Adaptation Aftereffects Research Articles

Haptic touch modulates size adaptation aftereffects on the hand.

When we interact with objects using our hands, we derive their size through our skin. Prolonged exposure to an object leads to a perceptual size aftereffect: adapting to a larger/smaller object makes a subsequently perceived object to appear smaller/larger than its actual size. This phenomenon has been described as haptic as tactile sensations with kinesthetic feedback are involved. However, the exact role of different haptic components in generating this aftereffect remains largely underexplored. Here, we investigated how different aspects of haptic touch influence size perception. After adaptation to a large sphere with one hand and a small sphere with the other, participants touched two test spheres of equal or different sizes and judged which one felt larger. Similar haptic size adaption aftereffects were observed (a) when participants repeatedly grasped on and off the adapters, (b) when they simply continued to grasp the adapters without further hand movements, and (c) when the adapters were grasped without involving the fingers. All these conditions produced stronger aftereffects than a condition where the palms were simply resting on the adapter. Our findings suggest that the inclusion of grasp markedly increased the aftereffects, highlighting the pivotal role of haptic interactions in determining perceptual size adaptation. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Cross-channel adaptation reveals shared emotion representation from face and biological motion.

Emotions in interpersonal interactions can be communicated simultaneously via various social signals such as face and biological motion (BM). Here, we demonstrate that even though BM and face are very different in visual properties, emotions conveyed by these two types of social signals involve dedicated and common processing mechanisms (N = 168, college students, 2020-2024). By utilizing the visual adaptation paradigm, we found that prolonged exposure to the happy BM biased the emotion perception of the subsequently presented morphed BM toward sad, and vice versus. The observed aftereffect disappeared when the BM adaptors were shown inverted, indicating that it arose from emotional information processing rather than being a result of adaptation to constitutive low-level features. Besides, such an aftereffect was also found for facial expressions and similarly vanished when the face adaptors were inverted. Critically, preexposure to emotional faces also exerted an adaptation aftereffect on the emotion perception of BMs. Furthermore, this cross-channel effect could not only happen from faces to BMs but also from BMs to faces, suggesting that emotion perception from face and BM are potentially driven by common underlying neural substrates. Overall, these findings highlighted a close coupling of BM and face emotion perception and suggested the existence of a dedicated emotional representation that can be shared across these two different types of social signals. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The Left Amygdala and Right Frontoparietal Cortex Support Emotional Adaptation Aftereffects.

Adaptation aftereffects-in which prolonged prior experience (adaptation) can bias the subsequent judgment of ambiguous stimuli-are a ubiquitous phenomenon. Numerous studies have found behaviorally stable adaptation aftereffects in a variety of areas. However, it is unclear which brain regions are responsible for this function, particularly in the case of high-level emotional adaptation aftereffects. To address this question, the present study used fMRI technology to investigate the neural mechanism of emotional adaptation aftereffects. Consistent with previous studies, we observed typical emotional adaptation effects in behavior. Specifically, for the same morphed facial images, participants perceived increased sadness after adapting to a happy facial image and increased happiness after adapting to a sad facial image. More crucially, by contrasting neural responses to ambiguous morphed facial images (i.e., facial images of intermediate morph levels) following adaptation to happy and sad expressions, we demonstrated a neural mechanism of emotional aftereffects supported by the left amygdala/insula, right angular gyrus, and right inferior frontal gyrus. These results suggest that the aftereffects of emotional adaptation are supported not only by brain regions subserving emotional processing but also by those subserving cognitive control.

Autistic and nonautistic adolescents do not differ in adaptation to gaze direction.

Predictive processing accounts of autism posit that autistic individuals' perception is less biased by expectations than nonautistic individuals', perhaps through stronger precision-weighting of prediction errors. Since precision-weighting is fundamental to all information processing, under this theory, the differences between autistic and nonautistic individuals should be domain-general and observable in both behavior and brain responses. This study used EEG, behavioral responses, and eye-tracking co-registration during gaze-direction adaptation, to investigate whether increased precision-weighting of prediction errors is evident through smaller adaptation after-effects in autistic adolescents compared with nonautistic peers. Multilevel modeling showed that autistic and nonautistic adolescents' responses were consistent with behavioral adaptation, with Bayesian statistics providing extremely strong evidence for the absence of a group difference. Cluster-based permutation testing of ERP responses did not show the expected adaptation after-effect but did show habituation to repeated stimulus presentation, and no group difference was detected, a result not consistent with the theoretical account. Combined with the few other available studies, the current findings raise challenges for the theory, suggesting no fundamental difference in precision-weighting of prediction errors in autism.

