mechanisms of learning transfer to different stimuli and tasks. Specifically, we aimed to assess whether visual perceptual learning based on illusory directional motion, triggered by form and motion cues (dynamic GPs), transfers to stimuli that elicit comparable illusory motion, such as mRDKs. Additionally, we examined whether training on form and motion coherence thresholds improves internal noise filtering and sampling efficiency. Results: Our results revealed significant learning effects on the trained task, enhancing the perception of dynamic GPs. Furthermore, there was a substantial learning transfer to the non-trained stimulus (mRDKs) and partial transfer to a different task. The data also showed differences in coherence thresholds between dynamic GPs and mRDKs, with GPs showing lower coherence thresholds than mRDKs. Finally, an interaction between visual stimulus type and session for sampling efficiency revealed that the effect of training session on participants' performance varied depending on the type of visual stimulus, with dynamic GPs being influenced differently than mRDKs. Conclusion: These findings highlight the complexity of perceptual learning and suggest that the transfer of learning effects may be influenced by the specific characteristics of both the training stimuli and tasks, providing valuable insights for future research in visual processing.

Single neuron responses to perceptual difficulty in the mouse auditory cortex

Perceptual learning leads to improvement in behavioral performance, yet how the brain supports challenging perceptual demands is unknown. We used two photon imaging in the mouse primary auditory cortex during behavior in a Go-NoGo task designed to test perceptual difficulty. Using general linear model analysis, we found a subset of neurons that increased their responses during high perceptual demands. Single neurons increased their responses to both Go and NoGo sounds when mice were engaged in the more difficult perceptual discrimination. This increased responsiveness contributes to enhanced cortical network discriminability for the learned sounds. Under passive listening conditions, the same neurons responded weaker to the more similar sound pairs of the difficult task, and the training protocol by itself induced specific suppression to the learned sounds. Our findings identify how neuronal activity in auditory cortex is modulated during high perceptual demands, which is a fundamental feature associated with perceptual improvement.

Visual perceptual learning is enhanced by training in the illusory far space

Visual objects in the peripersonal space (PPS) are perceived faster than farther ones appearing in the extrapersonal space (EPS). This shows preferential processing for visual stimuli near our body. Such an advantage should favour visual perceptual learning occurring near, as compared with far from observers, but opposite evidence has been recently provided from online testing protocols, showing larger perceptual learning in the far space. Here, we ran two laboratory-based experiments investigating whether visual training in PPS and EPS has different effects. We used the horizontal Ponzo Illusion to create a lateralized depth perspective while participants completed a visual search task in which they reported whether or not a specific target object orientation (e.g., a triangle pointing upwards) was present among distractors. This task was completed before and after a training phase in either the (illusory) near or far space for 1 h. In Experiment 1, the near space was in the left hemispace, whereas in Experiment 2, it was in the right. Results showed that, in both experiments, participants were more accurate after training in the far space, whereas training in the near space led to either improvement in the far space (Experiment 1), or no change (Experiment 2). Moreover, we found a larger visual perceptual learning when stimuli were presented in the left compared with the right hemispace. Differently from visual processing, visual perceptual learning is more effective in the far space. We propose that depth is a key dimension that can be used to improve human visual learning.

Visual perceptual learning is effective in the illusory far but not in the near space

Visual shape discrimination is faster for objects close to the body, in the peripersonal space (PPS), compared with objects far from the body. Visual processing enhancement in PPS occurs also when perceived depth is based on 2D pictorial cues. This advantage has been observed from relatively low-level (detection, size, orientation) to high-level visual features (face processing). While multisensory association also displays proximal advantages, whether PPS influences visual perceptual learning remains unclear. Here, we investigated whether perceptual learning effects vary according to the distance of visual stimuli (near or far) from the observer, illusorily induced by leveraging the Ponzo illusion. Participants performed a visual search task in which they reported whether a specific target object orientation (e.g., triangle pointing downward) was present among distractors. Performance was assessed before and after practicing the visual search task (30 minutes/day for 5 days) at either the close (near group) or far (far group) distance. Results showed that participants that performed the training in the near space did not improve. By contrast, participants that performed the training in the far space showed an improvement in the visual search task in both the far and near spaces. We suggest that such improvement following the far training is due to a greater deployment of attention in the far space, which could make the learning more effective and generalize across spaces.

Feature variability determines specificity and transfer in multiorientation feature detection learning

Historically, in many perceptual learning experiments, only a single stimulus is practiced, and learning is often specific to the trained feature. Our prior work has demonstrated that multi-stimulus learning (e.g., training-plus-exposure procedure) has the potential to achieve generalization. Here, we investigated two important characteristics of multi-stimulus learning, namely, roving and feature variability, and their impacts on multi-stimulus learning and generalization. We adopted a feature detection task in which an oddly oriented target bar differed by 16° from the background bars. The stimulus onset asynchrony threshold between the target and the mask was measured with a staircase procedure. Observers were trained with four target orientation search stimuli, either with a 5° deviation (30°-35°-40°-45°) or with a 45° deviation (30°-75°-120°-165°), and the four reference stimuli were presented in a roving manner. The transfer of learning to the swapped target-background orientations was evaluated after training. We found that multi-stimulus training with a 5° deviation resulted in significant learning improvement, but learning failed to transfer to the swapped target-background orientations. In contrast, training with a 45° deviation slowed learning but produced a significant generalization to swapped orientations. Furthermore, a modified training-plus-exposure procedure, in which observers were trained with four orientation search stimuli with a 5° deviation and simultaneously passively exposed to orientations with high feature variability (45° deviation), led to significant orientation learning generalization. Learning transfer also occurred when the four orientation search stimuli with a 5° deviation were presented in separate blocks. These results help us to specify the condition under which multistimuli learning produces generalization, which holds potential for real-world applications of perceptual learning, such as vision rehabilitation and expert training.

Profiles of visual perceptual learning in feature space

Visual perceptual learning (VPL), experience-induced gains in discriminating visual features, has been studied extensively and intensively for many years, its profile in feature space, however, remains unclear. Here, human subjects were trained to perform either a simple low-level feature (grating orientation) or a complex high-level object (face view) discrimination task over a long-time course. During, immediately after, and one month after training, all results showed that in feature space VPL in grating orientation discrimination was a center-surround profile; VPL in face view discrimination, however, was a monotonic gradient profile. Importantly, these two profiles can be emerged by a deep convolutional neural network with a modified AlexNet consisted of 7 and 12 layers, respectively. Altogether, our study reveals for the first time a feature hierarchy-dependent profile of VPL in feature space, placing a necessary constraint on our understanding of the neural computation of VPL.

