Mechanisms Of Perceptual Learning Research Articles

Noise reduction as a unified mechanism of perceptual learning in both artificial and biological visual systems

Noise reduction as a unified mechanism of perceptual learning in both artificial and biological visual systems

Audiovisual illusion training improves multisensory temporal integration

When we perceive external physical stimuli from the environment, the brain must remain somewhat flexible to unaligned stimuli within a specific range, as multisensory signals are subject to different transmission and processing delays. Recent studies have shown that the width of the ‘temporal binding window (TBW)’ can be reduced by perceptual learning. However, to date, the vast majority of studies examining the mechanisms of perceptual learning have focused on experience-dependent effects, failing to reach a consensus on its relationship with the underlying perception influenced by audiovisual illusion. The sound-induced flash illusion (SiFI) training is a reliable function for improving perceptual sensitivity. The present study utilized the classic auditory-dominated SiFI paradigm with feedback training to investigate the effect of a 5-day SiFI training on multisensory temporal integration, as evaluated by a simultaneity judgment (SJ) task and temporal order judgment (TOJ) task. We demonstrate that audiovisual illusion training enhances multisensory temporal integration precision in the form of (i) the point of subjective simultaneity (PSS) shifts to reality (0 ms) and (ii) a narrowing TBW. The results are consistent with a Bayesian model of causal inference, suggesting that perception learning reduce the susceptibility to SiFI, whilst improving the precision of audiovisual temporal estimation.

Comparing random dot motion in MATLAB vs. Inquisit Millisecond.

Random Dot Motion (RDM) displays refer to clouds of independently moving dots that can be parametrically manipulated to provide a perception of the overall cloud moving coherently in a specified direction of motion. As a well-studied probe of motion perception, RDMs have been widely employed to understand underlying neural mechanisms of motion perception, perceptual decision-making, and perceptual learning, among other processes. Despite their wide use, RDM stimuli implementation is highly dependent on the parameters and the generation algorithm of the stimuli; both can greatly influence behavioral performance on RDM tasks. With the advent of the COVID pandemic and an increased need for more accessible platforms, we aimed to validate a novel RDM paradigm on Inquisit Millisecond, a platform for the online administration of cognitive and neuropsychological tests and assessments. We directly compared, in the same participants using the same display, a novel RDM paradigm on both Inquisit Millisecond and MATLAB with Psychtoolbox. We found that psychometric functions of Coherence largely match between Inquisit Millisecond and MATLAB, as do the effects of Duration. These data demonstrate that the Millisecond RDM provides data largely consistent with those previously found in laboratory-based systems, and the present findings can serve as a reference point for expected thresholds for when these procedures are used remotely on different platforms.

Impaired grouping of ambient facial images in autism

Ambient facial images depict individuals from a variety of viewing angles, with a range of poses and expressions, under different lighting conditions. Exposure to ambient images is thought to help observers form robust representations of the individuals depicted. Previous results suggest that autistic people may derive less benefit from exposure to this exemplar variation than non-autistic people. To date, however, it remains unclear why. One possibility is that autistic individuals possess atypical perceptual learning mechanisms. Alternatively, however, the learning mechanisms may be intact, but receive low-quality perceptual input from face encoding processes. To examine this second possibility, we investigated whether autistic people are less able to group ambient images of unfamiliar individuals based on their identity. Participants were asked to identify which of four ambient images depicted an oddball identity. Each trial assessed the grouping of different facial identities, thereby preventing face learning across trials. As such, the task assessed participants’ ability to group ambient images of unfamiliar people. In two experiments we found that matched non-autistic controls correctly identified the oddball identities more often than our autistic participants. These results imply that poor face learning from variation by autistic individuals may well be attributable to low-quality perceptual input, not aberrant learning mechanisms.

Entrainment of somatosensory beta and gamma oscillations accompany improvement in tactile acuity after periodic and aperiodic repetitive sensory stimulation

Previous research showed that repetitive sensory stimulation entrains neural oscillations at the stimulation rate, facilitates long-term potentiation like perceptual learning, and improves behavioural performance. For example, short-time repetitive tactile stimulation improved tactile acuity measured with two-point or spatial orientation discrimination tests. The behavioural gain was maximal for a stimulation rate of 20 Hz, the same frequency at which repetitive somatosensory stimulation elicits a steady-state response with maximum amplitude. The current study investigated whether sensory stimulation must be strictly periodic to induce perceptual learning and whether the 20-Hz steady-state response plays a crucial role in the neural mechanisms of perceptual learning. In a crossover-designed experiment, young, healthy adults received sensory stimulation to the fingertip on three subsequent days. The stimulation was either periodic or temporally randomized (aperiodic) with the same number of stimuli. Tactile acuity was assessed with a grating orientation discrimination task, and brain activity was measured with magnetoencephalography (MEG). Stimulus type-by-session interactions were found for behavioural and brain data. Tactile acuity improved more after a session with aperiodic than periodic stimulation. Beta-band 20-Hz steady-state responses were localized in the primary somatosensory cortex contralateral to the stimulated finger and had larger amplitudes after periodic than aperiodic stimulation. Both stimulus types also elicited gamma oscillations, which increased in amplitude more with aperiodic than periodic stimulation. Sensory stimuli caused a phase reset of sensorimotor beta oscillations phase-coupled to alpha oscillations. The system of stimulus-related oscillations was discussed as underlying temporal processing. Learning may result from facilitating the temporal code. More pronounced behavioural gain with aperiodic than periodic stimulation suggests beneficial effects of temporal stimulus variability for perceptual learning.

