Interference effects demonstrate distinct roles for visual and motor imagery during the mental representation of human action

Four experiments were completed to characterize the utilization of visual imagery and motor imagery during the mental representation of human action. In Experiment 1, movement time functions for a motor imagery human locomotion task conformed to a speed-accuracy trade-off similar to Fitts' Law, whereas those for a visual imagery object motion task did not. However, modality-specific interference effects in Experiment 2 demonstrate visual and motor imagery as cooperative processes when the action represented is tied to visual coordinates in space. Biomechanic-specific motor interference effects found in Experiment 3 suggest one basis for separation of processing channels within motor imagery. Finally, in Experiment 4 representations of motor actions were found to be generated using only visual imagery under certain circumstances: namely, when the imaginer represented the motor action of another individual while placed at an opposing viewpoint. These results suggest that the modality of representation recruited to generate images of human action is dependent on the dynamic relationship between the individual, movement, and environment.     

视觉表象生成系统及其影响因素

视觉表象是在记忆基础上产生的类似知觉的信息表征, 也是人们在日常生活中不可或缺的心理活动之一。本综述介绍了该领域中比较有影响力的表象计算理论模型, 并进一步归纳了视觉表象生成系统的成分及其对应的神经基础。分析结果强调了初级视觉皮层作为“视觉缓冲器”是生成表象的主要机能结构, 以“视觉缓冲器”为基础的表象生成系统的机能受多重因素影响。本综述有助于对视觉表象生成系统形成全面的认识, 促进视觉表象实质的进一步研究。     

Vision and touch: multiple or multisensory representations of objects?

The relationship between visually and haptically derived representations of objects is an important question in multisensory processing and, increasingly, in mental representation. We review evidence for the format and properties of these representations, and address possible theoretical models. We explore the relevance of visual imagery processes and highlight areas for further research, including the neglected question of asymmetric performance in the visuo-haptic cross-modal memory paradigm. We conclude that the weight of evidence suggests the existence of a multisensory representation, spatial in format, and flexibly accessible by both bottom-up and top-down inputs, although efficient comparison between modality-specific representations cannot entirely be ruled out.     

Varieties of size-specific visual selection

Compared time to evaluate stimuli of varying sizes. When Ss expect an upcoming stimulus to be a certain size, response time increases with the disparity between expected and actual size. There are, however, 2 size adjustment processes, and they reflect 2 types of visual selection. In the first, a shape-specific image representation is used to separate a visual object from a superimposed distractor. These representations require the type of slow size scaling demonstrated in imagery experiments. The second size scaling process is faster and not shape-specific. At any given time the visual system is set to process information at a particular scale, and that scale can be adjusted to match an object's size. Because both selection mechanisms depend on size, they probably occur at a relatively low, spatially organized processing level. These findings lead to a new explanation for results that had been taken as evidence for attentional selection at the level of object representations.     

Visual mental imagery influences attentional guidance in a visual-search task

Visual mental imagery resembles visual working memory (VWM). Because both visual mental imagery and VWM involve the representation and manipulation of visual information, it was hypothesized that they would exert similar effects on visual attention. Several previous studies have demonstrated that working-memory representations guide attention toward a memory-matching task-irrelevant stimulus during visual-search tasks. Therefore, mental imagery may also guide attention toward imagery-matching stimuli. In the present study, five experiments were conducted to investigate the effects of visual mental imagery on visual attention during a visual-search task. Participants were instructed to visualize a color or an object clearly associated with a specific color, after which they were asked to detect a colored target in the visual-search task. Reaction times for target detection were shorter when the color of the target matched the imagined color, and when the color of the target was similar to that strongly associated with the imagined object, than when the color of the target did not match that of the mental representation. This effect was not observed when participants were not instructed to imagine a color. These results suggest that similar to VWM, visual mental imagery guides attention toward imagery-matching stimuli.     

