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PubMed2002

Dissociating 'what' and 'how' in visual form agnosia: a computational investigation.

Patients with visual form agnosia exhibit a profound impairment in shape perception (what an object is) coupled with intact visuomotor functions (how to act on an object), demonstrating a dissociation between visual perception and action. How can these patients act on objects that they cannot perceive? Although two explanations of this 'what-how' dissociation have been offered, each explanation has shortcomings. A 'pathway information' account of the 'what-how' dissociation is presented in this paper. This account hypothesizes that 'where' and 'how' tasks require less information than 'what' tasks, thereby allowing 'where/how' to remain relatively spared in the face of neurological damage. Simulations with a neural network model test the predictions of the pathway information account. Following damage to an input layer common to the 'what' and 'where/how' pathways, the model performs object identification more poorly than spatial localization. Thus, the model offers a parsimonious explanation of differential 'what-how' performance in visual form agnosia. The simulation results are discussed in terms of their implications for visual form agnosia and other neuropsychological syndromes.

Agnosia↗
PubMed2003

Visual agnosia in a child with non-lesional occipito-temporal CSWS.

In this paper we describe a case of severe visual agnosia in a child with an electrophysiological pattern of continuous spike-wave discharges in slow sleep (CSWS) in the occipito-temporal regions. The neuropsychological spectrum related to this phenomenon is discussed. Published paediatric reports associate visual agnosia (i.e. an inability to recognize objects without impairment of visual acuity) mainly with symptomatic occipito-temporal aetiology (e.g. cortical dysplasia, vascular insults) and other neurological symptoms (e.g. autism). We describe a detailed 2 year electrophysiological and neuropsychological follow-up of an 8-year-old boy with sporadic seizures, occipito-temporal CSWS and visual agnosia. The growth and neurological development of the child had been considered as normal, neurological examination did not reveal any focal signs, visual acuity was intact and MRI was normal. First EEG and six consecutive 24 h video EEG recordings during the follow-up of 22 months showed continuous spike-and-wave activity covering over 85% of the non-REM sleep. According to structured neuropsychological tests (Wechsler Intelligence Scale for Children--Third Edition, A Developmental Neuropsychological Assessment (NEPSY), Test of Visual-Perceptual Skills, Corsi block, Hooper Visual Organization Test) the boy had normal verbal intelligence but major deficits in visual perception, especially in object recognition, impaired shape discrimination and detection, and poor copying skills. Attention and executive functions were intact. There were no difficulties in short- or long-term memory. Verbal cues and naming the objects improved visual memory. Tracing the objects with a finger or by moving the head improved object recognition. Currently the boy attends a special school with a rehabilitation plan including neuropsychological and occupational therapies. This case adds a new facet to the spectrum of neuropsychological deficits in children with CSWS. Sleep EEG should be included in the etiological studies of children with specific neuropsychological problems and detailed neuropsychological assessment is needed for diagnostic and rehabilitation purposes.

Agnosia↗
PubMed1984

Taste agnosia following gustatory neocortex ablation: dissociation from odor and generality across taste qualities.

In Experiment 1, rats trained to avoid drinking in the presence of a compound odor (benzyl acetate) and taste (sucrose) conditional stimulus (CS) lost the taste habit but retained the odor habit following gustatory neocortex (GN) ablation. Conversely, olfactory bulb ablation resulted in loss of the odor habit but retention of the taste habit. In Experiment 2, rats lacking GN did not retain preoperatively instated learned aversions to a suprathreshold quinine hydrochloride (bitter) taste solution which had been employed as a CS. However, rats with GN lesions that were virtually identical to those of the bitter-trained group retained a preoperatively learned aversion to a hydrochloric acid (sour) CS. Experiment 3 demonstrated that reliable agnosia for an acid CS could be produced by lesions that extended more deeply into perirhinal areas near the claustrum at the level of the GN. It is concluded that the agnosia following GN ablation is relatively specific to gustation and that agnosia for preoperatively acquired taste aversion habits occurs for all four basic gustatory stimuli following anterolateral cortex ablations centered on the GN.

