We report the results of a study designed to assess age differences in the response to the formalin test, a model of tissue injury and inflammation, while controlling for differences in weight and motoric abilities in three groups of adult male Long-Evans rats: young (3 months old), middle-aged (18 months old), and old (24 months old). The first part of the study assessed initial differences in responsivity and found that the middle-aged group showed the greatest response, whereas the young and old groups did not differ from each other. In the second part of the study, the young and middle-aged animals were followed for a 4-month period. The formalin test was repeated at 2-month intervals. These results indicate that there may be an age-associated change in the sensitivity to tonic pain and that this sensitivity may peak at mid-life.

Age Distribution↗

PubMedDate not supplied

Phantom limb pain.

A phantom limb is universally experienced after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, phantom breasts, genitals and other body areas occur in a substantial number of people after surgical removal or denervation of the body part. The most astonishing feature of a phantom limb (or other body area) is its incredible "reality" to the person. An examination of phantom limb phenomena has led to a new theory. It is proposed that we are born with a widespread neural network--the "neuromatrix"--for the body-self, which is subsequently modified by experience. The neuromatrix imparts a pattern--the "neurosignature"--on all inputs from the body, so that experiences of one's own body have a quality of self and are imbued with affective tone and cognitive meaning. The theory is presented with supporting evidence as well as implications for research.

Humans↗

PubMedDate not supplied

Labat lecture. Phantom limbs.

A phantom limb is universally experienced after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, phantom breasts, genitals and other body areas occur in a substantial number of people after surgical removal or denervation of the body part. The most astonishing feature of a phantom limb (or other body area) is its incredible "reality" to the person. An examination of phantom limb phenomena has led to a new theory. It is proposed that we are born with a widespread neural network--the neuromatrix--for the body-self, which is subsequently modified by experience. The neuromatrix imparts a pattern--the neurosignature--on all inputs from the body, so that experiences of one's own body have a quality of self and are imbued with affective tone and cognitive meaning. The theory is presented with supporting evidence as well as implications for research.

Brain↗