Monthly Archives: April 2011

Why Do Some People Have Difficulty in Recognising Faces?

Prosopagnosia is the term used to describe an inability to recognise faces. This is a very specific impairment and there has been debate about whether such a specific impairment really exists. The alternative suggestion is that there is a more generic impairment in visual processing which partly manifests as an inability to recognise faces. In a PLOS One paper titled ‘Deficits in long-term recognition memory reveal dissociated subtypes in congential prosopagnosia’ (freely available here) the authors Stollhoff and colleagues investigate this further. They sample a group of people with Congenital Prosopagnosia (CP). In other words they have suffered with prosopagnosia since birth*(1). In the introduction the authors summarise previous research into prosopagnosia when we learn that researchers have tried to understand the phenomenon by comparing facial recognition with other important functions including object recognition, the processing of facial expressions and face detection. In this experiment the research team recruited 16 people with CP and 36 controls *(2).  Prosopagnosia was confirmed using a semi-structured interview examining difficulties with facial recognition as well as specialised assessments of visual processing. The researchers also wanted to exclude neurological and psychiatric illness *(3). Without going into too much detail the researchers used a number of tests to investigate visual processing. They investigated the ability of subjects to recognise famous faces, to access knowledge about visually presented information, to perceive visually presented information and to remember faces that had been presented one year previously.

Why Don’t Certain People Recognise Faces?

Comparing the subjects with CP to the control group the researchers found many differences. These differences may have been nothing more than associations. However the functions are similar in some ways to the function of recognising faces and so it can be reasonably assumed that there was some meaningful association between the phenomenon. Nevertheless even with these findings the researchers were unable to characterise the CP group as having a unique set of functional impairments. Instead they found that the subjects with CP had many different patterns of impairment. Some people had difficulty linking visual information to stored knowledge. Others had difficulty remembering previously presented faces. Yet other people had difficulty in processing the visual information. They concluded by suggesting that there were three types of congenital prosopagnosia (although these categories had been proposed prior to this study)

(1) Apperceptive Prosopagnosia: In this form, the person has difficulty in perceiving the face. The suggestion is that visual perception of faces is a two-stage process. In the first stage the person will retrieve visual information from the face. In this model, the face is properly considered as a3-dimensional object. In the second stage, this 3-dimensional information is then integrated into the visual perception of the face. Although the finer details of this model are not clear, the researchers note that in some cases of prosopagnosia, the person may inspect the face for a longer period of time and there may also cases in which it takes longer to integrate this information. Thus we can see that more general mechanisms of visual perception can potentially interfere with the visual perception of faces and it is important to be aware of these before concluding that the difficulty is more specifically related to faces.

(2) Associative Prosopagnosia: In this form of prosopagnosia, the person will be able to perceive the face correctly but will have difficulty in associating the face with stored knowledge.  The authors reference work by A Young on face recognition and presumably this is the same researcher who has proposed a model of facial recognition in the Delusional Misidentification Syndromes showing the potential relevance of this subject area to schizophrenia and other forms of psychosis. The researchers note that these two forms of prosopagnosia are unlikely to occur in an absolute form but rather that there should be an overlap of impairment in both stages of processing and this is what they find in the subjects in this study.

(3) Amnesic Prosopagnosia: In this form of prosopagnosiathe person has difficulty in retaining the association between the face and the associated semantic memory. In this study the subjects were tested at two points a year apart. They were asked to recall faces presented a year previously. The researchers found a significant group difference between the people with ‘congenital prosopagnosia’ and the control group. The people with prosopagnosia were significantly more likely to miss faces that were presented previously. Interestingly this didn’t hold for images of shoes that had been presented and so this was more convincing evidence for an impairment in visual processing specific to faces.

However even with these three categories there is still something of a black-box approach. We can see this by asking a few simple questions. What for instance is the process by which the spatial information about a face is integrated in the brain? Does it happen in the visual association cortices? How long does this take to occur? How many neurons are involved? Are certain types of face easier to remember? With such questions it is easy to see that the models are necessarily very simple and even with relatively sophisticated methodology it will likely be difficult to add more detail to these models.

