Prosopagnosia or Prosopdysgnosia : Facing up to a change of concepts

The term `Prosopagnosia' refers to the inability to identify people using visual facial cues as a result of brain injury [1]. A further term, `Developmental Prosopagnosia', has been proposed to refer to a condition with a similar dysfunction, but here there is an absence of any external brain injury. In recent years, these terms have been used increasingly, despite the lack of evidence about which specific functions are involved, and how they are affected during the development of human facial feature processing. Furthermore, most of these studies seem to address a dysfunction, rather than a function that never developed or has been lost altogether. We propose clarifying the terminology by distinguishing between whether the function is absent (prosopagnosia) or functioning at a suboptimal level (prosopdysgnosia). This distinction is particularly important as an increasing number of studies indicate varying degrees of function, rather than a function that is either present or not. Focusing on the variations of dysfunctions may help to form a better understanding of how facial features are processed and used by different observers. Moreover, studies describing functions that are lost can help us to understand which parts of a network are critical for face perception. One model that may prove particularly useful, both in the general understanding of the dysfunction and in the specific possibilities regarding rehabilitation is the Reorganization of Elementary Functions model (REF) [2]. This model has recently been applied both within consciousness studies [3] and blindsight [4].