Prosopagnosia: a bihemispheric disorder.

A 54-year-old, right-handed male suffered three sequential infarcts. The first two destroyed much of the right posterior parietal area, the posterior-medial portion of the right temporal lobe and virtually the entire right occipital lobe producing left homonymous hemianopsia and left visual neglect but no prosopagnosia. A third vascular accident involved the left parieto-occipital lobe and immediately produced prosopagnosia that has persisted. The sequential correlations of lesion and symptomatology in this case demonstrate that development of persistent prosopagnosia occurred only after bilateral damage.     

Cerebral lateralization of face-sensitive areas in left-handers: Only the FFA does not get it right

Face perception is highly lateralized to the right hemisphere (RH) in humans, as supported originally by observations of face recognition impairment (prosopagnosia) following brain damage. Divided visual field presentations, neuroimaging and event-related potential studies have supported this view. While the latter studies are typically performed in right-handers, the few reported cases of prosopagnosia with unilateral left damage were left-handers, suggesting that handedness may shift or qualify the lateralization of face perception. We tested this hypothesis by recording the whole set of face-sensitive areas in 11 left-handers, using a face-localizer paradigm in functional magnetic resonance imaging (fMRI) (faces, cars, and their phase-scrambled versions). All face-sensitive areas identified (superior temporal sulcus, inferior occipital cortex, anterior infero-temporal cortex, amygdala) were strongly right-lateralized in left-handers, this right lateralization bias being as large as in a population of right-handers (40) tested with the same paradigm (Rossion et al., 2012). The notable exception was the so-called ‘Fusiform face area’ (FFA), an area that was slightly left lateralized in the population of left-handers. Since the left FFA is localized closely to an area sensitive to word form in the human brain (‘Visual Word Form Area’ – VWFA), the enhanced left lateralization of the FFA in left-handers may be due to a decreased competition with the representation of words. The implications for the neural basis of face perception, aetiology of brain lateralization in general, and prosopagnosia are also discussed.     

A case of visual agnosia for picture with right occipital lobe infarction]

We report a 74-year-old right-handed man with visual agnosia for picture due to right occipital lobe infarction. The patient had a remarkable impairment in visual recognition for standardized pictures made by Snodgrass and Vanderwart, in addition to left hemianopsia, left visuospatial neglect, and mild prosopagnosia. The visual agnosia for picture was generally recognized as a mild-type of the visual object agnosia, which was extremely rare in the patients with right occipital lesion. We discussed the mechanism of the visual agnosia in the right occipital lesion. Therefore, it raises the possibility that the broad impairment of the right occipital artery territory including parahippocampal gyrus as well as corpus callosum can cause the visual agnosia for picture.     

Visual hypoemotionality and prosopagnosia associated with right temporal lobe isolation

Emotional hyporeactivity to visual stimuli (so-called visual hypoemotionality) was observed in a 71-yr-old woman following a cerebral infarction in the territory of the posterior cerebral arteries. Other visual disturbances included severe prosopagnosia, dense left hemianopia and mild left hemineglect. There was neither object agnosia nor any involvement of language, memory or intellectual functions. Hypoemotionality was found only for visual stimuli, since auditory and tactile modalities were totally spared, suggesting a visual-limbic disconnection mechanism. From CT data, and referring to previous evidence suggesting a right-hemisphere prevalence for emotional functions, it is postulated that the right occipital lesion, leading to a total right temporal lobe isolation, was mainly responsible for the patient's emotional disturbances.     

Ventral simultanagnosia and prosopagnosia for unfamiliar faces due to a right posterior superior temporal sulcus and angular gyrus lesion

We report a patient with ventral simultanagnosia, prosopagnosia for “unfamiliar faces” (dorsal prosopagnosia), spatial agraphia, and constructional disorder, particularly on the left spatial side, due to a lesion in the right posterior superior and middle temporal gyri and angular gyrus. The patient showed impairment of fundamental visual and visuospatial recognition, such as in object size, configuration, and horizontal point location, which probably underlay the mechanism of simultanagnosia and prosopagnosia. This case also suggests that the coexistence of simultanagnosia and prosopagnosia results from a right hemispheric insult, and damage to the temporoparietal area interrupts the incorporation of spatial information into object recognition. This disconnection of information flow, together with impaired object recognition per se, may impair the parallel processing of multiple objects, leading to object-by-object or part-by-part recognition.     

