My original intent in starting this blog was to post about my schoolwork. Cuz, uh, brains are cool. And I'm learning a lot about them. But I've feared that it wouldn't be relevant; most of the stuff I'm learning, of course, is old news to anyone actually in the field.
Not even a week ago, ScienceBlogger Neurophilosophy posted about body schema disorders, which are actually covered in the current exam block for one of my neuro courses.
Body schema disorders are disturbances in the way a person perceives relationships between body parts. Spatial relationships are mainly linked to parietal areas of the brain, so if you damage a specific area of your parietal lobe, you can mess up your personal conceptualization of how your limbs should relate to one another.
The left hemisphere, in general, tends to be used more for verbal or detail-oriented processes. So it's not surprising to see that left parietal damage can affect body schema that are related to what my book calls "linguistic representations of the body". For example, left parietal damage can lead to the inability to tell left from right. It might also lead to finger agnosia, which is the inability to tell one finger from another.
A different set of problems arise from damaging the right parietal lobe. There's anosognosia, which is when a person paralyzed on one side denies that their limb is paralyzed. Not only will they say that their limb moves, but if you ask them to raise or move the limb, the rest of their body will react as if they had (with appropriate facial expression, posture, gaze orientation). right parietal damage could also lead to somatoparaphrenia, or denial/loathing of a body part. Yes, as when that guy cut his hand off and stuck it in the microwave (though that had some Biblical-order craziness to it), and also the interview Neurophilosophy linked to.
Macrosomatagnosia and microsomatagnosia are perceiving a body part to be too big or too small, respectively. These disorders, along with somatoparaphrenia, also seem linked to the temporal lobe. According to this text, the temporal lobe and especially the insula help the parietal lobe map out body parts and aid in the emotional interpretation of body schema. I wonder if this has anything to do with gender identity dysmorphic disorder, or body image disorders like anorexia nervosa. If anyone has any links, I'd be appreciative.
And if not, that's ok, I can go back to my studying. ;)
Source: Banich, Marie T. (2004). Cognitive Neuroscience and Neuropsychology. Boston: Houghton Mifflin.