Stimulus variability and task relevance modulate binding-learning.

Classical theories of attention posit that integration of features into object representation (or feature binding) requires engagement of focused attention. Studies challenging this idea have demonstrated that feature binding can happen outside of the focus of attention for familiar objects, as well as for arbitrary color-orientation conjunctions. Detection performance for arbitrary feature conjunction improves with training, suggesting a potential role of perceptual learning mechanisms in the integration of features, a process called "binding-learning". In the present study, we investigate whether stimulus variability and task relevance, two critical determinants of visual perceptual learning, also modulate binding-learning. Transfer of learning in a visual search task to a pre-exposed color-orientation conjunction was assessed under conditions of varying stimulus variability and task relevance. We found transfer of learning for the pre-exposed feature conjunctions that were trained with high variability (Experiment1). Transfer of learning was not observed when the conjunction was rendered task-irrelevant during training due to pop-out targets (Experiment2). Our findings show that feature binding is determined by principles of perceptual learning, and they support the idea that functions traditionally attributed to goal-driven attention can be grounded in the learning of the statistical structure of the environment.

The Influences of Category Learning on Perceptual Reconstructions.

We explore different ways in which the human visual system can adapt for perceiving and categorizing the environment. There are various accounts of supervised (categorical) and unsupervised perceptual learning, and different perspectives on the functional relationship between perception and categorization. We suggest that common experimental designs are insufficient to differentiate between hypothesized perceptual learning mechanisms and reveal their possible interplay. We propose a relatively underutilized way of studying potential categorical effects on perception, and we test the predictions of different perceptual learning models using a two-dimensional, interleaved categorization-plus-reconstruction task. We find evidence that the human visual system adapts its encodings to the feature structure of the environment, uses categorical expectations for robust reconstruction, allocates encoding resources with respect to categorization utility, and adapts to prevent miscategorizations.

A Clinical Advantage: Experience Informs Recognition and Adaptation to a Novel Talker With Dysarthria

Purpose Perceptual training paradigms, which leverage the mechanism of perceptual learning, show that naïve listeners, those with no prior experience with dysarthria, benefit from explicit familiarization with a talker with dysarthria. It is theorized that familiarization affords listeners an opportunity to acquire distributional knowledge of the degraded speech signal. Here, we extend investigations to clinically experienced listeners, speech-language pathologists (SLPs), and advance models of listener recognition and adaptation to dysarthric speech. Method Forty-seven SLPs completed a standard three-phase perceptual training protocol (pretest, familiarization, and posttest) with a novel talker with dysarthria. Intelligibility scores were compared with historical data from naïve listeners. Potential relationships between intelligibility scores and characteristics of clinical experience were examined. Results Intelligibility scores of SLPs improved by an average of 19% from pretest to posttest. This intelligibility improvement was lower than naïve listeners, although the difference was small. Moreover, clinical characteristics related to level of dysarthria experience (e.g., percent of caseload composed of dysarthria) predicted pretest/initial intelligibility. No predictive relationships between clinical characteristics and intelligibility improvement were revealed. Conclusions As a group, SLPs benefitted from perceptual training, suggesting that, despite prior experience, the opportunity to acquire knowledge of talker-specific cue distributions is crucial for optimal adaptation. However, SLPs with greater dysarthria experience were better at initially understanding the talker with dysarthria. This suggests that, through regular interaction with individuals with dysarthria, clinicians acquire knowledge of the cue distributions of dysarthric speech more generally and can generalize this group-specific knowledge to aid in understanding other talkers with dysarthria. Consistent with theoretical models of perceptual learning, both talker- and group-specific knowledge informed recognition and adaptation to dysarthric speech.

Individual Differences in Lexical Contributions to Speech Perception.