Involuntary listening aids seeing: evidence from human electrophysiology

It is well known that sensory events of one modality can influence judgments of sensory events in other modalities. For example, people respond more quickly to a target appearing at the location of a previous cue than to a target appearing at another location, even when the two stimuli are from different modalities. Such cross-modal interactions suggest that involuntary spatial attention mechanisms are not entirely modality-specific. In the present study, event-related brain potentials (ERPs) were recorded to elucidate the neural basis and timing of involuntary, cross-modal spatial attention effects. We found that orienting spatial attention to an irrelevant sound modulates the ERP to a subsequent visual target over modality-specific, extrastriate visual cortex, but only after the initial stages of sensory processing are completed. These findings are consistent with the proposal that involuntary spatial attention orienting to auditory and visual stimuli involves shared, or at least linked, brain mechanisms.     

Parallel but temporally displaced visual half-field metacontrast functions

Using a classic letter-ring metacontrast paradigm, left and right visual field meta-contrast functions were separately determined. The parallel U-shaped recognition functions for both half-fields were found to interact differentially with stimulus onset asynchrony, the left visual field function being displaced by 13 ms toward longer test stimulus-masking stimulus separations. This result was consistent with the hypothesis of longer processing time requirements for verbal stimuli delivered to the right than to the left hemisphere. This indicates that the neural locus (loci) responsible for left visual field verbal processing delay is (are) capable of mediating metacontrast phenomena. It was tentatively concluded that a relative processing delay within the right hemisphere underlies the differing visual half-field metacontrast interaction with stimulus onset asynchrony.     

A simulation of visual imagery

This paper describes an operational computer simulation of visual mental imagery in humans. The structure of the simulation was motivated by results of experiments on how people represent information in, and access information from, visual images. The simulation includes a “surface representation,” which is spatial and quasi-pictorial, and an underlying “deep representation,” which contains “perceptual” information encoding appearance plus “propositional” information describing facts about an object. The simulation embodies a theory of how surface images are generated from deep representations, and how surface images are processed when one accesses information embedded in them. The simulation also offers an account of various sorts of imagery transformations.     

Mechanisms of imagery-perception interaction

A number of different research findings have shown that mental imagery can affect the perceptual processing of stimuli. The present research was aimed at characterizing the representations and processes underlying imagery-perception interactions. In four experiments, subjects mentally projected images of letters into the visual field, and either detected or detected and localized point threshold stimuli that fell on or off the image. Stimuli falling on the image were detected more often than stimuli falling off the image, consistent with the hypothesis that the representations at the interface between imagery and perception have an array format. When the facilitation was analyzed in terms of signal detection theory, it was found to consist only of criterion lowering, and not of enhanced sensitivity. The local criterion-lowering effect of imaged letters was then compared with the effect of perceiving a letter and attending to a letter. Perceiving a letter had no discernible effect on stimulus detection, whereas attending to the letter caused the same local criterion lowering, without sensitivity changes, as imaging the letter. This is consistent with the claims of Neisser (1976) and others that imagery is an attentional state.     

Exploring the relation between visual mental imagery and affect in the daily life of previously depressed and never depressed individuals

Previously depressed individuals experience disturbances in affect. Affective disturbances may be related to visual mental imagery, given that imagery-based processing of emotional stimuli causes stronger affective responses than verbal processing in experimental laboratory studies. However, the role of imagery-based processing in everyday life is unknown. This study assessed mental imagery in the daily life of previously and never depressed individuals. Higher levels of visual mental imagery was hypothesised to be associated with more affective reactivity to both negatively and positively valenced mental representations.

This study was the first to explore mental imagery in daily life using experience sampling methodology. Previously depressed (n?=?10) and matched never depressed (n?=?11) individuals participated in this study. Momentary affect and imagery-based processing were assessed using the “Imagine your mood” smartphone application. Participants recorded on average 136 momentary reports over a period of 8 weeks.

The expected association between visual mental imagery and affective reactivity was not found. Unexpectedly, in both previously and never depressed individuals, higher levels of imagery-based processing of mental representations in daily life were significantly associated with better momentary mood and more positive affect, regardless of valence.

The causality of effects remains to be examined in future studies.     

