Neurophilosophy has recently published two excellent articles that discuss the recent discovery of very selective psychological problems: one person can’t recognise people by their voice, the other can’t navigate through streets.
In themselves, these sorts of disorders are not that surprising, but they help us understand how the brain develops.
Actually, scratch that last sentence. If you’re familiar with the brain injury literature, these sorts of disorders are not that surprising, but if you’re not, they’re completely mind blowing.
Take prosopagnosia for example. Sometimes rather inaccurately called ‘face blindness’ (people see faces, they just don’t seem distinctive) it was first identified in a patient with a bullet wound to the head who lost the ability to recognise faces but could still recognise other objects.
If you think about it, this is incredible. When we look out onto the world, faces don’t seem different from the rest of the things we look at, but damage to a specific area of the brain (most commonly the right fusiform gyrus) can selectively damage our ability to see faces, suggesting that there are brain functions specialised for this task. How specialised, whether only for faces, is a matter of ongoing debate, but the fact that they are specialised at all is incredible enough.
The explanation for these selective impairments goes something like this: our brain functions are shaped by a combination of the broad outline of genetics and the fine tuning of experience during growth. When we reach adulthood they are fairly fixed. Damaged can knock out these fairly fixed pathways leading to selective impairments.
What has become clear over the last decade is that some people can have selective impairments without suffering brain injury. They seem to have them from birth.
This is the case with the two people discussed by Neurophilosophy. An inability to recognise people by just their voice or an inability to navigate streets after brain damage is interesting but not earth shattering. These sorts of cases have been reported before.
But the fact that these are developmental disorders is an interesting and important twist, not least for what they suggest about how much certain functions might be ‘set’ in the brain early on, but also for what they suggest about the ‘life history’ or our cognitive skills.
The two case studies discussed by Neurophilosophy are both fascinating as life stories of people with atypical difficulties but also scientifically compelling because they help us understand complex dance of brain growth and development.
Link to piece on developmental topographagnosia.
Link to piece on developmental phonagnosia.