Does hemineglect affect visual mental imagery? Imagery deficits in representational and perceptual neglect

Recent advances in treatment of spatial neglect: networks and neuropsychology

INTRODUCTION

Spatial neglect remains an underdiagnosed and undertreated consequence of stroke that imposes significant disability. A growing appreciation of brain networks involved in spatial cognition is helping us to develop a mechanistic understanding of different therapies under development.

AREAS COVERED

This review focuses on neuromodulation of brain networks for the treatment of spatial neglect after stroke, using evidence-based approaches including 1) Cognitive strategies that are more likely to impact frontal lobe executive function networks; 2) Visuomotor adaptation, which may depend on the integrity of parietal and parieto- and subcortical-frontal connections and the presence of a particular subtype of neglect labeled Aiming neglect; 3) Non-invasive brain stimulation that may modulate relative levels of activity of the two hemispheres and depend on corpus callosum connectivity; and 4) Pharmacological modulation that may exert its effect primarily via right-lateralized networks more closely involved in arousal.

EXPERT OPINION

Despite promising results from individual studies, significant methodological heterogeneity between trials weakened conclusions drawn from meta-analyses. Improved classification of spatial neglect subtypes will benefit research and clinical care. Understanding the brain network mechanisms of different treatments and different types of spatial neglect will make possible a precision medicine treatment approach.

Congenital lack and extraordinary ability in object and spatial imagery: An investigation on sub-types of aphantasia and hyperphantasia

Studies that have shown a distinction between object and spatial imagery suggest more than one type of aphantasia and hyperphantasia, yet this has not been systematically investigated in studies on imagery ability extremes. Also, if the involuntary imagery is preserved in aphantasia and how this condition affects other skills is not fully clear. We collected data on spatial and object imagery, retrospective, and prospective memory, face recognition, and sense of direction (SOD), suggesting a distinction between two subtypes of aphantasia/hyperphantasia. Spatial aphantasia is associated with difficulties in visuo-spatial mental imagery and SOD. Instead, in object aphantasia there are difficulties in imaging single items and events - with no mental visualization of objects, out-of-focus, and black-and-white mental images more frequent than expected - in SOD and face recognition. Furthermore, associative involuntary imagery can be spared in aphantasia. The opposite pattern of performance was found in spatial and object hyperphantasia.

Travel Planning Ability in Right Brain-Damaged Patients: Two Case Reports

Planning ability is fundamental for goal-directed spatial navigation. Preliminary findings from patients and healthy individuals suggest that travel planning (TP)-namely, navigational planning-can be considered a distinct process from visuospatial planning (VP) ability. To shed light on this distinction, two right brain-damaged patients without hemineglect were compared with a control group on two tasks aimed at testing VP (i.e., Tower of London-16, ToL-16) and TP (i.e., Minefield Task, MFT). The former requires planning the moves to reach the right configuration of three colored beads on three pegs, whereas the latter was opportunely developed to assess TP in the navigational environment when obstacles are present. Specifically, the MFT requires participants to plan a route on a large carpet avoiding some hidden obstacles previously observed. Patient 1 showed lesions encompassing the temporoparietal region and the insula; she performed poorer than the control group on the ToL-16 but showed no deficit on the MFT. Conversely, Patient 2 showed lesions mainly located in the occipitoparietal network of spatial navigation; she performed worse than the control group on the MFT but not on the ToL-16. In both cases performances satisfied the criteria for a classical dissociation, meeting criteria for a double dissociation. These results support the idea that TP is a distinct ability and that it is dissociated from VP skills.

Mental imagery skills predict the ability in performing environmental directional judgements

Mental imagery plays a crucial role in several cognitive processes, including human navigation. According to the Kosslyn's Model, mental imagery is subserved by three components: generation, inspection and transformation. The role of transformation, where by individuals recognise, from a different perspective, a place they have already visited, is no longer a matter of debate. However, the role of the other two components when recalling a map from different perspectives, has never been fully investigated. In the present study, we enrolled forty-nine college students and asked them to learn a schematic map and to provide directional judgements aligned or counter-aligned compared to the learnt map orientation. Their mental imagery generation, inspection and transformation skills were also investigated. Results demonstrated that all three visual mental imagery components negatively correlate with errors in providing directional judgements. Specifically, generation assumes a role in aligned directional judgements, while inspection and transformation predict the capability to provide counter-aligned directional judgements. Although all mental imagery components play a role in mentally recalling a map, only the proficiency in inspection and mental rotation can predict the accuracy in changing perspective.