Selective attention to the color and direction of moving stimuli: Electrophysiological correlates of hierarchical feature selection

Event-related brain potentials (ERPs) were recorded from subjects who attended to pairs of adjacent colored squares that were flashed sequentially to produce a perception of movement. The task was to attend selectively to stimuli in one visual field and to detect slower moving targets that contained the critical value of the attended feature, be it color or movement direction. Attention to location was reflected by a modulation of the early P1 and N1 components of the ERP, whereas selection of the relevant stimulus feature was associated with later selection negativity components. ERP indices of feature selection were elicited only by stimuli at the attended location and had distinctive scalp distributions for features mediated by “ventral” (color) and “dorsal” (motion) cortical areas. ERP indices of target selection were also contingent on the prior selection of location but initially did not depend on the selection of the relevant feature. These ERP data reveal the timing of sequential, parallel, and contingent stages of visual processing and support early-selection theories of attention that stipulate attentional control over the initial processing of stimulus features.     

Semantic interference from visual object recognition on visual imagery

A new technique for examining the interaction between visual object recognition and visual imagery is reported. The "image-picture interference" paradigm requires participants to generate and make a response to a mental image of a previously memorized object, while ignoring a simultaneously presented picture distractor. Responses in 2 imagery tasks (making left-right higher spatial judgments and making taller-wider judgments) were longer when the simultaneous picture distractor was categorically related to the target distractor relative to unrelated and neutral target-distractor combinations. In contrast, performance was not influenced in this way when the distractor was a related word, when a semantic categorization decision was made to the target, or when distractor and target were visually but not categorically related to one another. The authors discuss these findings in terms of the semantic representations shared by visual object recognition and visual imagery that mediate performance.     

Verbal recoding of visual stimuli impairs mentalimagetransformations

Two experiments were carried out to test the hypothesis that verbal recoding of visual stimuli in short-term memory influences long-term memory encoding and impairs subsequent mental image operations. Easy and difficult-to-name stimuli were used. When rotated 90 degrees counterclockwise, each stimulus revealed a new pattern consisting of two capital letters joined together. In both experiments, subjects first learned a short series of stimuli and were then asked to rotate mental images of the stimuli in order to detect the hidden letters. In Experiment 1, articulatory suppression was used to prevent subjects from subvocal rehearsal when learning the stimuli, whereas in Experiment 2, verbal labels were presented with each stimulus during learning to encourage a reliance on the verbal code. As predicted, performance in the imagery task was significantly improved by suppression when the stimuli were easy to name (Experiment 1) but was severely disrupted by labeling when the stimuli were difficult to name (Experiment 2). We concluded that verbal recoding of stimuli in short-term memory during learning disrupts the ability to generate veridical mental images from long-term memory.     

Interference in visual perception by verbal and spatial cognitive activity

In two experiments we tested the hypothesis that cognitive processing based on spatial imagery produces more deterioration of visual perception than cognitive processing based on verbal codes. So, we studied the effect on visual perception of two cognitive tasks, one of spatial imagery and the other a verbal task. In the first one, with 30 participants, we analyzed the mental load and ocular behaviors in both cognitive tasks. In the second experiment, with 29 participants, we studied the effect of both tasks on a visual search task, using a dual-task experimental paradigm. The verbal task presented higher mental load than the imagery task when both tasks were carried out with visual search task, and there was more deterioration in stimulus detection with the verbal task. We can conclude that: (1) cognitive tasks produce important deterioration in the capacities of visual search and identification of stimuli; (2) this deterioration has two components: (a) an inefficient search, associated with alterations of the gaze patterns while performing cognitive tasks, and (b) a general interference, nonspecific to spatial codes, in the process of identification of looked-at stimuli; (3) this cognitive interference is related to the mental load or effort required by the cognitive task.     

Age-related deficits in generation and manipulation of mental images: II. The role of dorsolateral prefrontal cortex.

