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PloS One 2023Bodily awareness arises from somatosensory, vestibular, and visual inputs but cannot be reduced to these incoming sensory signals. Cognitive factors are known to also...
Bodily awareness arises from somatosensory, vestibular, and visual inputs but cannot be reduced to these incoming sensory signals. Cognitive factors are known to also impact bodily awareness, though their specific influence is poorly understood. Here we systematically compared the effects of sensory (bottom-up) and cognitive (top-down) manipulations on the estimated size of body parts. Toward this end, in a repeated-measures design, we sought to induce the illusion that the right index finger was elongating by vibrating the biceps tendon of the left arm whilst participants grasped the tip of their right index finger (Lackner illusion; bottom-up) and separately by hypnotic suggestion (top-down), with a sham version of the Lackner illusion as an active control condition. The effects of these manipulations were assessed with perceptual and motor tasks to capture different components of the representation of body size. We found that hypnotic suggestion significantly induced the illusion in both tasks relative to the sham condition. The magnitudes of these effects were stronger than those in the Lackner illusion condition, which only produced a significantly stronger illusion than the sham condition in the perceptual task. We further observed that illusion magnitude significantly correlated across tasks and conditions, suggesting partly shared mechanisms. These results are in line with theories of separate but interacting representational processes for perception and action and highlight the influence of cognitive factors on low-level body representations.
Topics: Humans; Illusions; Body Size; Fingers; Hypnotics and Sedatives; Research Design
PubMed: 37699046
DOI: 10.1371/journal.pone.0291493 -
Philosophical Transactions of the Royal... Sep 2023Multisensory integration (MSI) occurs in a variety of brain areas, spanning cortical and subcortical regions. In traditional studies on sensory processing, the sensory... (Review)
Review
Multisensory integration (MSI) occurs in a variety of brain areas, spanning cortical and subcortical regions. In traditional studies on sensory processing, the sensory cortices have been considered for processing sensory information in a modality-specific manner. The sensory cortices, however, send the information to other cortical and subcortical areas, including the higher association cortices and the other sensory cortices, where the multiple modality inputs converge and integrate to generate a meaningful percept. This integration process is neither simple nor fixed because these brain areas interact with each other via complicated circuits, which can be modulated by numerous internal and external conditions. As a result, dynamic MSI makes multisensory decisions flexible and adaptive in behaving animals. Impairments in MSI occur in many psychiatric disorders, which may result in an altered perception of the multisensory stimuli and an abnormal reaction to them. This review discusses the diversity and flexibility of MSI in mammals, including humans, primates and rodents, as well as the brain areas involved. It further explains how such flexibility influences perceptual experiences in behaving animals in both health and disease. This article is part of the theme issue 'Decision and control processes in multisensory perception'.
Topics: Animals; Humans; Brain Mapping; Brain; Sensation; Cognition; Primates; Mammals
PubMed: 37545309
DOI: 10.1098/rstb.2022.0338 -
Cognition Sep 2023Bodily illusions have fascinated humankind for centuries, and researchers have studied them to learn about the perceptual and neural processes that underpin multisensory...
Bodily illusions have fascinated humankind for centuries, and researchers have studied them to learn about the perceptual and neural processes that underpin multisensory channels of bodily awareness. The influential rubber hand illusion (RHI) has been used to study changes in the sense of body ownership - that is, how a limb is perceived to belong to one's body, which is a fundamental building block in many theories of bodily awareness, self-consciousness, embodiment, and self-representation. However, the methods used to quantify perceptual changes in bodily illusions, including the RHI, have mainly relied on subjective questionnaires and rating scales, and the degree to which such illusory sensations depend on sensory information processing has been difficult to test directly. Here, we introduce a signal detection theory (SDT) framework to study the sense of body ownership in the RHI. We provide evidence that the illusion is associated with changes in body ownership sensitivity that depend on the information carried in the degree of asynchrony of correlated visual and tactile signals, as well as with perceptual bias and sensitivity that reflect the distance between the rubber hand and the participant's body. We found that the illusion's sensitivity to asynchrony is remarkably precise; even a 50 ms visuotactile delay significantly affected body ownership information processing. Our findings conclusively link changes in a complex bodily experience such as body ownership to basic sensory information processing and provide a proof of concept that SDT can be used to study bodily illusions.