The impact of ageing and gender on visual mental imagery processes: A study of performance on tasks from the Complete Visual Mental Imagery Battery (CVMIB)

In this study we aim to evaluate the impact of ageing and gender on different visual mental imagery processes. Two hundred and fifty-one participants (130 women and 121 men; age range = 18-77 years) were given an extensive neuropsychological battery including tasks probing the generation, maintenance, inspection, and transformation of visual mental images (Complete Visual Mental Imagery Battery, CVMIB). Our results show that all mental imagery processes with the exception of the maintenance are affected by ageing, suggesting that other deficits, such as working memory deficits, could account for this effect. However, the analysis of the transformation process, investigated in terms of mental rotation and mental folding skills, shows a steeper decline in mental rotation, suggesting that age could affect rigid transformations of objects and spare non-rigid transformations. Our study also adds to previous ones in showing gender differences favoring men across the lifespan in the transformation process, and, interestingly, it shows a steeper decline in men than in women in inspecting mental images, which could partially account for the mixed results about the effect of ageing on this specific process. We also discuss the possibility to introduce the CVMIB in clinical assessment in the context of theoretical models of mental imagery.

Domain-Specificity of Creativity: A Study on the Relationship Between Visual Creativity and Visual Mental Imagery

Creativity refers to the capability to catch original and valuable ideas and solutions. It involves different processes. In this study the extent to which visual creativity is related to cognitive processes underlying visual mental imagery was investigated. Fifty college students (25 women) carried out: the Creative Synthesis Task, which measures the ability to produce creative objects belonging to a given category (originality, synthesis and transformation scores of pre-inventive forms, and originality and practicality scores of inventions were computed); an adaptation of Clark’s Drawing Ability Test, which measures the ability to produce actual creative artworks (graphic ability, esthetic, and creativity scores of drawings were assessed) and three mental imagery tasks that investigate the three main cognitive processes involved in visual mental imagery: generation, inspection and transformation. Vividness of imagery and verbalizer–visualizer cognitive style were also measured using questionnaires. Correlation analysis revealed that all measures of the creativity tasks positively correlated with the image transformation imagery ability; practicality of inventions negatively correlated with vividness of imagery; originality of inventions positively correlated with the visualization cognitive style. However, regression analysis confirmed the predictive role of the transformation imagery ability only for the originality score of inventions and for the graphic ability and esthetic scores of artistic drawings; on the other hand, the visualization cognitive style predicted the originality of inventions, whereas the vividness of imagery predicted practicality of inventions. These results are consistent with the notion that visual creativity is domain- and task-specific.

Age effect in generating mental images of buildings but not common objects

Imagining a familiar environment is different from imagining an environmental map and clinical evidence demonstrated the existence of double dissociations in brain-damaged patients due to the contents of mental images. Here, we assessed a large sample of young and old participants by considering their ability to generate different kinds of mental images, namely, buildings or common objects. As buildings are environmental stimuli that have an important role in human navigation, we expected that elderly participants would have greater difficulty in generating images of buildings than common objects. We found that young and older participants differed in generating both buildings and common objects. For young participants there were no differences between buildings and common objects, but older participants found easier to generate common objects than buildings. Buildings are a special type of visual stimuli because in urban environments they are commonly used as landmarks for navigational purposes. Considering that topographical orientation is one of the abilities mostly affected in normal and pathological aging, the present data throw some light on the impaired processes underlying human navigation.

Visual Memory in Unilateral Spatial Neglect: Immediate Recall versus Delayed Recognition

Patients with unilateral spatial neglect (USN) often show impaired performance in spatial working memory tasks, apart from the difficulty retrieving “left-sided” spatial data from long-term memory, shown in the “piazza effect” by Bisiach and colleagues. This study's aim was to compare the effect of the spatial position of a visual object on immediate and delayed memory performance in USN patients. Specifically, immediate verbal recall performance, tested using a simultaneous presentation of four visual objects in four quadrants, was compared with memory in a later-provided recognition task, in which objects were individually shown at the screen center. Unlike healthy controls, USN patients showed a left-side disadvantage and a vertical bias in the immediate free recall task (69% vs. 42% recall for right- and left-sided objects, respectively). In the recognition task, the patients correctly recognized half of “old” items, and their correct rejection rate was 95.5%. Importantly, when the analysis focused on previously recalled items (in the immediate task), no statistically significant difference was found in the delayed recognition of objects according to their original quadrant of presentation. Furthermore, USN patients were able to recollect the correct original location of the recognized objects in 60% of the cases, well beyond chance level. This suggests that the memory trace formed in these cases was not only semantic but also contained a visuospatial tag. Finally, successful recognition of objects missed in recall trials points to formation of memory traces for neglected contralesional objects, which may become accessible to retrieval processes in explicit memory.

