功能磁共振技术在表象研究中得到广泛应用是表象研究追求客观化精确性的必然趋势。本文介绍了功能磁共振多变量模式分析方法及其演变历程,探讨了借助该方法实现"视觉表象可视化"的理论依据与亟待解决的关键问题。分析指出"视觉表象可视化"将为表象研究提供全新的研究视角与方法途径。

采用2个2×2×6三因素混合设计实验,以图形和数字为实验材料,探讨能反应个体能力水平差 异的场认知方式对心理旋转的影响。两个实验结果均表明：（1）场认知方式的主效应显著,场独立性的被试比场依存性的被试反应时短,且正确率高;两类被试的 反应时、正确率曲线具有一致的变化趋势;（2）图形和数字的心理旋转反应时呈倒“V”形状,反应时随着旋转角度的增加而增加,180°时反应时最长,以 180°为界,曲线两侧的变化趋势对称;（3）正确率随着旋转角度的增加而降低,呈现“V”状,180°时正确率最低,曲线两侧的变化趋势对称。

Despite mental imagery's ubiquitous role in human perception, cognition and behavior, one standout question remains unanswered: Why does imagery vary so much from one individual to the next? Here, we used a behavioral paradigm that measures the functional impact of a mental image on subsequent conscious perception and related these measures to the anatomy of the early visual cortex estimated by fMRI retinotopic mapping. We observed a negative relationship between primary visual cortex (V1) surface area and sensory imagery strength, but found positive relationships between V1 and imagery precision (spatial location and orientation). Hence, individuals with a smaller V1 tended to have stronger, but less precise imagery. In addition, subjective vividness of imagery was positively related to prefrontal cortex volume, but unrelated to V1 anatomy. Our findings present the first evidence for the importance of the V1 layout in shaping the strength of human imagination.

Optimism is associated with a range of benefits not only for general well-being, but also for mental and physical health. The development of psychological interventions to boost optimism derived from cognitive science would have the potential to provide significant public health benefits, yet cognitive markers of optimism are little understood. The current study aimed to take a first step in this direction by identifying a cognitive marker for optimism that could provide a modifiable target for innovative interventions. In particular we predicted that the ability to generate vivid positive mental imagery of the future would be associated with dispositional optimism. A community sample of 237 participants completed a survey comprising measures of mental imagery and optimism, and socio-demographic information. Vividness of positive future imagery was significantly associated with optimism, even when adjusting for socio-demographic factors and everyday imagery use. The ability to generate vivid mental imagery of positive future events may provide a modifiable cognitive marker of optimism. Boosting positive future imagery could provide a cognitive target for treatment innovations to promote optimism, with implications for mental health and even physical well-being.

In this article, we report a new image-scanning paradigm that allowed us to measure objectively individual differences in spatial mental imagery--specifically, imagery for location. Participants were asked to determine whether an arrow was pointing at a dot using a visual mental image of an array of dots. The degree of precision required to discriminate "yes" from "no" trials was varied. In Experiment 1, the time to scan increasing distances, as well as the number of errors, increased when greater precision was required to make a judgement. The results in Experiment 2 replicated those results while controlling for possible biases. When greater precision is required, the accuracy of the spatial image becomes increasingly important--and hence the effect of precision in the task reflects the accuracy of the image. In Experiment 3, this measure was shown to be related to scores on the Paper Folding test, on the Paper Form Board test, and on the visuospatial items on Raven's Advanced Progressive Matrices--but not to scores on questionnaires measuring object-based mental imagery. Thus, we provide evidence that classical standardized spatial tests rely on spatial mental imagery but not object mental imagery.

Abstract Functional MRI during performance of a validated mental rotation task was used to assess a neurobiological basis for sex differences in visuospatial processing. Between-sex group analysis demonstrated greater activity in women than in men in dorsalmedial prefrontal and other high-order heteromodal association cortices, suggesting women performed mental rotation in an effortful, "top-down" fashion. In contrast, men activated primary sensory cortices as well as regions involved in implicit learning (basal ganglia) and mental imagery (precuneus), consistent with a more automatic, "bottom-up" strategy. Functional connectivity analysis in association with a measure of behavioral performance showed that, in men (but not women), accurate performance was associated with deactivation of parieto-insular vestibular cortex (PIVC) as part of a visual-vestibular network. Automatic evocation by men to a greater extent than women of this network during mental rotation may represent an effective, unconscious, bottom-up neural strategy which could reasonably account for men's traditional visuospatial performance advantage.

