Texture Discrimination Task Research Articles

Nicotine facilitates memory consolidation in perceptual learning

Perceptual learning is a special type of non-declarative learning that involves experience-dependent plasticity in sensory cortices. The cholinergic system is known to modulate declarative learning. In particular, reduced levels or efficacy of the neurotransmitter acetylcholine were found to facilitate declarative memory consolidation. However, little is known about the role of the cholinergic system in memory consolidation of non-declarative learning. Here we compared two groups of non-smoking men who learned a visual texture discrimination task (TDT). One group received chewing tobacco containing nicotine for 1 h directly following the TDT training. The other group received a similar tasting control substance without nicotine. Electroencephalographic recordings during substance consumption showed reduced alpha activity and P300 latencies in the nicotine group compared to the control group. When re-tested on the TDT the following day, both groups responded more accurately and more rapidly than during training. These improvements were specific to the retinal location and orientation of the texture elements of the TDT suggesting that learning involved early visual cortex. A group comparison showed that learning effects were more pronounced in the nicotine group than in the control group. These findings suggest that oral consumption of nicotine enhances the efficacy of nicotinic acetylcholine receptors. Our findings further suggest that enhanced efficacy of the cholinergic system facilitates memory consolidation in perceptual learning (and possibly other types of non-declarative learning). In that regard acetylcholine seems to affect consolidation processes in perceptual learning in a different manner than in declarative learning. Alternatively, our findings might reflect dose-dependent cholinergic modulation of memory consolidation.This article is part of a Special Issue entitled ‘Cognitive Enhancers’.

Rodents Rely on Merkel Cells for Texture Discrimination Tasks

The cutaneous somatosensory system contains multiple types of mechanoreceptors that detect different mechanical stimuli (Johnson, 2001). These stimuli, either alone or in combination, are ultimately interpreted by the brain as different aspects of the sense of touch. Psychophysical and electrophysiological experiments in humans and other mammals implicate one of these mechanoreceptors, the Merkel cell/neurite complex, in two-point discrimination and the detection of curvature, shape, and texture (Johnson and Lamb, 1981; Johnson et al., 2000; Johnson, 2001). However, whether Merkel cell/neurite complex function is required for the detection of these stimuli is unknown. We genetically engineered mice that lack Merkel cells (Maricich et al., 2009; Morrison et al., 2009) to directly test the hypothesis that Merkel cell/neurite complexes are necessary to perform these types of sensory discrimination tasks. We found that mice devoid of Merkel cells could not detect textured surfaces with their feet while other measures of motor and sensory function were unaffected. Interestingly, these mice retained the ability to discriminate both texture and shape using their whiskers, suggesting that other somatosensory afferents can functionally substitute for Merkel cell/neurite complexes in this sensory organ. These findings suggest that Merkel cell/neurite complexes are essential for texture discrimination tasks involving glabrous skin but not whiskers.

Act Quickly, Decide Later: Long-latency Visual Processing Underlies Perceptual Decisions but Not Reflexive Behavior

Humans largely guide their behavior by their visual representation of the world. Recent studies have shown that visual information can trigger behavior within 150 msec, suggesting that visually guided responses to external events, in fact, precede conscious awareness of those events. However, is such a view correct? By using a texture discrimination task, we show that the brain relies on long-latency visual processing in order to guide perceptual decisions. Decreasing stimulus saliency leads to selective changes in long-latency visually evoked potential components reflecting scene segmentation. These latency changes are accompanied by almost equal changes in simple RTs and points of subjective simultaneity. Furthermore, we find a strong correlation between individual RTs and the latencies of scene segmentation related components in the visually evoked potentials, showing that the processes underlying these late brain potentials are critical in triggering a response. However, using the same texture stimuli in an antisaccade task, we found that reflexive, but erroneous, prosaccades, but not antisaccades, can be triggered by earlier visual processes. In other words: The brain can act quickly, but decides late. Differences between our study and earlier findings suggesting that action precedes conscious awareness can be explained by assuming that task demands determine whether a fast and unconscious, or a slower and conscious, representation is used to initiate a visually guided response.