I would interpret this as follows. There is utility in providing a label to investigate a phenomenon further. However in the case of prosopagnosia, given the complexity of the visual apparatus there are likely to be many different ways of interfering with the visual ‘machinery’ to effect the outcome of prosopagnosia. Once the process of face recognition is fully elucidated it will be possible to predict how pathological occurrences might occur within the system as well as relating actual clinical cases to this model. Until that stage is reached however the further classification offers an approximation to the ideal model. The ‘resolution’ of this model is determined by sophistication of the diagnostic apparatus becoming in effect a function of the resolution of the imaging equipment, reliability of the psychometric assessments, a function of the ‘models’ underlying the psychometric assessments as well as the clinical and imaging paradigms, the history taking characteristics, the limits of language (in the history taking) in describing visual phenomenon (in effect the ability of the mind to communicate phenomenological experiences in the perceptual domain) as just a few examples. This means that while the characterisation of the heterogeneity within this small population may represent an iterative process in the refinement of the model of CP (part of the normal science described by Thomas Kuhn (see here)), there is sufficient lax within the system to enable a different experiment using alternative assessment tools and a different population to entirely reframe the characteristics of the heterogenous CP population and offer a different model validated by that same CP population.

An Alternative Question

We can replace the question of ‘Why Don’t Certain People Recognise Faces?’ with the question of ‘What type of answer to this question would satisfy us?’. For instance at one level we might say that we want an answer that is simple to understand and remember. Someone in a research setting might want an answer that they can use to formulate an experimental paradigm to build upon this answer whilst another person might want an answer that they can challenge. For me the most satisfying answers would be those that offered for instance the clinician a pragmatic tool for use in a clinical assessment (interesting and similar is this recent BMJ paper) or for more abstract academic purposes a model which can be described with a specific language or framework which researchers in many fields of neuroscience could contribute to and which would enable the researchers to see where that specific model fits into the ‘bigger picture’. However this bigger picture itself is difficult to define but is needed ultimately to make sense of the huge global surge in clinical neuroscience and associated research that we are seeing.

Appendix

*(1)  This is perhaps something of a misnomer as visual perception takes some time to develop. Phenomenon such as ocular dominance columns present just one example of why it takes sufficient training for the visual cortex to process images and transform them into complex perceptions. Thus a newborn baby would not be expected to recognise faces. Thus there should be a critical point in development when face recognition ‘develops’ and it is at that point that prosopagnosia can be meaningfully discussed.

*(2) I wasn’t clear on how the people with CP were recruited but I assume that as part of the research took place at the Institute of Human Genetics there was some process which led to people with prosopagnosia being assessed at that centre and then  recruited for this study. The only alternative I can think of offhand is that the study was marketed to the general population although I couldn’t see any such details in the methodology section at the end of the paper.

*(3) The terms however are sufficiently broad to be difficult to interpret. For instance many people would reach the threshold for adjustment reactions during the course of a year as just one example. Possibly what the researchers are referring to are the more common illnesses including schizophrenia, bipolar, unipolar depression and so on. However this can be argued to be semantics as we might expect with sufficient technological resources to be able to identify the cause of the prosopagnosia and to couch it in diagnostic terms meaning that if it isn’t currently a neurological or psychiatric disorder (e.g neurodevelopmental disorder) then with this additional information and due process it soon would be.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

News Round-Up: April 2011 2nd Edition

The Lou Ruvo Center has recently opened in Las Vegas. This is a memory clinic with a large investment which impacts on the model of care. The facilities for the memory clinic are contained within a single building and these include a 3 Tesla MRI scanner, facilities for neuropsychology assessment and handheld computers for use in a streamlined process. Interestingly although the patients do not have to enrol in research their data can be compared to the Alzheimer’s Disease Neuroimaging Initiative (ADNI) dataset.