In primate area MT, direction-selective neurons convey information about a stimulus motion direction, as early as in their initial response. These neurons may also selectively signal transient changes in motion direction by increasing or decreasing their firing rate depending on whether the direction change deviated closer to or further away from their preferred direction. These properties may thus serve to detect and discriminate changes in a stimulus feature. Another potential source of neuronal encoding of motion direction relies on the activity of local field potentials (LFPs). Indeed, LFPs in area MT are tuned for motion direction, in a frequency-dependent manner. It is, however, unclear whether LFPs can provide a reliable signal to detect and discriminate changes in a stimulus feature. To investigate this issue, we recorded LFPs and spiking activity of direction-selective neurons in area MT of monkeys trained to covertly detect a 30-degree motion direction change in one of two moving RDPs. On each trial, both RDPs moved either in the preferred or antipreferred (AP) direction, and thus the actual motion direction after the change deviated away from either the preferred or the AP direction. Across the neuronal population (n=73), the motion direction change evoked a significant (p<0.05) decrease or increase in firing rates when the change deviated the motion direction away from preferred and AP, respectively. The direction change also induced changes in the LFP power in all frequency bands. However, only the gamma-band power reflected the identity of the change, being significantly larger when the change deviated the motion direction away from AP compared to away from preferred. These results indicate that the detection of transient stimulus changes can be encoded by LFPs in all frequency bands, while the discrimination of the type of change may be encoded by LFPs in the gamma band.

When asked to imagine a visual scene, such as an ant crawling on a checkered table cloth toward a jar of jelly, individuals subjectively report different vividness in their mental visualization. We show that reported vividness can be correlated with two objective measures: the early visual cortex activity relative to the whole brain activity measured by functional magnetic resonance imaging (fMRI) and the performance on a novel psychophysical task. These results show that individual differences in the vividness of mental imagery are quantifiable even in the absence of subjective report.

Abstract The authors investigated the relation between mental rotation (MR) and computer game-playing experience. Third grade boys (n = 24) and girls (n = 23) completed a 2-dimensional MR test before and after playing computer games (during 11 separate 30-min sessions), which either involved the use of MR skills (the experimental group) or did not involve the use of MR skills (the control group). The experimental group outperformed the control group on the MR posttest but not on the pretest. Boys outperformed girls on the pretest but not on the posttest. Children whose initial MR performance was low improved after playing computer games that entailed MR skills. The findings imply that computer-based instructional activities can be used in schools to enhance children's spatial abilities.

Research into the neural correlates of individual differences in imagery vividness point to an important role of the early visual cortex. However, there is also great fluctuation of vividness within individuals, such that only looking at differences between people necessarily obscures the picture. In this study we show that variation in moment-to-moment experienced vividness of visual imagery, within human subjects, depends on the activity of a large network of brain areas, including frontal, parietal and visual areas. Furthermore, using a novel multivariate analysis technique, we show that the neural overlap between imagery and perception in the entire visual system correlates with experienced imagery vividness. This shows that the neural basis of imagery vividness is much more complicated than studies of individual differences seemed to suggest.Significance statement: Visual imagery is the ability to visualise objects that are not in our direct line of sight; something that is important for memory, spatial reasoning and many other tasks. It is known that the better people are at visual imagery, the better they can perform these tasks. However, the neural correlates of moment-to-moment variation in visual imagery remain unclear. In this study we show that the more the neural response during imagery is similar to the neural response during perception, the more vivid or perception-like the imagery experience is.

ABSTRACT Reviews the literature on individual differences in imagery ability in the areas of learning, memory, perceptual, and conceptual processes over the past 10 yrs and attempts to place the imagery ability literature within the context of other operational approaches to imagery. The relative merits of self-ratings and objective measures of imagery as predictors of cognitive functioning are contrasted. It is concluded that (a) global statements concerning the predictive efficiency of self-ratings are inappropriate, (b) imagery control (whether measured by self-ratings or objective spatial tasks) seems to be an important element in predicting cognitive behavior, and (c) spatial-imagery differences in cognitive functioning manifest themselves when imagery is encouraged or primed and when the task is difficult. The need to investigate imagery ability in conjunction with verbal skills, verbal strategies and sex differences is discussed. (146 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

