Showing papers on "Perceptual learning published in 2018"

An Artificial Sensory Neuron with Tactile Perceptual Learning.

Abstract: Sensory neurons within skin form an interface between the external physical reality and the inner tactile perception. This interface enables sensory information to be organized identified, and interpreted through perceptual learning-the process whereby the sensing abilities improve through experience. Here, an artificial sensory neuron that can integrate and differentiate the spatiotemporal features of touched patterns for recognition is shown. The system comprises sensing, transmitting, and processing components that are parallel to those found in a sensory neuron. A resistive pressure sensor converts pressure stimuli into electric signals, which are transmitted to a synaptic transistor through interfacial ionic/electronic coupling via a soft ionic conductor. Furthermore, the recognition error rate can be dramatically decreased from 44% to 0.4% by integrating with the machine learning method. This work represents a step toward the design and use of neuromorphic electronic skin with artificial intelligence for robotics and prosthetics.

Learning and attention reveal a general relationship between population activity and behavior

Abstract: Prior studies have demonstrated that correlated variability changes with cognitive processes that improve perceptual performance. We tested whether correlated variability covaries with subjects’ performance—whether performance improves quickly with attention or slowly with perceptual learning. We found a single, consistent relationship between correlated variability and behavioral performance, regardless of the time frame of correlated variability change. This correlated variability was oriented along the dimensions in population space used by the animal on a trial-by-trial basis to make decisions. That subjects’ choices were predicted by specific dimensions that were aligned with the correlated variability axis clarifies long-standing paradoxes about the relationship between shared variability and behavior.

Towards a whole brain model of Perceptual Learning.

Abstract: A hallmark of modern Perceptual Learning (PL) is the extent to which learning is specific to the trained stimuli. Such specificity to orientation, spatial location and even eye of training has been used as psychophysical evidence of the neural basis of learning. This argument that specificity of PL implies regionalization of brain plasticity implicitly assumes that examination of a singular locus of PL is an appropriate approach to understand learning. However, recent research shows that learning effects once thought to be specific depend on subtleties of the training paradigm and that within even a simple training procedure there are multiple aspects of the task and stimuli that are learned simultaneously. Here, we suggest that learning on any task involves a broad network of brain regions undergoing changes in representations, read-out weights, decision rules, attention and feedback processes as well as oculomotor changes. However, importantly, the distribution of learning across the neural system depends upon the details of the training procedure and the characterstics of the individual being trained. We propose that to advance our understanding of PL, the field must move towards understanding how distributed brain processes jointly contribute to behavioral learning effects.

Mid-Level Visual Representations Improve Generalization and Sample Efficiency for Learning Visuomotor Policies

Abstract: How much does having visual priors about the world (e.g. the fact that the world is 3D) assist in learning to perform downstream motor tasks (e.g. delivering a package)? We study this question by integrating a generic perceptual skill set (e.g. a distance estimator, an edge detector, etc.) within a reinforcement learning framework--see Figure 1. This skill set (hereafter mid-level perception) provides the policy with a more processed state of the world compared to raw images. We find that using a mid-level perception confers significant advantages over training end-to-end from scratch (i.e. not leveraging priors) in navigation-oriented tasks. Agents are able to generalize to situations where the from-scratch approach fails and training becomes significantly more sample efficient. However, we show that realizing these gains requires careful selection of the mid-level perceptual skills. Therefore, we refine our findings into an efficient max-coverage feature set that can be adopted in lieu of raw images. We perform our study in completely separate buildings for training and testing and compare against visually blind baseline policies and state-of-the-art feature learning methods.

Attention and Perceptual Learning Interact in the Development of the Other-Race Effect:

Abstract: Face-processing abilities are biased such that some faces are differentiated, recognized, and identified more readily than others. Across the first year of life, experience with faces shapes the de...

Speech categorization develops slowly through adolescence.