Agnosia↗
PubMed1986

Auditory agnosia. Analysis of a case with bilateral subcortical lesions.

We report a case of typical auditory agnosia. It is unique in that the clinical picture began with generalized auditory agnosia for verbal and nonverbal sounds and changed, over a period of two months, to a restricted auditory agnosia, confined to the recognition of nonverbal sounds. The lesions, confirmed by CT scanning and MRI, were subcortical bilaterally, without evidence of cortical damage, and have not previously been described. The results of audiological studies on temporal discrimination were similar to those described for bilateral temporal lobe lesions. The relationships between click intervals and the threshold to detect sound, and between numbers of clicks and the threshold, were also examined. We observed a tendency for the threshold to decline as the number of clicks was increased or the interval between two clicks was shortened. These phenomena are similar to temporal summation in cellular neurophysiology and we speculate that this phenomenon is an important factor in the auditory disturbances shown by the present case.

Aged↗
PubMed1987

A case of integrative visual agnosia.

A single case study of a patient with visual agnosia is presented. The patient had a marked impairment in visual object recognition along with good tactile object identification and a preserved ability to copy. Detailed investigations demonstrated impaired perceptual processes, with the patient's identification strongly affected by duration of stimulus exposure and by using overlapping figures. However, his stored knowledge of objects was shown to be intact. The results demonstrate that agnosia may be determined by a specific deficit in integrating form information; and that the input description for visual object recognition, disrupted in this patient, is functionally separate from stored object descriptions, which are intact. The implications of the results for understanding visual agnosia and for theories of normal visual object recognition are discussed.

Agnosia↗
PubMed2000

Patterns of music agnosia associated with middle cerebral artery infarcts.

The objective of the study is to evaluate if the rupture of an aneurysm located on the middle cerebral artery (MCA) results in disorders of music recognition. To this aim, 20 patients having undergone brain surgery for the clipping of a unilateral left (LBS), right (RBS) or bilateral (BBS) aneurysm(s) of the MCA and 20 neurologically intact control subjects (NC) were evaluated with a series of tests assessing most of the abilities involved in music recognition. In general, the study shows that a ruptured aneurysm on the MCA that is repaired by brain surgery is very likely to produce deficits in the auditory processing of music. The incidence of such a deficit was not only very high but also selective. The results show that the LBS group was more impaired than the NC group in all three tasks involving musical long-term memory. The study also uncovered two new cases of apperceptive agnosia for music. These two patients (N.R. and R.C.) were diagnosed as such because both exhibit a clear deficit in each of the three music memory tasks and both are impaired in all discrimination tests involving musical perception. Interestingly, the lesions overlap in the right superior temporal lobe and in the right insula, making the two new cases very similar to an earlier case report. Altogether, the results are also consistent with the view that apperceptive agnosia results from damage to right hemispheric structures while associative agnosia results from damage to the left hemisphere.

Adult↗
PubMed1997

Visual agnosia with bilateral temporo-occipital brain lesions in a child with autistic disorder: a case study.

A 2-year-old boy meeting the criteria for autistic disorder was diagnosed 2 years later with a visual agnosia characterised by a combination of certain aspects of associative and apperceptive agnosia. MRI then revealed a severe encephalomalacia of the right temporal lobe and bilateral temporo-occipital areas. This association is discussed in terms of a clinical and aetiological relation between autistic disorder and visual agnosia.

Agnosia↗
PubMed1979

Prosopo-affective agnosia as a symptom of cerebral organic disease.