ABSTRACT Reviews recent experimental work on imagery, identifying specific levels of information processing within the visual system at which mental images and physical objects and events are functionally equivalent, as revealed by their perceptual and behavioral effects. Findings demonstrate that these functional equivalences can extend even to levels of the visual system where the effects produced cannot be explained by what people might know about objects and events, or by how they expect to perform. Effects produced when images are formed are often smaller than corresponding effects produced when objects and events are observed, and vivid imagers often show larger effects when forming images than nonvivid imagers. On the basis of these findings, it is argued that mental imagery can result in the activation of information-processing mechanisms at many levels of the visual system, even those mechanisms whose operating characteristics are not influenced by how objects and events might be conceptualized. (63 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Regional cerebral blood flow patterns were investigated by means of single photon emission computerized tomography in subjects who solved cognitive tasks which either did or did not require the use of visual imagery. In a first experiment judging the correctness of visual imagery sentences like “a grapefruit is bigger than an orange” led to increases of regional activity in inferior temporal and in the left inferior-occipital region when compared to blood flow patterns elicited by judgements about low imagery sentences or by responding differentially to “yes” and “no”. Motor imagery sentences did not cause such an increase. In a second experiment a condition in which visual images were used for counting the corners of letters was compared to a condition in which subjects internally rehearsed the alphabet. The only difference concerned the inferior frontal regions which showed higher activity in rehearsing the alphabet. However, activity in inferior temporal and inferior occipital regions showed a positive correlation to the self-rated vividness of the visual images in the corner counting condition. The results of both experiments yield converging evidence that visual imagery is selectively related to activity of inferior-temporal and occipital regions. They thus support the hypothesis that the cerebral correlate of visual imagery is different from that of non-imaginal thinking.

Everyone has seen a human face in a cloud, a pebble, or blots on a wall. Evidence of superstitious perceptions has been documented since classical antiquity, but has received little scientific attention. In the study reported here, we used superstitious perceptions in a new principled method to reveal the properties of unobservable object representations in memory. We stimulated the visual system with unstructured white noise. Observers firmly believed that they perceived the letter S in Experiment 1 and a smile on a face in Experiment 2. Using reverse correlation and computational analyses, we rendered the memory representations underlying these superstitious perceptions.

The purpose of this study was to identify the movement characteristics associated with positive and negative emotions experienced during walking. Joy, contentment, anger, sadness, and neutral were elicited in 16 individuals, and motion capture data were collected as they walked while experiencing the emotions. Observers decoded the target emotions from side and front view videos of the walking trials; other observers viewed the same videos to rate the qualitative movement features using an Effort-Shape analysis. Kinematic analysis was used to quantify body posture and limb movements during walking with the different emotions. View did not affect decoding accuracy except for contentment, which was slightly enhanced with the front view. Walking speed was fastest for joy and anger, and slowest for sadness. Although walking speed may have accounted for increased amplitude of hip, shoulder, elbow, pelvis and trunk motion for anger and joy compared to sadness, neck and thoracic flexion with sadness, and trunk extension and shoulder depression with joy were independent of gait speed. More differences among emotions occurred with the Effort-Shape rather than the kinematic analysis, suggesting that observer judgments of Effort-Shape characteristics were more sensitive than the kinematic outcomes to differences among emotions.

Abstract Much of the debate surrounding the precise functional role of brain mechanisms implicated in the processing of human faces can be explained when considering that studies into early-stage neural representations of the spatial arrangement of facial features are potentially contaminated by "higher-level" cognitive attributes associated with human faces. One way to bypass such attributes would be to employ ambiguous stimuli that are not biased toward any particular object class and analyze neural activity in response to those stimuli in a manner similar to traditional reverse correlation for mapping visual receptive fields. Accordingly, we sought to derive whole face representations directly from neural activity in the human brain using electroencephalography (EEG). We presented ambiguous fractal noise stimuli to human participants and asked them to rate each stimulus along a "face not present" to "face present" continuum while simultaneously recording EEGs. All EEGs were subjected to a time-frequency analysis near 170 ms (negative amplitudes near 170 ms post-stimulus onset have been linked to early face processing) for five different frequency bands (delta, theta, alpha, beta, and gamma) on a trial-by-trial basis, independent of the behavioral responses. Images containing apparent face-like structure were obtained for theta through gamma frequency bands for strong negative amplitudes near 170 ms post-stimulus onset. The presence of the face-like structure in the spatial images derived from brain signals was objectively verified using both Fourier methods and trained neural networks. The results support the use of a modified reverse correlation technique with EEG as a non-biased assessment of brain processes involved in the complex integration of spatial information into objects such as human faces. Copyright (c) 2010 Elsevier Inc. All rights reserved.