Topics: Humans; Illusions; Visual Perception; Ownership; Touch; Hand; Touch Perception; Body Image; Proprioception
PubMed: 37178590
DOI: 10.1016/j.cognition.2023.105491 -
The Journal of Neuroscience : the... Sep 2023Reward-related activity in the dopaminergic midbrain is thought to guide animal behavior, in part by boosting the perceptual and attentional processing of...
Reward-related activity in the dopaminergic midbrain is thought to guide animal behavior, in part by boosting the perceptual and attentional processing of reward-predictive environmental stimuli. In line with this incentive salience hypothesis, studies of human visual search have shown that simple synthetic stimuli, such as lines, shapes, or Gabor patches, capture attention to their location when they are characterized by reward-associated visual features, such as color. In the real world, however, we commonly search for members of a category of visually heterogeneous objects, such as people, cars, or trees, where category examples do not share low-level features. Is attention captured to examples of a reward-associated real-world object category? Here, we have human participants search for targets in photographs of city and landscapes that contain task-irrelevant examples of a reward-associated category. We use the temporal precision of EEG machine learning and ERPs to show that these distractors acquire incentive salience and draw attention, but do not capture it. Instead, we find evidence of rapid, stimulus-triggered attentional suppression, such that the neural encoding of these objects is degraded relative to neutral objects. Humans appear able to suppress the incentive salience of reward-associated objects when they know these objects will be irrelevant, supporting the rapid deployment of attention to other objects that might be more useful. Incentive salience is thought to underlie key behaviors in eating disorders and addiction, among other conditions, and the kind of suppression identified here likely plays a role in mediating the attentional biases that emerge in these circumstances. Like other animals, humans are prone to notice and interact with environmental objects that have proven rewarding in earlier experience. However, it is common that such objects have no immediate strategic use and are therefore distracting. Do these reward-associated real-world objects capture our attention, despite our strategic efforts otherwise? Or are we able to strategically control the impulse to notice them? Here we use machine learning classification of human electrical brain activity to show that we can establish strategic control over the salience of naturalistic reward-associated objects. These objects draw our attention, but do not necessarily capture it, and this kind of control may play an important role in mediating conditions like eating disorder and addiction.
Topics: Humans; Motivation; Vision, Ocular; Evoked Potentials; Electroencephalography; Reward
PubMed: 37562963
DOI: 10.1523/JNEUROSCI.0766-23.2023 -
PloS One 2023Pareidolias, or the misperception of ambiguous stimuli as meaningful objects, are complex visual illusions thought to be phenomenologically similar to Visual...
Pareidolias, or the misperception of ambiguous stimuli as meaningful objects, are complex visual illusions thought to be phenomenologically similar to Visual Hallucination (VH). VH are a major predictor of dementia in Parkinson's Disease (PD) and are included as a core clinical feature in Dementia with Lewy Bodies (DLB). A newly developed Noise Pareidolia Test (NPT) was proposed as a possible surrogate marker for VH in DLB patients as increased pareidolic responses correlated with informant-corroborated accounts of VH. This association could, however, be mediated by visuoperceptual impairment. To understand the drivers of performance on the NPT, we contrasted performances in patient groups that varied both in terms of visuoperceptual ability and rates of VH. N = 43 patients were studied of whom n = 13 had DLB or PD with Dementia (PDD); n = 13 had PD; n = 12 had typical, memory-onset Alzheimer's Disease (tAD); and n = 5 had Posterior Cortical Atrophy (PCA) due to Alzheimer's disease. All patient groups reported pareidolias. Within the Lewy body disorders (PD, DLB, PDD), there was no significant difference in pareidolic response rates between hallucinating and non-hallucinating patients. Visuoperceptual deficits and pareidolic responses were most frequent in the PCA group-none of whom reported VH. Regression analyses in the entire patient cohort indicated that pareidolias were strongly predicted by visuoperceptual impairment but not by the presence of VH. These findings suggest that pareidolias reflect the underlying visuoperceptual impairment of Lewy body disorders, rather than being a direct marker for VH.