A previously described test for prosopo-affective agnosia (impairment of facial affect recognition) had been applied in 14 disoriented elderly patients with chronic organic brain syndrome, 14 fully oriented elderly patients with non-organic psychiatric disorders, and 14 normal volunteers. In this re-test study of 37 of the 42 subjects, after a six-month interval, the test was found to be reliable (r = .75, p less than .001). The test was also more sensitive in detecting organic disorders than were other frequently applied neuropsychiatric tests. Prosopo-affective agnosia (PAA) appeared unrelated to prosopo-agnosia (PA) (r = .082, ns). Some patients who had the ability to recognize famous faces and faces of ward personnel were severely impaired in the ability to recognize facial affect. The deterioration was more pronounced for the recognition of sadness and anger than for happiness, indicating that patients with this impairment had reverted to an infantile mode of facial-affect recognition. This reversal is another example of the neurologic regression that characterizes dementia.

Affect↗
PubMed1998

Autism and visual agnosia in a child with right occipital lobectomy.

OBJECTIVES: Autistic disorder is a developmental handicap with an unknown neurological basis. Current neuropsychological models for autism suggest an abnormal construction of visual perceptual representation or a deficit in executive functions. These models predict cerebral lesions in the temporo-occipital or frontal regions of autistic patients. The present study aimed at studying the presence of symptoms of autism and visual agnosia in a 13 year old girl who had a right temporo-occipital cortical dysplasia that was surgically removed at the age of 7. METHODS: Neuropsychological evaluation included Wechsler and Kaufman intelligence scales, a test of word fluency, digit span, Corsi block, California verbal learning, Trail making, Benton facial recognition, Snoodgrass object recognition tests, Rivermead face learning subtest, and developmental test of visual perception. The ADI-R was used to show current and retrospective diagnosis of autistic disorder. Neuroimagery included brain MRI, single photon emission computed tomography (SPECT), and PET. RESULTS: Brain MRI showed a right occipital defect and an abnormal hyperintensity of the right temporal cortex. PET and SPECT disclosed a left frontal hypometabolism together with the right occipital defect. Neuropsychological testing showed a visual apperceptive agnosia and executive function deficits. Psychiatric study confirmed the diagnosis of autistic disorder. CONCLUSIONS: Although the possibility that autism and visual agnosia were dissociable factors in this patient cannot be excluded, the finding of both deficits supports the possibility that occipito-temporal lesions can predispose to the development of autism.

Adolescent↗
PubMed1988

Visual agnosia and amnesia from a left unilateral lesion.

This case report describes the behavior of a patient with a visual agnosia of the associative type, developing to optic agnosia at a later stage. Language, general intelligence and right hemisphere functions were well preserved, but recognition of visually presented objects, colors, faces, words, and complex stimuli was impaired. Agnosia was accompanied by a multimodal amnestic syndrome. CT displayed a focal left hemisphere lesion. The observed pathomorphology is not consistent with a bilateral visuolimbic disconnection syndrome, as suggested from previous case studies. Significant components of visual semantic processing may be executed by the left hemisphere.

Adult↗
PubMed2005

Behavioral change and its neural correlates in visual agnosia after expertise training.

Agnosia, the impairment in object and face recognition despite intact vision and intelligence, is one of the most intriguing and debilitating neuropsychological deficits. The goal of this study was to determine whether S.M., an individual with longstanding visual agnosia and concomitant prosopagnosia, can be retrained to perform visual object recognition and, if so, what neural substrates mediate this reacquisition. Additionally, of interest is the extent to which training on one type of visual stimulus generalizes to other visual stimuli, as this informs our understanding of the organization of ventral visual cortex. Greebles were chosen as the stimuli for retraining given that, in neurologically normal individuals, these stimuli can engage the fusiform face area. Posttraining, S.M. showed significant improvement in recognizing Greebles, although he did not attain normal levels of performance. He was also able to recognize untrained Greebles and showed improvement in recognizing common objects. Surprisingly, his performance on face recognition, albeit poor initially, was even more impaired following training. A comparison of pre- and postintervention functional neuroimaging data mirrored the behavioral findings: Face-selective voxels in the fusiform gyrus prior to training were no longer so and were, in fact, more Greeble-selective. The findings indicate potential for experience-dependent dynamic reorganization in agnosia with the possibility that residual neural tissue, with limited capacity, will compete for representations.