A large number of imaging studies have identified a role for the posterior parietal lobe, in particular Brodmann's area 7 and the intraparietal sulcus (IPS), in mental rotation. Here we investigated whether neural activity in the posterior parietal lobe is essential for successful mental rotation performance by observing the effects of interrupting this activity during the execution of a mental rotation task. Repetitive transcranial magnetic stimulation (rTMS) was applied to posterior parietal locations estimated to overlie Brodmann's area 7 in the right and the left hemisphere, or to a posterior midline location (sham condition). In three separate experiments, rTMS (four pulses, 20 Hz) was delivered at these locations either 200–400, 400–600, or 600–800 msec after the onset of a mental rotation trial. Disrupting neural activity in the right parietal lobe interfered with task performance, but only when rTMS was delivered 400 to 600 msec after stimulus onset. Stimulation of the left parietal lobe did not reliably affect mental rotation performance at any of the time points investigated. The time-limited effect of rTMS was replicated in a fourth experiment that directly compared the effects of rTMS applied to the right parietal lobe either 200–400 or 400–600 msec into the mental rotation trial. The results indicate that the right superior posterior parietal lobe plays an essential role in mental rotation, consistent with its involvement in a variety of visuospatial and visuomotor transformations.

Visual imagery during sleep has long been a topic of persistent speculation, but its private nature has hampered objective analysis. Here we present a neural decoding approach in which machine-learning models predict the contents of visual imagery during the sleep-onset period, given measured brain activity, by discovering links between human functional magnetic resonance imaging patterns and verbal reports with the assistance of lexical and image databases. Decoding models trained on stimulus-induced brain activity in visual cortical areas showed accurate classification, detection, and identification of contents. Our findings demonstrate that specific visual experience during sleep is represented by brain activity patterns shared by stimulus perception, providing a means to uncover subjective contents of dreaming using objective neural measurement.

Abstract The strongest sex differences on any cognitive task, favoring men, are found for tasks that require the mental rotation of three-dimensional objects. A number of studies have explored functional brain activation during mental rotation tasks, and sex differences have been noted in some. However, in these studies there was a substantial confounding factor because male and female subjects differed in overall performance levels. In contrast, our functional brain activation study examined cortical activation patterns for males and females who did not differ in overall level of performance on three mental rotation tasks. This allowed us to eliminate any confounding influences of overall performance levels. Women exhibited significant bilateral activations in the intraparietal sulcus (IPS) and the superior and inferior parietal lobule, as well as in the inferior temporal gyrus (ITG) and the premotor areas. Men showed significant activation in the right parieto-occitpital sulcus (POS), the left intraparietal sulcus and the left superior parietal lobule (SPL). Both men and women showed activation of the premotor areas but men also showed an additional significant activation of the left motor cortex. No significant activation was found in the inferior temporal gyrus. Our results suggest that there are genuine between-sex differences in cerebral activation patterns during mental rotation activities even when performances are similar. Such differences suggest that the sexes use different strategies in solving mental rotation tasks.

Strategic differences in spatial tasks can be explained in terms of different cognitive coordinate systems that subjects adopt. The strategy of mental rotation (of the type used in most mental rotation experiments and in some psychometric tests of spatial ability) uses a coordinate system defined by the standard axes of our visual world (i.e. horizontal, vertical, and depth axes). Within this strategy, rotations are performed around one or more of the standard axes. The paper provides a detailed theoretical account of the mental rotation of individuals of low and high spatial ability as they solve problems taken from psychometric tests. The theory is instantiated as two related computer simulation models that not only solve the problems, but also match the response times for the two groups. The simulation models contain modularized units of procedural knowledge called productions, that select and execute the appropriate actions at each knowledge state. Small localized differences between the two models simulate the large quantitative and qualitative differences between the two groups of subjects.

Various cognitive theories aim to explain human deductive reasoning: (1) mental logic theories claim syntactic language-based proofs of derivation, (2) the mental model theory proposes cognitive processes of constructing and manipulating spatially organized mental models, and (3) imagery theories postulate that such abilities are based on visual mental images. To explore the neural substrates of human deductive reasoning, we examined BOLD (blood oxygen level dependent) contrasts of twelve healthy participants during relational and conditional reasoning with whole-brain functional magnetic resonance imaging (fMRI). The results indicate that, in the absence of any correlated visual input, reasoning activated an occipitoparietal rontal network, including parts of the prefrontal cortex (Brodmann area, BA, 6, 9) and the cingulate gyrus (BA 32), the superior and inferior parietal cortex (BA 7, 40), the precuneus (BA 7), and the visual association cortex (BA 19). In the discussion, we first focus on the activated occipito-parietal pathway that is well known to be involved in spatial perception and spatial working memory. Second, we briefly relate the activation in the prefrontal cortical areas and in the anterior cingulate gyrus to other imaging studies on higher cognitive functions. Finally, we draw some general conclusions and argue that reasoners envisage and inspect spatially organized mental models to solve deductive inference problems.

