A motion aftereffect from visual imagery of motion

Mental imagery is thought to share properties with perception. To what extent does the process of imagining a scene share neural circuits and computational mechanisms with actually perceiving the same scene? Here, we investigated whether mental imagery of motion in a particular direction recruits neural circuits tuned to the same direction of perceptual motion. To address this question we made use of a visual illusion, the motion aftereffect. We found that following prolonged imagery of motion in one direction, people are more likely to perceive real motion test probes as moving in the direction opposite to the direction of motion imagery. The transfer of adaptation from imagined to perceived motion provides evidence that motion imagery and motion perception recruit shared direction-selective neural circuitry. Even in the absence of any visual stimuli, people can selectively recruit specific low-level sensory neurons through mental imagery.     

The Two Faces of Mental Imagery

Mental imagery has often been taken to be equivalent to “sensory imagination”, the perception-like type of imagination at play when, for example, one visually imagines a flower when none is there, or auditorily imagines a music passage while wearing earplugs. I contend that the equation of mental imagery with sensory imagination stems from a confusion between two senses of mental imagery. In the first sense, mental imagery is used to refer to a psychological attitude, which is perception-like in nature. In the second sense, mental imagery refers to a mental content, which can be grasped via different attitudes. I will show that failure to acknowledge the distinction between these senses of mental imagery has muddled philosophical discussion. This distinction brings much needed clarity to debates where sensory imagination and mental imagery are invoked, shedding light on issues such as the nature of imagistic mental states, and the representational powers and limits of mental imagery. I will conclude by sketching a general attitudinal account of imagination that does justice to both senses of mental imagery, outlining a promising framework for understanding imagination.     

A century of imagery research: reflections on Cheves Perky's contribution to our understanding of mental imagery

We review contemporary scientific research on the relationship between visual perception and visual mental imagery in the context of Cheves Perky's (1910) landmark article on imagery and imagination. This body of research has firmly established a strong connection between the psychology of imagery and perception and has contributed a strong voice to the imagery debate. We then use the concept of embodiment to discuss additional avenues of inquiry at which Perky's work hinted. These include a more thorough examination of the relationship between imagery and emotion, the creative, active aspects of imagery and imagination, and the methods we can bring to bear on understanding imagery and imagination as a human experience.     

从表征和认知过程上看表象与知觉、记忆的关系

表象、知觉和记忆是一个整合的认知系统。由于知觉和记忆提供了表象生成的材料,因而三者共享相似的表征,并激活广泛而相似的脑区。然而在认知加工过程上三者存在一定的差异。与知觉相比,表象的编码方式更抽象、更依赖过去经验的参与且处理细节能力更弱;与记忆相比,表象更容易受无关信息的干扰。未来对三者关系的研究应关注不同来源和不同类型的表象与知觉、记忆之间的关系,以及工作记忆在三者关系中所起的作用。     

Perception and imagery of faces generate similar gender aftereffects

Visual adaptation is known to bias perception away from the properties of the adapting stimuli, toward opposite properties, resulting in perceptual aftereffects. For example, prolonged exposure to a face has been shown to produce an identity aftereffect, biasing perception of a subsequent face toward the opposite identity. Such repulsive aftereffects have been observed for both visually perceived and visually imagined faces, suggesting that both perception and imagery yield typical aftereffects. However, recent studies have reported opposite patterns of aftereffects for perception and imagery of face gender. In these studies, visually perceived faces produced typical effects in which perception of androgynous faces was biased away from the gender of the adaptor, whereas imagery of the same stimuli produced atypical aftereffects, biasing the perceived gender of androgynous faces toward the gender of the adaptor. These findings are highly unusual and warrant further research. The present study aimed to gather new evidence on the direction of gender aftereffects following perception and imagery of faces. Experiment 1 had participants view and imagine female and male faces of famous and non-famous individuals. To determine the effect of concomitant visual stimulation on imagery and adaptation, participants visualized faces both in the presence and in the absence of a visual input. In Experiment 2, participants were adapted to perceived and imagined faces of famous and non-famous actors matched on gender typicality. This manipulation allowed us to determine the effect of face familiarity on the magnitude of gender aftereffects. Contrary to evidence from previous studies, our results demonstrated that both perception and imagery produced typical aftereffects, biasing the perceived gender of androgynous faces in the opposite direction to the gender of the adaptor. Famous faces yielded largest adaptation effects across tasks. Experiment 2 confirmed that these effects depended on familiarity rather than on sexual dimorphism. In both experiments, this effect was greater for perception than imagery. Additionally, imagery of famous faces produced strongest aftereffects when it was performed in the absence of visual stimulation. The implications of these findings are discussed.     