Exposure to temporal variability promotes subsequent adaptation to new temporal regularities

Noise is intuitively thought to interfere with perceptual learning; However, human and machine learning studies suggest that, in certain contexts, variability may reduce overfitting and improve generalizability. Whereas previous studies have examined the effects of variability in learned stimuli or tasks, it is hitherto unknown what are the effects of variability in the temporal environment. Here, we examined this question in two groups of adult participants (N = 40) presented with visual targets at either random or fixed temporal routines and then tested on the same type of targets at a new nearly-fixed temporal routine. Findings reveal that participants of the random group performed better and adapted quicker following a change in the timing routine, relative to participants of the fixed group. Corroborated with eye-tracking and computational modeling, these findings suggest that prior exposure to temporal variability promotes the formation of new temporal expectations and enhances generalizability in a dynamic environment. We conclude that noise plays an important role in promoting perceptual learning in the temporal domain: rather than interfering with the formation of temporal expectations, noise enhances them. This counterintuitive effect is hypothesized to be achieved through eliminating overfitting and promoting generalizability.

Empirical validation of QUEST+ in PSE and JND estimations in visual discrimination tasks

One of the most precise methods to establish psychometric functions and estimate threshold and slope parameters is the constant stimuli procedure. The large distribution of predetermined stimulus values presented to observers enables the psychometric functions to be fully developed, but makes this procedure time-consuming. Adaptive procedures enable reliable threshold estimation while reducing the number of trials by concentrating stimulus presentations around observers' supposed threshold. Here, the stimulus value for the next trial depends on observer's responses to the previous trials. One recent improvement of these procedures is to also estimate the slope (related to discrimination sensitivity). The Bayesian QUEST+ procedure (Watson Journal of Vision, 17(3), 10, 2017), a generalization and extension of the QUEST procedure, includes this refinement. Surprisingly, this procedure is barely used. Our goal was to empirically assess its precision to evaluate size, orientation, or temporal perception, in three yes/no discrimination tasks that increase in demands. In 72 adult participants in total, we compared points of subjective equivalence (PSEs) or simultaneity (PSSs) as well as discrimination sensitivity obtained with the QUEST+, constant stimuli, and simple up-down staircase procedures. While PSEs did not differ between procedures, sensitivity estimates obtained with the 64-trials QUEST+ procedure were overestimated (i.e., just-noticeable differences, or JNDs, were underestimated). Overall, agreement between procedures was good, and was at its best for the easiest tasks. This study empirically confirmed that the QUEST+ procedure can be considered as a method of choice to accelerate PSE estimation, while keeping in mind that sensitivity estimation should be handled with caution.

Against cortical reorganisation

Neurological insults, such as congenital blindness, deafness, amputation, and stroke, often result in surprising and impressive behavioural changes. Cortical reorganisation, which refers to preserved brain tissue taking on a new functional role, is often invoked to account for these behavioural changes. Here, we revisit many of the classical animal and patient cortical remapping studies that spawned this notion of reorganisation. We highlight empirical, methodological, and conceptual problems that call this notion into doubt. We argue that appeal to the idea of reorganisation is attributable in part to the way that cortical maps are empirically derived. Specifically, cortical maps are often defined based on oversimplified assumptions of 'winner-takes-all', which in turn leads to an erroneous interpretation of what it means when these maps appear to change. Conceptually, remapping is interpreted as a circuit receiving novel input and processing it in a way unrelated to its original function. This implies that neurons are either pluripotent enough to change what they are tuned to or that a circuit can change what it computes. Instead of reorganisation, we argue that remapping is more likely to occur due to potentiation of pre-existing architecture that already has the requisite representational and computational capacity pre-injury. This architecture can be facilitated via Hebbian and homeostatic plasticity mechanisms. Crucially, our revised framework proposes that opportunities for functional change are constrained throughout the lifespan by the underlying structural 'blueprint'. At no period, including early in development, does the cortex offer structural opportunities for functional pluripotency. We conclude that reorganisation as a distinct form of cortical plasticity, ubiquitously evoked with words such as 'take-over'' and 'rewiring', does not exist.

Modulating temporal dynamics of performance across retinotopic locations enhances the generalization of perceptual learning

Human visual perception can be improved through perceptual learning. However, such learning is often specific to stimulus and learning conditions. Here, we explored how temporal dynamics of performance across conditions impact learning generalization. Participants performed a visual task, with the target at retinotopic location A. Then, the target was presented at location B either immediately after location A (same-session performance) or following a 48h consolidation period (different-session performance). Long-term generalization was measured the following week. Following initial training, both groups demonstrated generalization, consistent with previous accounts of fast learning. However, long-term generalization was enhanced in the same-session performance group. Consistently, improvements at locations A and B were correlated only following same-session performance, implying an integrated learning process across locations. The results support a new account of perceptual learning and generalization dynamics, suggesting that the temporal proximity of learning and consolidation of different conditions may integrate correlated learning processes, facilitating generalized learning.

Only cortical prediction error signals are involved in visual learning, despite availability of subcortical prediction error signals

Both the midbrain systems, encompassing the ventral striatum (VS), and the cortical systems, including the dorsal anterior cingulate cortex (dACC), play roles in reinforcing and enhancing learning. However, the specific contributions of signals from these regions in learning remains unclear. To investigate this, we examined how VS and dACC are involved in visual perceptual learning (VPL) through an orientation discrimination task. In the primary experiment, subjects fasted for 5 hours before each of 14 days of training sessions and 3 days of test sessions. Subjects were rewarded with water for accurate trial responses. During the test sessions, BOLD signals were recorded from regions including VS and dACC. Although BOLD signals in both areas were associated with positive and negative RPEs, only those in dACC associated with negative RPE showed a significant correlation with performance improvement. Additionally, no significant correlation was observed between BOLD signals associated with RPEs in VS and dACC. These results suggest that although signals associated with positive and negative RPEs from both midbrain and cortical systems are readily accessible, only RPE signals in the prefrontal system, generated without linking to RPE signals in VS, are utilized for the enhancement of VPL.

Visual perceptual learning modulates microsaccade rate and directionality

Microsaccades, incessant "fixational eye movements" (< 1°), are an important window into cognitive functions. Yet, its role in visual perceptual learning (VPL)-improvements in visual discrimination due to practice-remains practically unexplored. Here we investigated whether and how microsaccades change in VPL. Human observers performed a Landolt acuity task for 5 consecutive days and were assigned to the Neutral or Attention group. On each trial, two peripheral Landolt squares were presented briefly along a diagonal. Observers reported the gap side of the target stimulus. Training improved acuity and modified the microsaccade rate; with training, the rate decreased during the fixation period but increased during the response cue. Furthermore, microsaccade direction during the response cue was biased toward the target location, and training enhanced and sped up this bias. Finally, the microsaccade rate during a task-free fixation period correlated with observers' initial acuity threshold, indicating that the fewer the microsaccades during fixation the better the individual visual acuity. All these results, which were similar for both the Neutral and Attention groups and at both trained and untrained locations, suggest that microsaccades could serve as a physiological marker reflecting functional dynamics in human perceptual learning.

