Imagery Deficits Research Articles

Face imagery and its relation to perception and covert recognition in prosopagnosia.

Face imagery can access facial memories without the use of perceptual stimuli. Current data on the relation of imagery to the perceptual function and neuroanatomy of prosopagnosic patients are mixed, and little is known about the type of facial information patients can access through imagery. The authors wished to determine 1) which lesions abolished face imagery in prosopagnosia, 2) if deficits in perceiving facial structure were paralleled by similar deficits in imagery, and 3) if covert recognition of faces correlated with the degree of residual imagery for faces. The authors tested nine prosopagnosic patients who had been tested previously for perception of facial configuration and covert recognition of famous faces. The authors constructed a battery of 37 questions that asked subjects to imagine the faces of two celebrities and to choose which one had a certain facial property. Half were questions about facial features and half were about overall facial shape. Imagery was abolished only by anterior temporal lesions. Imagery for facial shape but not features was degraded by lesions of the right hemisphere's fusiform face area, which severely impaired perception of facial configuration. Feature imagery was degraded only when there was associated left occipito-temporal damage. Covert recognition was found when either configural perception or imagery was severely damaged, but not when both were abnormal. In patients with impaired configural perception, covert recognition correlated with feature imagery, suggesting that feature-based processing may drive residual covert abilities in these patients. Although anterior temporal cortex may be the site of facial memory stores, these data also support hypotheses that perceptual areas like the fusiform face area have parallel contributions to mental imagery. The data on covert recognition are consistent with a view that it is the residue of a partially damaged face-recognition network. Covert recognition may reflect the degree of damage across components of a network rather than mark a specific form of prosopagnosia or a dissociated pathway.

Letter assembling and handwriting share a common allographic code

A patient is reported who presented with severe agraphia encompassing handwriting, letter assembling and oral spelling disorders. Her writing problems could not be accounted for in terms of apraxia, alexia, aphasia, visual imagery, perceptual or intellectual deficits. She made phonologically plausible errors in all writing modalities, but showed letter substitutions or letter omissions only in handwriting and letter assembling tasks. A common allographic mechanism is postulated which specifies case and style information for all visually based spelling tasks. The pattern of the patient's performances is interpreted assuming a deficit at the output orthographic lexicon, which accounts for phonologically plausible errors, coupled with an allographic disorder thought to be responsible for errors occurring at single letter level.

The ability to execute saccades on the basis of efference copy: impairments in double-step saccade performance in children with developmental co-ordination disorder.

The double-step saccade task (DSST) was used to test the hypothesis that children with developmental co-ordination disorder (DCD) who experience deficits in motor imagery have difficulty processing the visual spatial consequences of intended movements using efference copy signals. In order to ensure that the second saccade in the DSST was executed in the absence of visual cues and had to be programmed on the basis of extra-retinal information (efference copy), we analysed only those double-step ensembles where latency plus duration of first saccades was greater than 240 ms (total presentation time of the targets). No significant differences between DCD and control children were evident on measures of latency of first saccades, intersaccadic interval and first saccade error. As predicted, children with DCD who have impaired motor imagery demonstrated specific deficits on the DSST where efference copy had been used to program the saccade sequence. More specifically, these children were less accurate in terms of final eye position on second saccades. Our results raise the possibility that abnormalities in the processing of efference copy signals could underlie motor clumsiness in the majority of children with DCD. Furthermore, the origin of this deficit in efference copy probably exists at the level of the parietal lobe.

The functional anatomy of imagining and perceiving colour.

We report two functional magnetic resonance imaging experiments which reveal similarities and differences between perceptual and imaginal networks within the single visual submodality of colour. The first experiment contrasted viewing of a coloured and grey-scale Mondrian display, while the second contrasted a relative colour judgement with a spatial task and required the generation of mental images. Our results show that colour perception activates the posterior fusiform gyrus bilaterally (area V4), plus right-sided anterior fusiform and lingual gyri, striate cortex (area V1), and the left and right insula. Colour imagery activated right anterior fusiform gyrus, left insula, right hippocampus and parahippocampal gyrus, but not V4 or V1. The findings reconcile neurological case studies suggesting a double dissociation between deficits in colour imagery and perception and point to anterior fusiform, parahippocampal gyri and hippocampus as the location for stored representations of coloured objects.

