Visual agnosia without alexia. A 41-year-old man presented with bilateral posterior cerebral artery infarcts. He had visual object agnosia and prosopagnosia with preservation of reading abilities. There was also defective visual memory, topographic orientation, and color perception, as well as simultanagnosia. From the clinical facts and CT findings, it was postulated that bilateral visual-limbic disconnection accounted for the patient's visual agnosia and related disturbances. Published in Neurology (1984)

Background: Agnosia for objects is often overlooked in neuropsychology, especially with respect to rehabilitation. Prosopagnosia has been studied more extensively, yet there have been few attempts at training it. The lack of training protocols may partially be accounted for by their relatively low incidence and specificity to sensory modality. However, finding effective rehabilitations for such deficits may help to reduce their impact on the social and psychological functioning of individuals. Objective: Our aim in this study was to provide clinicians and researchers with useful information with which to conduct new studies on the rehabilitation of object agnosia and prosopagnosia. To accomplish this, we performed a systematic and comprehensive review of the effect of neuropsychological rehabilitation on visual object and prosopagnosia. Methods: The Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines were followed. In addition, the Single-Case Experimental Design (SCED) and the Critical Appraisal Skills Programme (CASP) scales were used to assess the quality of reporting. Results: Seven articles regarding object agnosia, eight articles describing treatments for prosopagnosia, and two articles describing treatments for both deficits were included. Conclusions: In the light of the studies reviewed, treatments based on analysis of parts seem effective for object agnosia, while prosopagnosia appears to benefit most from treatments relying on holistic/configural processing. However, more attempts at rehabilitation of face and object agnosia are needed to clarify the mechanisms of these processes and possible rehabilitations. Moreover, a publication bias could mask a broader attempt to find effective treatments for visual agnosia and leaving out studies that are potentially more informative.

[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. Published in Recenti progressi in medicina (1989)

Pure alexia and right hemiachromatopsia in posterior dementia. A 66 year old, right handed woman presented with pure alexia and right hemiachromatopsia (PARH) in the context of a posterior dementia. PARH was accompanied by prosopagnosia, 2-D object agnosia, and environmental agnosia. Visual fields were normal to confrontation testing. The pathological anatomy of PARH involves circumscribed damage to the lingual and fusiform gyri and paraventricular white matter of the left occipital cortex, two contiguous cortical regions functionally specialised for processing colour and word form information, respectively. Published in Journal of neurology, neurosurgery, and psychiatry (1992)

Alexia without agraphia in a left-handed patient with prosopagnosia. A left-handed patient was studied who had the acute onset of alexia without agraphia, a left homonymous hemianopia, and prosopagnosia. Neurodiagnostic tests including computerized axial tomography and angiography disclosed bilateral lesions in the posterior cerebral hemispheres involving the splenium of the corpus callosum. Neuropsychologic examination indicated marked impairment of facial discrimination, deficient naming and memory of presented visual material, and mild visual agnosia with relative preservation of other cognitive functions. These findings are consistent with a double disconnection syndrome involving disconnection of the dominant angular gyrus and right inferotemporal cortex from their bilateral visual inputs. Published in Neurology (1977)

The ventral temporal cortex hosts key regions for the high-level visual processing of object shape and color. These areas represent nodes of large-scale neural circuits dedicated to object recognition. In the language-dominant hemisphere, some of these regions communicate with the language systems; by assigning verbal labels to percepts, these circuits speedup stimulus categorization, and permit fast and accurate interindividual communication. By impairing the functioning of these circuits, neurological damage may provoke disabling disorders of the processing of visual objects and of their colors. Brain damage of vascular, degenerative, toxic, or traumatic origin can induce deficits at different levels of visual processing, from the building of shape- or wavelength-invariant percepts, to their connections with semantic knowledge and with the appropriate lexical entry. After an overview of the neuroimaging of domain-preferring regions for object shape and color in the ventral temporal cortex, this chapter reviews evidence from historical and recent cases of acquired visual agnosia and color processing deficits. A recurrent motif emerging from patients' patterns of performance and lesion locations is the existence of caudo-rostral gradients in the ventral occipito-temporal cortex, spanning from more perceptual to more cognitive stages of processing.