Revisiting the effects of configuration, predictability, and relevance on visual detection during interocular suppression

Statistical regularities and predictions can influence the earliest stages of visual processing. Studies examining their effects on detection, however, have yielded inconsistent results. In continuous flash suppression (CFS), where a static image projected to one eye is suppressed by a dynamic image presented to the other, the predictability of the suppressed signal may facilitate or delay detection. To identify the factors that differentiate these outcomes and dissociate the effects of expectation from those of behavioral relevance, we conducted three CFS experiments that addressed confounds related to the use of reaction time measures and complex images. In experiment 1, orientation recognition performance and visibility rates increased when a suppressed line segment completed a partial shape surrounding the CFS patch, demonstrating that valid configuration cues facilitate detection. In Experiment 2, however, predictive cues marginally affected visibility and did not modulate localization performance, challenging existing findings. In experiment 3, a relevance manipulation was introduced; participants pressed a key upon detecting lines of a particular orientation, ignoring the other possible orientation. Visibility and localization were enhanced for relevant orientations. Predictive cues modulated visibility, orientation recognition sensitivity, and response latencies, but not localization-an objective measure sensitive to partial breakthrough. Thus, while a consistent surround can strongly enhance detection during passive observation, predictive cueing primarily affects post-detection factors such as response readiness and recognition confidence. Relevance and predictability did not interact, suggesting that the contributions of these two processes to detection are mostly orthogonal.

Perceptual learning: Breaking specificity by variability

A new psychophysical study in humans suggests that increasing the variability of task-irrelevant features during training enhances the generalization of visual perceptual learning to untrained stimuli and locations.

Many Roads Lead to Rome: Differential Learning Processes for the Same Perceptual Improvement

Repeatedly exercising a perceptual ability usually leads to improvement, yet it is unclear whether the mechanisms supporting the same perceptual learning could be flexibly adjusted according to the training settings. Here, we trained adult observers in an orientation-discrimination task at either a single (focused) retinal location or multiple (distributed) retinal locations. We examined the observers' discriminability (N = 52) and bias (N = 20) in orientation perception at the trained and untrained locations. The focused and distributed training enhanced orientation discriminability by the same amount and induced a bias in perceived orientation at the trained locations. Nevertheless, the distributed training promoted location generalization of both practice effects, whereas the focused training resulted in specificity. The two training tactics also differed in long-term retention of the training effects. Our results suggest that, depending on the training settings of the same task, the same discrimination learning could differentially engage location-specific and location-invariant representations of the learned stimulus feature.

The Role of Foveal Cortex in Discriminating Peripheral Stimuli: The Sketchpad Hypothesis

Foveal (central) and peripheral vision are strongly interconnected to provide an integrated experience of the world around us. Recently, it has been suggested that there is a feedback mechanism that links foveal and peripheral vision. This peripheral-to-foveal feedback differs from other feedback mechanisms in that during visual processing a novel representation of a stimulus is formed in a different cortical region than that of the feedforward representation. The functional role of foveal feedback is not yet completely understood, but some evidence from neuroimaging studies suggests a link with peripheral shape processing. Behavioural and transcranial magnetic stimulation studies show impairment in peripheral shape discrimination when the foveal retinotopic cortex is disrupted post stimulus presentation. This review aims to link these findings to the visual sketchpad hypothesis. According to this hypothesis, foveal retinotopic cortex stores task-relevant information to aid identification of peripherally presented objects. We discuss how the characteristics of foveal feedback support this hypothesis and rule out other possible explanations. We also discuss the possibility that the foveal feedback may be independent of the sensory modality of the stimulation.

Microsaccades as a long-term oculomotor correlate in visual perceptual learning

Human perceptual learning, experience-induced gains in sensory discrimination, typically yields long-term performance improvements. Recent research revealed long-lasting transfer at the untrained location enabled by feature-based attention (FBA), reminiscent of its global effect (Hung & Carrasco, Scientific Reports, 11(1), 13914, (2021)). Visual Perceptual Learning (VPL) is typically studied while observers maintain fixation, but the role of fixational eye movements is unknown. Microsaccades - the largest of fixational eye movements - provide a continuous, online, physiological measure from the oculomotor system that reveals dynamic processing, which is unavailable from behavioral measures alone. We investigated whether and how microsaccades change after training in an orientation discrimination task. For human observers trained with or without FBA, microsaccade rates were significantly reduced during the response window in both trained and untrained locations and orientations. Critically, consistent with long-term training benefits, this microsaccade-rate reduction persisted over a year. Furthermore, microsaccades were biased toward the target location prior to stimulus onset and were more suppressed for incorrect than correct trials after observers' responses. These findings reveal that fixational eye movements and VPL are tightly coupled and that learning-induced microsaccade changes are long lasting. Thus, microsaccades reflect functional dynamics of the oculomotor system during information encoding, maintenance and readout, and may serve as a reliable long-term physiological correlate in VPL.

Training With Simulated Scotoma Leads to Behavioral Improvements Through at Least Two Distinct Mechanisms

Purpose

Individuals with central vision loss due to macular degeneration (MD) often spontaneously develop a preferred retinal locus (PRL) outside the area of retinal damage, which they use instead of the fovea. Those who develop a stable PRL are more successful at coping with their vision loss. However, it is unclear whether improvements in visual performance at the PRL are specific to that retinal location or are also observed in other parts of the retina. Perceptual learning literature suggests that the retinal specificity of these effects provides insight about the mechanisms involved. Better understanding of these mechanisms is necessary for the next generation of interventions and improved patient outcomes.

Methods

To address this, we trained participants with healthy vision to develop a trained retinal locus (TRL), analogous to the PRL in patients. We trained 24 participants on a visual search task using a gaze-contingent display to simulate a central scotoma.

Results

Results showed retinotopically specific improvements in visual crowding only at the TRL; however, visual acuity improved in both the TRL and in an untrained retinal locus.

Conclusions

These results suggest that training with an artificial scotoma involves multiple mechanistic levels, some location-specific and some not, and that simulated scotoma training paradigms likely influence multiple mechanisms simultaneously. Eye movement analysis suggests that the non-retinotopic learning effects may be related to improvements in the capability to maintain a stable gaze during stimulus presentation. This work suggests that effective interventions promoting peripheral viewing may influence multiple mechanisms simultaneously.

Oculomotor changes following learned use of an eccentric retinal locus

People with bilateral central vision loss sometimes develop a new point of oculomotor reference called a preferred retinal locus (PRL) that is used for fixating and planning saccadic eye movements. How individuals develop and learn to effectively use a PRL is still debated; in particular, the time course of learning to plan saccades using a PRL and learning to stabilize peripheral fixation at the desired location. Here we address knowledge limitations through research describing how eye movements change as a person learns to adopt an eccentric retinal locus. Using a gaze-contingent, eye tracking-guided paradigm to simulate central vision loss, 40 participants developed a PRL by engaging in an oculomotor and visual recognition task. After 12 training sessions, significant improvements were observed in six eye movement metrics addressing different aspects involved in learning to use a PRL: first saccade landing dispersion, saccadic re-referencing, saccadic precision, saccadic latency, percentage of useful trials, and fixation stability. Importantly, our analyses allowed separate examination of the stability of target fixation separately from the dispersion and precision of the landing location of saccades. These measures explained 50% of the across-subject variance in accuracy. Fixation stability and saccadic precision showed a strong, positive correlation. Although there was no statistically significant difference in rate of learning, individuals did tend to learn saccadic precision faster than fixation stability. Saccadic precision was also more associated with accuracy than fixation stability for the behavioral task. This suggests effective intervention strategies in low vision should address both fixation stability and saccadic precision.