Adult↗
PubMed1993

Development of aphasia, apraxia, and agnosia and decline in Alzheimer's disease.

OBJECTIVE: The purpose of this study was to compare the stage and the subtype models of disease progression in Alzheimer's disease. The authors address the issue of whether the overall rate of clinical decline is different in Alzheimer's disease patients with and without early development of aphasia, apraxia, or agnosia. METHOD: The study was a case series study. Two separate cohorts of Alzheimer's disease patients were used, one from an ongoing single center study at Stanford University (N = 57) and the other from a multicenter project across the state of California (N = 70). Patients were assessed every 6 months in the Stanford study and yearly in the state study. All patients were assessed at least three times. The outcome measure was the average rate of decline on the Mini-Mental State examination. RESULTS: The average rates of decline on the Mini-Mental State were computed for each subject. Subjects were then divided among groups according to whether and when they exhibited aphasia, agnosia, or apraxia. The effects of the presence of aphasia, agnosia, or apraxia were assessed by comparing the average rates of decline on the Mini-Mental State. CONCLUSIONS: Alzheimer's disease patients who developed aphasia or apraxia declined more rapidly than those patients who did not develop either sign. These results were not attributable to differences in Mini-Mental State scores at entry into the study. The results suggest the presence of subtypes of Alzheimer's disease in which accelerated decline is associated with the early appearance of certain neurological signs.

Age Factors↗
PubMed2000

The influence of premorbid language skills and behavior on language recovery in children with verbal auditory agnosia.

Previous studies of children with Landau-Kleffner syndrome and related language-epilepsy syndromes have focused on the relationship of seizure control to language recovery. We examined the effect of premorbid language skills and behavior, as well as some characteristics of clinical seizures and electroencephalograms, on language recovery in a retrospective study of 67 children with the severe receptive and expressive language disorder, verbal auditory agnosia. Fifty-eight percent of these children had seizures, 76% were autistic, and 24% had a history of language regression after showing previously normal language skills. The duration of language loss was not influenced by the persistence of clinical seizures. Premorbid language and behavior were more predictive of language recovery in these children. Most children with normal early language (acquired verbal auditory agnosia) had onset of language loss after age 3 years, in contrast to those with abnormal early language. Children with acquired verbal auditory agnosia were more likely to show fluctuations in language skills than those in other groups. Autistic children were more likely to begin having seizures before age 3 years, and had a longer duration of language loss and lower educational placement at time of last follow-up than those with normal behavior. This study emphasizes the importance of assessing premorbid language and behavior in predicting recovery of language skills in children with language-epilepsy syndromes.

Adolescent↗
PubMed2000

Long-term follow-up of auditory agnosia as a sequel of herpes encephalitis in a child.

We report a pediatric patient with auditory agnosia as a sequel of herpes encephalitis. His early development was completely normal. He uttered three words at 12 months old. Disease onset was 1 year and 2 months of age. He was discharged from the hospital seemingly with no sequel; however, he could not recover his intelligible words even at age 2 years. He was diagnosed as having auditory agnosia caused by bilateral temporal lobe injury. We began to train him at once, individually and intensively. Adult patients with pure auditory agnosia followed by two episodes of temporal lobe infarction have impairment in central hearing but not inner language. Therefore, they can communicate by reading and writing. Moreover, impairment in hearing is not always severe and is often transient. However, despite long-term (more than 15 years) energetic education and almost normal intellectual ability (Performance IQ of Wechsler Intelligence Scale for Children-Revised was 91), our patient's language ability was extremely poor. Cerebral plasticity could not work fully on our patient, whose bilateral temporal lobe was severely injured in early childhood. The establishment of a systematic training method in such patients is an urgent objective in this field.

Adolescent↗
PubMed1988

Visuoperceptual function in visual agnosia.

