Imagine for a second feeling “overcomplete.” You have all of your limbs, and they are perfectly healthy. Yet, you feel as though your leg doesn’t belong to you. It shouldn’t be there, and you know it needs to go. The only way you can feel “whole” again is through its removal. You might be wondering why anyone would want to get rid of a perfectly healthy limb. Well, this phenomenon is the result of apotemnophilia, or Body Integrity Identity Disorder (BIID), a condition characterized “by the intense and long-standing desire for the amputation of a specific limb.” Most know exactly where they want the line of amputation to be, and this place stays fairly constant as time passes. Since it is rare for a surgeon to agree to amputate a healthy limb, many suffering from this condition will unfortunately resort to attempting the amputation themselves. In the past, this rare disorder was thought to be only psychological, and that perhaps the yearning for amputation was simply a way of seeking attention. However, in recent years, studies have shown otherwise.
One study performed by David Brang, Paul D. McGeoch and Vilayanur S. Ramachandran suggests that apotemnophilia is indeed a neurological disorder. The otherwise healthy subjects of the study went through a series of blind skin conductance response tests where they were pinpricked above and below the line where the amputation was. The responses to the pinpricking below the line were much greater than those above it. The resulting differences found suggest some abnormalities with the somatosensory input to the body part in question.
They suspect the disorder to be a consequence of damage to the right parietal lobe, which is responsible for processing sensory input from certain areas and forming our sense of body image. It could be the dysfunction within the right parietal lobe, specifically the right superior parietal lobe, causing irregular sympathetic output. The discrepancy between the signals and body image can lead to the feeling that a certain limb doesn’t belong and should be removed in order to feel “complete.” In addition, most patients have dealt with these feelings since childhood suggesting that the dysfunction is congenital.
Philosophy of Mind came into its most compelling forms during the age of modern philosophy beginning with René Descartes. Perhaps infamously, Descartes claimed that mind and body are two distinct substances – philosophical jargon for what exists without the aid of any other thing. For Descartes, the world was clearly and distinctly physical in one sense and entirely mental in another. This seems perplexing, and Descartes did concede that the mind and body were closely intertwined and appeared to act with respect to one another, but his arguments clearly press that they are not causally connected in any way. These notions of dualism seem nearly preposterous with the advent of modern science, but were nonetheless important in developing our thought about the mind in the modern era.
Dualism gave rise to other interesting, yet now strongly refuted movements. One of these was idealism, or the doctrine argued famously by George Berkeley that states that all that exists are either ‘ideas’ or minds that perceive them. In this sense, an idea is defined as that which is perceived, inclusive of information imprinted on the senses, passions and operations of the mind, and conceptions formed by imagination and memory. Importantly, Berkeley argues that these ideas exist ‘in the mind’ exclusively: that is, they are purely mental and all things are simply combinations and aggregations of ideas. These immaterial ‘ideas’ then, are the only objects of human knowledge under idealism, and this theory denies the existence of physical objects entirely! The notion seems preposterous, but there is a very interesting argument found within idealism that can throw our conception of perception for quite the proverbial loop. More
Most would agree that the most important of our basic senses is sight. Without it, many basic forms of communication fall apart, the vibrance of the world around us dulls, and our understanding and ability to sense the complexity of the physical world diminishes. Without the ability to see, it would logically be impossible to portray our surroundings artistically in a coherent and visually realistic manner…
How you feel influences what you see, it is not just what you see that influences how you feel; a top down approach to understanding the visual system.
Affective Circumplex: Affect can vary in terms of valence (positive/negative) and arousal (high/low).
A great analogy for understanding how affect (the experience of an emotion) influences perception is to think of affect as a spotlight, or a source of “attention” that sheds light on the external world. This is known as a top-down process because the cortical and sub cortical levels of the brain directly influence what one externally experiences. This is opposed to a bottom-up process wherein external stimuli influences processing in the brain (an example of this process would be hearing something hit the floor behind you and immediately shifting your attention to that object). The brain uses both of these processes interchangeably, but it has only been recently that a top-down understanding of the visual system (a system that has classically been believed to be primarily regulated by external stimuli and how such stimuli influence attention) has been accepted. Many studies by Lisa Feldman Barrett and the Interdisciplinary Affective Sciences lab at Northeastern University seem to have proved strong evidence against the popular claim that the bottom-up system is the sole means by which perception can be influenced. More
“Magic mirror on the wall, who is the fairest one of all” says the evil Queen of Snow White and the Seven Dwarfs. I don’t deny that growing up on Disney gave me a somewhat skewed sense of reality at times. Wouldn’t it be nice to all have our own magic mirrors, constantly reminding us how wonderful and beautiful we are in the midst of the stress that is life?
A recent study by researchers at Cornell University have shown that we may actually have such a magic mirror – Facebook, as fate would have it. There are varying opinions concerning internet use on our personalities, but this study shows that Facebook can have a short term positive effect on self esteem. More
In early 2007, a 64-year-old Swiss woman was admitted to the emergency room of a local hospital after having suffered a moderate right hemispheric stroke. Several days following her hospitalization, the woman began to experience what she described to her physicians as a “pale,” “transparent” arm that began at her elbow, which she could move and utilize to complete actions. The phenomenon the Swiss woman experienced was a Supernumerary Phantom Limb (SPL), which is characterized by the sensation of possessing an extra limb that did not exist previously. Though uncommon, conditions such as SPL and phantom limb (the sensation that a missing limb is still attached to the body) typically arise due to some form of insult to the somatosensory region of the brain or from the removal or lack of body parts.