A preference to look closer to the eyes is associated with a position-invariant face neural code

When looking at faces, humans invariably move their eyes to a consistent preferred first fixation location on the face. While most people have the preferred fixation location just below the eyes, a minority have it between the nose-tip and mouth. Not much is known about whether these long-term differences in the preferred fixation location are associated with distinct neural representations of faces. To study this, we used a gaze-contingent face adaptation aftereffect paradigm to test in two groups of observers, one with their mean preferred fixation location closer to the eyes (upper lookers) and the other closer to the mouth (lower lookers). In this task, participants were required to maintain their gaze at either their own group’s mean preferred fixation location or that of the other group during adaptation and testing. The two possible fixation locations were 3.6° apart on the face. We measured the face adaptation aftereffects when the adaptation and testing happened while participants maintained fixation at either the same or different locations on the face. Both groups showed equally strong adaptation effects when the adaptation and testing happened at the same fixation location. Crucially, only the upper lookers showed a partial transfer of the FAE across the two fixation locations, when adaptation occurred at the eyes. Lower lookers showed no spatial transfer of the FAE irrespective of the adaptation position. Given the classic finding that neural tuning is increasingly position invariant as one moves higher in the visual hierarchy, this result suggests that differences in the preferred fixation location are associated with distinct neural representations of faces.

Poster Session: A direct measure of adaptation and visual salience.

One hypothesized function of adaptation is to increase the salience of novel targets by discounting the properties of the ambient environment. Previous studies have suggested this by finding faster search times for novel targets when searching on backgrounds observers are currently adapted to. However, this provides only an indirect measure of salience. Here, we developed a more direct measure of the impact of adaptation on feature salience. Backgrounds were oriented 1/f noise images with power confined within 15 deg of horizontal or vertical. Targets were 5 c/deg Gabor patches centered on the 8 deg backgrounds. Observers simultaneously adapted to the horizontal or vertical backgrounds shown on the left or right of fixation. A 250ms test probe then showed the Gabor patch on the same background (horizontal or vertical) on both sides. The target orientation was adjusted on one side until it appeared as conspicuous as a fixed target on the other side. Settings were made for fixed targets ranging from 10 to 45 deg from the backgrounds. For most conditions/observers, the salience matches required a smaller orientation offset on the same- vs. different-adapt background. These results support a functional role of adaptation in highlighting novelty by potentially "unmasking" the target from its background, and emphasize the importance of considering adaptation aftereffects not only for isolated targets but within the stimulus contexts they are embedded in.

Prism adaptation during balance standing enhances the transfer after-effect on standing postural displacement

Prism adaptation (PA) is a sensorimotor adaptation paradigm that induces after-effects of adapted tasks and transfer after-effects of non-adapted tasks. Previous studies showed inconsistent results of transfer after-effects of adaptation to a leftward prismatic shift on the center-of-pressure (COP) displacement during eyes-closed standing. Challenging balance during PA increases the generalization of the internal model to untrained movements, resulting in increased transfer after-effects. The present study aimed to investigate the transfer after-effects of PA with challenging balance on standing postural displacement. Thirty healthy young adults were grouped into floor standing and balance-disc standing groups during leftward PA and pointed to targets while adapting to a leftward visual shift (30 diopters) for 20 min. After leftward PA, both groups had a significant rightward displacement of straight-ahead pointing with eyes closed. However, the COP position during eyes-closed standing with feet-closed was significantly displaced rightward only in the balance-disc standing group after leftward PA. These results show that challenging balance might increase the somatosensory and proprioceptive information for standing postural control, resulting in increased transfer after-effects of leftward PA on rightward standing postural displacement.

Perceptual aftereffects of adiposity transfer from hands to whole bodies.

Adaptation aftereffects for features such as identity and gender have been shown to transfer between faces and bodies, and faces and body parts, i.e. hands. However, no studies have investigated transfer of adaptation aftereffects between whole bodies and body parts. The present study investigated whether visual adaptation aftereffects transfer between hands and whole bodies in the context of adiposity judgements (i.e. how thin or fat a body is). On each trial, participants had to decide whether the body they saw was thinner or fatter than average. Participants performed the task before and after exposure to a thin/fat hand. Consistent with body adaptation studies, after exposure to a slim hand participants judged subsequently presented bodies to be fatter than after adaptation to a fat hand. These results suggest that there may be links between visual representations of body adiposity for whole bodies and body parts.