Topics: Humans; Lewy Body Disease; Alzheimer Disease; Parkinson Disease; Hallucinations; Illusions
PubMed: 37930972
DOI: 10.1371/journal.pone.0293942 -
Journal of Geriatric Psychiatry and... Nov 2023Approximately 15% of older adults may experience psychotic phenomena. Primary psychiatric disorders that manifest with psychosis (delusions, hallucinations, and... (Review)
Review
Approximately 15% of older adults may experience psychotic phenomena. Primary psychiatric disorders that manifest with psychosis (delusions, hallucinations, and disorganized thought or behavior) account for less than half. Up to 60% of late-life psychotic symptoms are due to systemic medical or neurological conditions, particularly neurodegenerative diseases. A thorough medical workup including laboratory tests, additional procedures if indicated, and neuroimaging studies is recommended. This narrative review summarizes current evidence regarding the epidemiology and phenomenology of psychotic symptoms encountered as part of the neurodegenerative disease continuum (including prodromal and manifest stages). Prodromes are constellations of symptoms that precede the onset of overt neurodegenerative syndromes. Prodromal psychotic features, particularly delusions, have been associated with an increased likelihood of receiving a neurodegenerative disease diagnosis within several years. Prompt prodrome recognition is crucial for early intervention. The management of psychosis associated with neurodegenerative diseases includes behavioral and somatic strategies, although evidence is scarce and mostly limited to case reports, case series, or expert consensus guidelines, with few randomized controlled trials. The complexity of psychotic manifestations warrants management by interprofessional teams that provide coordinated, integrated care.
Topics: Humans; Aged; Neurodegenerative Diseases; Psychotic Disorders; Hallucinations; Neuroimaging
PubMed: 36941085
DOI: 10.1177/08919887231164357 -
Ear and HearingEveryday listening environments are filled with competing noise and distractors. Although significant research has examined the effect of competing noise on speech...
OBJECTIVES
Everyday listening environments are filled with competing noise and distractors. Although significant research has examined the effect of competing noise on speech recognition and listening effort, little is understood about the effect of distraction. The framework for understanding effortful listening recognizes the importance of attention-related processes in speech recognition and listening effort; however, it underspecifies the role that they play, particularly with respect to distraction. The load theory of attention predicts that resources will be automatically allocated to processing a distractor, but only if perceptual load in the listening task is low enough. If perceptual load is high (i.e., listening in noise), then resources that would otherwise be allocated to processing a distractor are used to overcome the increased perceptual load and are unavailable for distractor processing. Although there is ample evidence for this theory in the visual domain, there has been little research investigating how the load theory of attention may apply to speech processing. In this study, we sought to measure the effect of distractors on speech recognition and listening effort and to evaluate whether the load theory of attention can be used to understand a listener's resource allocation in the presence of distractors.
DESIGN
Fifteen adult listeners participated in a monosyllabic words repetition task. Test stimuli were presented in quiet or in competing speech (+5 dB signal-to-noise ratio) and in distractor or no distractor conditions. In conditions with distractors, auditory distractors were presented before the target words on 24% of the trials in quiet and in noise. Percent-correct was recorded as speech recognition, and verbal response time (VRT) was recorded as a measure of listening effort.
RESULTS
A significant interaction was present for speech recognition, showing reduced speech recognition when distractors were presented in the quiet condition but no effect of distractors when noise was present. VRTs were significantly longer when distractors were present, regardless of listening condition.
CONCLUSIONS
Consistent with the load theory of attention, distractors significantly reduced speech recognition in the low-perceptual load condition (i.e., listening in quiet) but did not impact speech recognition scores in conditions of high perceptual load (i.e., listening in noise). The increases in VRTs in the presence of distractors in both low- and high-perceptual load conditions (i.e., quiet and noise) suggest that the load theory of attention may not apply to listening effort. However, the large effect of distractors on VRT in both conditions is consistent with the previous work demonstrating that distraction-related shifts of attention can delay processing of the target task. These findings also fit within the framework for understanding effortful listening, which proposes that involuntary attentional shifts result in a depletion of cognitive resources, leaving less resources readily available to process the signal of interest; resulting in increased listening effort (i.e., elongated VRT).