Assessment of human expertise and movement kinematics in first-person shooter games

In contrast to traditional professional sports, there are few standardized metrics in professional esports (competitive multiplayer video games) for assessing a player's skill and ability. We assessed the performance of professional-level players in Aim LabTM, a first-person shooter training and assessment game, with two target-shooting tasks. These tasks differed primarily in target size: the task with large targets provided an incentive to be fast but imprecise and the task with large targets provided an incentive to be precise but slow. Each player's motor acuity was measured by characterizing the speed-accuracy trade-off in shot behavior: shot time (elapsed time for a player to shoot at a target) and shot spatial error (distance from center of a target). We also characterized the fine-grained kinematics of players' mouse movements. Our findings demonstrate that: 1) movement kinematics depended on task demands; 2) individual differences in motor acuity were significantly correlated with kinematics; and 3) performance, combined across the two target sizes, was poorly characterized by Fitts Law. Our approach to measuring motor acuity has widespread applications not only in esports assessment and training, but also in basic (motor psychophysics) and clinical (gamified rehabilitation) research.

Unifying framework for cognitive training interventions in brain aging

Cognitive training is a promising tool for slowing or preventing cognitive decline in older adults at-risk for dementia. Its success, however, has been limited by a lack of evidence showing that it reliably causes broad training effects: improvements in cognition across a range of domains that lead to real-world benefits. Here, we propose a framework for enhancing the effect of cognitive training interventions in brain aging. The focus is on (A) developing cognitive training task paradigms that are informed by population-level cognitive characteristics and pathophysiology, and (B) personalizing how these sets are presented to participants during training via feedback loops that aim to optimize "mismatch" between participant capacity and training demands using both adaptation and random variability. In this way, cognitive training can better alter whole-brain topology in a manner that supports broad training effects in the context of brain aging.

Training attentive individuation leads to visuo-spatial working memory improvement in low-performing older adults: An online study

Cognitive decrements are typical of physiological aging. Among these age-related cognitive changes, visuo-spatial working memory (vWM) decline has a prominent role due to its effects on other cognitive functions and daily routines. To reinforce vWM in the aging population, several cognitive training interventions have been developed in the past years. Given that vWM functioning depends (at least partially) on the efficiency of attention selection of the relevant objects, in the present study we implemented a short (five sessions), online intervention that primarily trained attentive individuation of target items and tested training effects on a vWM task. Attention training effects were compared with practice (i.e., a group that repeatedly performed the same vWM task) and test-retest effects (i.e., a passive group). After the training, the results showed attention training effects of the same magnitude as practice effects, confirming that the enhancement of attentive individuation has a positive cascade influence on maintaining items in vWM. Moreover, training and practice effects were only evident in low-performing older adults. Thus, interindividual differences at baseline crucially contribute to training outcomes and are a fundamental factor to be accounted for in the implementation of cognitive training protocols.

Familiarization with meaningless sound patterns facilitates learning to detect those patterns among distracters

Initially “meaningless” and randomly generated sounds can be learned over exposure. This is demonstrated by studies where repetitions of randomly determined sound patterns are detected better if they are the same sounds presented on previous trials than if they are novel. This experiment posed two novel questions about this learning. First, does familiarization with a sound outside of the repetition detection context facilitate later performance? Second, does familiarization enhance performance when repeats are interleaved with distracters? Listeners were first trained to categorize a unique pattern of synchronous complex tone trains (210 ms in duration) from other tone trains with similar qualities (familiarization phase). They were then tasked to detect repeated pattern presentations interleaved with similar distracters in 4.2 s long excerpts (repetition detection phase). The familiarized pattern (Familiar Fixed – FF), an unfamiliar pattern that remained fixed throughout (Unfamiliar Fixed – UF), or patterns that were uniquely determined on each trial (Unfamiliar Unfixed – UU) could be presented as repeats. FF patterns were learned at a faster rate and achieved higher repetition detection sensitivity than UF and UU patterns. Similarly, FF patterns also showed steeper learning slopes in their response times (RTs) than UF patterns. The data show that familiarity with a “meaningless” sound pattern on its own (i.e., without repetition) can facilitate repetition detection even in the presence of distracters. Familiarity effects become most apparent in the potential for learning.

Vision recovery with perceptual learning and non-invasive brain stimulation: Experimental set-ups and recent results, a review of the literature

BACKGROUND

Vision is the sense which we rely on the most to interact with the environment and its integrity is fundamental for the quality of our life. However, around the globe, more than 1 billion people are affected by debilitating vision deficits. Therefore, finding a way to treat (or mitigate) them successfully is necessary.

OBJECTIVE

This narrative review aims to examine options for innovative treatment of visual disorders (retinitis pigmentosa, macular degeneration, optic neuropathy, refractory disorders, hemianopia, amblyopia), especially with Perceptual Learning (PL) and Electrical Stimulation (ES).

METHODS

ES and PL can enhance visual abilities in clinical populations, inducing plastic changes. We describe the experimental set-ups and discuss the results of studies using ES or PL or their combination in order to suggest, based on literature, which treatment is the best option for each clinical condition.

RESULTS

Positive results were obtained using ES and PL to enhance visual functions. For example, repetitive transorbital Alternating Current Stimulation (rtACS) appeared as the most effective treatment for pre-chiasmatic disorders such as optic neuropathy. A combination of transcranial Direct Current Stimulation (tDCS) and visual training seems helpful for people with hemianopia, while transcranial Random Noise Stimulation (tRNS) makes visual training more efficient in people with amblyopia and mild myopia.

CONCLUSIONS

This narrative review highlights the effect of different ES montages and PL in the treatment of visual disorders. Furthermore, new options for treatment are suggested. It is noteworthy to mention that, in some cases, unclear results emerged and others need to be more deeply investigated.

Evaluating environmental and inhibitory control strategies to improve outcomes in a widely available weight loss program

BACKGROUND

Although many people try to lose weight, a large proportion of individuals do not achieve clinically significant weight loss. Nonresponse and relapse rates in lifestyle interventions are largely explained by challenges in avoiding or resisting temptation in the context of omnipresent food access. Innovative enhancement strategies are needed to help individuals manage temptation in evidence-based lifestyle interventions.