Frequency of adapting events affects face aftereffects but not blur aftereffects

The dynamics of visual adaptation remain poorly understood. Recent studies have found that the strength of adaptation aftereffects in the perception of numerosity depends more strongly on the number of adaptation events than on the duration of the adaptation. We investigated whether such effects can be observed for other visual attributes. We measured blur (perceived focus-sharp vs blurred adapt) and face (perceived race- Asian vs. White adapt) aftereffects by varying the number of adaptation events (4 or 16) and the duration of each adaptation event (0.25 s or 1 s). We found evidence for an effect of event number on face but not on blur adaptation, though the effect for faces was significant for only one of the two face adapt conditions (Asian). Our results suggest that different perceptual dimensions may vary in how adaptation effects accrue, potentially because of differences in factors such as the sites (early or late) of the sensitivity changes or nature of the stimulus. These differences may impact how and how rapidly the visual system can adjust to different visual properties.

Object Image Size Is a Fundamental Coding Dimension in Human Vision: New Insights and Model

In previous psychophysical work we found that luminance contrast is integrated over retinal area subject to contrast gain control. If different mechanisms perform this operation for a range of superimposed retinal regions of different sizes, this could provide the basis for size-coding. To test this idea we included two novel features in a standard adaptation paradigm to discount more pedestrian accounts of repulsive size-aftereffects. First, we used spatially jittering luminance-contrast adaptors to avoid simple contour displacement aftereffects. Second, we decoupled adaptor and target spatial frequency to avoid the well-known spatial frequency shift aftereffect. Empirical results indicated strong evidence of a bidirectional size adaptation aftereffect. We show that the textbook population model is inappropriate for our results, and develop our existing model of contrast perception to include multiple size mechanisms with divisive surround-suppression from the largest mechanism. For a given stimulus patch, this delivers a blurred step-function of responses across the population, with contrast and size encoded by the height and lateral position of the step. Unlike for textbook population coding schemes, our human results (N = 4 male, N = 4 female) displayed two asymmetries: (i) size aftereffects were greatest for targets smaller than the adaptor, and (ii) on that side of the function, results did not return to baseline, even when targets were 25% of adaptor diameter. Our results and emergent model properties provide evidence for a novel dimension of visual coding (size) and a novel strategy for that coding, consistent with previous results on contrast detection and discrimination for various stimulus sizes.

Biases in the spectral amplitude distribution of a natural scene modulate horizontal size perception.

Visual perception is a complex process that involves the analysis of different spatial and temporal features of the visual environment. One critical aspect of this process is adaptation, which allows the visual system to adjust its sensitivity to specific features based on the context of the environment. Numerous theories highlight the significance of the visual scene and its spectral properties in perceptual and adaptation mechanisms. For example, size perception is known to be influenced by the spatial frequency content of the visual scene. Nonetheless, several inquiries still exist, including how specific spectral properties of the scene play a role in size perception and adaptation mechanisms. In this study, we explore aftereffects on size perception following adaptation to a natural scene with a biased spectral amplitude distribution. Twenty participants had to manually estimate the horizontal size of a projected rectangle after adaptation to three visually biased conditions: vertical-biased, non-biased, and horizontal-biased. Size adaptation aftereffects were quantified by comparing the perceptual responses from the non-biased condition with the vertical- and horizontal-biased conditions. We found size perception shifts which were contingent upon the specific orientation and spatial frequency distribution inherent in the amplitude spectra of the adaptation stimuli. Particularly, adaptation to vertical-biased produced a horizontal enlargement, while adaptation to horizontal-biased generated a decrease in the horizontal size perception of the rectangle. On average, size perception was modulated by 5-6%. These findings provide supporting evidence for the hypothesis that the neural mechanisms responsible for processing spatial frequency channels are involved in the encoding and perception of size information. The implications for neural mechanisms underlying spatial frequency and size information encoding are discussed.

Individual differences in the tuning of the face adaptation aftereffect to the preferred fixation location on the face

Individual differences in the tuning of the face adaptation aftereffect to the preferred fixation location on the face

Tilt adaptation aftereffects reveal fundamental perceptual characteristics of tactile orientation processing on the hand.

Orientation information contributes substantially to our tactile perception, such as feeling an object's shape on the skin. For vision, a perceptual adaptation aftereffect (tilt aftereffect; TAE), which is well explained by neural orientation selectivity, has been used to reveal fundamental perceptual properties of orientation processing. Neural orientation selectivity has been reported in somatosensory cortices. However, little research has investigated the perceptual characteristics of the tactile TAE. The aim of the current study was to provide the first demonstration of a tactile TAE on the hand and investigate the perceptual nature of tactile TAE on the hand surface. We used a 2-point stimulation with minimal input for orientation. We found clear TAEs on the hand surface: Adaptation induced shifts in subjective vertical sensation toward the orientation opposite to the adapted orientation. Further, adaptation aftereffects were purely based on orientation processing given that the effects transferred between different lengths across adaptor and test stimuli and type of stimuli. Finally, adaptation aftereffects were anchored to the hand: tactile TAE occurred independently of hand rotation and transferred from palm to dorsum sides of the hand, while the effects did not transfer between hands. Our findings demonstrate the existence of hand-centered perceptual processing for basic tactile orientation information. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The development of adaptation aftereffects in the vibrotactile domain.