A Critical Review of Mental Imagery Defects

A critical, clinical review of single-case reports and group studies on visual mental imagery deficits is offered. Neuropsychological findings demonstrate that mental imagery relies upon dissociable processes which are localized in left-hemisphere posterior areas. Imagery defects thus may often be associated with visual recognition and naming impairments. On the other hand, the right hemisphere seems to play an analogous role in imagery and perception. Current theoretical models of imagery do not appear fully capable of accounting for available clinical data.

Visual Imagery Skills and Language Abilities of Normal and Language-Learning-Disabled Children

This study was designed to explore the relation between specific language skills and visual imagery skills of children with language disabilities. The subjects were 15 language-learning-disabled (LLD) and 15 normally achieving children (aged 6–6 to 8–9) with nonverbal IQ scores in the average range. All subjects' language skills were measured by the Test of Language Development-Primary (TOLD-P). Subjects were also presented with three multiple-choice tasks involving the imagined movement and/or rotation of geometric figures. An analysis of covariance (controlling for perceptual discrimination of the task designs) showed a significant difference between groups in accuracy of performance on the imagery tasks. For the LLD group, a significant positive correlation was found between the severity of the language disability (TOLD-P total score) and accuracy on two of the three imagery tasks (with nonverbal IQ controlled). Imagery ability was found to be related more strongly to a measure of semantics than to syntax. Performance on one imagery task was also related significantly to reading achievement. Implications of imagery deficits for academic performance are discussed in terms of the value of imaging for comprehension.

Two systems for colour-naming defects: Verbal disconnection vs colour imagery disorder

Two subjects affected by pure alexia and showing no central dyschromatopsia or generalized aphasia, performed poorly on traditional tasks with visually-presented colour stimuli and on tasks with objects presented verbally. Three experiments were conducted to evaluate the possible role of mental colour imagery in recalling the colours of objects from memory. It was concluded that Case I, with left occipital lobe softening, had preserved imagery systems, but failed to recode the colours of mentally generated colour images, just as he failed to name visually presented colours, suggesting a language-imagery disconnection. In contrast, Case II, with a bilateral occipital lesion, had sustained damage to her long-term visual memories for colours as chromatic attributes of objects. This content-specific imagery deficit was concomitant with colour agnosia. The present findings are discussed in terms of current cognitive theories on imagery deficits.

Principles of mental imagery

Imagery can be used to improve memory, perceptual skills, even creativity. Numerous experiments carried out over the past 20 years have probed the nature of mental imagery and unlocked its powers. Principles of Mental Imagery offers a broad, balanced, and up to date introduction to the major findings of this research and identifies 5 general principles that can account for most of them. It considers the development of experimental techniques that have solved many of the challenging methodological problems inherent in imagery research and includes recent experimental findings not covered in other imagery books.Principles of Mental Imagery brings together work by all of the key imagery researchers, among them Roger Shepard, Stephen Kosslyn, Allen Paivio, Lynn Cooper, Steven Pinker and the author. Chapters present new research on the role that imagery plays in human memory, new findings on how mental imagery influences perception (one of the dominant issues in modern imagery research), recent studies on representational momentum experimental demonstrations of how imagery can be used to make creative, visual discoveries, and recent work on imagery deficits in brain damaged patients. And, a new argument is made for why the study of mental imagery should be motivated by general principles, rather than formal models. Each chapter concludes with convenient summaries and suggestions for further exploration.Ronald A. Fluke is Associate Professor of Psychology at Texas A & M University. A Bradford Book

On the different roles of the cerebral hemispheres in mental imagery: The “o'Clock Test” in two clinical cases

This paper develops the hypothesis of different roles of the two hemispheres in imaginal processes. A test designated the “o'Clock Test” is proposed, which contains closely confrontable perceptual and imaginal tasks. It enables examination of the abilities both to generate mental images and to explore them in their right and left halves (R + L Condition). This test was used to examine two patients, one severely affected by hemi-inattention resulting from a right posterior lesion, and the other with a selective deficit of imagery due to a left occipital lesion. The former demonstrated left neglect in both perceptive and imaginal capacities, while the latter was able to perform correctly only the perceptive tasks. These results suggest that the right hemisphere has functions of organization and spatial exploration at both perceptive and imaginal levels, and that the left hemisphere's role is to generate mental images.