METHODS

This prospective, four-parallel-arm, randomized controlled trial tests the efficacy of two weight management enhancement strategies on weight and dietary outcomes among individuals with overweight or obesity: (1) an environmental control strategy combining modification of the home food environment and grocery delivery (AVOID) and (2) an impulse control strategy involving daily, gamified inhibitory control training (RESIST). Women and men (n = 500) with overweight or obesity (Body Mass Index between 25 and 40.0 kg/m2) will be enrolled in a 12-month commercial weight-loss program (WW, formerly Weight Watchers©) and randomly assigned to one of four conditions: (1) WW alone, (2) WW + AVOID, (3) WW + RESIST, or (4) WW + AVOID + RESIST. Anthropometric, dietary, cognitive, and household food environment assessments will be conducted in English or Spanish at enrollment and at 6- and 12-month follow-up.

DISCUSSION

This research addresses the pragmatic question of how to best optimize behavior change: Should we modify the choice environment, strengthen individuals' self-regulation, or both, to maximize behavior change? This work can inform the development of enhancement strategies to promote adherence to lifestyle recommendations and other impulse control challenges.

Change-detection training and its effects on visual processing skills

Previous cognitive training research with the change-detection paradigm found only sparse effects that went beyond improvements in the training task but stressed an increase in fidelity of internal memory representations. Motivated by the demanding visual processing requirements of change-detection training, we extended this work by focusing on whether training on a change-detection task would improve visual processing skills. Fifty participants were randomly assigned to train on a change-detection task or on a control task for seven sessions. Participants' visual processing skills were assessed before and after the intervention, focusing on visual search, contrast sensitivity, and contour integration. Our results suggest a general improvement in perceptual skills that was primarily driven by a conjunction search task and to a much lesser extent by a complex visual search task and a contrast sensitivity task. The data from the conjunction search task further suggest a causal link between training and improvements of perceptual as opposed to attentional processes. Since the change-detection paradigm is commonly used to assess working memory capacity, future research needs to investigate how much of its variance is explained by memory performance and how much is explained by perceptual processes.

Aerobic Exercise and Human Visual Cortex Neuroplasticity: A Narrative Review

There is compelling evidence from animal models that physical exercise can enhance visual cortex neuroplasticity. In this narrative review, we explored whether exercise has the same effect in humans. We found that while some studies report evidence consistent with exercise-induced enhancement of human visual cortex neuroplasticity, others report no effect or even reduced neuroplasticity following exercise. Differences in study methodology may partially explain these varying results. Because the prospect of exercise increasing human visual cortex neuroplasticity has important implications for vision rehabilitation, additional research is required to resolve this discrepancy in the literature.

Statistical Learning in Vision

Vision and learning have long been considered to be two areas of research linked only distantly. However, recent developments in vision research have changed the conceptual definition of vision from a signal-evaluating process to a goal-oriented interpreting process, and this shift binds learning, together with the resulting internal representations, intimately to vision. In this review, we consider various types of learning (perceptual, statistical, and rule/abstract) associated with vision in the past decades and argue that they represent differently specialized versions of the fundamental learning process, which must be captured in its entirety when applied to complex visual processes. We show why the generalized version of statistical learning can provide the appropriate setup for such a unified treatment of learning in vision, what computational framework best accommodates this kind of statistical learning, and what plausible neural scheme could feasibly implement this framework. Finally, we list the challenges that the field of statistical learning faces in fulfilling the promise of being the right vehicle for advancing our understanding of vision in its entirety. Expected final online publication date for the Annual Review of Vision Science, Volume 8 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Rapid but specific perceptual learning partially explains individual differences in the recognition of challenging speech

Perceptual learning for speech, defined as long-lasting changes in speech recognition following exposure or practice occurs under many challenging listening conditions. However, this learning is also highly specific to the conditions in which it occurred, such that its function in adult speech recognition is not clear. We used a time-compressed speech task to assess learning following either brief exposure (rapid learning) or additional training (training-induced learning). Both types of learning were robust and long-lasting. Individual differences in rapid learning explained unique variance in recognizing natural-fast speech and speech-in-noise with no additional contribution for training-induced learning (Experiment 1). Rapid learning was stimulus specific (Experiment 2), as in previous studies on training-induced learning. We suggest that rapid learning is key for understanding the role of perceptual learning in online speech recognition whereas longer training could provide additional opportunities to consolidate and stabilize learning.

Perspectives on the Combined Use of Electric Brain Stimulation and Perceptual Learning in Vision

A growing body of literature offers exciting perspectives on the use of brain stimulation to boost training-related perceptual improvements in humans. Recent studies suggest that combining visual perceptual learning (VPL) training with concomitant transcranial electric stimulation (tES) leads to learning rate and generalization effects larger than each technique used individually. Both VPL and tES have been used to induce neural plasticity in brain regions involved in visual perception, leading to long-lasting visual function improvements. Despite being more than a century old, only recently have these techniques been combined in the same paradigm to further improve visual performance in humans. Nonetheless, promising evidence in healthy participants and in clinical population suggests that the best could still be yet to come for the combined use of VPL and tES. In the first part of this perspective piece, we briefly discuss the history, the characteristics, the results and the possible mechanisms behind each technique and their combined effect. In the second part, we discuss relevant aspects concerning the use of these techniques and propose a perspective concerning the combined use of electric brain stimulation and perceptual learning in the visual system, closing with some open questions on the topic.

Whole-Brain Network Models: From Physics to Bedside

Computational neuroscience has come a long way from its humble origins in the pioneering work of Hodgkin and Huxley. Contemporary computational models of the brain span multiple spatiotemporal scales, from single neuronal compartments to models of social cognition. Each spatial scale comes with its own unique set of promises and challenges. Here, we review models of large-scale neural communication facilitated by white matter tracts, also known as whole-brain models (WBMs). Whole-brain approaches employ inputs from neuroimaging data and insights from graph theory and non-linear systems theory to model brain-wide dynamics. Over the years, WBM models have shown promise in providing predictive insights into various facets of neuropathologies such as Alzheimer's disease, Schizophrenia, Epilepsy, Traumatic brain injury, while also offering mechanistic insights into large-scale cortical communication. First, we briefly trace the history of WBMs, leading up to the state-of-the-art. We discuss various methodological considerations for implementing a whole-brain modeling pipeline, such as choice of node dynamics, model fitting and appropriate parcellations. We then demonstrate the applicability of WBMs toward understanding various neuropathologies. We conclude by discussing ways of augmenting the biological and clinical validity of whole-brain models.