This experiment was designed to explore the spatial and structural properties of visual imagery. Forty Ss were shown drawings and later asked to verify pictorial features of the drawings from memory One group of Ss was instructed to be able to recall an image of each drawing and to focus initially on one specified end of their images during the subsequent verification task. Another group of Ss were asked to recall a verbal description of each drawing and initially to describe one specified end of a drawing during the verification task. Time to verify pictorial properties was a function of the spatial distance of a property from an initial focus point for both groups, but Ss in the verbal description group experienced much greater difficulty in performing the task. Comparison of these times with those from additional imagery, encoding and verbal encoding groups ~ven no focusing instructions indicated that focusing instructions effectively directed scanning strategies.

This article is founded on the bold claim that mental imagery is a basic building block of all consciousness. Conscious mental imagery is reported in association with waking, dreaming and intermediate states of consciousness. Meta-cognitive theory claims that the individual may be treated as an imperfect measuring device of his or her own consciousness. This is supported by the evidence on the psychological correlates of imagery vividness reported using the Vividness of Visual Imagery Questionnaire (VVIQ) (Marks, 1973). Meta-analysis of 150 studies has demonstrated high levels of reliability, content validity and criterion validity (McKelvie, 1995 a, b). This analysis demonstrates that under controlled conditions, verbal reports provide reliable and valid measures of conscious experience. The activity cycle theory of conscious imagery claims that a primary function of consciousness is the mental rehearsal of adaptive, goal-directed action through the experimental manipulation of perceptual-motor imagery. As predicted by this theory, the meta-analysis shows that the vividness of conscious mental imagery is strongly associated with precisely those performances most likely to benefit from the use of perceptual-motor imagery and mental practice. The theory helps to explain the existence and function of conscious experience.

Recurrent distressing intrusive images are a common experience in hypochondriasis. The aim of the current study was to assess the impact of mindfulness-based cognitive therapy (MBCT) for hypochondriasis on the occurrence and nature of distressing intrusive imagery in hypochondriasis. A semistructured interview was used to assess intrusive imagery, and an adapted version of the Southampton Mindfulness Questionnaire (SMQ) was used to assess participants’ relationship with their intrusive images. A consecutive series of participants ( N 65=6520) who were receiving MBCT for hypochondriasis as part of an ongoing research program were assessed prior to participating in an 8-week MBCT intervention, immediately following the intervention, and at 3-month follow-up. As compared to the baseline assessment, the frequency of intrusive images, the distress associated with them, and the intrusiveness of the images were all significantly reduced at the post-MBCT assessment. Participants’ adapted SMQ scores were significantly increased following the MBCT intervention, suggesting that participants’ relationship with their intrusive images had changed in that they had developed a more “mindful” and compassionate response to the images when they did occur. Effect sizes from pre- to post-intervention were medium to large (Cohen’s d 65=650.75–1.50). All treatment gains were maintained at 3-month follow-up. Results suggest that MBCT may be an effective intervention for addressing intrusive imagery in hypochondriasis.

