Congenital Prosopagnosia

Congenital Prosopagnosia: What is it and Why do We Study it?

From this description it appears that MJ suffers from congenital prosopagnosia — a term used in indicating people with difficulties in face recognition from birth without any obvious evidence of any neurologic and/or psychiatric disorder.

Since the first case study description of congenital prosopagnosia, a 12 years old girl who reported having severe difficulties recognizing faces that she was not extremely familiar with (McConachie, 1976), many laboraties extensively investigated face processing in this condition.

One of the main differences between acquired Opens in new window and congenital prosopagnosia is that the former, given its traumatic origin, gets immediately recognized, whereas the congenital form can get undetected for a long time as the individual has no means of comparison with normal face processing skills. Also, because congenital prosopagnosics have had a lifetime to develop compensatory strategies, they are adept at using salient features such as hairline or eye brows for recognition.

Given the absence of any evident sign of brain lesion, its developmental nature and its face-specificity (i.e., face recognition very often represents the only identifiable problem), congenital prosopagnosia represents a unique opportunity for the investigation of the cognitive and neural aspects of normal face processing.

Furthermore, congenital prosopagnosia allows us to explore the necessary and sufficient brain activations that are required to ensure intact face recognition. In addition, given that CP individuals never develop normal face recognition despite seemingly normal exposure to faces throughout their life, congenital prosopagnosia raises numerous theoretical questions regarding the psychological and neural conditions required for the initial acquisition of normal face processing and possible limitations on the time period during which this acquisition can occur.

Intriguingly, congenital prosopagnosia also serves as a model to explore whether, and to what extent, face processing is amenable to target intervention programs and, if so, what underlying neural changes might serve as the correlative accompanying the behavioral improvement (Schmalzl, 2007).

Before providing further details on congenital prosopagnosia, it is important to clarify some potentially confusing aspects regarding the names with whom this condition has been referred to. Some researchers refer to congenital prosopagnosia using the name developmental prosopagnosia (Duchanine et al., 2006; Kress & Daum, 2003).

Both congenital and developmental prosopagnosia have often been used as synonyms, to indicate people with difficulties in face recognition from birth without any obvious evidence of any neurologic and/or psychiatric disorder.

I have to note however that some researchers adopted the term developmental prosopagnosia to indicate people who developed prosopagnosia Opens in new window as a consequence of sustained brain damage before, during or immediately after birth, i.e., prior to any visual experience with faces (Barton et al., 2003).

Within the context of this entry, and in line with other researchers (Behrmann & Avidan, 2005), these cases are referred as developmental prosopagnosia whereas cases of prosopagnosia Opens in new window from birth without any history of brain damage as congenital prosopagnosia.

Behavioral Features of Congenital Prosopagnosia: Towards the Diagnosis

How is it possible to identify congenital prosopagnosia?

In order to study, and potentially treat it, it is first necessary to identify some features that can constitute a diagnosis for this condition. Despite the existence of a general consensus on the fact that the core feature of congenital prosopagnosia is an utter failure in the identification of familiar faces, there are still not standard diagnostic criteria that virtually all people in the field can follow.

Luckily however, there are some very well done behavioral tasks to use and some general criteria that must be considered in order to formulate a diagnosis of congenital prosopagnosia.

People can be considered as suffering from a “pure” form of congenital prosopagnosics if they show:

• Impairment on behavioral tasks that measure face processing skills such as face memory, face recognition and face perception;
• Normal, or relatively normal, performance on tasks that measure the memory, recognition and perception of non-face visual stimuli such as objects;
• Normal general intelligence   Opens in new window (IQ);
• Normal overall cognitive functioning such as normal memory and attention;
• Normal social skills (i.e., no autistic traits);
• Normal low-level vision (e.g., contrast sensitivity, acuity, color perception);
• Absence of evident signs of neurological (e.g., epilepsy) and/or psychiatric (e.g., psychosis) conditions.

Note that these tools are not specific for congenital prosopagnosia, but can be well adopted if it is suspected that, for instance, face processing impairments are due to ictus, epilepsy Opens in new window, head trauma or Alzheimer disease.

Prevalence of Congenital Prosopagnosia

Until recently, congenital prosopagnosia was believed to be an extremely rare condition, with only a few published case studies before the year 2000 (Kress & Daum, 2003).

However, a very rapidly increasing number of congenital prosopagnosia cases have been described during the past few years (Duchaine & Nakayama, 2006b; Le Grand et al., 2006), and a recent study estimated the prevalence of the condition to be around 2.5% of the general population (Kennerknecht et al., 2006).

Kennerknecht and colleagues performed a large-scale questionnaire based screening of 750 individuals from secondary schools and Muenster (Germany) University’s medical school. Out of the 689 students who completed the screening questionnaire, 43 were rated as being “highly suspicious” of having congenital prosopagnosia and underwent an in depth semi structured interview.

Based on their answers on the interview, 17 of them (6 males and 11 females) were confirmed to be affected, which constituted 2.5% of the initially screened sample. Even though the main limitation of this study is that none of the individuals underwent a formal assessment of their face processing skills, a recent study that investigated face processing in 241 individuals using standard tasks (CFMT, CFPT) indicated that congenital prosopagnosia could be diagnosed in 2-2.9% of them (Bowles, et al., 2009).

These two studies agree that the prevalence of congenital prosopagnosia is between 2-3% of the general population. It may be surprising to note that even an estimated prevalence of 2% means that congenital prosopagnosia affects, for instance, as many as 2 million people in Germany, 400,000 people in Australia, 1.2 million people in the UK and 6 million people in the US!

Congenital prosopagnosia may have often been undetected for a variety of reasons in the past. In contrast to individuals who acquire their prosopagnosia in adulthood Opens in new window, people with congenital prosopagnosia may be unaware of their face recognition impairments, as they are born with the condition and thus have no means of comparison with normal face processing abilities. They may simply learn to adjust to their difficulties and develop compensatory strategies for recognizing people in everyday life.

Also, in contrast to individuals with prosopagnosia following acquired brain injury, people with congenital prosopagnosia are less likely to be in contact with medical practitioners and neuropsychologists who assess face recognition abilities and diagnose impairments thereof. In addition, since face processing difficulties often impact on the development of social skills (Schultz, 2005), children with congenital prosopagnosia may be misdiagnosed as having behavioral problems or even autistic tendencies (Dalrymple et al., 2003).

Until recently there has been very little public awareness of congenital prosopagnosia as such. Now people with congenital prosopagnosia share their stories on the Internet through various email lists and forums, thus leading to increased awareness.

From the perspective of a person with congenital prosopagnosia:

Until recently I believe it was some aberrant aspect of my personality, rather than something that has a name and a history.(case reported in Schmalzl, 2007).

It is important to note that, despite the fact that research tends to consider genital prosopagnosia as a unique condition, behavioral studies underlie great performance variability. Thus, according to the structure of the Bruce and Young model, cases of congenital prosopagnosia can be classified as being either “apperceptive” (e.g. De Haan & Campbell, 1991) or “associative” (e.g. Jones & Tranel, 2001), depending on whether the individual showed a deficit in structural encoding or not respectively.

Other researchers use the term “prosopamnesia” to indicate a subtype of prosopagnosia characterized by intact face perception (e.g., they can tell when two images are of the same person), but with specific problems in memorizing faces (Williams et al., 2007).

Despite the theoretical importance these distinctions have, for simplicity reasons, we conclude this entry referring to congenital prosopagnosia as a single condition, without referring to specific subtypes.