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PubMed1989

[Agnosia].

The term agnosia defines an impairment of stimulus recognition, limited to one modality and not explainable in terms of sensory deficits or general mental deterioration. Visual object agnosia refers to the inability to recognize objects and prosopagnosia to the failure to recognize faces that are well familiar to the patient, when stimuli are visually perceived. Both deficits may appear in an apperceptive form, where it is the internal and external structure of the stimulus to be unrecognized and an associative form where the patient achieves a good percept, but cannot assign it a meaning. Apperceptive forms are preferentially associated with bilateral occipital damage, object associative agnosia with left occipital damage and associative prosopagnosia with right occipital damage.

Agnosia↗
PubMed1977

[The syndrome of auditory agnosia. A case report and an attempt of neuropsychological qualification (author's transl)].

Proceeding from the neuropsychological examination of a patient with an exceptionally selective impairment of auditory gnosis of vascular origin, we make an attempt to analyze structurally the syndrome of auditory agnosia, a study of which has been neglected in comparison with analyses of visual agnosia. In our analysis we refer to 28 case reports, documented in the literature. Decisive syndromal points of view are: a) there is an absence of significant audiological deficiencies; b) errors of the acoustic-discriminative type prevail in auditory-visual matching tasks; c) the gnostic deficit is modality specific; d) the same items are variably reproduced on repeated presentation; e) there is marked fluctuation of performance; f) there is exceptional irreversibility of the impairment; g) amusia is a more or less obligatory accompanying phenomenon; h) in cases of vascular origin there is always a history of repeated temporal lobe damage, this damage being predominantly in the form of bilateral lesions. This analysis indicates a close structural analogy to the syndrome of perceptive visual agnosia. We place great importance in the relationship between approaches and models of cognitive psychology (Neisser, 1967) which we see as important for further theoretical development in neuropsychology.

Adolescent↗
PubMed1980

[Clinico-experimental study of auditory-speech agnosia (case with anatomo-histologic verification)].

Under observation there was a female patient (a right-hander) who had three ischemic cerebral strokes within a year. After the first stroke she developed an amnestic-sensory aphasia, after the second an auditory and speech agnosia with a complete loss of the ability to understand the speech addressed to her, and after the third stroke she died. Macro- and microscopic examinations showed that the first stroke caused a destruction in the region of the left temporal lobe cortex involving a part of the Heschl convolution; the second stroke resulted in destruction of the right temporal lobe involving almost the whole Heschl convolution. Thus, it has been confirmed that the syndrome can develop only in case of a grave bitemporal damage. Comparative examinations of the speech and audition after the first and the second stroke have shown that in auditory and speech agnosia, the auditory discernment of phonemes, their combinations and the speech prosodic elements is pronouncedly deranged, the formation of conditioned reflexes to sounds of a supraliminal force is disturbed, the detection of short acoustic messages and acoustic filtration are hampered (mainly on the side contralateral to the affected one) the amusia gets more marked and the discernment of rhythms more difficult. All these disturbances are highly dynamic. A question on the role of defects of the right and the left hemispheres in the clinical picture of the auditory and speech agnosia is discussed.

Aged↗
PubMed1981

[Associative visual agnosia: role of the left hemisphere in visual perception (author's transl)].

Visual agnosia following ischaemic accidents of the left posterior cerebral artery is often associated with intellectual deficiencies, memory disorders, elementary perceptive disturbances and elements of visuoverbal disconnection, with the result that some authors reject the notion of visual agnosia. By using a relatively simple examination procedure it is, however, possible to clearly differentiate the various disturbances, as shown by the case of a right-handed 66-year-old man in whom this type of vascular accident occurred. Neither the reduced intellectual capacities nor the memory disorders can explain the differences observed in the treatment of visual stimuli, which was very disturbed, and the normal treatment of other types of stimulus. Elementary difficulties are not sufficient to prevent correct discrimination, as all tests of matching object, images, colours, and graphic signs were successfully accomplished. Identification was disturbed however: the patient could not show the use of objects presented visually, and this disorder is related to the visual characteristics of the stimuli, which excludes a simple visuogestural disconnection; results of tests of classifying types of object images, colours, and graphic signs were markedly abnormal. Naming of these stimuli was also affected, even when they were correctly identified; this results from the visuoverbal disconnection associated with the agnosia, but it is insufficient to account for it, as the patient could correctly use objects that had been wrongly named, but could not use those that had been poorly identified. This case, therefore, has enabled a visual identification disorder to be isolated independently from a discrimination problem, and visuoverbal or visuogestural disconnections. It is the significance of ths stimulus that is disturbed. In contrast, functional or categorical classification is respected in right temporo-occipital lesions. It is the individuality of a stimulus within a physical category which is disturbed.