Abstract: The development of the ability to categorize speech sounds is often viewed as occurring primarily during infancy via perceptual learning mechanisms. However, a number of studies suggest that even after infancy, children's categories become more categorical and well defined through about age 12. We investigated the cognitive changes that may be responsible for such development using a visual world paradigm experiment based on (McMurray, Tanenhaus, & Aslin, 2002). Children from 3 age groups (7-8, 12-13, and 17-18 years) heard a token from either a b/p or s/∫ continua spanning 2 words (beach/peach, ship/sip) and selected its referent from a screen containing 4 pictures of potential lexical candidates. Eye movements to each object were monitored as a measure of how strongly children were committing to each candidate as perception unfolds in real-time. Results showed an ongoing sharpening of speech categories through 18, which was particularly apparent during the early stages of real-time perception. When analysis targeted to specifically within-category sensitivity to continuous detail, children exhibited increasingly gradient categories over development, suggesting that increasing sensitivity to fine-grained detail in the signal enables these more discrete categorizations. Together these suggest that speech development is a protracted process in which children's increasing sensitivity to within-category detail in the signal enables increasingly sharp phonetic categories. (PsycINFO Database Record

Sensory Substitution and the Neural Correlates of Navigation in Blindness

Abstract: This chapter reviews the most recent advances in sensory substitution and the neural correlates of navigation in congenital blindness . Studies have established the superior ability of congenitally blind (CB) participants with the aid of Sensory Substitution Devices (SSDs) to navigate new environments and detect the size and shape of obstacles in order to avoid them. These studies suggest that with training, CB can achieve a representation of space that is equivalent to that of the sighted. From a phenomenological point of view, sensation and perception provided by SSDs have been likened to real vision, but the question remains as to the subjective sensations (qualia) felt by users. We review recent theories on the phenomenological properties of sensory substitution and the recent literature on spatial abilities of participants using SSDs. From these different sources of research, we conclude that training-induced plastic changes enable task-specific brain activations. The recruitment of the primary visual cortex by nonvisual SSD stimulations and, the subsequent activations of associative visual cortices in the congenitally blind, suggest that the sensory information is treated in an amodal fashion; i.e.,: in terms of the task being performed rather than the sensory modality. These anatomical changes enable the embodiment of nonvisual information allowing SSD users to accomplish a multitude of “visual” tasks. We will emphasize here the abilities of CB individuals to navigate in real and virtual environments in spite of a large volumetric reduction in the posterior segment of the hippocampus , a key area involved in navigation . In addition, the superior behavioral performance of CB in a variety of sensory and cognitive tasks, combined with anatomical and functional MRI, underlines the susceptibility of the brain to training-induced plasticity.

GABA, not BOLD, reveals dissociable learning-dependent plasticity mechanisms in the human brain.

Abstract: Experience and training have been shown to facilitate our ability to extract and discriminate meaningful patterns from cluttered environments. Yet, the human brain mechanisms that mediate our ability to learn by suppressing noisy and irrelevant signals remain largely unknown. To test the role of suppression in perceptual learning, we combine fMRI with MR Spectroscopy measurements of GABA, as fMRI alone does not allow us to discern inhibitory vs. excitatory mechanisms. Our results demonstrate that task-dependent GABAergic inhibition relates to functional brain plasticity and behavioral improvement. Specifically, GABAergic inhibition in the occipito-temporal cortex relates to dissociable learning mechanisms: decreased GABA for noise filtering, while increased GABA for feature template retuning. Perturbing cortical excitability during training with tDCs alters performance in a task-specific manner, providing evidence for a direct link between suppression and behavioral improvement. Our findings propose dissociable GABAergic mechanisms that optimize our ability to make perceptual decisions through training.

High reward enhances perceptual learning.

Abstract: Studies of perceptual learning have revealed a great deal of plasticity in adult humans. In this study, we systematically investigated the effects and mechanisms of several forms (trial-by-trial, block, and session rewards) and levels (no, low, high, subliminal) of monetary reward on the rate, magnitude, and generalizability of perceptual learning. We found that high monetary reward can greatly promote the rate and boost the magnitude of learning and enhance performance in untrained spatial frequencies and eye without changing interocular, interlocation, and interdirection transfer indices. High reward per se made unique contributions to the enhanced learning through improved internal noise reduction. Furthermore, the effects of high reward on perceptual learning occurred in a range of perceptual tasks. The results may have major implications for the understanding of the nature of the learning rule in perceptual learning and for the use of reward to enhance perceptual learning in practical applications.