Internal and external spatial attention examined with lateralized EEG power spectra

Several authors argued that retrieval of an item from visual short term memory (internal spatial attention) and focusing attention on an externally presented item (external spatial attention) are similar. Part of the neuroimaging support for this view may be due to the employed experimental procedures. Furthermore, as internal spatial attention may have a more induced than evoked nature some effects may not have been visible in event related analyses of the electroencephalogram (EEG), which limits the possibility to demonstrate differences. In the current study, a colored frame cued which stimulus, one out of four presented in separate quadrants, required a response, which depended on the form of the cued stimulus (circle or square). Importantly, the frame occurred either before (precue), simultaneously with (simultaneous cue), or after the stimuli (postcue). The precue and simultaneous cue condition both concern external attention, while the postcue condition implies the involvement of internal spatial attention. Event-related lateralizations (ERLs), reflecting evoked effects, and lateralized power spectra (LPS), reflecting both evoked and induced effects, were determined. ERLs revealed a posterior contralateral negativity (PCN) only in the precue condition. LPS analyses on the raw EEG showed early increased contralateral theta power at posterior sites and later increased ipsilateral alpha power at occipito-temporal sites in all cue conditions. Responses were faster when the internally or externally attended location corresponded with the required response side than when not. These findings provide further support for the view that internal and external spatial attention share their underlying mechanism.

Looking for the compass in a case of developmental topographical disorientation: a behavioral and neuroimaging study

Developmental topographical disorientation (DTD) is the presence of navigational deficits in the context of normal intellectual ability and in the absence of any perinatal, neurological, or psychiatric disorder. As only three cases of DTD have been fully described thus far, we are still unable to draw definitive conclusions about its nature and relationship with other visuospatial competencies, such as mental rotation. The case of Mr. L.A., a 38-year-old man with no history of neurological or psychiatric disorders, sheds some light on these open questions. A neuropsychological assessment including IQ, memory, visuospatial, visuoconstructive, and navigational tests showed that Mr. L.A. has pure navigational deficits affecting both route knowledge and cognitive map processing. Unlike previously described cases of DTD, Mr. L.A. was not affected by any other visuospatial or visuoconstructive deficits. In a functional magnetic resonance imaging (fMRI) task involving the recall of route knowledge, Mr. L.A. showed activation in the occipital areas, involved in low-level perceptual analysis of the stimuli, and showed no activation in the areas activated in controls with regard to route knowledge. The present case suggests that different types of DTD exist, which are characterized by different navigational difficulties and anomalous/lacking functional brain activities in specific navigational networks.

Neglecting the left side of a city square but not the left side of its clock: prevalence and characteristics of representational neglect

Representational neglect, which is characterized by the failure to report left-sided details of a mental image from memory, can occur after a right hemisphere lesion. In this study, we set out to verify the hypothesis that two distinct forms of representational neglect exist, one involving object representation and the other environmental representation. As representational neglect is considered rare, we also evaluated the prevalence and frequency of its association with perceptual neglect. We submitted a group of 96 unselected, consecutive, chronic, right brain-damaged patients to an extensive neuropsychological evaluation that included two representational neglect tests: the Familiar Square Description Test and the O'Clock Test. Representational neglect, as well as perceptual neglect, was present in about one-third of the sample. Most patients neglected the left side of imagined familiar squares but not the left side of imagined clocks. The present data show that representational neglect is not a rare disorder and also support the hypothesis that two different types of mental representations (i.e. topological and non-topological images) may be selectively damaged in representational neglect.

Refractive errors affect the vividness of visual mental images

The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception.

