Mirror Image Agnosia (original) (raw)
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Neurodegeneration and mirror image agnosia
North American Journal of Medical Sciences, 2014
Background: Normal Percept with abnormal meaning (Agnosias) has been described from nineteenth century onwards. Later literature became abundant with information on the spectrum of Prosopagnosias. However, selective diffi culty in identifying refl ected self images with relatively better cognitive functions leads to problems in differentiating it from non-organic psychosis. Aim: In the present study, we investigated patients with dementia who showed diffi culty in identifying refl ected self images while they were being tested for problems in gnosis with reference to identifi cation of refl ected objects, animals, relatives, and themselves and correlate with neuropsychological and radiological parameters. Patients and Methods: Five such patients were identifi ed and tested with a 45 cm × 45 cm mirror kept at 30-cm distance straight ahead of them. Results: Mirror image agnosia is seen in patients with moderate stage posterior dementias who showed neuropsychological and radiological evidence of right parietal dysfunction. Conclusion: Interpretation of refl ected self images perception in real time probably involves distinct data-linking circuits in the right parietal lobe, which may get disrupted early in the course of the disease.
Pure agnosia for mirror stimuli after right inferior parietal lesion
Brain, 2003
Summary This study reports the experimental investigation of G.R., a patient suffering from a highly specific disorder in discriminating mirror stimuli following a right tem- poroparietal cerebrovascular accident. G.R. showed intact perceptual, attentional, mnestic, linguistic and executive abilities. Object recognition was accurate even under unusual viewing conditions. He was highly accur- ate in defining the canonical orientation of common objects
Mirror agnosia and mirror ataxia constitute different parietal lobe disorders
2001
We describe two new clinical syndromes, mirror agnosia and mirror ataxia, both characterized by the deficit of reaching for an object through a mirror in association with a lesion of either parietal lobe. Clinical investigation of 13 patients demonstrated that the impairments affected both sides of the body. In mirror agnosia, the patients always reached toward the virtual object in the mirror and they were not capable of changing their behavior even after presentation of the position of the object in real visual space. In mirror ataxia (resembling optic ataxia) although some patients initially tended to reach for the virtual object in the mirror, they soon learned to guide their arms toward the real object, all of them producing many directional errors. Both patient groups performed poorly on mental rotation, but only the patients with mirror agnosia were impaired in line orientation. Only 1 of the patients suffered from neglect and 3 from apraxia. Magnetic resonance imaging showed that in mirror agnosia the common zone of lesion overlap was scattered around the posterior angular gyrus/superior temporal gyrus and in mirror ataxia around the postcentral sulcus. We propose that both these clinical syndromes may represent different types of dissociation of retinotopic space and body scheme, or likewise, of allocentric and egocentric space normally adjusted in the parietal lobe.
Mirrored-self Misidentification: Two Cases of Focal Onset Dementia
Neurocase, 2001
We present two patients in whom the mirror sign, the inability to recognize one's own reflected image, was a stable and persisting symptom signalling the onset of a progressive dementing illness. Extensive neuropsychological testing was conducted with both patients, with particular emphasis on face processing and the understanding of reflected space. Both patients were also investigated with structural imaging techniques (computed tomography and magnetic resonance imaging). Although the neuroimaging results were not strongly lateralizing for either patient, neuropsychological testing revealed striking right hemisphere dysfunction with relatively intact left hemisphere cognitive function in both patients. Of particular interest was the patients' dissociation on tests of face processing; one patient, FE, had significant face processing deficits while the other patient, TH, had relatively intact face processing. Further testing with TH revealed striking deficits in his ability to interpret reflected space. The results of the face processing tests are discussed in the context of current models of normal face processing, with particular emphasis on the affective component in face recognition. We propose that a combination of cognitive deficits underlie the mirror sign delusion, including perceptual, affective and reasoning impairments, and also discuss the contributions of cortical and subcortical lesions in these two patients and in delusions in general.