In the healthy brain, multisensory circuits organize visual, tactile, and proprioceptive inputs to the brain in order to compose a somatotopic map of which body parts are inherently our own. However, even the normal brain can be manipulated into believing in the existence of an extra limb. More
A little self-education goes a long way. Let Richard Dawkins enlighten you (and if you’ve seen this already, it’s never a bad idea to brush up on the basics of life):
In Disney/Pixar’s “Finding Nemo,” Marlin and Dory are swimming through murky waters en route to Sydney Harbor. Marlin suddenly exclaims, “Wait, I have definitely seen this floating speck before. That means we’ve passed it before and that means we’re going in circles and that means we’re not going straight!” – and he is probably right.
Is it really possible that when we cannot see where we are going, we actually travel in circles? Souman et al. tested this belief through a variety of experiments. They found in all cases that when deprived of a visual stimulus, it is actually impossible to travel in a straight line.
The first set of experiments had participants travel through a wood without visual impediments (such as blindfolds). One set of subjects traveled through the woods when it was cloudy, the second set when it was sunny. All of the cloudy group walked in circles and walked in areas that they had previously been, without noticing they had crossed a previous path. In contrast, all of the subjects who could see the sun were able to maintain a course that was relatively straight and had no circles.
The experiment was also performed on blindfolded subjects in an open field.
The blue paths correspond to the subjects that walked on cloudy days. Their paths are mostly curved with many circles. The small straight areas of walking are most likely caused by the setup of the trial – participants walked for a period of time, then were unblindfolded and allowed to walk to the starting point of the next walking block. Even so, when blindfolded, lack of a visual stimulus when blindfolded always resulted in walking in curved motions or in circles. This contrasts the yellow path; this subject walked on a sunny day, and maintained a straight course for a long distance.
What causes this strange phenomenon? Could it perhaps be subtle differences in leg length that introduce a bias to walk in one direction, thus accounting for the circular motion? Nope – the circle directions were still random. Adding shoe soles to add a more than subtle difference in leg length didn’t make a difference: the participants continued to walk in random circles.
Perhaps the only explanation is that our vision is so necessary for our daily lives that our body randomizes without it. This idea is demonstrated in studies in which subjects are kept in a room with constant lighting: their biological clocks become completely randomized with no night and day inputs. More studies should be performed to truly understand the importance of the visual system. Since we rely so heavily on vision, is it natural for movements to become randomized without it? Do those who are blind from birth experience the same walking in circles phenomenon? For now, the conclusion here is that the sensory systems are complex and there is still much work to be done in understanding this strange phenomenon. So, if you ever find yourself lost in murky Australian waters, you probably should not just keep swimming, but rather, ask a friendly passing whale for directions.
Walking Straight into Circles – Current Biology
It was an average Wednesday night at 8, and I was channel surfing. As I changed the channels I heard singing; I knew instantly that the show was American Idol. Most of you watch or have watched the show in the past and time and time again it befuddles me to think how these individuals think that they can sing. Most of the singers not only have piercing voices, but they are off key and sound terrible. After most auditions, the contestants – although I know it was horrible – still believe their rendition of a Whitney Houston song was outstanding. If you are like me then you want to know why.
Tone-deaf individuals do not have brain damage or trouble hearing, and they are definitely not suffering from a lack of exposure to music. So what actually makes people unable to understand their inability to sing? Researchers conducted an experiment that tested the connectivity of the arcuate fasciculus (AF), which connects the temporoparietal junction (the place where the temporal and parietal lobes meet), with the frontal cortex in the brain. This junction allows neural substrates of sound perception and production to be connected. The researchers hypothesized that there are structural and functional abnormalities that contribute to tone deafness.
To test their hypothesis, structural MRIs with diffusion tensor imaging (DTI) were performed on the patients. DTI is a type of MRI that allows researchers to map internal structures with the diffusion of water. After processing the information, the maps identified that the right superior AF was diminished compared to control, signifying that the AF is disrupted in tone-deaf individuals. Also, resultant fibers in tone-deaf individuals projected dorsally toward the parietal lobe and/or translocally to the left hemisphere and not toward the ipsilateral inferior frontal gyrus where normal individuals have projections.The imaging and testing of the AF led researchers to conclude that the superior branch is responsible for fine-grained discrimination, and the inferior branch is responsible for automatic matching of sound output to its target. They also tested the volume of the fibers connecting each part of the brain and discovered that tone-deaf individuals have a lower volume of fibers than the control, which is important for conscious pitch determination and the degree of action-perception mismatch. According to the experiment, both the superior and inferior branches of the AF are needed for accurate perception and production.
Figure 1: A comparison between the regions of interest of the posterior superior temporal gyrus (pSTG) and the posterior inferior frontal gyrus (pIFG) of the right side of the brain
Tone-deafness is a new disconnection syndrome that deals with impaired pitch perception and vocal sound projection. There are no known genes that are associated with this condition that affects the AF fibers and their connection between the superior and inferior areas of the brain. So for all of you non-tone-deaf American Idol viewers, you will just have to sit through the next episode and know that most of singers cannot help but obliviously sing off-key.
Other Reading of Interest:
Tone Deafness – Scientific American
The amusic brain – BRAIN: A Journal of Neurology