Right perceptual bias and self-face recognition in individuals with congenital prosopagnosia

The existence of a drift to base judgments more on the right half-part of facial stimuli, which falls in the observer's left visual field (left perceptual bias (LPB)), in normal individuals has been demonstrated. However, less is known about the existence of this phenomenon in people affected by face impairment from birth, namely congenital prosopagnosics. In the current study, we aimed to investigate the presence of the LPB under face impairment conditions using chimeric stimuli and the most familiar face of all: the self-face. For this purpose we tested 10 participants with congenital prosopagnosia and 21 healthy controls with a face matching task using facial stimuli, involving a spatial manipulation of the left and the right hemi-faces of self-photos and photos of others. Even though congenital prosopagnosics performance was significantly lower than that of controls, both groups showed a consistent self-face advantage. Moreover, congenital prosopagnosics showed optimal performance when the right side of their face was presented, that is, right perceptual bias, suggesting a differential strategy for self-recognition in those subjects. A possible explanation for this result is discussed.     

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.     

Non-verbal facial and topographic visual object agnosia--a problem of familiarity in prosopagnosia and topographic disorientation

In recent years, prosopagnosia is defined as the "loss of ability to recognize the well-acquainted persons like the family members by their physiognomy." There are many reports based on this definition. However, from the viewpoint of symptomatology, there are many problems not entirely solved yet. And the mechanism of its manifestation is not clearly explained. Topographic disorientation, which often accompanies prosopagnosia, is studied even less. From the results of the postmortem examination in the literature, bilateral occipito-temporal lesions have been known to cause prosopagnosia. However, the recent radiographical examination by the computed tomography revealed that the prosopagnosia is also caused by the right occipito-temporal lesions only. We experienced a case with prosopagnosia and topographic disorientation which were considered to be caused by infarction in the territory of the right posterior cerebral artery. Detailed symptomatological, morphological and functional examinations were carried out by means of various psychological testing, X-ray computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). The patient was a 70-year-old right-handed man who suffered from sudden visual loss on both eyes, and was admitted to our hospital after four weeks. On examination, a decrease of visual acuity and right homonymous hemianopsia were recognized. When visual acuity was recovered, he was unable to recognize the faces of his relatives and friends, with whom he has been well acquainted for many years. He also found his own house, the buildings and streets around it as entirely unfamiliar. Seven months after the onset of the disease, examination showed he had definite prosopagnosia and topographic disorientation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Congenital prosopagnosia: multistage anatomical and functional deficits in face processing circuitry

Face recognition is a primary social skill which depends on a distributed neural network. A pronounced face recognition deficit in the absence of any lesion is seen in congenital prosopagnosia. This study investigating 24 congenital prosopagnosic subjects and 25 control subjects aims at elucidating its neural basis with fMRI and voxel-based morphometry. We found a comprehensive behavioral pattern, an impairment in visual recognition for faces and buildings that spared long-term memory for faces with negative valence. Anatomical analysis revealed diminished gray matter density in the bilateral lingual gyrus, the right middle temporal gyrus, and the dorsolateral prefrontal cortex. In most of these areas, gray matter density correlated with memory success. Decreased functional activation was found in the left fusiform gyrus, a crucial area for face processing, and in the dorsolateral prefrontal cortex, whereas activation of the medial prefrontal cortex was enhanced. Hence, our data lend strength to the hypothesis that congenital prosopagnosia is explained by network dysfunction and suggest that anatomic curtailing of visual processing in the lingual gyrus plays a substantial role. The dysfunctional circuitry further encompasses the fusiform gyrus and the dorsolateral prefrontal cortex, which may contribute to their difficulties in long-term memory for complex visual information. Despite their deficits in face identity recognition, processing of emotion related information is preserved and possibly mediated by the medial prefrontal cortex. Congenital prosopagnosia may, therefore, be a blueprint of differential curtailing in networks of visual cognition.     