Topics: Adult; Humans; Speech Perception; Acoustic Stimulation; Speech; Listening Effort; Noise
PubMed: 36935395
DOI: 10.1097/AUD.0000000000001356 -
Science Advances Nov 2023Visual illusions provide valuable insights into the brain's interpretation of the world given sensory inputs. However, the precise manner in which brain activity...
Visual illusions provide valuable insights into the brain's interpretation of the world given sensory inputs. However, the precise manner in which brain activity translates into illusory experiences remains largely unknown. Here, we leverage a brain decoding technique combined with deep neural network (DNN) representations to reconstruct illusory percepts as images from brain activity. The reconstruction model was trained on natural images to establish a link between brain activity and perceptual features and then tested on two types of illusions: illusory lines and neon color spreading. Reconstructions revealed lines and colors consistent with illusory experiences, which varied across the source visual cortical areas. This framework offers a way to materialize subjective experiences, shedding light on the brain's internal representations of the world.
Topics: Humans; Illusions; Form Perception; Brain; Neural Networks, Computer; Visual Cortex; Visual Perception
PubMed: 37967184
DOI: 10.1126/sciadv.adj3906 -
Investigative Ophthalmology & Visual... Dec 2023Visual snow syndrome-characterized by flickering specks throughout the visual field and accompanied by other symptoms-can disrupt daily life and affects roughly 2% of...
PURPOSE
Visual snow syndrome-characterized by flickering specks throughout the visual field and accompanied by other symptoms-can disrupt daily life and affects roughly 2% of the population. However, its neural bases remain mysterious, and treatments are lacking. Here, we report the first intervention that can temporarily eliminate the visual snow symptom, allowing many observers to see the world without snow for the first time since symptom onset. Prolonged viewing of a visual stimulus strongly reduces the responsiveness of the visual pathways to subsequent stimuli, and we tested whether such adaptation could affect visual snow.
METHODS
Participants with visual snow (total n = 27) viewed high-contrast dynamic noise patterns, resembling television static, and then judged the strength of the symptom.
RESULTS
Visual snow was temporarily reduced in strength to the point that it was invisible at longer adaptation durations for most observers. The effect followed typical trends of adaptation for physical stimuli in normally sighted observers: Effect duration increased monotonically with duration of exposure to the adapter and was specific to dynamic noise.
CONCLUSIONS
These results establish that spontaneous neural activity in the visual system is causally related to the visual snow percept. Because they perceive this activity, people with visual snow may provide a unique window into the generation and suppression of noise in the visual system. Adaptation allows reliable experimental control over visual snow, and so is a strong candidate for diagnostic testing and a promising tool for further understanding its neural origins, which could in turn aid the development of treatments.
Topics: Humans; Perceptual Disorders; Software; Visual Fields; Visual Pathways
PubMed: 38117246
DOI: 10.1167/iovs.64.15.23 -
CoDAS 2023To evaluate the immediate effect of the incentive spirometer on acoustic measures, aerodynamic measures and on the auditory-perceptual assessment of vocal quality in...
PURPOSE
To evaluate the immediate effect of the incentive spirometer on acoustic measures, aerodynamic measures and on the auditory-perceptual assessment of vocal quality in vocally healthy women.
METHODS
This is an experimental intra-subject comparison study with the participation of 22 women without vocal complaints. Acoustic measures, aerodynamic measures and auditory-perceptual assessment of vocal quality were obtained before and immediately after using the incentive spirometer by the participants. The device was used in the orthostatic position and the participants performed three sets of ten repetitions with a one-minute interval between sets.
RESULTS
After using the incentive spirometer, there was a significant reduction in jitter, shimmer and PPQ (period perturbation quotient) measurements and an increase in maximum expiratory volume, while the other acoustic and aerodynamic measurements were not significantly impacted. In addition, there was improvement in vocal quality in eight (36.4%) participants and 11 (50.0%) participants showed no changes in the auditory perceptual assessment of voice quality after using the incentive spirometer.
CONCLUSION
The use of the incentive spirometer is safe and, in its immediate effect, positively impacts the acoustic measures of short-term aperiodicity of frequency and intensity and increases the maximum expiratory volume in women with healthy voices.
Topics: Humans; Female; Motivation; Voice; Voice Quality; Voice Disorders; Acoustics; Speech Acoustics; Phonation
PubMed: 37970892
DOI: 10.1590/2317-1782/20232022291pt