Don't neglect 'neglect'- an update on post stroke neglect

OBJECTIVES

Post-stroke neglect is common and an independent predictor of functional outcome. Assessment of neglect is very demanding, the treatment extremely difficult and the literature vast; we performed a literature search for all aspects of this difficult subject.

METHODS

We searched the PubMed, EMBASE databases and historical manuals for authoritative studies on post stroke neglect between 1951 and 2011.

FINDINGS

There is a great dearth of randomised controlled data on neglect because standardised assessment does not occur frequently. Eighty-eight manuscripts were identified in the literature, which were quite heterogeneous in their content and addressing diverse aspects of this clinical entity.

INTERPRETATION AND IMPLICATIONS

The most important historical papers were selected along with the most widely accepted and proven strategies for assessment and treatment. Standardised assessment of neglect does not always occur, but several useful strategies are available and are described in the following sections.

Assessing mental imagery in clinical psychology: a review of imagery measures and a guiding framework

Mental imagery is an under-explored field in clinical psychology research but presents a topic of potential interest and relevance across many clinical disorders, including social phobia, schizophrenia, depression, and post-traumatic stress disorder. There is currently a lack of a guiding framework from which clinicians may select the domains or associated measures most likely to be of appropriate use in mental imagery research. We adopt an interdisciplinary approach and present a review of studies across experimental psychology and clinical psychology in order to highlight the key domains and measures most likely to be of relevance. This includes a consideration of methods for experimentally assessing the generation, maintenance, inspection and transformation of mental images; as well as subjective measures of characteristics such as image vividness and clarity. We present a guiding framework in which we propose that cognitive, subjective and clinical aspects of imagery should be explored in future research. The guiding framework aims to assist researchers in the selection of measures for assessing those aspects of mental imagery that are of most relevance to clinical psychology. We propose that a greater understanding of the role of mental imagery in clinical disorders will help drive forward advances in both theory and treatment.

Where Am I? A new case of developmental topographical disorientation

Recently, developmental topographical disorientation (DTD) was described (Bianchini et al., 2010, J Clin Exp Neuropsychol, 20, 807-27; Iaria & Barton, 2010, Exp Brain Res, 206, 189-96; Iaria, Bogod, Fox, & Barton, 2009, Neuropsychologia, 47, 30-40) as a navigational deficit in the absence of neurological or psychiatric disorders. Here, we reported the case of a healthy subject who presented this disorder. Dr. WAI was a 29-year-old right-handed man with normal development and no clinical history of neurological or psychiatric diseases who was affected by a very pervasive topographical orientation and navigational disorder. A neuroradiological exam confirmed the absence of structural and anatomical alterations of the brain. Dr. WAI was submitted to an extensive neuropsychological examination and to a battery of tests specifically developed to assess developmental topographical disorder. Using this battery, we analysed Dr. WAI's acquisition of navigational information and re-orientation processes. He showed severe DTD accompanied by deficits of different cognitive processes directly or indirectly involved in navigational skills. Dr. WAI showed a deficit in developing cognitive maps, already found in previous cases, plus difficulties in evaluating distances and computing metric environmental features. He represents a further confirmation of the existence of DTD suggesting dissociations within the disorder related to the level of development of the ability to build cognitive maps and the association of different imagery deficits. Dr. WAI can help in shedding some light on the mechanisms underlying lack of development of navigational skills.

Cognitive maps in imagery neglect

Patients with imagery neglect (RI+) show peculiar difficulties in orienting themselves in the environment. Navigational impairments could be due to a deficit in creating or using a mental representation of the environment (Guariglia, Piccardi, Iaria, Nico, & Pizzamiglio, 2005) or, according to the BBB model (Burgess, Becker, King, & O'Keefe, 2001), to a specific deficit in a mechanism that transforms an allocentric representation into an egocentric one and vice versa. Previous studies, however, do not allow discerning between a deficit in forming or in using a cognitive map, taking no notice of the fact that these are two different abilities underlain by different neuroanatomical areas, which could be independently impaired. Furthermore, the BBB model has never been verified in a population of brain-damaged patients. Therefore, we administered two tasks that separately assess the ability to create and use a cognitive map of the environment to 28 right brain-damaged patients (4 patients with imagery neglect and 4 patients with perceptual neglect) and 11 healthy participants. RI+ patients showed no specific deficit in creating or using a cognitive map, but failed to transform an egocentric representation of the environment into an allocentric one and vice versa, as predicted by the BBB model.