Aged↗
PubMedDate not supplied

[Color agnosia: a brief review].

An introductory historical reminder situates the problem of color agnosia in the global frame of neuropsychological research and emphasizes the relevance of old questions. One examines later the description of agnosia, which indicates the polymorphic character of this trouble, its limits concerning linguistic and perceptual troubles, and the principal associated symptoms. The most important explanatory hypothesis are also studied, mainly according to the Italian school of Milan (conceptual and associative deficit) and the group of "La Salpétrière" in Paris (regression of past-acquisitions). The methodology then describes the most frequent means used in neuropsychology to analyze color agnosia. Finally, questions of anatomy and lesional localisation (left associative visual cortex) are also described.

Agnosia↗
PubMed1976

[Digital agnosia and lesions of the parietal lobe].

130 patients with focal brain damage have been submitted to non-verbal finger identification tasks. The results of this research can be summarized as follows: -when bilateral finger agnosia is studied with non-verbal tasks, no difference can be shown between right and left parietal lesions; -in left brain damaged patients the bilateral form of finger agnosia is generally due to large lesions involving the parietal lobe; -in right brain damaged patients the unilateral form of finger agnosia is almost always due to lesions centered on the parietal region.

Agnosia↗
PubMed1995

Eclamptogenic Gerstmann's syndrome in combination with cortical agnosia and cortical diplopia.

Cortical blindness is defined as a loss of vision due to bilateral retrogeniculate lesions (geniculocalcarine blindness). Gerstmann's syndrome is a combination of disorientation for left and right, finger agnosia, and profound agraphia, alexia, and acalculia. It is due to a lesion in the left angular gyrus, situated at the confluence of the temporal, parietal, and occipital lobes. We report on a patient who suffered from severe underdiagnosed eclampsia and who developed bilateral extensive medial temporal, parietal, and calcarine ischemic infarctions during an eclamptic fit. In addition, ischemia destroyed the left angular gyrus. The combination of these lesions led to Gerstmann's syndrome with additional cortical agnosia and cortical diplopia. For the first few months following the ischemic insult, the patient had been cortically blind. Thereafter, the patient slowly regained a visual acuity of 0.1 in both eyes. She then experienced monocular and binocular diplopia. Her ocular motility was normal; there was no phoria or tropia. Monocular and binocular diplopia slowly became less severe over the following year. Now, 2 years after the incident, the patient has a visual acuity of 0.2 in both eyes and no double vision. However, the handicapping symptoms of Gerstmann's syndrome, which make leading a normal life impossible, have persisted--the patient still cannot cope alone, mainly due to the severe disorientation for left and right. The picture of cortical agnosia, cortical diplopia, and Gerstmann's syndrome is a very rare combination. Visual recovery and rehabilitation in cortical blindness are severely affected and made difficult by the symptoms of Gerstmann's syndrome. In our case the reason for such a dramatic clinical picture was eclampsia, whose prodomes had not been diagnosed in time.

Adult↗
PubMed1997

Object recognition difficulty in visual apperceptive agnosia.

Two patients with visual apperceptive agnosia were examined on tasks assessing the appreciation of visual material. Elementary visual functioning was relatively preserved, but they had profound difficulty recognizing and naming line drawings. More detailed evaluation revealed accurate recognition of regular geometric shapes and colors, but performance deteriorated when the shapes were made more complex visually, when multiple-choice arrays contained larger numbers of simple targets and foils, and when a mental manipulation such as a rotation was required. The recognition of letters and words was similarly compromised. Naming, recognition, and anomaly judgments of colored pictures and real objects were more accurate than similar decisions involving black-and-white line drawings. Visual imagery for shapes, letters, and objects appeared to be more accurate than visual perception of the same materials. We hypothesize that object recognition difficulty in visual apperceptive agnosia is due to two related factors: the impaired appreciation of the visual perceptual features that constitute objects, and a limitation in the cognitive resources that are available for processing demanding material within the visual modality.

Aged↗
PubMed2001

Animals and artifacts may not be treated equally: differentiating strong and weak forms of category-specific visual agnosia.