Effects of meditation on consolidation of perceptual learning

Meditative practices can enhance visuospatial working memory (Kozhevnikov et al., 2009) and sensory acuity (Kerr et al., 2005). It is thought that these effects are caused by enhanced attention to a given task, due to meditation. However, it is not clear whether meditation facilitates other forms of implicit processing that do not directly relate to attention. Here we investigated the effects of meditation on perceptual learning stabilization that occurs after training on a texture discrimination task (TDT) (Karni and Sagi, 1992). Zen meditators and non-meditators were trained in TDT. Previous studies have reported that learning of TDT with a background orientation (training A) is impaired by subsequent learning of TDT with a different background orientation (training B) (Yotsumoto et al., 2009). It is thought that such impairment is due to the interference effects of training B on the consolidation/stabilization processes of training A (Shadmehr and Holcomb, 1997; Seitz et al., 2005). We examined whether this interference effect could be reduced or overcome by meditation. Participants completed a total of ten sessions that were administered in five consecutive days. Within each day, successive sessions consisted of two training conditions, A and B, that were separated by a 20 minute interval, during which participants were instructed to engage in either meditation or relaxation (“mind-wandering”). The two training conditions differed only in the orientation of background elements. The results show that the amount of interference was smaller for the meditation group compared to relaxation controls. These results suggest that meditation enhances the consolidation process of perceptual learning.

What is learned in perceptual learning of the classical texture discrimination task?

What is learned in perceptual learning of the classical texture discrimination task?

Hippocampal Representation of Touch-Guided Behavior in Rats: Persistent and Independent Traces of Stimulus and Reward Location

Understanding the mechanisms by which sensory experiences are stored remains a compelling challenge for neuroscience. Previous work has described how the activity of neurons in the sensory cortex allows rats to discriminate the physical features of an object contacted with their whiskers. But to date there is no evidence about how neurons represent the behavioural significance of tactile stimuli, or how they are encoded in memory. To investigate these issues, we recorded single-unit firing and local field potentials from the CA1 region of hippocampus while rats performed a task in which tactile stimuli specified reward location. On each trial the rat touched a textured plate with its whiskers, and then turned towards the Left or Right water spout. Two textures were associated with each reward location. To determine the influence of the rat's position on sensory coding, we placed it on a second platform in the same room where it performed the identical texture discrimination task. Over 25 percent of the sampled neurons encoded texture identity – their firing differed for two stimuli associated with the same reward location – and over 50 percent of neurons encoded the reward location with which the stimuli were associated. The neuronal population carried texture and reward location signals continuously, from the moment of stimulus contact until the end of reward collection. The set of neurons discriminating between one texture pair was found to be independent of, and partially overlapping, the set of neurons encoding the discrimination between a different texture pair. In a given neuron, the presence of a tactile signal was uncorrelated with the presence, magnitude, or timing of reward location signals. These experiments indicate that neurons in CA1 form a texture representation independently of the action the stimulus is associated with and retain the stimulus representation through reward collection.

Transcranial direct current stimulation at training can improve subsequent consolidation of a visual perceptual skill

Event Abstract Back to Event Transcranial direct current stimulation at training can improve subsequent consolidation of a visual perceptual skill Katia Boumghar1*, Katja Laske1, Matthias Mölle1, Jan Born1 and Lisa Marshall1 1 Department of Neuroendocrinology, University of Lübeck, Germany In humans, transcranial direct current stimulation (tDCS) is used to induce cortical polarization and excitability shifts which can result in acute as well as longer lasting effects. Here we investigated at the behavioral level the effects of cathodal and anodal tDCS applied during learning on the overnight improvement in a visual texture discrimination task (VDT). The VDT requires learning of a procedural skill in which robust improvement is typically obtained only after post-training retention periods containing sleep. In the VDT learning and retest are spaced 24h apart. On each trial, subjects fix a central cross and activate the beginning of each trial consisting of the target and mask for which the time interval of separation (stimulus-to-mask-onset, SOA) decreases over time. Subjects are to judge the orientation of target-lines (horizontal or vertical). The subjects of both experimental groups receive on one of two weeks either anodal (cathodal) or sham stimulation over V1. Cathodal tDCS applied during learning led to a significant decrease in the discrimination threshold measured at retesting the following day, as compared to a sham stimulation control condition. No acute effect of stimulation during training was found, nor did anodal tDCS affect performance. We propose that the effect of cathodal tDCS in the VDT reflects the ability of endogenous polarization fields as induced by simple neuronal processing steps or attentional shifts to impact latent improvement in performance. Differences in the early component of the visual potential dependent upon learning on the VDT task have been reported (Pourtois et al., 2008). In order to assess possible underlying mechanisms the visual evoked potentials (VEP) are currently being recorded. Funding: Supported by BMBF, DFG. Keywords: Learning, tDCS Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neural Bases of Memory and Learning Citation: Boumghar K, Laske K, Mölle M, Born J and Marshall L (2011). Transcranial direct current stimulation at training can improve subsequent consolidation of a visual perceptual skill. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00408 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 24 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Katia Boumghar, Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany, boumghar@kfg.uni-luebeck.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall Google Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall Google Scholar Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall PubMed Katia Boumghar Katja Laske Matthias Mölle Jan Born Lisa Marshall Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Perceptual learning, aging, and improved visual performance in early stages of visual processing