A case of topographic disorientation without right occipital lesion]

A 73-year-old right-handed man developed topographical disorientation, left homonymous hemiianopsia, left visuospatial neglect and mild visual memory disturbance following the right hemispheric infarction. The visual agnosia is very similar to agnosia for streets because he could not identify familiar buildings and streets even though he could remember their way. He did not have prosopagnosia. His brain MRI demonstrated infarction at the right anterior choroidal artery area, including right thalamus, caudate tail and optic radiation. SPECT showed the mild decrease of rCBF at the right temporoparietal cortex. His topographic disorientation faded and finally disappeared about 3 weeks after its onset. Our case is atypical because of sparing the posterior part of the right parahippocampal gyrus where plays an important role in the development of agnosia for streets.     

Transient postoperative prosopagnosia

A 23-year-old right-handed woman developed isolated transient prosopagnosia following surgical resection of a right posterior temporal seizure focus. At 18 years of age she had developed secondarily generalized tonic-clonic seizures. Preoperative neuropsychological evaluation was normal, and neurological examination revealed only a left superior quadrant achromatopsia. MRI revealed a circumscribed lesion in the right inferolateral temporo-occipital junction. Following surgery she was agitated for 36 hours, and afterward, when her attention and orientation improved, she was unable to recognize familiar faces. She could, however, recognize familiar voices. Her prosopagnosia resolved over the next 6-7 days. This case demonstrates that isolated prosopagnosia can occur in patients with lesions restricted to the right inferior posterior temporal-anterior occipital region. The temporary nature of the prosopagnosia may result from postsurgical tissue injury, including focal cerebral edema, with compensation by ipsilateral or contralateral areas.     

Selective impairment of facial recognition due to a haematoma restricted to the right fusiform and lateral occipital region

A 67 year old right handed Japanese man developed prosopagnosia caused by a haemorrhage. His only deficit was the inability to perceive and discriminate unfamiliar faces, and to recognise familiar faces. He did not show deficits in visual or visuospatial perception of non-facial stimuli, alexia, visual agnosia, or topographical disorientation. Brain MRI showed a haematoma limited to the right fusiform and the lateral occipital region. Single photon emission computed tomography confirmed that there was no decreased blood flow in the opposite left cerebral hemisphere. The present case indicates that a well placed small right fusiform gyrus and the adjacent area can cause isolated impairment of facial recognition. As far as we know, there has been no published case that has demonstrated this exact lesion site, which was indicated by recent functional MRI studies as the most critical area in facial recognition.     

Attentional mechanisms and perceptual asymmetries in tachistoscopic recognition of words and faces.

In simultaneous bilateral tachistoscopic recognition tasks, normal right-handers named more words in the right visual field and recognized more faces in the left visual field. Priming the left hemisphere with a verbal task diminished the left field superiority for faces, and priming the right hemisphere with a face-recognition task, reduced the right visual field superiority for words. These priming effects disappeared when a recognition procedure was used. When words and faces were presented simultaneously, subjects required to attend to the faces and report them first showed a left visual field superiority for faces and a right visual field superiority for words. Subjects told to attend to the words and report them first showed only the right visual field superiority for words.     

Symptoms and lesion localization in visual agnosia]

There are two cortical visual processing streams, the ventral and dorsal stream. The ventral visual stream plays the major role in constructing our perceptual representation of the visual world and the objects within it. Disturbance of visual processing at any stage of the ventral stream could result in impairment of visual recognition. Thus we need systematic investigations to diagnose visual agnosia and its type. Two types of category-selective visual agnosia, prosopagnosia and landmark agnosia, are different from others in that patients could recognize a face as a face and buildings as buildings, but could not identify an individual person or building. Neuronal bases of prosopagnosia and landmark agnosia are distinct. Importance of the right fusiform gyrus for face recognition was confirmed by both clinical and neuroimaging studies. Landmark agnosia is related to lesions in the right parahippocampal gyrus. Enlarged lesions including both the right fusiform and parahippocampal gyri can result in prosopagnosia and landmark agnosia at the same time. Category non-selective visual agnosia is related to bilateral occipito-temporal lesions, which is in agreement with the results of neuroimaging studies that revealed activation of the bilateral occipito-temporal during object recognition tasks.     