Neurochemical and functional interactions for improved perceptual decisions through training

Learning and experience are known to improve our ability to make perceptual decisions. Yet, our understanding of the brain mechanisms that support improved perceptual decisions through training remains limited. Here, we test the neurochemical and functional interactions that support learning for perceptual decisions in the context of an orientation identification task. Using magnetic resonance spectroscopy (MRS), we measure neurotransmitters (i.e., glutamate, GABA) that are known to be involved in visual processing and learning in sensory [early visual cortex (EV)] and decision-related [dorsolateral prefrontal cortex (DLPFC)] brain regions. Using resting-state functional magnetic resonance imaging (rs-fMRI), we test for functional interactions between these regions that relate to decision processes. We demonstrate that training improves perceptual judgments (i.e., orientation identification), as indicated by faster rates of evidence accumulation after training. These learning-dependent changes in decision processes relate to lower EV glutamate levels and EV-DLPFC connectivity, suggesting that glutamatergic excitation and functional interactions between visual and dorsolateral prefrontal cortex facilitate perceptual decisions. Further, anodal transcranial direct current stimulation (tDCS) in EV impairs learning, suggesting a direct link between visual cortex excitation and perceptual decisions. Our findings advance our understanding of the role of learning in perceptual decision making, suggesting that glutamatergic excitation for efficient sensory processing and functional interactions between sensory and decision-related regions support improved perceptual decisions.NEW & NOTEWORTHY Combining multimodal brain imaging [magnetic resonance spectroscopy (MRS), functional connectivity] with interventions [transcranial direct current stimulation (tDCS)], we demonstrate that glutamatergic excitation and functional interactions between sensory (visual) and decision-related (dorsolateral prefrontal cortex) areas support our ability to optimize perceptual decisions through training.

Exogenous attention generalizes location transfer of perceptual learning in adults with amblyopia

Visual perceptual learning (VPL) is a behavioral manifestation of brain neuroplasticity. However, its practical effectiveness is limited because improvements are often specific to the trained conditions and require significant time and effort. It is critical to understand the conditions that promote learning and transfer. Covert endogenous (voluntary) and exogenous (involuntary) spatial attention help overcome VPL location specificity in neurotypical adults, but whether they also do so for people with atypical visual development is unknown. This study investigates the role of exogenous attention during VPL in adults with amblyopia, an ideal population given their asymmetrically developed, but highly plastic, visual cortex. Here we show that training on a discrimination task leads to improvements in foveal contrast sensitivity, acuity, and stereoacuity. Notably, exogenous attention helps generalize learning beyond trained spatial locations. Future large-scale studies can verify the extent to which attention enhances the effectiveness of perceptual learning during rehabilitation of visual disorders.

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Contrast sensitivity (CS)-based VPL in amblyopes improves CS, acuity and stereoacuity

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Similar improvement in trained amblyopic eye and untrained fellow eye

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Exogenous spatial attention facilitates location transfer of VPL in amblyopic adults

Training peripheral vision to read: Using stimulus exposure and identity priming

Reading in the periphery can be improved with perceptual learning. A conventional training paradigm involves repeated practice on a character-based task (e.g., recognizing random letters/words). While the training is effective, the hours of strenuous effort required from the trainees makes it difficult to implement the training in low-vision patients. Here, we developed a training paradigm utilizing stimulus exposure and identity priming to minimize training effort and improve training accessibility while maintaining the active engagement of observers through a stimulus visibility task. Twenty-one normally sighted young adults were randomly assigned to three groups: a control group, a with-repetition training group, and a without-repetition training group. All observers received a pre-test and a post-test scheduled 1 week apart. Each test consisted of measurements of reading speed, visual-span profile, the spatial extent of crowding, and isolated-letter profiles at 10° eccentricity in the lower visual field. Training consists of five daily sessions (a total of 7,150 trials) of viewing trigram stimuli (strings of three letters) with identity priming (prior knowledge of target letter identity). The with-repetition group was given the option to replay each stimulus (averaged 0.4 times). In comparison to the control group, both training groups showed significant improvements in all four performance measures. Stimulus replay did not yield a measurable benefit on learning. Learning transferred to various untrained tasks and conditions, such as the reading task and untrained letter size. Reduction in crowding was the main basis of the training-related improvement in reading. We also found that the learning can be partially retained for a minimum of 3 months and that complete retention is attainable with additional monthly training. Our findings suggest that conventional training task that requires recognizing random letters or words is dispensable for improving peripheral reading. Utilizing stimulus exposure and identity priming accompanied by a stimulus visibility task, our novel training procedure offers effective intervention, simple implementation, capability for remote and self-administration, and an easy translation into low-vision reading rehabilitation.

Long-Term Motor Learning in the "Wild" With High Volume Video Game Data

Motor learning occurs over long periods of practice during which motor acuity, the ability to execute actions more accurately, precisely, and in less time, improves. Laboratory-based studies of motor learning are typically limited to a small number of participants and a time frame of minutes to several hours per participant. There is a need to assess the generalizability of theories and findings from lab-based motor learning studies on larger samples and time scales. In addition, laboratory-based studies of motor learning use relatively simple motor tasks which participants are unlikely to be intrinsically motivated to learn, limiting the interpretation of their findings in more ecologically valid settings ("in the wild"). We studied the acquisition and longitudinal refinement of a complex sensorimotor skill embodied in a first-person shooter video game scenario, with a large sample size (N = 7174, 682,564 repeats of the 60 s game) over a period of months. Participants voluntarily practiced the gaming scenario for up to several hours per day up to 100 days. We found improvement in performance accuracy (quantified as hit rate) was modest over time but motor acuity (quantified as hits per second) improved considerably, with 40-60% retention from 1 day to the next. We observed steady improvements in motor acuity across multiple days of video game practice, unlike most motor learning tasks studied in the lab that hit a performance ceiling rather quickly. Learning rate was a non-linear function of baseline performance level, amount of daily practice, and to a lesser extent, number of days between practice sessions. In addition, we found that the benefit of additional practice on any given day was non-monotonic; the greatest improvements in motor acuity were evident with about an hour of practice and 90% of the learning benefit was achieved by practicing 30 min per day. Taken together, these results provide a proof-of-concept in studying motor skill acquisition outside the confines of the traditional laboratory, in the presence of unmeasured confounds, and provide new insights into how a complex motor skill is acquired in an ecologically valid setting and refined across much longer time scales than typically explored.

Stimulation of the ventral tegmental area induces visual cortical plasticity at the neuronal level

fMRI studies have shown that pairing a task-irrelevant visual feature with electrical micro-stimulation of the ventral tegmental area (VTA-EM) is sufficient to increase the sensory cortical representation of the paired feature and to improve perceptual performance. However, since fMRI provides an indirect measure of neural activity, the neural response changes underlying the fMRI activations are unknown. Here, we pair a task-irrelevant grating orientation with VTA-EM while attention is directed to a difficult orthogonal task. We examine the changes in neural response properties in macaques by recording spiking activity in the posterior inferior temporal cortex, the locus of fMRI-defined plasticity in previous studies. We observe a relative increase in mean spike rate and preference for the VTA-EM paired orientation compared to an unpaired orientation, which is unrelated to attention. These results demonstrate that VTA-EM-stimulus pairing is sufficient to induce sensory cortical plasticity at the spiking level in nonhuman primates.