Sensory adaptation is a feature-specific modulation of neural responses and is potentially fundamental to maximizing perceptual sensitivity. Despite its function being unclear, it has been hypothesized that sensory adaptation modifies the neurons' response codes, increasing the ability to process sensory signals on a larger scale. To better understand how such flexibility of our brain is possible, we investigated the effect of high- and low-frequency vibrotactile adaptation on perceived tactile temporal frequency during childhood, a time known for the brain to experience varying levels of plasticity. We tested tactile temporal frequency discrimination thresholds in both children and adults before and after tactile adaptation. Our results demonstrate that sensory adaptation does not consistently change perceived tactile temporal frequency in younger children as it does in adults, as adult-like trends begin to emerge at around 8 years of age but consolidate only in 10-year-old children. The absence of adaptation aftereffects suggests that, under certain conditions, sensory history does not affect perception in younger children in a similar way to adults. Surprisingly, younger children proved to be less flexible in modulating neural responses after prolonged exposure to an adapting stimulus, a tendency conflicting with the high plasticity levels the brain experiences during the early stages of life. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Looking more masculine among females: Spatial context modulates gender perception of face and biological motion.

Perception of visual information highly depends on spatial context. For instance, perception of a low-level visual feature, such as orientation, can be shifted away from its surrounding context, exhibiting a simultaneous contrast effect. Although previous studies have demonstrated the adaptation aftereffect of gender, a high-level visual feature, it remains largely unknown whether gender perception can also be shaped by a simultaneously presented context. In the present study, we found that the gender perception of a central face or a point-light walker was repelled away from the gender of its surrounding faces or walkers. A norm-based opponent model of lateral inhibition, which accounts for the adaptation aftereffect of high-level features, can also excellently fit the simultaneous contrast effect. But different from the reported contextual effect of low-level features, the simultaneous contrast effect of gender cannot be observed when the centre and the surrounding stimuli are from different categories, or when the surrounding stimuli are suppressed from awareness. These findings on one hand reveal a resemblance between the simultaneous contrast effect and the adaptation aftereffect of high-level features, on the other hand highlight different biological mechanisms underlying the contextual effects of low- and high-level visual features.

Visuomanual Vertical Prism Adaptation: Aftereffects on Visuospatial and Auditory Frequency Representations.

Sensorimotor aftereffects have been widely studied after lateral prism adaptation but not after vertical prism adaptation. It is thus well-known that lateral prism adaptation produces aftereffects on visuospatial representation and, recently, on auditory perception. This study aimed to explore the sensorimotor after-effects of vertical prism adaptation as well as its aftereffects on vertical visuospatial representation (Experiment 1) and on auditory frequency representation (Experiment 2). The experimental procedure was similar in both experiments: before and after prism adaptation to an upward or a downward optical deviation, healthy young participants performed an visual open-loop pointing task and a visual (Experiment 1) or an auditory (Experiment 2) perceptual bisection task. In the visual task, the participants had to indicate if they perceived the bisection as higher or lower than the true center of a line. In the auditory task, the participants had to indicate if they perceived the target auditory frequency closer to the low or the high limit of an auditory interval. For sensorimotor aftereffects, pointing errors were computed by means of a vertical touchscreen. For the perceptual bisection task, we measured the percentage of “down” (Experiment 1) or “low” responses (Experiment 2), and we computed the visual (Experiment 1) or the auditory (Experiment 2) subjective center for each participant. Statistical analyses were carried out separately for each optical deviation in each experiment. Sensorimotor aftereffects were observed in both experiments, in the opposite direction to the optical deviation (all ps < 0.01). No significant aftereffects occurred on visuospatial representation (all ps > 0.5), whereas the percentage of “low” responses and the auditory subjective center significantly increased after adaptation to a downward optical deviation (all ps < 0.05). Unlike lateral prism adaptation aftereffects that have been previously shown in both visuospatial horizontal representation and auditory frequency representation, aftereffects of vertical prism adaptation occurred in the auditory frequency representation but not in the vertical visuospatial representation. These results suggest that both vertical and lateral prism adaptations share a common substrate dedicated to the auditory modality (probably the temporal cortex), and that vertical adaptation does not act on the neural substrate of vertical visuospatial representation.