We examined a categorical dissociation hypothesis of category-specific agnosia using hierarchical regression to predict the naming responses of three agnosia patients while controlling a wide variety of perceptual and conceptual between-category differences. The living-nonliving distinction remained a significant predictor for two of the patients after controlling for all the other factors. For one remaining patient, the categorical variable was not significant once the form-function correlation of different objects was controlled. We argue that the visual system may use various subprocesses at different stages, some of which reflect true categorical organization and some of which reflect a unitary feature-based system that distinguishes kinds.

Agnosia↗
PubMed1982

Clinical and audiological findings in a case of auditory agnosia.

A case is reported of severe agnosia for verbal and non-verbal sounds without associated aphasic disorder. A CT scan revealed bilateral, temporal lobe lesions from two ischaemic accidents that had occurred 9 months apart. The search for subtle deficits in the patient showed normal sensitivity to changes in the intensity and frequency of simple sounds; in contrast, his ability to discriminate sound duration and musical note sequences was severely impaired. The simultaneous recording of the whole auditory-evoked response pattern revealed no abnormality in the early components, which reflect the activation of the auditory nuclei and pathways of the brain stem. However, the middle and late components were delayed and slowed. These results and others in the literature suggest that the neocortex in man, as in other mammals, plays an essential role in the temporal aspects of hearing. Also, the two main ingredients commonly recognized in auditory agnosia, i.e. word deafness and the inability to interpret non-verbal sounds, are caused by the disruption of elementary, bilaterally represented cortical functions which start the processing of every kind of auditory information.

Agnosia↗
PubMed1994

Prosopagnosia without topographagnosia and object agnosia associated with a lesion confined to the right occipitotemporal region.

A patient is presented who developed prosopagnosia with a recent occipitotemporal infarct in the distribution of the right posterior cerebral artery. He did not have topographical agnosia or object agnosia. He regained the ability to recognize faces of familiar persons, whereas he remained unable to identify faces of persons whom he met after the disease onset. This case demonstrates that prosopagnosia may occur as a deficit of matching a perceived face to a memory store of the face, and that the failure to recognize unfamiliar faces may be due to the inability to form memory stores of new faces. These deficits can occur in association with a lesion confined to the right occipitotemporal region.

Agnosia↗
PubMed2006

Intact automatic avoidance of obstacles in patients with visual form agnosia.

In everyday life our reaching behaviour has to be guided not only by the location and properties of the target object, but also by the presence of potential obstacles in the workspace. Recent evidence from neglect and optic ataxia patients has suggested that this automatic obstacle avoidance is mediated by the dorsal, rather than the ventral, stream of visual processing. We tested this idea in two studies involving patients with visual form agnosia resulting from bilateral ventral-stream damage. In the first study, we asked patient DF to reach out and pick up a target object in the presence of obstacles placed at varying distances to the left or right of the target. We found that both DF and controls shifted their trajectories away from the potential obstacles and adjusted their grip aperture in such a way as to minimize risk of collision. In a second study, we asked DF and a second patient, SB, to either reach between, or to bisect the space between, two cylinders presented at varying locations. We found that both patients adjusted their reach trajectories to account for shifts in cylinder location in the reaching task, despite showing significantly worse performance than control subjects when asked to make a bisection judgement. Taken together, these data indicate that automatic obstacle avoidance behaviour is spared in our patients with visual form agnosia. We attribute their ability to the functional intactness of the dorsal stream of visual processing, and argue that the ventral stream plays no important role in automatic obstacle avoidance.

Adult↗
PubMed2001

Monocular and binocular distance cues: insights from visual form agnosia I (of III).

The human nervous system constructs a Euclidean representation of near (personal) space by combining multiple sources of information (cues). We investigated the cues used for the representation of personal space in a patient with visual form agnosia (DF). Our results indicated that DF relies predominantly on binocular vergence information when determining the distance of a target despite the presence of other (retinal) cues. Notably, DF was able to construct an Euclidean representation of personal space from vergence alone. This finding supports previous assertions that vergence provides the nervous system with veridical information for the construction of personal space. The results from the current study, together with those of others, suggest that: (i) the ventral stream is responsible for extracting depth and distance information from "monocular" retinal cues (i.e. from shading, texture, perspective) and (ii) the dorsal stream has access to binocular information (from horizontal image disparities and vergence). These results also indicate that DF was not able to use size information to gauge target distance, suggesting that intact temporal cortex is necessary for "learned size" to influence distance processing. Our findings further suggest that in neurologically intact humans, object information extracted in the ventral pathway is combined with the products of dorsal stream processing for guiding prehension. Finally, we studied the "size-distance paradox" in visual form agnosia in order to explore the cognitive use of size information. The results of this experiment were consistent with a previous suggestion that the paradox is a cognitive phenomenon.

