Associative Prosopagnosia

Prosopagnosia is a rare neurobehavioral disorder in which the ability to recognise previously familiar faces is impaired. The sufferer is unable to identify familiar individuals by their facial features, and in some cases cannot recognize a face at all. In the latter, the patient cannot combine facial features together as a whole unit to form and recognise it as a face. However, such patients are fully aware that some sort of visual stimulus is present and can easily describe particular elements of it. Other than that, many patients also have difficulties in other parts of face processing, for instance, judging people’s age or gender and recognising certain emotional expressions. Some reported problems with navigation as well. In many of the

In associative prosopagnosia, the sufferer cannot match and link the content of perception to his previous experience, whereas in apperceptive prosopagnosia, the individual is unable to piece together the sensory impressions into a perceptual whole (Lissauer 1889). Etcoff et al. (1991) described LH who performed well on perceptual tasks that needed configural processing but who was nevertheless prosopagnosic. As LH could deal with the processing of configuration of a face, it can be assumed his prosopagnosia was more associative in nature; he experienced difficulty in accessing visual memories of previously learned faces. De Renzi et al. (1991) reported two patients GD and VA from whom they argued for a separation between an apperceptive prosopagnosia and an associative type of the condition. GD performed better on tests involving memory for famous faces compared to perceptual tasks. On the other hand, VA had the reverse deficit; he performed more poorly on memory tasks than perceptual tasks. VA 's case can be explained similarly to LH: perceptual processing was reasonably unimpaired, so VA 's difficulty with faces can be considered as an associative deficit. GD, however, had a perceptual problem which means the facial deficit may be caused by perceptual

The former type of prosopagnosia arises due to neurological damage such as stroke or traumatic head injury that affects the inferior temporal cortex (IT), the part of the brain which mediates face recognition. These patients had normal facial recognition abilities that were then impaired due to the lesions to the IT. In some cases, the individuals have cerebral lesions with physical signs suggesting bilateral involvement but in other cases there is clinical evidence only for right hemisphere lesions (Meadows 1974). It is well-established that recognition, matching and discrimination of facial material are way more frequently impaired in patients with lesions in the posterior right hemisphere than in those in the left hemisphere (Tranel et al.