Purpose The extant literature suggests that individual differences in speech perception can be linked to broad receptive language phenotype. For example, a recent study found that individuals with a smaller receptive vocabulary showed diminished lexically guided perceptual learning compared to individuals with a larger receptive vocabulary. Here, we examined (a) whether such individual differences stem from variation in reliance on lexical information or variation in perceptual learning itself and (b) whether a relationship exists between lexical recruitment and lexically guided perceptual learning more broadly, as predicted by current models of lexically guided perceptual learning. Method In Experiment 1, adult participants (n = 70) completed measures of receptive and expressive language ability, lexical recruitment, and lexically guided perceptual learning. In Experiment 2, adult participants (n = 120) completed the same lexical recruitment and lexically guided perceptual learning tasks to provide a high-powered replication of the primary findings from Experiment 1. Results In Experiment 1, individuals with weaker receptive language ability showed increased lexical recruitment relative to individuals with higher receptive language ability; however, receptive language ability did not predict the magnitude of lexically guided perceptual learning. Moreover, the results of both experiments converged to show no evidence indicating a relationship between lexical recruitment and lexically guided perceptual learning. Conclusion The current findings suggest that (a) individuals with weaker language ability demonstrate increased reliance on lexical information for speech perception compared to those with stronger receptive language ability; (b) individuals with weaker language ability maintain an intact perceptual learning mechanism; and, (c) to the degree that the measures used here accurately capture individual differences in lexical recruitment and lexically guided perceptual learning, there is no graded relationship between these two constructs.

Mechanisms of perceptual learning: Prolonged intermixed preexposure reduces the effectiveness of the unique and the common elements.

In three experiments, rats were given intermixed or blocked preexposure to two similar compound stimuli, AX and BX. In Experiment 1, following preexposure, animals were given appetitive conditioning training with the compound AX. A subsequent generalization test showed better discrimination between AX and BX in the group given intermixed than in the one given blocked preexposure. Experiments 2 and 3 assessed the nature of the learning mechanisms underlying this instance of the perceptual learning effect. Experiment 2 assessed the associability of the common and unique elements (X and A); animals in the group given intermixed preexposure showed poorer conditioning with both the X and the A elements than those given blocked preexposure. Experiment 3 further assessed the perceptual effectiveness of the distinctive element A using a superimposition test (the capacity of A to interfere with the conditioned response commanded by an independent conditioned stimulus). The results showed, in line with the outcome of Experiment 2, that the unique element A is more salient following blocked than intermixed preexposure. These results are discussed by reference to current theories of perceptual learning. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Fundamental Differences in Visual Perceptual Learning between Children and Adults

It has remained uncertain whether the mechanisms of visual perceptual learning (VPL)1-4 remain stable across the lifespan or undergo developmental changes. This uncertainty largely originates from missing results about the mechanisms of VPL in healthy children. We here investigated the mechanisms of task-irrelevant VPL in healthy elementary school age children (7-10 years old) and compared their results to healthy young adults (18-31 years old). Subjects performed a rapid-serial-visual-presentation (RSVP) task at central fixation over the course of several daily sessions while coherent motion was merely exposed as a task-irrelevant feature in the visual periphery either at threshold or suprathreshold levels for coherent motion detection. As a result of this repeated exposure, children and adults both showed enhanced discrimination performance for the threshold task-irrelevant feature as in previous studies with adults.5-8 However, adults demonstrated a decreased performance for the suprathreshold task-irrelevant feature whereas children increased performance. One possible explanation for this difference is that children cannot effectively suppress salient task-irrelevant features because of weaker selective attention ability compared to that of adults.9-11 However, our results revealed to the contrary that children with stronger selective attention ability, as measured by the useful field of view (UFOV) test, showed greater increases in performance for the suprathreshold task-irrelevant feature. Together, these results suggest that the mechanisms of VPL change dramatically from childhood to adulthood due to a change in the way learners handle salient task-irrelevant features.

Perceptual Learning: How Does the Visual Circuit Change through Experience?

New research establishes that high-field functional imaging in humans can distinguish laminar specificity of visual circuit plasticity in humans. By simultaneously imaging fine-scale brain circuitry while measuring large-scale brain connectivity we can further unravel the mechanisms of perceptual learning.

Novel mechanisms of rapid reactivation-induced perceptual learning

Novel mechanisms of rapid reactivation-induced perceptual learning

Dramatic Changes in Mechanisms of Task-Irrelevant Visual Perceptual Learning from Childhood to Adulthood

Dramatic Changes in Mechanisms of Task-Irrelevant Visual Perceptual Learning from Childhood to Adulthood

Attenuating Neural Threat Expression with Imagination

Imagination is an internal simulation of real-life events and a common treatment tool for anxiety disorders; however, the neural processes by which imagination exerts behavioral control are unclear. This investigation tests whether and how imagined exposures to a threatening stimulus, conditioned in the real world, influence neural and physiological manifestations of threat. We found that imagined and real extinction are equally effective in the reduction of threat-related neural patterns and physiological responses elicited upon re-exposure to real-world threatening cues. Network connectivity during the extinction phase showed that imagined, like real, extinction engaged the ventromedial prefrontal cortex (vmPFC) as a central hub. vmPFC, primary auditory cortex, and amygdala activation during imagined and real extinction were predictive of individual differences in extinction success. The nucleus accumbens, however, predicted extinction success in the imagined extinction group alone. We conclude that deliberate imagination can attenuate reactions to threat through perceptual and associative learning mechanisms.