There is a write-up at the Schizophrenia Research Forum on some new trial data on approaches to cognitive and negative symptoms in Schizophrenia. The new approaches include the use of alpha-7 nicotinic cholinergic receptor agonists as well as a GABA-phenothiazine compound although the results from Phase III trials will be needed.

Researchers in a large multicentre trial (n=1080) investigated hallucinations in people with schizophrenia and found that there was geographical variation in the presentation of hallucinations. They suggest that this is evidence in support of cultural interactions with psychosis.

A moderately sized study (n=200) investigated gender differences in presentation of acute mania. The researchers found that there were statistically significant differences between men and women in presentation and that

a predominance of anxiety and depressive symptoms was found in women, whereas increased psychomotor activity was prevalent in men

A short small-sized trial compared risperidone and escitalopram for treatment of psychosis and agitation showed no difference in efficacy although it would be interesting to see the results of a larger longer-term replication study.

A small study showed preliminary evidence that not recognising difficulties with memory (anosognosia for amnesia) is present not only in people with Alzheimer’s Disease but also in people with amnestic Mild Cognitive Impairment. This was based on an assessment of 25 people with Mild Cognitive Impairment compared with 21 controls.

A systematic review examining a number of studies (with a total of 768 people with Vascular Dementia and 9857 controls) reinforced the important relationship between hypertension and increased risk of vascular dementia.

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.

The Origins of A Kiss?

There’s been a thought at the back of my mind for a while about the origins of kissing. Recently though a comment on a video I’d taken sparked a connection and suddenly everything seemed to fall into place. At the end of it, I perceived a chain of events that could feasibly have led to the origins of kissing in humans.  Although there is evidence to support my arguments it does however remain as biologically informed speculation and I will leave the reader to decide just how plausible it is.

A few years back on a trip to Twycross Zoo, I had taken some footage of Bonobos and uploaded them to YouTube. In one of the videos I’d shortened the video to the most relevant parts and called it ‘Bonobos Kissing’ and in the other I’d called it ‘Bonobos Grooming’. Both videos were uploaded on the same day. However 1.5 years down the line and there is a big difference in the number of viewings these videos have received.

The videos differ in their length and the titles. While the length may be sufficient to account for the difference, my choice of the term kissing in favour of grooming most likely contributed to the added interest in the ‘kissing’ video. The original video is shown below.

However the choice of the term kissing soon generated controversy and it was noted by one reader with an interest in primatology that this type of behaviour was typical grooming behaviour and therefore the term kissing was somewhat misleading. Convinced that there was something there however it lingered in the back of my mind and I was sure I was onto something. A year down the line and I received a comment on another video I had taken of bonobos. This video is shown below.

The comment was simple ‘nice footage’. Having taken a lot of footage of primates over the past few years in order to gather data and without a clear hypothesis, I thought that I had gathered enough to be able to use it to investigate generated hypotheses. I inspected the video again and saw something that I had overlooked the first time around. Perhaps the commenter had seen this. The Bonobo uses its teeth to pull at the hairs on the other Bonobo. There is nothing too unusual. This is a variation on the standard grooming type of behaviour which involves the use of the fingers. What is very interesting however is that Bonobos are less hairy than Chimpanzees and have a relatively hairless face. The Bonobo can be seen to initiate a grooming behaviour with its mouth which as a necessity must convert into a kissing type behaviour in the regions of the other Bonobos face that are not covered in hair.  Suddenly everything seems to fall into place although it does so through a convoluted path.

So here are 5 phases that I propose for the evolution of the kiss in humans.

Phase 1. In Phase 1 there is a grooming behaviour which is used in groups to facilitate social bonding. The evidence for the importance of grooming behaviour in primates is incontrovertible. This primarily involves pulling at the hairs of the group members. It is thought that this produces a pleasant sensation in the group member that is being groomed. More powerful members of the groups are more likely to be groomed by other members of the group although the details are far from straightforward. Professor Robin Dunbar has proposed a theory about the transformation of grooming behaviour in humans as discussed in the video below.

Phase 2. In Phase 2 the primate loses some of its hair. There are two good examples of this. Firstly there are cases of Chimpanzees that have developed alopecia. One example is Jambo, a chimpanzee at Twycross Zoo who can be seen in the video below.