In the present study, we examined whether perceptual learning methods can be used to improve performance of older individuals. Subjects performed a texture discrimination task in the peripheral visual field and a letter discrimination task in central vision. The SOA threshold was derived by presenting a mask following the stimuli. Older subjects (age greater than 65 years) were either trained for 2 days using near threshold stimuli (experimental group) or were trained with the task with supra-threshold stimuli (older control group). The experimental group showed significant improvement in the task as a result of training whereas the older control group showed no significant improvement. The improved performance post-training equaled that of a younger control group and was maintained for at least 3 months. The results of two additional experiments indicate that the improved performance was not due to changes in divided attention, that the effect of perceptual learning was location specific, and that the pattern of learning was similar to that of younger subjects. These results indicate that perceptual learning with near threshold training can be used to improve visual performance among older individuals, that the improvements are not the result of practice with the visual task, and that the improvements do not transfer to non-trained locations.

Lesions in Posterior Parietal Area 5 in Monkeys Result in Rapid Behavioral and Cortical Plasticity

We examined the effects of focal lesions of posterior parietal area 5 in macaque monkeys on bimanual behavior performed with and without visual guidance. The animals were trained on two reaching tasks and one tactile texture discrimination task. Task 1 simply involved reaching toward and grasping a reward from one of five well positions. Task 2 required the monkey to use both hands simultaneously to obtain a reward. The tactile texture discrimination task required the monkey to signal the roughness of a passively delivered texture using its jaw. After lesions to area 5, the monkeys showed a decrease in hand use for tasks 1 and 2 and an inability to perform task 2 in specific locations in visual space. These deficits recovered within several days. No deficits were observed in the tactile texture discrimination task or in an analgesic control monkey. Electrophysiological recordings made just before the lesion, immediately after the lesion, and 2 months after the lesion demonstrated that cortical areas just rostral to the lesioned area 5, and areas 1 and 2, were topographically reorganized and that receptive fields for neurons in these fields changed location on the body surface. These cortical map changes are correlative and may, in part, contribute to the rapid behavioral recovery observed. The mechanism for such rapid changes may be the unmasking of existing divergent and convergent thalamocortical connections that are part of the normal cortical circuitry.

REM sleep prevents interference in the texture discrimination task

Improvement in the texture discrimination task (TDT) depends on sleep, shows feature and retinotopic specificity, varies with stimulus exposure, and is vulnerable to interference. Using a classic interference paradigm, Yotsumoto et al (2009) showed that two-part training on competing background orientations blocked learning of the initial stimulus set. We examined the role of sleep in perceptual interference on a short version of the TDT (to avoid deterioration effects). Interference was tested using two-part training with vertical or horizontal background orientations, which were presented in either the same or different retinotopic locations (lower left and upper right). We examined three nap conditions: naps (with and without rapid eye movement (REM) sleep) compared with quiet rest. We found that quiet rest showed no improvement in the interference condition, whereas naps with REM sleep eliminated interference effects. In fact, REM naps showed more than double the magnitude of learning in the interference condition compared with the non-interference condition. Learning in the interference condition was significantly correlated with the amount of REM sleep in the nap, no other sleep stage was related to performance changes. Interestingly, quiet rest produced perceptual learning to the same degree as sleep in the non-interference conditions. In conclusion, when the brain is serially presented with competing information, such as discriminating a target embedded within two different background orientations, REM sleep appears to enhance memory for information presented first. Thus, the memory trace becomes resilient to interference from subsequent competing targets. Furthermore, although prior studies have compared sleep to active waking controls, we find that quiet rest maybe as effective for learning as REM sleep.