A particular difficulty in discriminating between mirror images
Neuropsychologia, 2001
We investigated the selective impairment of mirror image discrimination in a patient with bilateral parieto-occipital lesions (FIM). We report a difficulty with the discrimination between mirror images more selective than has been previously reported (Turnbull OH, McCarthy RA. Failure to discriminate between mirror-image objects: a case of viewpoint-independent object recognition? Neurocase 1996;2:63). FIM was asked to judge, in five same/different experiments, whether pairs of simultaneously presented line drawings of objects were identical. FIM demonstrated only a minor impairment in discriminating between orientations in the picture plane but was at chance in making discrimination between mirror images. An experiment with normal observers established that our results were not due to differences in task difficulty. Two further experiments investigated the effects of rotation on the discrimination of letters and geometric shapes. FIM's impairment extended to geometric shapes but not to letters. These results would be consistent with the preservation of an abstract representation for object recognition that did not code the difference between mirror image views.
Delusional Misidentification of the Mirror Image
Current Neurology and Neuroscience Reports, 2019
Purpose of Review Delusional misidentification syndromes (DMS) include conditions in which a false belief about the identity of a person, place, or object occurs in the context of psychiatric or neurological disorders. One form of DMS involves the delusion that the patient's mirror image is a separate individual. This review of reported cases characterizes the psychiatric, neuropathological, and neuropsychological aspects of DMS for the mirror image. An individual case presentation highlights the patient's subjective experience. Finally, the impact of this syndrome on the sense of self is considered. Recent Findings Mirror DMS is a persistent delusion that occurs in the context of neurological illness. It is associated with right hemisphere impairment and a variety of neuropsychological and neuroimaging abnormalities. This phenomenon contributes to our understanding of a range of neurobehavioral syndromes that can be classified as neuropathologies of the self (NPS). Summary DMS for the mirror image is a neurobehavioral syndrome in which the inability to recognize oneself in the mirror entails neurological, neuropsychological, as well as psychiatric aspects of the sense of self.
Prosopagnosia and object agnosia without covert recognition
Neuropsychologia, 1989
Investigations of the visual recognition abilities of the patient M.S. are reported. MS. is unable to achieve overt recognition of any familiar faces, and many everyday objects. In Task 1 he showed semantic priming from name primes but not from face primes in a name recognition task. In Task 2 he showed no advantage in learning true (face+correct name) rather than untrue (face+someone else's name) pairings of faces and names. In Task 3 semantic priming of lexical decision was only found for object picture primes that M.S. was able to recognize overtly. In Task 4 faster matching of photographs of familiar than unfamiliar objects was only found for objects that MS. was able to recognize overtly. These findings demonstrate an absence of covert recognition effects for MS., consistent with the view that his impairment is primarily "perceptual" in nature.
Experimental Brain Research, 2003
Mirror apraxia is a condition in which patients with lesions of the posterior parietal cortex have deficits in reaching to objects presented through a mirror. The aim of the present study was to investigate possible mechanisms underlying this disorder. First, we addressed the question of whether mirror apraxia is exhibited to the same extent in peripersonal and in body space. Four patients with lesions of the posterior parietal lobe on either side and with marked mirror apraxia were required to reach for objects that were presented to them through a mirror and located either in body space (i.e. on the body surface) or in peripersonal space (i.e. in the reaching distance). Whereas reaching for objects located in body space was flawless in all patients, the performance deteriorated when the same objects were transferred to the peripersonal space. Although the objects were located only a few centimetres above the body surface, the patients reached towards the virtual object in the mirror. Based on these results we suggest that mirror apraxia may originate from a dissociation between the representations of body schema and peripersonal space and that objects located on the body surface become integrated into the body schema. In the second part of the study, using positron emission tomography study (PET), we studied the cerebral activation pattern during reaching to objects presented through a mirror in the peripersonal space in healthy subjects. The results show that increased neural activity in the anterior part of the intraparietal sulcus and in the dorsal premotor cortex was bound to the transformation of the target position from the mirror space to the real space. In contrast, the activity related to object localization in the mirror occurred at the parieto-occipital junction. Both mirror and arm transformation involved the medial posterior part of the superior parietal lobule, putatively area V6a. The results demonstrate that acting through a mirror is processed in a number of cortical areas of the dorsal stream.