Two patients with visual agnosia underwent visual recognition and neuropsychological tests to characterize their perceptual functioning. Both had an initial "apperceptive profile" and evolved from cortical blindness. One had carbon monoxide intoxication and incidental agenesis of the splenium of the corpus callosum; the other had the clinical features of MELAS (mitochondrial encephalopathy, lactic acidosis, and stroke-like syndrome). The agnosia profile showed impaired object recognition but adequate visual matching and copying of unrecognized items. The patients were successful on form discrimination, mental rotation, and visuospatial skills, but did poorly on figure-ground discrimination, visual integration, facial discrimination, and constructional tasks. Their performances were characterized by slow, serial analysis of visual features and a decreased useful field of view. The pattern of results suggests a form of visual agnosia caused by disturbances of parallel distributed processing.

Adult↗
PubMed1999

[The significance of the study of aphasia, apraxia and agnosia at present time].

Neuropsychology initiated by the study of aphasia, apraxia and agnosia had been regarded as one division of psychiatry. This is one of the reasons why neuropsychology is minor territory in neurology. Some people say that neuropsychology seems difficult to understand, not scientific, not useful and is rather a man's taste than a medicine. I try to respond in this paper to these critics by way of analyzing our own cases while insisting on the today's importance of the study of aphasia, apraxia and agnosia. Our personal cases consist of the following three categories. 1) Primary progressive apraxia: proposal of the symptomatic concept suggested by the investigation of our own eight cases and those in the literature. 2) Musical alexia with agraphia in a trombone player: study of the cerebral localization in a person with special ability. 3) Disturbance of reaching proposal of intracerebral pathways in kinesthesia. Therefore it is highly possible that the significance of the study of aphasia, apraxia and agnosia should become enlarged now and after; and it seems urgent to answer its need that younger neurologists participate in this area.

Aged↗
PubMed2000

[A study of measles encephalitis with focal changes on MRI, auditory agnosia and expressive aphasia].

Acute measles encephalitis is a typical parainfectious encephalitis in which the brain is diffusely affected clinically and neuropathologically. We present here a 5-year-old case of measles encephalitis with intractable seizures, bitemporal MRI abnormalities, and neurological sequelae of auditory agnosia and aphasia. Pathophysiology of the focal MRI lesions and of expressive aphasia due to auditory agnosia was discussed. We stressed that the status convulsions and its ischemic effect played an important role on the development of the focal lesions rather than focal encephalitis or ADEM. In the course of auditory agnosia and acquired aphasia, the patient transiently expressed some meaningful words. The significance of this episode was discussed based on the sequential changes of symptoms and neuroimaging findings.

Acute Disease↗
PubMed1992

[Visual agnosia evolving to optic aphasia--a case study].

The underlying mechanism of visual agnosia and optic aphasia has not been fully elucidated, although a number of hypotheses have been proposed. Besides, the difference between these two conditions has been a matter of debate. We report here the result of neuropsychological evaluation in a case of associative visual agnosia evolving to optic aphasia. A 64-year-old right-handed patient was found to be disoriented and confused after undergoing the operation of gastrectomy. CT scan revealed a large infarction in the territory of left posterior cerebral artery. Since 3 weeks after onset, neuropsychological investigations were carried out during 5 months. He was alert and co-operative. Right homonymous hemianopia with macular sparing was noted, but his visual acuity was normal. There was neither a global deterioration of intellectual capacities nor aphasia. Most striking finding was his difficulty in identifying common objects and colours along with a profound alexia. Prosopagnosia was absent. Visual naming both for objects and line drawings was severely impaired. He was unable to describe or demonstrate the use of the objects which could not be named. Pointing to objects named by the examiner was also severely impaired. Although tactile naming was also impaired, both of auditory naming for environmental sounds and naming objects in response to verbal descriptions were preserved. While he was not able to copy the objects skillfully, matching of identical objects and matching objects to line drawings were normal. Clumsiness of coping was thought to be due to his constructional apraxia and visuomotor ataxia. Therefore, his deficit in visual domain was considered to be associative visual agnosia.(ABSTRACT TRUNCATED AT 250 WORDS)

Agnosia↗