Early Age-Related Macular Degeneration Impairs Tolerance to Stimulus Degradation

Pathologic changes of retinal photoreceptors associated with early age-related macular degeneration (AMD) have been well established, but the disease is usually asymptomatic at the early stage, and traditional suprathreshold clinical tests often fail to reveal functional deficiencies. The aim of this study is to demonstrate subtle changes of one suprathreshold visual function in early AMD eyes. The quality of preattentively discriminable texture stimuli was systematically degraded through random deletion of texture checks. The task of the subject was to make a forced choice decision on whether two equally degraded patches contained samples of the same or different types of textures. Tolerance to texture stimulus degradation was measured in young and elderly normal controls and in patients with early AMD. Subjects were trained to perform the texture discrimination task until they made few errors in discriminating intact textures. Texture discrimination deteriorated with increasing stimulus degradation in all subjects. There was no significant difference between performance of young and elderly normal controls. Early AMD eyes showed significantly less tolerance to stimulus degradation than age-similar normal controls at a range of degradation levels. After controlling for visual acuity, normal subjects still performed significantly better than early AMD eyes at approximately 22% check deletion. There was no significant difference between better eyes of early AMD patients and fellow eyes of late AMD eyes. Performance on the degraded texture task was not correlated with visual acuity. A mild blur of the stimulus had little effect on discrimination of degraded textures. Early AMD may not directly affect suprathreshold visual functions when the stimuli are intact and contain redundant information but may manifest itself as a reduction of tolerance to stimulus degradation in the form of localized information loss. The performance of patients with early AMD may be compromised when the visual stimulus contains less redundant information.

Two phases of offline learning in contour integration

We demonstrate daytime and overnight offline modulations of perceptual learning in a visual integration task. We employed a contour integration task, which requires longer range spatial integration than the more commonly used texture discrimination task, yet, still addresses the earliest cortical processing levels. In order to dissociate the effect of daytime and overnight offline modulations on perceptual learning, we introduced a 12-h shift between the practice times of two groups of subjects. Throughout the five practice sessions, the 12-h shift resulted in stepwise modulation of a typical learning curve, with a phase shift between the two groups. Between sessions (offline) improvement during the day was relatively small and only occurred in the first few sessions, while it was always significant after a night of sleep. Our results extend the body of evidence on the potential role of sleep in perceptual learning and generalize it to integrative visual processes. We have clearly distinguished two phases of learning: both daytime and overnight improvements in the initial phase, and only overnight improvements in the later phase.

Electrophysiological correlates of performance and learning in the backward-masked texture-discrimination task

Electrophysiological correlates of performance and learning in the backward-masked texture-discrimination task

Perceptual learning

Perceptual learning

A MEMS-based tactile sensor to study human digital touch: mechanical transduction of the tactile information and role of fingerprints

We present recent results showing that human epidermal ridges (fingerprints) could play a central role in fine texture discrimination tasks by spatially modulating the contact stress field between the fingertip and the substrate. Using an original biomimetic finger whose surface is patterned with parallel ridges, we demonstrate that the subsurface stress signals elicited by continuous rubbing of randomly textured substrates is dominated by fluctuations at a frequency defined by the inter-ridge distance divided by the rubbing velocity. In natural exploratory conditions, this frequency matches the best frequency of one type of mechanoreceptors, namely the Pacinian corpuscles, which are specifically involved in the tactile coding of fine textures. The use of white-noise patterned stimuli has alloowed us to extract, using a reverse-correlation analysis, the stimulus-signal response function associated with roughness modality. Its shape could provides spectral, spatial and directional selectivity to the digital tactile system. It offers a physiological basis for the recently proposed hypothesis of a dual-coding (spatio-temporal and vibratory) of tactile information.

Interference and feature specificity in visual perceptual learning

Perceptual learning (PL) often shows specificity to a trained feature. We investigated whether feature specificity is related to disruption in PL using the texture discrimination task (TDT), which shows learning specificity to background element but not to target element. Learning was disrupted when orientations of background elements were changed in two successive training sessions (interference) but not in a random order from trial to trial (roving). The presentation of target elements seemed to have reversed effect; learning occurred in two-parts training but not with roving. These results suggest that interference in TDT is feature specific while disruption by roving is not.

Sleep and time course of consolidation of visual discrimination skills in patients with narcolepsy–cataplexy

The level of procedural skills improves in normal individuals when the acquisition is followed by a period of sleep rather than wake. If sleep plays an important role in the consolidation process the advantage it provides should be reduced or delayed when its organization is altered, as in patients with chronic sleep disorders. To test this prediction in patients with narcolepsy-cataplexy (NC), who usually have a more fragmented organization of sleep than normals, we compared the initial, intermediate and delayed level of consolidation of visual skills. Twenty-two drug-naive NC patients and 22 individually-matched controls underwent training at a texture discrimination task (TDT) and were re-tested on the next morning (after a night spent in laboratory with polysomnography) and after another six nights (spent at home). TDT performance was worse in patients than controls at training and at both retrieval sessions and the time course of consolidation was different in NC patients (who improved mainly from next-day to 7th-day retrieval session) compared with controls. Moreover, the less-improving patients at next-day retrieval had a wider disorganization of sleep, probably because of an episode of rapid eye movement (REM) sleep at sleep onset REM, on post-training night more frequently than more-improving patients. These findings suggest that the time course of the consolidation process of procedural skills may be widely influenced by the characteristics of sleep organization (varying night-by-night much more in NC patients than controls) during post-training night.

