For many years, neuroscientists believed that the “headquarters” of human self-awareness were located in a portion of the brain called the insula, which allows us to realize the things that go on inside the body. For just as many years, this explanation had sufficed, and experts moved onwards with their research, to other areas of the human brain. However, the recent case of a patient with severe damage to the insula and still able to be self-aware has thrown the old theory into disarray and brought it back to the attention of the international scientific community,
ScienceNow reports.
The reason why the insula remained the favored explanation for so many years is the fact that it's responsible for integrating a number of pieces of information the cortex receives from the body. The most important ones include things such as realizing that you have a full stomach, becoming aware of changes in body temperature, as well as a host of other internal sensations. Knowing this, experts have hypothesized that the insula somehow transforms these stimuli into conscious sensations, but the exact mechanisms employed to do this have proven to be extremely difficult to test.
But a patient named “Roger” has brought the existing theory to its knees. He developed a disease known as the herpes simplex encephalitis as far back as the 1980s. The condition destroyed between 25 and 35 percent of his brain, including his insula. Yet, the patient is perfectly able to communicate, has excellent language skills and a normal IQ. The only differences between him and a “normal” person are that he has bouts of amnesia, as well as the fact that he misses the senses of smell and taste. University of Iowa researchers Sahib Khalsa and David Rudrauf have been curious to know how Roger interprets visceral sensations, so they have asked him to undergo a few tests.
When compared with 11 healthy subjects undergoing the same trials, the patient proves just as able to detect changes going on inside him as any other individual. However, in a test where a drug was given to the participants that increased their heart rates, Roger could not feel the increase in beats when his chest was rubbed with an anesthetic cream. This means that parallel pathways in the brain might be at work, and that one of them integrates the sense of touch. The find is detailed in this week's online issue of the respected journal Nature Neuroscience.
Find us on Google+