In the video Jambo can be seen to engage in a type of self-grooming behaviour playing with his skin with his teeth. Jambo has a son who also has alopecia and it is therefore likely that this characteristic was transmitted as a dominant trait. However it does not mean that Chimpanzees lost their hair on the path to becoming humans as there is a slight catch. The catch is that humans didn’t evolve from Chimpanzees. Both Chimpanzees and humans evolved from a common ancestor (or concestor as Dawkins refers to it). Nevertheless Jambo demonstrates the existence of a possible dominant trait which could influence selective fitness through the loss of hair.

The second piece of evidence relating to the loss of hair is to be seen in Bonobos. Bonobos are distinguished from Chimpanzees by their relative lack of facial hair. Bonobos are well researched and in my brief observations they are the most human like of the primates that I have seen. They are less closely related to us than Chimpanzees in the evolutionary timeline however. Bonobos walking upright, using branches as tools and utilising a matrilinear society are just a few examples of Bonobo behaviour that have been observed.

Phase 3. In Phase 3 the primate with reduced hair is able to travel longer distances in hot climates than its hairier relatives. Although there are various lines of research about this, the importance of this was brought home to me after watching the BBC series ‘The Incredible Human Journey‘ presented by Dr Alice Roberts. In hot climates, the hair acts as an insulating layer reduced the loss of heat from the body through convection. The end result is that a loss of body hair should enable the primate to travel longer distances in hot climates without developing hyperthermia.

Phase 4. In Phase 4, the primate with reduced hair travels further distances and acquires more fruit than its hairier relatives. The primate provides potential mates with the fruit in exchange for mating opportunities. Evidence for this has come from a study by Kimberley Hockings and colleagues involving field observations of Chimpanzees in West Africa and published in PLOS One (see write-up of study here also).

Image of Chimpanzee taking Papaya fruits from PLOS One paper here (Under Creative Commons License)

Phase 5: Through a mechanism which is unclear to me the kissing behaviour on hairless skin becomes rewarding to the hairless primate. This is a necessary condition since kissing behaviour in humans is considered a pleasant experience in pair bonding. Thus the presumed pleasant experience of pulling on hair is replaced with direct contact with the skin. No doubt if this is correct, the answer will come from an understanding of the different types of skin receptors.

As by-products of these 5 phases there are two additional characteristics that would be enhanced

(a) Altruistic Behaviour. Through the exchange of fruits for mating opportunities, generations of hairless primates would have the benefits of ‘altruistic behaviour’ positively reinforced. Of course this is not completely altruistic behaviour but instead the primate learns that by making short term sacrifices of gathered fruits it will gain mating opportunities.

(b) Working Memory. In one piece of research, the researchers concluded that Chimpanzees were able to identify how productive trees are in terms of the fruits they produce at different times of the year. Indeed the researchers suggest that the Chimpanzees are able to navigate within a forest of some 12,000 trees to those that are ‘in season’ at a given time.

What are the Implications in Humans?

If we return to humans what are the implications of this? One obvious implication is that in pair bonding, kissing has taken over the role of grooming in other primates. However there are two notable examples of kissing in other scenarios that might be explained by this interpretation.

The Social Kiss

In many cultures greetings are often made with a kiss and such greetings have been refined in terms of etiquette. If such behaviours are equivalent to grooming behaviours then it is possible to suggest that they mean ‘You are invited into my group’.

Kissing as Greeting Behaviour (from Wikimedia Commons – see here for further details)

The Abstraction

In many sports particularly group sports, the winner(s) will often kiss the trophy. In such cases the trophy can be seen to represent a validation of the winning group as well as approval from the much wider societal ‘group’. In such cases the seemingly unusual behaviour of kissing an inanimate object can mean ‘I welcome the status symbol to my group’.

                                                  Kissing a Football Trophy (from Wikimedia Commons – see here for further details)

Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail justinmarley17@yahoo.co.uk. Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.