This is not exactly precise, since it is still a point of contention in the relevant literature. In fact there are free nerve endings and mechanoreceptors that will send somatic sensations and pain sensations to the brain, and there is an ongoing debate concerning the source of the phenomenon of phantom pain.
The two major theories concern whether or not free nerve endings from the amputated limb are sending these signals or whether it is plasticity (change) within the somatotopic organization of the somatosensory cortical areas that is giving rise to the perception of the phantom limb. (Okay some people also think that it's purely psychological, but what that really means is difficult to pin down.)
In either situation, it is well understood that there are long term changes occurring in the area of the somatosensory cortex that now is deprived of input from the amputated limb. Adjacent cortical areas are known to reutilize some or all of the somatotopic space in the cortex, but what we are probably seeing is the reverting of that reorganization back to something that was closer to the "normal" case. Jon Kaas and Tim Pons have done some nice work showing this, and there is a good paper by Florence, Jain, and Kaas (1997) showing similar cortical reorganization in monkeys.
Just goes to show that the brain is yet again proving to be amazing, and it's capable of long term change - even in adults!
Reader Comments (Page 1 of 1)
shaninho @ Nov 14th 2006 11:02PM
" ... all pain is generated in the brain ... "
This is not exactly precise, since it is still a point of contention in the relevant literature. In fact there are free nerve endings and mechanoreceptors that will send somatic sensations and pain sensations to the brain, and there is an ongoing debate concerning the source of the phenomenon of phantom pain.
The two major theories concern whether or not free nerve endings from the amputated limb are sending these signals or whether it is plasticity (change) within the somatotopic organization of the somatosensory cortical areas that is giving rise to the perception of the phantom limb. (Okay some people also think that it's purely psychological, but what that really means is difficult to pin down.)
In either situation, it is well understood that there are long term changes occurring in the area of the somatosensory cortex that now is deprived of input from the amputated limb. Adjacent cortical areas are known to reutilize some or all of the somatotopic space in the cortex, but what we are probably seeing is the reverting of that reorganization back to something that was closer to the "normal" case. Jon Kaas and Tim Pons have done some nice work showing this, and there is a good paper by Florence, Jain, and Kaas (1997) showing similar cortical reorganization in monkeys.
Just goes to show that the brain is yet again proving to be amazing, and it's capable of long term change - even in adults!