A case of agnosia for streets without visual memory disturbance]

A 70-year-old, right-handed man was admitted to our hospital for his sudden-onset topographical disorientation. He failed to find his way to familiar places, but he knew distance and direction to the places. Neurological examination revealed homonymous left-upper quadrantanopsia on Goldmann perimeter and hypoesthesia over the left side of his body. Magnetic resonance imaging showed an abnormal intensity area at the right medial temporo-occipital region, due to the infarct of the right posterior cerebral arterial territory. The neuropsychological examination revealed agnosia for streets, and prosopagnosia without any other disturbance of visual perception. Both visual and topographical memories were intact. It is suggested that, in this case, the agnosia for streets was caused by impairment of recognizing familiar streets and houses or disconnection between their recognition and memory.     

A longitudinal study of the development of visual field advantage for letter matching

The visual field advantage for letter matching was investigated longitudinally from 5 to 7 yr. A right visual advantage was found with very little indication of any increase with age. Cross-sectional controls exhibited somewhat less of a right visual field advantage. In a group of 4-yr-olds who could not name letters a left visual field advantage was observed for boys. It is suggested that the right visual field advantage for visual-verbal material occurs from a mapping on to an already existing left hemisphere language system.     

A case of prosopagnosia following moderate closed head injury with left hemisphere focal lesion

This study describes a left handed woman with prosopagnosia following traumatic brain injury with a focal lesion confined to the left-posterior hemisphere. Few cases of prosopagnosia following unilateral left hemisphere lesions have previously been reported in the literature. Corrected visual acuity was 20/70 (binocular), color vision was intact on screening, and shape detection was borderline. Impairments in higher order visual perception were evident to varying degrees on nonfacial tasks. Matching of unfamiliar faces was very slow but accurate. A marked impairment in the ability to recognize familiar faces and learn new face-name associations was evident on experimental tasks relative to the performance of healthy control subjects. In contrast, identification of characteristics of faces (gender, age) and identification and matching of facial expressions were relatively preserved. We discuss the cognitive processing stages that appear to be disrupted using Bruce and Young's (1986) model of facial recognition and perception as a framework.     

Emotional attention in acquired prosopagnosia

The present study investigated whether emotionally expressive faces guide attention and modulate fMRI activity in fusiform gyrus in acquired prosopagnosia. Patient PS, a pure case of acquired prosopagnosia with intact right middle fusiform gyrus, performed two behavioral experiments and a functional imaging experiment to address these questions. In a visual search task involving face stimuli, PS was faster to select the target face when it was expressing fear or happiness as compared to when it was emotionally neutral. In a change detection task, PS detected significantly more changes when the changed face was fearful as compared to when it was neutral. Finally, an fMRI experiment showed enhanced activation to emotionally expressive faces and bodies in right fusiform gyrus. In addition, PS showed normal body-selective activation in right fusiform gyrus, partially overlapping the fusiform face area. Together these behavioral and neuroimaging results show that attention was preferentially allocated to emotional faces in patient PS, as observed in healthy subjects. We conclude that systems involved in the emotional guidance of attention by facial expression can function normally in acquired prosopagnosia, and can thus be dissociated from systems involved in face identification.     

Perceptual asymmetries in greyscales: object-based versus space-based influences

Neurologically normal individuals exhibit leftward spatial biases, resulting from object- and space-based biases; however their relative contributions to the overall bias remain unknown. Relative position within the display has not often been considered, with similar spatial conditions being collapsed across. Study 1 used the greyscales task to investigate the influence of relative position and object- and space-based contributions. One image in each greyscale pair was shifted towards the left or the right. A leftward object-based bias moderated by a bias to the centre was expected. Results confirmed this as a left object-based bias occurred in the right visual field, where the left side of the greyscale pairs was located in the centre visual field. Further, only lower visual field images exhibited a significant left bias in the left visual field. The left bias was also stronger when images were partially overlapping in the right visual field, demonstrating the importance of examining proximity. The second study examined whether object-based biases were stronger when actual objects, with directional lighting biases, were used. Direction of luminosity was congruent or incongruent with spatial location. A stronger object-based bias emerged overall; however a leftward bias was seen in congruent conditions and a rightward bias was seen in incongruent conditions. In conditions with significant biases, the lower visual field image was chosen most often. Results show that object- and space-based biases both contribute; however stimulus type allows either space- or object-based biases to be stronger. A lower visual field bias also interacts with these biases, leading the left bias to be eliminated under certain conditions. The complex interaction occurring between frame of reference and visual field makes spatial location extremely important in determining the strength of the leftward bias.