Perceptual learning as a result of concerted changes in prefrontal and visual cortex

Our perceptual ability remarkably improves with training. Some studies on visual perceptual learning have shown refined neural representation of the trained stimulus in the visual cortex, whereas others have exclusively argued for improved readout and decision-making processes in the frontoparietal cortex. The mixed results have rendered the underlying neural mechanisms puzzling and hotly debated. By simultaneously recording from monkey visual area V4 and ventrolateral prefrontal cortex (PFC) implanted with microelectrode arrays, we dissected learning-induced cortical changes over the course of training the monkeys in a global form detection task. Decoding analysis dissociated two distinct components of neuronal population codes that were progressively and markedly enhanced in both V4 and PFC. One component was closely related to the target stimulus feature and was subject to task-dependent top-down modulation; it emerged earlier in V4 than PFC and its enhancement was specific to the trained configuration of the target stimulus. The other component of the neural code was entirely related to the animal's behavioral choice; it emerged earlier in PFC than V4 and its enhancement completely generalized to an untrained stimulus configuration. These results implicate two concurrent and synergistic learning processes: a perceptual process that is specific to the details of the trained stimulus feature and a cognitive process that is dependent on the total amount of learning experience in the trained task. When combined, these two learning processes were well predictive of the animal's learning behavior.

Action video game play facilitates "learning to learn"

Previous work has demonstrated that action video game training produces enhancements in a wide range of cognitive abilities. Here we evaluate a possible mechanism by which such breadth of enhancement could be attained: that action game training enhances learning rates in new tasks (i.e., "learning to learn"). In an initial controlled intervention study, we show that individuals who were trained on action video games subsequently exhibited faster learning in the two cognitive domains that we tested, perception and working memory, as compared to individuals who trained on non-action games. We further confirmed the causal effect of action video game play on learning ability in a pre-registered follow-up study that included a larger number of participants, blinding, and measurements of participant expectations. Together, this work highlights enhanced learning speed for novel tasks as a mechanism through which action video game interventions may broadly improve task performance in the cognitive domain.

Training with an auditory perceptual learning game transfers to speech in competition

Understanding speech in the presence of acoustical competition is a major complaint of those with hearing difficulties. Here, a novel perceptual learning game was tested for its effectiveness in reducing difficulties with hearing speech in competition. The game was designed to train a mixture of auditory processing skills thought to underlie speech in competition, such as spectral-temporal processing, sound localization, and auditory working memory. Training on these skills occurred both in quiet and in competition with noise. Thirty college-aged participants without any known hearing difficulties were assigned either to this mixed-training condition or an active control consisting of frequency discrimination training within the same gamified setting. To assess training effectiveness, tests of speech in competition (primary outcome), as well as basic supra-threshold auditory processing and cognitive processing abilities (secondary outcomes) were administered before and after training. Results suggest modest improvements on speech in competition tests in the mixed-training compared to the frequency-discrimination control condition (Cohen’s d = 0.68). While the sample is small, and in normally hearing individuals, these data suggest promise of future study in populations with hearing difficulties.

Broad and Long-Lasting Vision Improvements in Youth With Infantile Nystagmus After Home Training With a Perceptual Learning App

Current treatments for infantile nystagmus (IN), focused on dampening the oscillating eye movements, yield little to no improvement in visual functioning. It makes sense, however, to treat the visual impairments associated with IN with tailored sensory training. Recently, we developed such a training, targeting visual crowding as an important bottleneck in visual functioning with an eye-movement engaging letter discrimination task. This training improved visual performance of children with IN, but most children had not reached plateau performance after 10 supervised training sessions (3,500 trials). Here, we evaluate the effects of prolonged perceptual learning (14,000 trials) in 7-18-year-old children with IN and test the feasibility of tablet-based, at-home intervention. Results demonstrate that prolonged home-based perceptual training results in stable, long lasting visual acuity improvements at distance and near, with remarkably good transfer to reading and even stereopsis. Improvements on self-reported functional vision scores underline the clinical relevance of perceptual learning with e-health apps for individuals with IN.

The iSTOPP study: Protocol for a proof-of-concept randomised clinical trial of sensory discrimination training in people with persistent neck pain

BACKGROUND

Neck pain can be associated with a reduction in tactile acuity that is thought to reflect disrupted sensory processing. Tactile acuity training may normalise sensory processing and improve symptoms. This proof-of-concept trial will assess the feasibility of a novel tactile acuity training method and whether this intervention improves tactile acuity in people with persistent neck pain.

METHODS

and analysis: In this two-arm randomised clinical proof-of-concept trial we will recruit participants with neck pain receiving usual care physiotherapy in a secondary outpatient healthcare setting. Thirty-six participants will be randomised 2:1 to receive four weeks of either tactile acuity training using the Imprint Tactile Acuity Device (iTAD) or a placebo intervention, in addition to usual care. The placebo intervention will consist of a de-activated TENS machine (iTENS) said to deliver a sub-threshold inhibitory therapy. Outcomes will be assessed at baseline, mid-treatment, and at 5-weeks and 2-months follow-up. The primary outcome tactile acuity will be evaluated using the two-point discrimination test and locognosia tests. Feasibility will be informed by recruitment and attrition rates, adherence, credibility of the interventions, treatment satisfaction and blinding. Pain intensity and anatomical spread will be analysed as secondary outcomes. The effect of iTAD training on tactile acuity will be assessed using a 2 (Group: iTAD vs. iTENS) x 4 (Time: baseline, mid-treatment, 5-week and 2-month outcome assessment) mixed ANOVA. Secondary outcomes including pain and pain spread, will be analysed with a focus on informing sample size calculations in future trials.

ETHICS AND DISSEMINATION

Risks associated with this study are minor. Usual care is not withheld, and participants consent to random allocation of either iTAD or iTENS. Potential benefits to participants include any benefit associated with the interventions and contributing to research that may assist people with chronic pain in the future. Trial results will be disseminated via academic journals and conference presentations. The study is approved by the Human Research Ethics Committee of Griffith University (2017/128).

Feature-based attention enables robust, long-lasting location transfer in human perceptual learning

Visual perceptual learning (VPL) is typically specific to the trained location and feature. However, the degree of specificity depends upon particular training protocols. Manipulating covert spatial attention during training facilitates learning transfer to other locations. Here we investigated whether feature-based attention (FBA), which enhances the representation of particular features throughout the visual field, facilitates VPL transfer, and how long such an effect would last. To do so, we implemented a novel task in which observers discriminated a stimulus orientation relative to two reference angles presented simultaneously before each block. We found that training with FBA enabled remarkable location transfer, reminiscent of its global effect across the visual field, but preserved orientation specificity in VPL. Critically, both the perceptual improvement and location transfer persisted after 1 year. Our results reveal robust, long-lasting benefits induced by FBA in VPL, and have translational implications for improving generalization of training protocols in visual rehabilitation.