Visual motion influences the contingent auditory motion aftereffect

In this study, we show that the contingent auditory motion aftereffect is strongly influenced by visual motion information. During an induction phase, participants listened to rightward-moving sounds with falling pitch alternated with leftward-moving sounds with rising pitch (or vice versa). Auditory aftereffects (i.e., a shift in the psychometric function for unimodal auditory motion perception) were bigger when a visual stimulus moved in the same direction as the sound than when no visual stimulus was presented. When the visual stimulus moved in the opposite direction, aftereffects were reversed and thus became contingent upon visual motion. When visual motion was combined with a stationary sound, no aftereffect was observed. These findings indicate that there are strong perceptual links between the visual and auditory motion-processing systems.     

Colour, face, and visuospatial imagery abilities in low-vision individuals with visual field deficits

This study investigates to what extent visual perception integrity is necessary for visual mental imagery. Sixteen low-vision participants with severe peripheral visual field loss, 16 with severe central field loss, 6 left brain-damaged patients with right homonymous hemianopia, 6 right brain-damaged patients with left homonymous hemianopia, and 16 normally sighted controls performed perceptual and imagery tasks using colours, faces, and spatial relationships. Results showed that (a) the perceptual and mental image>ry disorders vary according to the type of visual field loss, (b) hemianopics had no more difficulties imagining spatial stimuli in their contralesional hemispace than in their ipsilesional one, and (c) the only hemianopic participant to have perceptual and mental imagery impairments suffered from attentional deficits. Results suggest that (a) visual memory is not definitively established, but rather needs perceptual practice to be maintained, and (b) that visual mental imagery may involve some of the attentional-exploratory mechanisms that are employed in visual behaviour.     

Colour,face, and visuospatial imagery abilities in low-vision individuals with visual field deficits

This study investigates to what extent visual perception integrity is necessary for visual mental imagery. Sixteen low-vision participants with severe peripheral visual field loss, 16 with severe central field loss, 6 left brain-damaged patients with right homonymous hemianopia, 6 right brain-damaged patients with left homonymous hemianopia, and 16 normally sighted controls performed perceptual and imagery tasks using colours, faces, and spatial relationships. Results showed that (a) the perceptual and mental image>ry disorders vary according to the type of visual field loss, (b) hemianopics had no more difficulties imagining spatial stimuli in their contralesional hemispace than in their ipsilesional one, and (c) the only hemianopic participant to have perceptual and mental imagery impairments suffered from attentional deficits. Results suggest that (a) visual memory is not definitively established, but rather needs perceptual practice to be maintained, and (b) that visual mental imagery may involve some of the attentional–exploratory mechanisms that are employed in visual behaviour.     

初级视觉皮层在表象表征方式研究中的作用

表象的信息表征方式一直是心理学研究的热点问题,脑成像技术在该问题的研究中发挥了巨大作用。本文以初级视觉皮层(V1)在表象表征方式研究中的作用为主线,系统梳理了基于脑成像技术开展的表象实质争论的核心问题,归纳分析了相关争论问题演绎发展的内在逻辑脉络,在此基础上指出了表象研究中需要进一步解决的关键问题,以期能够促进相关研究问题的进一步开展。     

Visual perception and visual mental imagery of emotional faces generate similar expression aftereffects

What is the relationship between visual perception and visual mental imagery of emotional faces? We investigated this question using a within-emotion perceptual adaptation paradigm in which adaptation to a strong version of an expression was paired with a test face displaying a weak version of the same emotion category. We predicted that within-emotion adaptation to perception and imagery of expressions would generate similar aftereffects, biasing perception of weak emotional test faces toward a more neutral value. Our findings confirmed this prediction. Adaptation to mental images yielded aftereffects that inhibited emotion recognition of test expressions, as participants were less accurate at recognising these stimuli compared to baseline. While the same inhibitory effect was observed when expressions were visually perceived, the size of the aftereffects was greater for perception than imagery. These findings suggest the existence of expression-selective neural mechanisms that subserve both visual perception and visual mental imagery of emotional faces.     