Rich perceptual content and aesthetic properties

Abstract: Both common sense and dominant traditions in art criticism and philosophical aesthetics maintain that aesthetic features or properties are perceived. However, there are many reasons to be sceptical of this. This chapter defends the thesis—that aesthetic properties are sometimes represented in perceptual experience—against one of those sceptical opponents who maintains that perception represents only low-level properties, and since all theorists agree that aesthetic properties are not low-level properties, perception does not represent aesthetic properties. This chapter offers a novel argument—the argument from seeing-as—against that sceptic which moves from consideration of ambiguous figures to consideration of visual art, concluding that aesthetic properties are sometimes perceived and delivers a general lesson for philosophy of perception. Contrary to extant theories of rich perceptual content, aesthetic properties are better candidates for high-level perceptual contents than standardly theorized rich contents like natural kinds.

Endogenous spatial attention during perceptual learning facilitates location transfer.

Abstract: Covert attention and perceptual learning enhance perceptual performance. The relation between these two mechanisms is largely unknown. Previously, we showed that manipulating involuntary, exogenous spatial attention during training improved performance at trained and untrained locations, thus overcoming the typical location specificity. Notably, attention-induced transfer only occurred for high stimulus contrasts, at the upper asymptote of the psychometric function (i.e., via response gain). Here, we investigated whether and how voluntary, endogenous attention, the top-down and goal-based type of covert visual attention, influences perceptual learning. Twenty-six participants trained in an orientation discrimination task at two locations: half of participants received valid endogenous spatial precues (attention group), while the other half received neutral precues (neutral group). Before and after training, all participants were tested with neutral precues at two trained and two untrained locations. Within each session, stimulus contrast varied on a trial basis from very low (2%) to very high (64%). Performance was fit by a Weibull psychometric function separately for each day and location. Performance improved for both groups at the trained location, and unlike training with exogenous attention, at the threshold level (i.e., via contrast gain). The neutral group exhibited location specificity: Thresholds decreased at the trained locations, but not at the untrained locations. In contrast, participants in the attention group showed significant location transfer: Thresholds decreased to the same extent at both trained and untrained locations. These results indicate that, similar to exogenous spatial attention, endogenous spatial attention induces location transfer, but influences contrast gain instead of response gain.

Does physical exercise improve perceptual skills and visuospatial attention in older adults? A review

Abstract: Neuroimaging studies suggest that when the brain ages, more areas are involved to perform a task in order to obtain the same results. This, together with the increase in crystalized intelligence and wisdom, is usually considered as a compensatory strategy. Research has demonstrated that physical activity might also act as a strategy and be one of the main factors that can slow down age-related perceptual and cognitive decline. Research also suggests that different types of physical exercise and sport lead to different changes in perceptual and cognitive skills as well as in several areas of the brain, especially those involving multiple domains, such as exergaming, dance or some sports. This review summarizes the findings of recent studies with older adults investigating the brain and cognitive benefits of different forms of physical exercise. Visuospatial attention, which plays a critical role in our daily lives, especially for older adults, is a central part of this analysis.

Axonal plasticity associated with perceptual learning in adult macaque primary visual cortex.

Abstract: Perceptual learning is associated with changes in the functional properties of neurons even in primary sensory areas. In macaque monkeys trained to perform a contour detection task, we have observed changes in contour-related facilitation of neuronal responses in primary visual cortex that track their improvement in performance on a contour detection task. We have previously explored the anatomical substrate of experience-dependent changes in the visual cortex based on a retinal lesion model, where we find sprouting and pruning of the axon collaterals in the cortical lesion projection zone. Here, we attempted to determine whether similar changes occur under normal visual experience, such as that associated with perceptual learning. We labeled the long-range horizontal connections in visual cortex by virally mediated transfer of genes expressing fluorescent probes, which enabled us to do longitudinal two-photon imaging of axonal arbors over the period during which animals improve in contour detection performance. We found that there are substantial changes in the axonal arbors of neurons in cortical regions representing the trained part of the visual field, with sprouting of new axon collaterals and pruning of preexisting axon collaterals. Our findings indicate that changes in the structure of axonal arbors are part of the circuit-level mechanism of perceptual learning, and further support the idea that the learned information is encoded at least in part in primary visual cortex.