Biofeedback to enhance psychophysiological effects of imagery

Unlike most applications of biofeedback, the outcome goal and the aim of the present investigation was to increase arousal by the provision of feedback. The ability to generate psychophysiological arousal during noxious imagery may be therapeutically beneficial to individuals receiving emotive imagery therapies, and in the present study we evaluated biofeedback as a means of correcting psychophysiological deficits in imagery. Thirty psychophysiologically unreactive undergraduates were randomly assigned to skin-resistance-level biofeedback, false-feedback, or no-feedback conditions for six sessions of assessment and treatment. The methodology controlled for placebo, practice, and initial value effects. Significant increases in skin resistance level, heart rate, and frontalis electromyography accrued to the biofeedback group but not the control groups, and these gains persisted when biofeedback was withdrawn. Subjective measures showed no changes. The results support the usefulness of biofeedback as a remedy for imagery underarousal.

A case study of mental imagery deficit

We describe a patient with a deficit in imagery ability, following a left posterior cerebral artery infarction and possible anoxic episode. This deficit was inferred from the patient's performance on several tasks, including one in which normal adults are known to rely on imagery and two that tested imagery nonverbally, allowing us to examine the possibility of a language-imagery disconnection. In addition, we queried the patient on some cognitive capacities related to visual imagery: dreaming, geographical knowledge, and introspection regarding visual and auditory imagery. Hypotheses concerning the critical lesion site and underlying cognitive mechanism of image generation deficits are discussed in relation to this and other recent cases of impaired imagery ability with intact recognition ability, and the relevance of this deficit to the “imagery debate” is discussed.

Optic aphasia, optic apraxia, and loss of dreaming

A 47-year-old man with a left temporo-occipital infarct in the area of the posterior cerebral artery is presented. The neuropsychological examination did not reveal aphasia or gross mental deficits. The patient presented with alexia without agraphia, color agnosia, but few visual perceptual deficits. The main impairment was in confrontation naming; he was incapable of naming objects and pictures, not from lack of recognition (excluding visual agnosia) but from lack of access to the appropriate word (optic aphasia). The patient also exhibited a deficit in the evocation of gesture from the visual presentation of an object (optic apraxia) and a dífficulty in “conjuring up” visual images of objects (impaired visual imagery) and loss of dreams. The fundamental deficit of this patient is tentatively explained in terms of visuoverbal and visuogestural disconnection and a deficit of mental imagery.

Defective Revisualization: Dissociation Between Cognitive and Imagistic Thought Case Report and Short Review of the Literature

A 38-year-old shifted-sinistral patient displayed a definite deficit in visual imagery accompanied by defective dreaming capacity, loss of hypnagogic imagery, some defects in topographical memory, a mild unilateral right spatial neglect and mild difficulties in right-left orientation on the examiner's body. CT-scan and NMR studies showed evidence of an inborn hypoplasia of the right hemisphere and a stretched corpus callosum in its posterior and superior part. The vicarious compensatory action of the cognitive-verbal function of the defect of visual imagery was obvious. It is concluded that: (i) there are various forms of visual imagery deficits: some are “pure” whereas in the great majority of reported cases the loss of visual imagery is associated to different forms of visual agnosia; (ii) the brain mechanisms underlying cognitive thought and imagistic thought could be obviously dissociated.

Imagery and hallucination in schizophrenic patients.

Volitional auditory imagery and spontaneous imagery/fantasy are examined in schizophrenic vs. nonschizophrenic psychiatric inpatients. Imaginal aspects of schizophrenia are also studied with regard to concurrent presence or absence of hallucination. Comparisons of imaginal function between diagnostic groups and among hallucinatory subgroups turned up few significant differences. Findings do not support the Mintz and Alpert (Mintz, S., and Alpert, M. Imagery vividness, reality testing, and schizophrenic hallucinations. J. Abnorm. Psychol., 79: 310-316, 1972) enhanced vividness model of schizophrenic hallucination but do provide some support for an imagery deficit model.

Transformational deficits in cognition of schizophrenic children

This study examined schizophrenic children for cognitive deficits in logical thinking, symbolic imagery, and conservation. Evaluation revealed persistent failure of the aberrant subjects to achieve at the level of age expectancy. Comparison with nonpsychotic, institutionalized children demonstrated no effect due to institutionalization. By mid-teens not one of the subjects had accomplished formal operations and very few were able to master concrete operations. Implications for development and treatment were discussed.