Opposite effects of visual versus imagined presentation of faces on subsequent sex perception

Viewing faces of one sex changes the perception of subsequently seen ambiguous faces. Here we investigate if the mechanisms responsible for this sex aftereffect are also activated during mental imagery of faces. Participants categorized the sex of ambiguous faces after either viewing images of male or female actors' faces or imagining these same faces. As in previous studies, the ambiguous images were categorized as female more often after viewing male faces than after viewing female faces. The opposite effect was found for imagined faces, however; the ambiguous images were categorized as female more often after imagining female faces than after imagining male faces. Although our results are inconsistent with findings that imagined faces cause either no aftereffects or similar aftereffects to visually presented faces, our results are consistent with recent evidence that visual and imagined presentation of faces cause opposite adaptation effects on an early electrophysiological response associated with face processing.     

Orientation-selective adaptation to crowded illusory lines

Visual adaptation has been successfully used as a psychophysical tool for studying the functional organisation of visual awareness. It has been shown that orientation-selective adaptation to a grating pattern occurs in crowded conditions. In such conditions, simultaneous presentation of flanking distractors pushes the target stimulus out of conscious perception and severely impairs orientation discrimination in the periphery of the visual field. In the present study, orientation-selective adaptation to illusory lines induced by two line gratings abutting each other with a phase shift was examined in crowded and non-crowded conditions. To rule out the effects of lower level adaptations we used an animation paradigm in which the orientations of the two line gratings were altered repeatedly during adaptation phase without any change in the orientation of the resulting illusory line. Although performance of subjects in reporting the orientation of crowded illusory lines was at chance level, orientation-selective adaptation was preserved for crowded as well as non-crowded adapting targets. Two control experiments demonstrated that adaptation to endpoints of real lines at the location of abutting grating lines had minimal effect on the adaptation to illusory lines; and changes in the configuration of endpoints could not be responsible for better performance when adapting and test stimuli were different. We conclude that a crowding effect occurs after illusory lines have been processed in the visual stream. Since illusory lines seem to be represented at relatively early stages of visual processing (e.g. area V2), adaptation to crowded illusory stimuli suggests that neuronal activation in those early stages is not necessarily correlated with conscious perception.     

The oblique effect in a vernier acuity situation

Observers viewed either vertical or obliquely oriented vernier targets from either an upright position or with their heads tilted. Vernier acuity was consistently better for retinally vertical than for gravitationally vertical targets, even when presented against a background context of vertical stripes designed to aid veridical perception of gravitational orientation. These results indicate that vernier acuity depends on retinal image orientation rather than on perceived orientation. The high contrast of the vernier lines ensures that their gravitational orientation is clearly perceived. Thus the present results provide a stronger basis for ruling out the effects of perceptual orientation than previous studies involving grating contrast-threshold measurements. Since the vernier targets were presented as brief flashes, it is unlikely that the measured oblique effect is attributable to differences in eye-movement patterns.     

For the mind’s eye the world is two-dimensional

The nature of visual mental images is a topic that has puzzled neuroscientists, psychologists, and philosophers alike. On the one hand, mental images might preserve the 3-D properties of our perceptual world. On the other hand, they might be akin to 2-D pictures, such as photographs, paintings, or drawings. In the present study, 16 observers judged where real objects (Experiment 1) or photographs thereof (Experiment 2) were pointing. Both experiments contained a perception condition and an imagery condition. In Experiment 1, there was a significant difference between the pointing errors in the perception and the imagery conditions, whereas there was no such difference in Experiment 2. In imagined objects, actual photographs, and imagined photographs, the direction in which the objects pointed followed the observer, regardless of his or her vantage point. The results from this study extend the rotation effect, typically found in pictures, to the domain of mental imagery. We found the rotation effect in pictures and mental images alike, but not in direct perception of 3-D objects; thus, we provide evidence that mental images share main characteristics of 2-D pictures.     