Speech categorization develops slowly through adolescence.

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

Structural and Functional Connectivity Changes Beyond Visual Cortex in a Later Phase of Visual Perceptual Learning

The neural mechanisms of visual perceptual learning (VPL) remain unclear. Previously we found that activation in the primary visual cortex (V1) increased in the early encoding phase of training, but returned to baseline levels in the later retention phase. To examine neural changes during the retention phase, we measured structural and functional connectivity changes using MRI. After weeks of training on a texture discrimination task, the fractional anisotropy of the inferior longitudinal fasciculus, a major tract connecting visual and anterior areas, was increased, as well as the functional connectivity between V1 and anterior regions mediated by the ILF. These changes were strongly correlated with behavioral performance improvements. These results suggest a two-phase model of VPL in which localized functional changes in V1 in the encoding phase of training are followed by changes in both structural and functional connectivity in ventral visual processing, perhaps leading to the long-term stabilization of VPL.

Initiating language in LIDA: Learning the meaning of vervet alarm calls

Abstract This paper initiates language in LIDA by using the Learning Intelligent Decision 1 Agent’s (LIDA) perceptual learning mechanism to suggest how an infant vervet, Chlorocebus pygerthrus, learns the meanings of vervet monkey alarm calls. We consider a multiple meanings approach which includes a feeling-based meaning, an action-based meaning, and a referential meaning. Simulations first test the learning of the meanings of these alarm calls while the infant is physically attached to the mother. The second simulations study the infant’s understanding of these alarm calls while the infant is detached physically from the mother. Our results confirm that a LIDA based agent simulating a vervet infant is capable of learning such multiple meanings. The agent learned in sequence the feeling-based meaning, the action-based meaning, and the referential meaning. The LIDA agent achieved a good understanding of each of these meanings. This work can be seen as a starting step toward modeling the learning of human language in the LIDA cognitive architecture. Such modeling of language use would be a significant addition to the LIDA model.

Neural mechanisms of motion perceptual learning in noise.

Practice improves our perceptual ability. However, the neural mechanisms underlying this experience-dependent plasticity in adult brain remain unclear. Here, we studied the long-term neural correlates of motion perceptual learning. Subjects' behavioral performance and BOLD signals were tracked before, immediately after, and 2 weeks after practicing a motion direction discrimination task in noise over six daily sessions. Parallel to the specificity and persistency of the behavioral learning effect, we found that training sharpened the cortical tuning in MT, and enhanced the connectivity strength from MT to the intraparietal sulcus (IPS, a motion decision-making area). In addition, the decoding accuracy for the trained motion direction was improved in IPS 2 weeks after training. The dual changes in the sensory and the high-level cortical areas suggest that learning refines the neural representation of the trained stimulus and facilitates the information transmission in the decision process. Our findings are consistent with the functional specialization in the visual cortex, and provide empirical evidence to the reweighting theory of perceptual learning at a large spatial scale. Hum Brain Mapp 38:6029-6042, 2017. © 2017 Wiley Periodicals, Inc.

Organization of Orientation-Specific Whisker Deflection Responses in Layer 2/3 of Mouse Somatosensory Cortex

The rodent whisker-barrel system is characterized by its patterned somatotopic mapping between the sensory periphery and multiple regions of the brain. While somatotopy in the whisker system is established, we know far less about how preferences for stimulus orientation or other features are organized. Mouse somatosensation is an increasingly popular model for circuit-based dissection of perceptual decision making and learning, yet our understanding of how stimulus feature representations are organized in the cortex is incomplete. Here, we used in vivo two-photon calcium imaging to monitor activity of populations of layer (L) 2/3 neurons in the mouse primary somatosensory cortex during deflections of a single whisker in two orthogonal orientations (azimuthal or elevational). We split the population response to whisker deflections into an orientation-specific component and a non-specific component that reflected overall excitability in response to deflection of a single whisker. Orientation-specific responses were organized in a locally heterogeneous and spatially distributed manner. Correlations in the stimulus-independent trial-to-trial variability of pairs of neurons were higher among neurons that preferred the same orientation. These correlations depended on similarity in both orientation-specific and non-specific components of responses to single-whisker deflections. Our results shed light on L2/3 organization in mouse somatosensory cortex, and lay a foundation for dissecting circuit mechanisms of perceptual learning and decision-making during orientation discrimination tasks.