Sensory-Induced Human LTP-Like Synaptic Plasticity - Using Visual Evoked Potentials to Explore the Relation Between LTP-Like Synaptic Plasticity and Visual Perceptual Learning

Objective

Stimulus-selective response modulation (SRM) of sensory evoked potentials represents a well-established non-invasive index of long-term potentiation-like (LTP-like) synaptic plasticity in the human sensory cortices. Although our understanding of the mechanisms underlying stimulus-SRM has increased over the past two decades, it remains unclear how this form of LTP-like synaptic plasticity is related to other basic learning mechanisms, such as perceptual learning. The aim of the current study was twofold; firstly, we aimed to corroborate former stimulus-SRM studies, demonstrating modulation of visual evoked potential (VEP) components following high-frequency visual stimulation. Secondly, we aimed to investigate the association between the magnitudes of LTP-like plasticity and visual perceptual learning (VPL).

Methods

42 healthy adults participated in the study. EEG data was recorded during a standard high-frequency stimulus-SRM paradigm. Amplitude values were measured from the peaks of visual components C1, P1, and N1. Embedded in the same experimental session, the VPL task required the participants to discriminate between a masked checkerboard pattern and a visual “noise” stimulus before, during and after the stimulus-SRM probes.

Results

We demonstrated significant amplitude modulations of VEPs components C1 and N1 from baseline to both post-stimulation probes. In the VPL task, we observed a significant change in the average threshold levels from the first to the second round. No significant association between the magnitudes of LTP-like plasticity and performance on the VPL task was evident.

Conclusion

To the extent of our knowledge, this study is the first to examine the relationship between the visual stimulus-RM phenomenon and VPL in humans. In accordance with previous studies, we demonstrated robust amplitude modulations of the C1 and N1 components of the VEP waveform. However, we did not observe any significant correlations between modulation magnitude of VEP components and VPL task performance, suggesting that these phenomena rely on separate learning mechanisms implemented by different neural mechanisms.

Individuals with autism spectrum disorder have altered visual encoding capacity

Perceptual anomalies in individuals with autism spectrum disorder (ASD) have been attributed to an imbalance in weighting incoming sensory evidence with prior knowledge when interpreting sensory information. Here, we show that sensory encoding and how it adapts to changing stimulus statistics during feedback also characteristically differs between neurotypical and ASD groups. In a visual orientation estimation task, we extracted the accuracy of sensory encoding from psychophysical data by using an information theoretic measure. Initially, sensory representations in both groups reflected the statistics of visual orientations in natural scenes, but encoding capacity was overall lower in the ASD group. Exposure to an artificial (i.e., uniform) distribution of visual orientations coupled with performance feedback altered the sensory representations of the neurotypical group toward the novel experimental statistics, while also increasing their total encoding capacity. In contrast, neither total encoding capacity nor its allocation significantly changed in the ASD group. Across both groups, the degree of adaptation was correlated with participants’ initial encoding capacity. These findings highlight substantial deficits in sensory encoding—independent from and potentially in addition to deficits in decoding—in individuals with ASD.

It is increasingly recognized that individuals with Autism Spectrum Disorder (ASD) show anomalies in perception, and these have been recently attributed to altered decoding (i.e. interpretation of sensory signals). This study reveals that independent of these changes, individuals with ASD show upstream deficits in sensory encoding (i.e., how samples are drawn from the environment).

Perceptual Learning beyond Perception: Mnemonic Representation in Early Visual Cortex and Intraparietal Sulcus

The ability to discriminate between stimuli relies on a chain of neural operations associated with perception, memory and decision-making. Accumulating studies show learning-dependent plasticity in perception or decision-making, yet whether perceptual learning modifies mnemonic processing remains unclear. Here, we trained human participants of both sexes in an orientation discrimination task, while using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) to separately examine training-induced changes in working memory (WM) representation. fMRI decoding revealed orientation-specific neural patterns during the delay period in primary visual cortex (V1) before, but not after, training, whereas neurodisruption of V1 during the delay period led to behavioral deficits in both phases. In contrast, both fMRI decoding and disruptive effect of TMS showed that intraparietal sulcus (IPS) represented WM content after, but not before, training. These results suggest that training does not affect the necessity of sensory area in representing WM information, consistent with the sensory recruitment hypothesis in WM, but likely alters the coding format of the stored stimulus in this region. On the other hand, training can render WM content to be maintained in higher-order parietal areas, complementing sensory area to support more robust maintenance of information.SIGNIFICANCE STATEMENT There has been accumulating progresses regarding experience-dependent plasticity in perception or decision-making, yet how perceptual experience moulds mnemonic processing of visual information remains less explored. Here, we provide novel findings that learning-dependent improvement of discriminability accompanies altered WM representation at different cortical levels. Critically, we suggest a role of training in modulating cortical locus of WM representation, providing a plausible explanation to reconcile the discrepant findings between human and animal studies regarding the recruitment of sensory or higher-order areas in WM.

Efficacy of Perceptual Learning-Based Vision Training as an Adjuvant to Occlusion Therapy in the Management of Amblyopia: A Pilot Study

A retrospective study was conducted to evaluate preliminarily the efficacy of perceptual learning (PL) visual training in medium-term follow-up with a specific software (Amblyopia iNET, Home Therapy Systems Inc., Gold Canyon, AZ, USA) for visual acuity (VA) and contrast sensitivity (CS) recovering in a sample of 14 moderate to severe amblyopic subjects with a previously unsuccessful outcome or failure with patching (PL Group). This efficacy was compared with that achieved in a patching control group (13 subjects, Patching 2). At one-month follow-up, a significant VA improvement in the amblyopic eye (AE) was observed in both groups, with no significant differences between them. Additionally, CS was measured in PL Group and exhibited a significant improvement in the AE one month after the beginning of treatment for 3, 6, 12, and 18 cycles/º (p = 0.003). Both groups showed long-lasting retention of visual improvements. A combined therapy of PL-based visual training and patching seems to be effective for improving VA in children with amblyopia who did not recover vision with patching alone or had a poor patching compliance. This preliminary outcome should be confirmed in future clinical trials.

Individual difference predictors of learning and generalization in perceptual learning

Given appropriate training, human observers typically demonstrate clear improvements in performance on perceptual tasks. However, the benefits of training frequently fail to generalize to other tasks, even those that appear similar to the trained task. A great deal of research has focused on the training task characteristics that influence the extent to which learning generalizes. However, less is known about what might predict the considerable individual variations in performance. As such, we conducted an individual differences study to identify basic cognitive abilities and/or dispositional traits that predict an individual's ability to learn and/or generalize learning in tasks of perceptual learning. We first showed that the rate of learning and the asymptotic level of performance that is achieved in two different perceptual learning tasks (motion direction and odd-ball texture detection) are correlated across individuals, as is the degree of immediate generalization that is observed and the rate at which a generalization task is learned. This indicates that there are indeed consistent individual differences in perceptual learning abilities. We then showed that several basic cognitive abilities and dispositional traits are associated with an individual's ability to learn (e.g., simple reaction time; sensitivity to punishment) and/or generalize learning (e.g., cognitive flexibility; openness to experience) in perceptual learning tasks. We suggest that the observed individual difference relationships may provide possible targets for future intervention studies meant to increase perceptual learning and generalization.