We investigated the temporal dynamics and changes in connectivity in the mental rotation network through the application of spatio-temporal support vector machines (SVMs). The spatio-temporal SVM [Mourao-Miranda, J., Friston, K. J., et al. (2007). Dynamic discrimination analysis: A spatial-temporal SVM. Neuroimage, 36, 88–99] is a pattern recognition approach that is suitable for investigating dynamic changes in the brain network during a complex mental task. It does not require a model describing each component of the task and the precise shape of the BOLD impulse response. By defining a time window including a cognitive event, one can use spatio-temporal fMRI observations from two cognitive states to train the SVM. During the training, the SVM finds the discriminating pattern between the two states and produces a discriminating weight vector encompassing both voxels and time (i.e., spatio-temporal maps). We showed that by applying spatio-temporal SVM to an event-related mental rotation experiment, it is possible to discriminate between different degrees of angular disparity (0° vs. 20°, 0° vs. 60°, and 0° vs. 100°), and the discrimination accuracy is correlated with the difference in angular disparity between the conditions. For the comparison with highest accuracy (0° vs. 100°), we evaluated how the most discriminating areas (visual regions, parietal regions, supplementary, and premotor areas) change their behavior over time. The frontal premotor regions became highly discriminating earlier than the superior parietal cortex. There seems to be a parcellation of the parietal regions with an earlier discrimination of the inferior parietal lobe in the mental rotation in relation to the superior parietal. The SVM also identified a network of regions that had a decrease in BOLD responses during the 100° condition in relation to the 0° condition (posterior cingulate, frontal, and superior temporal gyrus). This network was also highly discriminating between the two conditions. In addition, we investigated changes in functional connectivity between the most discriminating areas identified by the spatio-temporal SVM. We observed an increase in functional connectivity between almost all areas activated during the 100° condition (bilateral inferior and superior parietal lobe, bilateral premotor area, and SMA) but not between the areas that showed a decrease in BOLD response during the 100° condition.

61A model of representation in early visual cortex decodes mental images of complex scenes.61Mental imagery depends directly upon the encoding of low-level visual features.61Low-level visual features of mental images are encoded by activity in early visual cortex.61Depictive theories of mental imagery are strongly supported by our results.61Brain activity evoked by mental imagery can be used to guide internet image search.

A key challenge for cognitive neuroscience is determining how mental representations map onto patterns of neural activity. Recently, researchers have started to address this question by applying sophisticated pattern-classification algorithms to distributed (multi-voxel) patterns of functional MRI data, with the goal of decoding the information that is represented in the subject's brain at a particular point in time. This multi-voxel pattern analysis (MVPA) approach has led to several impressive feats of mind reading. More importantly, MVPA methods constitute a useful new tool for advancing our understanding of neural information processing. We review how researchers are using MVPA methods to characterize neural coding and information processing in domains ranging from visual perception to memory search.

What happens in the brain when you conjure up a mental image in your mind's eye? We tested whether the particular regions of extrastriate cortex activated during mental imagery depend on the content of the image. Using functional magnetic resonance imaging (fMRRI), we demonstrated selective activation within a region of cortex specialized for face perception during mental imagery of faces, and selective activation within a place-selective cortical region during imagery of places. In a further study, we compared the activation for imagery and perception in these regions, and found greater response magnitudes for perception than for imagery of the same items. Finally, we found that it is possible to determine the content of single cognitive events from an inspection of the fMRI data from individual imagery trials. These findings strengthen evidence that imagery and perception share common processing mechanisms, and demonstrate that the specific brain regions activated during mental imagery depend on the content of the visual image.

Abstract In the present fMRI study the issue of the specific cortices activation during imagery generation in different sensory modalities is addressed. In particular, we tested whether the vividness variability of imagery was reflected in the BOLD signal within specific sensory cortices. Subjects were asked to generate a mental image for each auditory presented sentence. Each imagery modality was contrasted with an abstract sentence condition. In addition, subjects were asked to fill the Italian version of the Questionnaire Upon Mental Imagery (QMI) prior to each neuroimaging session. In general, greater involvement of sensory specific cortices in high-vivid versus low-vivid subjects was found for visual (occipital), gustatory (anterior insula), kinaesthetic (pre-motor), and tactile and for somatic (post-central parietal) imagery modalities. These results support the hypothesis that vividness is related to image format: high-vivid subjects would create more analogical representations relying on the same specific neural substrates active during perception with respect to low-vivid subjects. Results are also discussed according to the simulation perspective.

Mental imagery research has weathered both disbelief of the phenomenon and inherent methodological limitations. Here we review recent behavioral, brain imaging, and clinical research that has reshaped our understanding of mental imagery. Research supports the claim that visual mental imagery is a depictive internal representation that functions like a weak form of perception. Brain imaging work has demonstrated that neural representations of mental and perceptual images resemble one another as early as the primary visual cortex (V1). Activity patterns in V1 encode mental images and perceptual images via a common set of low-level depictive visual features. Recent translational and clinical research reveals the pivotal role that imagery plays in many mental disorders and suggests how clinicians can utilize imagery in treatment.