Intermodal sensory image generation: An fMRI analysis

Although both imagery and perception may be related to more than one sensory input, and information coming from different sensory channels is often integrated in a unique mental representation, most recent neuroimaging literature has focused on visual imaging. Contrasting results have been obtained concerning the sharing of the same mechanisms by visual perception and visual imagery, in part due to assessment techniques and to interindividual variability in brain activation. In recent years, an increasing number of researchers have adopted novel neuroimaging techniques in order to investigate intermodal connections in mental imagery and have reported a high degree of interaction between mental imagery and other cognitive functions. In the present study the specific nature of mental imagery was investigated by means of fMRI on a more extensive set of perceptual experiences (shapes, sounds, touches, odours, flavours, self‐perceived movements, and internal sensations). Results show that the left middle‐inferior temporal area is recruited by mental imagery for all modalities investigated and not only for the visual one, while parietal and prefrontal areas exhibit a more heterogeneous pattern of activation across modalities. The prominent left lateralisation observed for almost all the conditions suggests that verbal cues affect the processes underlying the generation of images.     

知觉与表象过程中不同线索表情的启动效应研究

探讨情绪性面孔的知觉和表象过程中,不同类型线索表情的启动效应,并关注不同类型表情表象难易的差异。选取NimStim数据库中20位演员的愉快、愤怒和中性表情作为启动刺激,随后呈现同一演员不同表情的图片,或通过颜色提示被试对不同表情进行表象,并同时进行表情类型判断。研究发现,情绪性面孔知觉与表象任务中均存在启动效应,之前呈现的线索面孔将会对接下来呈现的相同效价的面孔产生启动效应,对相反效价及中性面孔产生抑制; 在平衡不同类型面孔可能存在的启动效应后,正性、负性及中性表情是同样易于表象的。     

Perception and imagination: amodal perception as mental imagery

When we see an object, we also represent those parts of it that are not visible. The question is how we represent them: this is the problem of amodal perception. I will consider three possible accounts: (a) we see them, (b) we have non-perceptual beliefs about them and (c) we have immediate perceptual access to them, and point out that all of these views face both empirical and conceptual objections. I suggest and defend a fourth account, according to which we represent the occluded parts of perceived objects by means of mental imagery. This conclusion could be thought of as a (weak) version of the Strawsonian dictum, according to which “imagination is a necessary ingredient of perception itself”.     

Electrophysiological evidence for a shared representational medium for visual images and visual percepts

Does mental imagery involve the activation of representations in the visual system? Systematic effects of imagery on visual signal detection performance have been used to argue that imagery and the perceptual processing of stimuli interact at some common locus of activity (Farah, 1985). However, such a result is neutral with respect to the question of whether the interaction occurs during modality-specific visual processing of the stimulus. If imagery affects stimulus processing at early, modality-specific stages of stimulus representation, this implies that the shared stimulus representations are visual, whereas if imagery affects stimulus processing only at later, amodal stages of stimulus representation, this implies that imagery involves more abstract, postvisual stimulus representations. To distinguish between these two possibilities, we repeated the earlier imagery-perception interaction experiment while recording event-related potentials (ERPs) to stimuli from 16 scalp electrodes. By observing the time course and scalp distribution of the effect of imagery on the ERP to stimuli, we can put constraints on the locus of the shared representations for imagery and perception. An effect of imagery was seen within 200 ms following stimulus presentation, at the latency of the first negative component of the visual ERP, localized at the occipital and posterior temporal regions of the scalp, that is, directly over visual cortex. This finding provides support for the claim that mental images interact with percepts in the visual system proper and hence that mental images are themselves visual representations.