Tactile acuity in the blind: A closer look reveals superiority over the sighted in some but not all cutaneous tasks

Previous studies have shown that blind subjects may outperform the sighted on certain tactile discrimination tasks. We recently showed that blind subjects outperformed the sighted in a haptic 2D-angle discrimination task. The purpose of this study was to compare the performance of the same blind ( n = 16) and sighted ( n = 17, G1) subjects in three tactile discrimination tasks dependent solely on cutaneous inputs from the fingertip of the index finger, D2. A second group of sighted subjects ( n = 30, G2) were also tested. Texture discrimination thresholds were 0.62 (G1)–0.80 mm (G2) for the sighted subjects, and 0.64 mm for the blind (standard, 2 mm spatial period). Grating orientation thresholds were 0.99 (G1)–1.12 mm (G2) for the sighted subjects, and 0.96 mm for the blind. Finally, vibrotactile frequency discrimination thresholds (100 Hz standard) were 19.5 (G2) and 20.0 Hz (G1) for the sighted, and 16.5 Hz for the blind subjects. There were no significant differences in performance between the blind and the sighted subjects for the grating orientation or vibrotactile frequency discrimination tasks. In contrast, blind subjects outperformed the sighted for the texture discrimination task (G2 only), possibly reflecting the fact that the raised dot surfaces were similar to the dots forming Braille characters (all were fluent Braille readers).

Sleep architecture, cocaine and visual learning.

Disturbances in sleep associated with chronic cocaine use may underlie abstinence-related cognitive dysfunction. We hypothesized that sleep-related cognitive function would be impaired in chronic cocaine users, and that this impairment would be associated with abstinence-related changes in sleep architecture. Twelve chronic cocaine users completed a 23-day in-patient study that included randomized, placebo-controlled, cocaine self-administration sessions. We report polysomnographic measurement of rapid eye-movement (REM) sleep and slow-wave activity, and performance on a visual texture discrimination task. Progressive abstinence from cocaine was associated with characteristic changes in REM sleep. REM sleep was shortest on nights following cocaine use and rebounded in the first week of abstinence before diminishing with progressive abstinence, following a pattern opposite that of slow-wave activity. Overnight visual learning was observed over the first night following 3 consecutive days of laboratory cocaine use; however, learning was not observed at 3 days or 17 days of abstinence. Across all points of abstinence, early-night slow-wave activity was associated strongly with non-deterioration of visual performance overnight. Furthermore, overnight enhancement of visual performance was predicted by the co-occurrence of sufficient early-night slow-wave activity and late night REM sleep, similar to results from studies in healthy subjects. These results suggest that abstinence-associated sleep-dependent learning deficits are related to characteristic changes in sleep architecture, and promote the idea that treatments directed at sleep ('somno-tropic' treatments) could be helpful in offsetting physiological consequences of cocaine abstinence.

Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory

Caffeine, the world's most common psychoactive substance, is used by approximately 90% of North Americans everyday. Little is known, however, about its benefits for memory. Napping has been shown to increase alertness and promote learning on some memory tasks. We directly compared caffeine (200 mg) with napping (60–90 min) and placebo on three distinct memory processes: declarative verbal memory, procedural motor skills, and perceptual learning. In the verbal task, recall and recognition for unassociated words were tested after a 7 h retention period (with a between-session nap or drug intervention). A second, different, word list was administered post-intervention and memory was tested after a 20 min retention period. The non-declarative tasks (finger tapping task (FTT) and texture discrimination task (TDT)) were trained before the intervention and then retested afterwards. Naps enhanced recall of words after a 7 h and 20 min retention interval relative to both caffeine and placebo. Caffeine significantly impaired motor learning compared to placebo and naps. Napping produced robust perceptual learning compared with placebo; however, naps and caffeine were not significantly different. These findings provide evidence of the limited benefits of caffeine for memory improvement compared with napping. We hypothesize that impairment from caffeine may be restricted to tasks that contain explicit information; whereas strictly implicit learning is less compromised.