Mental imagery has been proposed to contribute to a variety of high-level cognitive functions, including memory encoding and retrieval, navigation, spatial planning, and even social communication and language comprehension [1 5]. However, it is debated whether mental imagery relies on the same sensory representations as perception [1, 6 10], and if so, what functional consequences such an overlap might have on perception itself. We report novel evidence that single instances of imagery can have a pronounced facilitatory influence on subsequent conscious perception. Either seeing or imagining a specific pattern could strongly bias which of two competing stimuli reach awareness during binocular rivalry. Effects of imagery and perception were location and orientation specific, accumulated in strength over time, and survived an intervening visual task lasting several seconds prior to presentation of the rivalry display. Interestingly, effects of imagery differed from those of feature-based attention. The results demonstrate that imagery, in the absence of any incoming visual signals, leads to the formation of a short-term sensory trace that can bias future perception, suggesting a means by which high-level processes that support imagination and memory retrieval may shape low-level sensory representations.

Abstract The possible ways that information can be represented mentally have been discussed often over the past thousand years. However, this issue could not be addressed rigorously until late in the 20th century. Initial empirical findings spurred a debate about the heterogeneity of mental representation: Is all information stored in propositional, language-like, symbolic internal representations, or can humans use at least two different types of representations (and possibly many more)? Here, in historical context, we describe recent evidence that humans do not always rely on propositional internal representations but, instead, can also rely on at least one other format: depictive representation. We propose that the debate should now move on to characterizing all of the different forms of human mental representation.

Abstract The visual system has an extraordinary capability to extract categorical information from complex natural scenes. For example, subjects are able to rapidly detect the presence of object categories such as animals or vehicles in new scenes that are presented very briefly. This is even true when subjects do not pay attention to the scenes and simultaneously perform an unrelated attentionally demanding task, a stark contrast to the capacity limitations predicted by most theories of visual attention. Here we show a neural basis for rapid natural scene categorization in the visual cortex, using functional magnetic resonance imaging and an object categorization task in which subjects detected the presence of people or cars in briefly presented natural scenes. The multi-voxel pattern of neural activity in the object-selective cortex evoked by the natural scenes contained information about the presence of the target category, even when the scenes were task-irrelevant and presented outside the focus of spatial attention. These findings indicate that the rapid detection of categorical information in natural scenes is mediated by a category-specific biasing mechanism in object-selective cortex that operates in parallel across the visual field, and biases information processing in favour of objects belonging to the target object category.

Visually perceiving a stimulus activates a pictorial representation of that item in the brain, but how pictorial is the representation of a stimulus in the absence of visual stimulation? Here I address this question with a review of the literatures on visual imagery (VI), visual working memory (VWM), and visual preparatory templates, all of which require activating visual information in the absence of sensory stimulation. These processes have historically been studied separately, but I propose that they can provide complimentary evidence for the pictorial nature of their contents. One major challenge in studying the contents of visual representations is the discrepant findings concerning the extent of overlap (both cortical and behavioral) between externally and internally sourced visual representations. I argue that these discrepancies may in large part be due to individual differences in VI vividness and precision, the specific representative abilities required to perform a task, appropriateness of visual preparatory strategies, visual cortex anatomy, and level of expertise with a particular object category. Individual differences in visual representative abilities greatly impact task performance and may influence the likelihood of experiences such as intrusive VI and hallucinations, but research still predominantly focuses on uniformities in visual experience across individuals. In this paper I review the evidence for the pictorial content of visual representations activated for VI, VWM, and preparatory templates, and highlight the importance of accounting for various individual differences in conducting research on this topic.

Abstract Traditionally studies of brain function have focused on task-evoked responses. By their very nature, such experiments tacitly encourage a reflexive view of brain function. Although such an approach has been remarkably productive, it ignores the alternative possibility that brain functions are mainly intrinsic, involving information processing for interpreting, responding to and predicting environmental demands. Here I argue that the latter view best captures the essence of brain function, a position that accords well with the allocation of the brain's energy resources. Recognizing the importance of intrinsic activity will require integrating knowledge from cognitive and systems neuroscience with cellular and molecular neuroscience where ion channels, receptors, components of signal transduction and metabolic pathways are all in a constant state of flux.