Color Sensitivity of the Duration Aftereffect Depends on Sub- and Supra-second Durations.

The perception of duration becomes biased after repetitive duration adaptation; this is known as the duration aftereffect. The duration aftereffect exists in both the sub-second and supra-second ranges. However, it is unknown whether the properties and mechanisms of the adaptation aftereffect differ between sub-second and supra-second durations. In the present study, we addressed this question by investigating the color sensitivity of the duration aftereffect in the sub-second (Experiment 1) and supra-second (Experiment 2) ranges separately. We found that the duration aftereffect in the sub-second range could only partly transfer across different visual colors, whereas the duration aftereffect in the supra-second range could completely transfer across different visual colors. That is, the color-sensitivity of the duration aftereffect in the sub-second duration was stronger than that in the supra-second duration. These results imply that the mechanisms underlying the adaptation aftereffects of the sub-second and supra-second ranges are distinct.

Are adaptation aftereffects for facial emotional expressions affected by prior knowledge about the emotion?

ABSTRACT Accurate perception of the emotional signals conveyed by others is crucial for successful social interaction. Such perception is influenced not only by sensory input, but also by knowledge we have about the others’ emotions. This study addresses the issue of whether knowing that the other’s emotional state is congruent or incongruent with their displayed emotional expression (“genuine” and “fake”, respectively) affects the neural mechanisms underpinning the perception of their facial emotional expressions. We used a visual adaptation paradigm to investigate this question in three experiments employing increasing adaptation durations. The adapting stimuli consisted of photographs of emotional facial expressions of joy and anger, purported to reflect (in-)congruency between felt and expressed emotion, displayed by professional actors. A Validity checking procedure ensured participants had the correct knowledge about the (in-)congruency. Significantly smaller adaptation aftereffects were obtained when participants knew that the displayed expression was incongruent with the felt emotion, following all tested adaptation periods. This study shows that knowledge relating to the congruency between felt and expressed emotion modulates face expression aftereffects. We argue that this reflects that the neural substrate responsible for the perception of facial expressions of emotion incorporates the presumed felt emotion underpinning the expression.

Contributed Session II: Effects of event number and adaptation duration on blur and face aftereffects

Previous studies have revealed that the strength of adaptation aftereffects can depend on both the number of adaptation events (trials) and the duration of each event. However, how these effects depend on the stimulus property adapted remains unknown. In the present study, we compared the influence of adaptation event number vs event duration on the strength of adaptation for blur or face aftereffects. For blur adaptation, we filtered a natural image's amplitude spectrum over slopes between -1 (blurred) to +1 (sharpened) relative to the original image to create a series of blurred/sharpened images. For face adaptation, we morphed an Asian and Caucasian face image resulting in a finely graded series of images spanning the two ethnicities. During each top-up adapting period, we varied the number of adaptation events (4 or 16) and duration of each event (250ms or 1s), resulting in 4 event number-event duration conditions. Our results suggest that the effects of event number and event duration on the strength of aftereffects are similar for blur and face adaptation.

Cross-modal aftereffects of visuo-manual prism adaptation: Transfer to auditory divided attention in healthy subjects.

Prism adaptation was shown to modify auditory perception. Using a dichotic listening task, which assesses auditory divided attention, benefits of a rightward prism adaptation were demonstrated in neglect patients (i.e., a syndrome following right hemisphere brain damage) by reducing their left auditory extinction. It is currently unknown whether prism adaptation affects auditory divided attention in healthy subjects. In the present study, we investigated the aftereffects of prism adaptation on dichotic listening. A sample of 47 young adults performed a dichotic listening task, in which pairs of words were presented with two words sounded simultaneously, one in each ear. Three parameters were measured: The percentage of recalled words, the percentage of correctly recalled words, and the laterality index (LI). Prism adaptation to a leftward optical deviation (L-PA) significantly increased the overall percentage of recalled words (p = .044) and that from the right ear (p = .002), and the overall LI (p = .049). For the first time, these findings demonstrate that L-PA produced an orientation of the auditory divided attention in favor of the right ear in healthy participants. This asymmetrical aftereffect provides a new argument in favor of the cross-modal dimension of prism adaptation, although an acclimatization effect of the dichotic listening task is also discussed. Our study opens up a new avenue for using prism adaptation in the field of auditory rehabilitation requiring a modulation of auditory attention. (PsycInfo Database Record (c) 2022 APA, all rights reserved).