Agnosia↗
PubMed1995

Mutism and auditory agnosia due to bilateral insular damage--role of the insula in human communication.

We report a case of transient mutism and persistent auditory agnosia due to two successive ischemic infarcts mainly involving the insular cortex on both hemispheres. During the 'mutic' period, which lasted about 1 month, the patient did not respond to any auditory stimuli and made no effort to communicate. On follow-up examinations, language competences had re-appeared almost intact, but a massive auditory agnosia for non-verbal sounds was observed. From close inspection of lesion site, as determined with brain resonance imaging, and from a study of auditory evoked potentials, it is concluded that bilateral insular damage was crucial to both expressive and receptive components of the syndrome. The role of the insula in verbal and non-verbal communication is discussed in the light of anatomical descriptions of the pattern of connectivity of the insular cortex.

Adult↗
PubMed1991

Speech discrimination and lip reading in patients with word deafness or auditory agnosia.

The purpose of this study was to assess the ability of four patients with word deafness or auditory agnosia to discriminate speech by reading lips. The patients were studied using nonsense monosyllables to test for speech discrimination, a lip reading test, the Token Test for auditory comprehension, and the Aphasia test. Our results show that patients with word deafness or auditory agnosia without aphasia can improve speech comprehension by reading lips in combination with listening, as compared with lip reading or listening alone. In conclusion, lip reading was shown to be useful for speech comprehension among these patients.

Adult↗
PubMedDate not supplied

2D but not 3D: pictorial-depth deficits in a case of visual agnosia.

Patients with visual agnosia exhibit acquired impairments in visual object recognition, that may or may not involve deficits in low-level perceptual abilities. Here we report a case (patient DM) who after head injury presented with object-recognition deficits. He still appears able to extract 2D information from the visual world in a relatively intact manner; but his ability to extract pictorial information about 3D object-structure is greatly compromised. His copying of line drawings is relatively good, and he is accurate and shows apparently normal mental rotation when matching or judging objects tilted in the picture-plane. But he performs poorly on a variety of tasks requiring 3D representations to be derived from 2D stimuli, including: performing mental rotation in depth, rather than in the picture-plane; judging the relative depth of two regions depicted in line-drawings of objects; and deciding whether a line-drawing represents an object that is 'impossible' in 3D. Interestingly, DM failed to show several visual illusions experienced by normals (Muller-Lyer and Ponzo), that some authors have attributed to pictorial depth cues. Taken together, these findings indicate a deficit in achieving 3D intepretations of objects from 2D pictorial cues, that may contribute to object-recognition problems in agnosia.

Adult↗
PubMed2001

The influence of misnaming on object recognition: a case of multimodal agnosia.

We present a case of multimodal agnosia in the visual and tactile modality due to an infarction in the territory of the left posterior cerebral artery. The patient's ability to recognize objects fluctuated depending on his verbal activity. When he misnamed presented objects, he tended to use them and to draw them in keeping with the wrong name. We submit that the mechanism causing associative agnosia is more dynamic than it was hitherto considered. It originates from the rivalry between top-down central regulation and bottom-up peripheral flow.

Aged↗
PubMed1998

Prosopagnosia and alexia without object agnosia.

Following a trauma causing bilateral posterior brain damage, a patient complained of dyslexia and prosopagnosia, but not object agnosia. On testing she showed intact recognition of object drawings, even when it was assessed with perceptually demanding tasks such as Ghent's overlapping figures and Street completion test. This pattern of deficit is inconsistent with Farah's (1990) prediction that the simultaneous occurrence of alexia and prosopagnosia is invariably associated with object agnosia. The patient's reading performance had the features typically found in letter-by-letter readers. On face tests, she showed a discrepancy between the impairment exhibited in familiarity recognition and famous face naming and the correct (though slow) performance in matching the names of famous persons with their photographs. This apparent contradiction was clarified by showing that the patient had maintained the ability to generate the mental images of famous faces in response to the presentation of their names. We assume that face recognition units were intact, but partially disconnected from the output of perceptual processing.

Adult↗