The area of cognitive research that has produced the most consistent sex differences is spatial ability. In particular, men usually perform better on mental rotation tasks than women. Performance on mental rotation tasks has been associated with right parietal activation levels, both during task performance and prior to performance during baseline recordings. This study examined the relations among sex, age, electroencephalogram (EEG) hemispheric activation (at the 10.5 Hz to 13.5 Hz frequency band), and 2-D mental rotation task ability. Nineteen 8-year-olds (10 boys) and 20 college students (10 men) had EEG recorded at baseline and while performing a mental rotation task. Men had a faster reaction time on the mental rotation task than women, whereas there were no differences between boys and girls. After covarying for baseline EEG power values, men exhibited more activation (lower EEG power values) than women in the parietal and posterior temporal regions, whereas boys' and girls' power values did not differ in the parietal or posterior temporal regions. Furthermore, during the baseline condition, men generally exhibited more activation (lower EEG power values) throughout all regions of the scalp. Results support the hypothesis that a change that affects both brain activation and performance on mental rotation tasks occurs sometime between childhood and adulthood.

On each trial Ss viewed one of the patterns of six connected squares that result when the faces of a cube are unfolded onto a flat surface. The Ss tried, as rapidly as possible, to decide whether two arrows, each marked on an edge of a (different) square, would or would not meet if the squares were folded back up into the cube. The time required to make such decisions increased linearly (from 2 to about 15 sec) with the sum of the number of squares that would be involved in each fold, if those folds were actually performed physically.

The time required to recognize that two perspective drawings portray objects of the same three-dimensional shape is found to be (i) a linearly increasing function of the angular difference in the portrayed orientations of the two objects and (ii) no shorter for differences corresponding simply to a rigid rotation of one of the two-dimensional drawings in its own picture plane than for differences corresponding to a rotation of the three-dimensional object in depth.

78 We provide a method to visualize the content of subjective internal representations 78 We show where and when the brain uses this knowledge to interpret the visual input

When asked to perform the same task, different individuals exhibit markedly different patterns of brain activity. This variability is often attributed to volatile factors, such as task strategy or compliance. We propose that individual differences in brain responses are, to a large degree, inherent to the brain and can be predicted from task-independent measurements collected at rest. Using a large set of task conditions, spanning several behavioral domains, we train a simple model that relates task-independent measurements to task activity and evaluate the model by predicting task activation maps for unseen subjects using magnetic resonance imaging. Our model can accurately predict individual differences in brain activity and highlights a coupling between brain connectivity and function that can be captured at the level of individual subjects.

Abstract A new paper-and-pencil test of spatial visualization was constructed from the figures used in the chronometric study of Shepard and Metzler (1971). In large samples, the new test displayed substantial internal consistency (Kuder-Richardson 20 = .88), a test-retest reliability (.83), and consistent sex differences over the entire range of ages investigated. Correlations with other measures indicated strong association with tests of spatial visualization and virtually no association with tests of verbal ability.

Abstract Brain functions during the resting state have attracted considerable attention in the past several years. However, little has been known about spontaneous activity in the sensory cortices in the task-free state. This study used functional magnetic resonance imaging (fMRI) to investigate the existence of spontaneous activity in the primary visual areas (PVA) of normal-sighted subjects and to explore the physiological implications of such activity. Our results revealed that we were able to detect spontaneous activity, which was nonrandom in that it was distinctly clustered both temporally and spatially in the PVA of each subject. In addition, the neural network associated with the PVA-related spontaneous activity included the visual association areas, the precuneus, the precentral/postcentral gyrus, the middle frontal gyrus, the fusiform gyrus, the inferior/middle temporal gyrus, and the parahippocampal gyrus. After considering the functions of these regions, we speculated that the PVA-related spontaneous activity may be associated with memory-related mental imagery and/or visual memory consolidation processes. These findings confirm the presence of spontaneous activity in the PVA and related brain areas. This confirmation supports the perspective that brain is a system intrinsically operating on its own, and sensory information interacts with rather than determines the operation of the system.

Background: Mental spatial transformations are ubiquitous and necessary for everyday spatial cognition, such as packing luggage into a car or repairing a broken vase. The posterior parietal cortex is known to be involved in performing such transformations. Objective: To measure reorganization after lesioning of posterior parietal cortex areas subserving spatial transformation. Method: Brain activity in a patient who underwent a resection of right parietal cortex to manage intractable epilepsy was measured using fMRI while he performed a set of spatial transformation tasks. These data were compared with data from a group of healthy control subjects. Results: During spatial transformations, activity in the regions overlapping the resection was reduced in the patient compared with control subjects, but activity in the contralateral cortex was greater than that of control subjects. Conclusions: After a lesion the left hemisphere can adopt components of spatial reasoning normally subserved by the right hemisphere. This converges with evidence that components of language proces sing normally subserved by the left hemisphere can be taken over by the right hemisphere, suggesting that plasticity of function in the adult human cortex is a general characteristic.