In defense of hearing meanings

Abstract: According to the inferential view of language comprehension, we hear a speaker’s utterance and infer what was said, drawing on our competence in the syntax and semantics of the language together with background information. On the alternative perceptual view, fluent speakers have a non-inferential capacity to perceive the content of speech. On this view, when we hear a speaker’s utterance, the experience confers some degree of justification on our beliefs about what was said in the absence of defeaters. So, in the absence of defeaters, we can come to know what was said merely on the basis of hearing the utterance. Several arguments have been offered against a pure perceptual view of language comprehension, among others, arguments pointing to its alleged difficulties accounting for homophones and the context-sensitivity of ordinary language. After responding to challenges to the perceptual view of language comprehension, I provide a new argument in favor of the perceptual view by looking closer at the dependence of the justificatory qualities of experience on the notion of a defeater as well as the perceptual nature of language learning and language processing.

Age, Hearing, and the Perceptual Learning of Rapid Speech.

Abstract: The effects of aging and age-related hearing loss on the ability to learn degraded speech are not well understood. This study was designed to compare the perceptual learning of time-compressed speech and its generalization to natural-fast speech across young adults with normal hearing, older adults with normal hearing, and older adults with age-related hearing loss. Early learning (following brief exposure to time-compressed speech) and later learning (following further training) were compared across groups. Age and age-related hearing loss were both associated with declines in early learning. Although the two groups of older adults improved during the training session, when compared to untrained control groups (matched for age and hearing), learning was weaker in older than in young adults. Especially, the transfer of learning to untrained time-compressed sentences was reduced in both groups of older adults. Transfer of learning to natural-fast speech occurred regardless of age and hearing, but it was limited to sentences encountered during training. Findings are discussed within the framework of dynamic models of speech perception and learning. Based on this framework, we tentatively suggest that age-related declines in learning may stem from age differences in the use of high- and low-level speech cues. These age differences result in weaker early learning in older adults, which may further contribute to the difficulty to perceive speech in daily conversational settings in this population.

Retained capacity for perceptual learning of degraded speech in primary progressive aphasia and Alzheimer's disease

Abstract: Processing of degraded speech is a promising model for understanding communication under challenging listening conditions, core auditory deficits and residual capacity for perceptual learning and cerebral plasticity in major dementias. We compared the processing of sine-wave-degraded speech in 26 patients with primary progressive aphasia (non-fluent, semantic, and logopenic variants), 10 patients with typical Alzheimer’s disease and 17 healthy control subjects. Participants were required to identify sine-wave words that were more predictable (three-digit numbers) or less predictable (place names). The change in identification performance within each session indexed perceptual learning. Neuroanatomical associations of degraded speech processing were assessed using voxel-based morphometry. Patients with non-fluent and logopenic progressive aphasia and typical Alzheimer’s disease showed impaired identification of sine-wave numbers, whereas all syndromic groups showed impaired identification of sine-wave place names. A significant overall identification advantage for numbers over place names was shown by patients with typical Alzheimer’s disease, patients with semantic progressive aphasia and healthy control participants. All syndromic groups showed spontaneous perceptual learning effects for sine-wave numbers. For the combined patient cohort, grey matter correlates were identified across a distributed left hemisphere network extending beyond classical speech-processing cortices. These findings demonstrate resilience of auditory perceptual learning capacity across dementia syndromes, despite variably impaired perceptual decoding of degraded speech and reduced predictive integration of semantic knowledge. This work has implications for the neurobiology of dynamic sensory processing and plasticity in neurodegenerative diseases and for development of novel biomarkers and therapeutic interventions.

Perceptual learning of fine contrast discrimination changes neuronal tuning and population coding in macaque V4.