The authors investigated neural substrates of age-related declines in mental imagery. Healthy adult participants (ages 19 to 77) performed a series of visual-spatial mental imagery tasks that varied in apparent difficulty and involved stimuli of varying graphic complexity. The volumes of the dorsolateral frontal cortex (DLPFC) and posterior visual processing areas were estimated from magnetic resonance imaging scans. The volume of the DLPFC and the fusiform cortex, working-memory capacity, and performance on the tasks involving image generation and manipulation were significantly reduced with age. Further analyses suggested that age-related deficits in performance on mental imagery tasks may stem in part from age-related shrinkage of the prefrontal cortex and age-related declines in working memory but not from age-related slowing of sensorimotor reaction time. The volume of cortical regions associated with modality-specific visual information processing did not show a consistent relationship with specific mental imagery processes.     

Multisensory numerosity judgments for visual and tactile stimuli

To date, numerosity judgments have been studied only under conditions of unimodal stimulus presentation. It is therefore unclear whether the same limitations on correctly reporting the number of unimodal visual or tactile stimuli presented in a display might be expected under conditions in which participants have to count stimuli presented simultaneously in two or more different sensory modalities. In Experiment 1, we investigated numerosity judgments using both unimodal and bimodal displays consisting of one to six vibrotactile stimuli (presented over the body surface) and one to six visual stimuli (seen on the body via mirror reflection). Participants had to count the number of stimuli regardless of their modality of presentation. Bimodal numerosity judgments were significantly less accurate than predicted on the basis of an independent modality-specific resources account, thus showing that numerosity judgments might rely on a unitary amodal system instead. The results of a second experiment demonstrated that divided attention costs could not account for the poor performance in the bimodal conditions of Experiment 1. We discuss these results in relation to current theories of cross-modal integration and to the cognitive resources and/or common higher order spatial representations possibly accessed by both visual and tactile stimuli.     

Tracking the processes behind conscious perception: a review of event-related potential correlates of visual consciousness

Event-related potential (ERP) studies have attempted to discover the processes that underlie conscious visual perception by contrasting ERPs produced by stimuli that are consciously perceived with those that are not. Variability of the proposed ERP correlates of consciousness is considerable: the earliest proposed ERP correlate of consciousness (P1) coincides with sensory processes and the last one (P3) marks postperceptual processes. A negative difference wave called visual awareness negativity (VAN), typically observed around 200 ms after stimulus onset in occipitotemporal sites, gains strong support for reflecting the processes that correlate with, and possibly enable, aware visual perception. Research suggests that the early parts of conscious processing can proceed independently of top-down attention, although top-down attention may modulate visual processing even before consciousness. Evidence implies that the contents of consciousness are provided by interactions in the ventral stream, but indispensable contributions from dorsal regions influence already low-level visual responses.     

The construction of large number representations in adults

What is the nature of our mental representation of quantity? We find that human adults show no performance cost of comparing numerosities across vs. within visual and auditory stimulus sets, or across vs. within simultaneous and sequential sets. In addition, reaction time and performance in such tasks are determined by the ratio of the numerosities to be compared; absolute set size has no effect. These findings suggest that modality-specific stimulus properties undergo a non-iterative transformation into representations of quantity that are independent of the modality or format of the stimulus.     

Vividness of positive mental imagery predicts positive emotional response to visually presented Project Soothe pictures

Lang's bioinformational theory of mental imagery proposes that mental imagery and external stimuli engage emotional information-processing systems in similar ways. However, the positive and negative systems are thought to be distinct, so this similarity is likely to show a valence-specific effect. Therefore, we hypothesized that an individual's ability to construct vivid positive, but not negative, mental imagery would predict positive emotional responding to positive visual stimuli, independently of depressive symptoms. Our stimuli were pictures collected through Project Soothe for possible use in psychotherapy ( www.projectsoothe.com ); as these pictures were intended to induce soothing emotion, we hypothesized that theoretically linked variables Self-compassion and Self-criticism would also predict positive responding to the stimuli. A total of 214 participants completed an online study including validated questionnaire measures, mental imagery tasks, and a picture-rating exercise. Only Positive Imagery Vividness and Self-compassion were significant predictors of positive responding to the soothing pictures, even controlling for depressive symptoms, and Negative and General Imagery Vividness. These findings support Lang's theory and provide evidence for individual differences in a positive processing tendency shared across mental imagery-based and perceptual representations. As this relationship is distinct from depressive symptoms, future imagery-based psychotherapies might aim to influence this positive processing tendency.