Abstract: Perceptual learning, the improvement in perceptual abilities with training, is thought to be mediated by an alteration of neuronal tuning. It remains poorly understood how tuning properties change as training progresses, whether improved stimulus tuning directly links to increased behavioural readout of sensory information, or how population coding mechanisms change with training. Here, we recorded continuously from multiple neuronal clusters in area V4 while macaque monkeys learned a fine contrast categorization task. Training increased neuronal coding abilities by shifting the steepest point of contrast response functions towards the categorization boundary. Population coding accuracy of difficult discriminations resulted largely from an increased information coding of individual channels, particularly for those channels that in early learning had larger ability for easy discriminations, but comparatively small encoding abilities for difficult discriminations. Population coding was also enhanced by specific changes in correlations. Neuronal activity became more indicative of upcoming choices with training.

A review of plasticity induced by auditory and visual tetanic stimulation in humans.

Abstract: Long-term potentiation is a form of synaptic plasticity thought to play an important role in learning and memory. Recently noninvasive methods have been developed to induce and measure activity similar to long-term potentiation in humans. Sensory tetani (trains of quickly repeating auditory or visual stimuli) alter the electroencephalogram in a manner similar to electrical stimulation that results in long-term potentiation. This review briefly covers the development of long-term potentiation research before focusing on in vivo human studies that produce long-term potentiation-like effects using auditory and visual stimulation. Similarities and differences between traditional (animal and brain tissue) long-term potentiation studies and human sensory tetanization studies will be discussed, as well as implications for perceptual learning. Although evidence for functional consequences of sensory tetanization remains scarce, studies involving clinical populations indicate that sensory induced plasticity paradigms may be developed into diagnostic and research tools in clinical settings. Individual differences in the effects of sensory tetanization are not well-understood and provide an interesting avenue for future research. Differences in effects found between research groups that have emerged as the field has progressed are also yet to be resolved.

The Role of Lexical Status and Individual Differences for Perceptual Learning in Younger and Older Adults.

Abstract: Purpose This study examined whether older adults remain perceptually flexible when presented with ambiguities in speech in the absence of lexically disambiguating information. We expected older adu...

Attention enhances apparent perceptual organization.

Abstract: Perceptual organization and selective attention are two crucial processes that influence how we perceive visual information. The former structures complex visual inputs into coherent units, whereas the later selects relevant information. Attention and perceptual organization can modulate each other, affecting visual processing and performance in various tasks and conditions. Here, we tested whether attention can alter the way multiple elements appear to be perceptually organized. We manipulated covert spatial attention using a rapid serial visual presentation task, and measured perceptual organization of two multielements arrays organized by luminance similarity as rows or columns, at both the attended and unattended locations. We found that the apparent perceptual organization of the multielement arrays is intensified when attended and attenuated when unattended. We ruled out response bias as an alternative explanation. These findings reveal that attention enhances the appearance of perceptual organization, a midlevel vision process, altering the way we perceive our visual environment.

An Empirical Study on Short- and Long-Term Effects of Self-Correction in Crowdsourced Microtasks.

Abstract: Self-correction for crowdsourced tasks is a two-stage setting that allows a crowd worker to review the task results of other workers; the worker is then given a chance to update his/her results according to the review.Self-correction was proposed as an approach complementary to statistical algorithms in which workers independently perform the same task. It can provide higher-quality results with few additional costs. However, thus far, the effects have only been demonstrated in simulations, and empirical evaluations are needed. In addition, as self-correction gives feedback to workers, an interesting question arises: whether perceptual learning is observed in self-correction tasks. This paper reports our experimental results on self-corrections with a real-world crowdsourcing service.The empirical results show the following: (1) Self-correction is effective for making workers reconsider their judgments. (2) Self-correction is more effective if workers are shown task results produced by higher-quality workers during the second stage. (3) Perceptual learning effect is observed in some cases. Self-correction can give feedback that shows workers how to provide high-quality answers in future tasks.The findings imply that we can construct a positive loop to improve the quality of workers effectively.We also analyze in which cases perceptual learning can be observed with self-correction in crowdsourced microtasks.