On Self Recognition

from reference 1

Ascribing human characteristics to animals based on behaviors that resemble our own is a dangerous game. However, scientists studying the brain and behavior are often left with little choice. Thus, the “spot-test” has become the best experiment we have for answering the question: “does a given species have the capacity for self-recognition.” In this test, a colored spot is put on an animal, the animal is placed in front of a mirror, and the experimenter looks to see if the animal will attempt to remove the spot, thus associating the figure in the mirror with itself. So far, the four great apes, bottlenose dolphins, and Asian elephants have shown the ability to pass this test. New research adds the magpie to this list1. An interesting commentary was also published in the same issue of PLoS Biology as the study itself, and I reproduce an excerpt from that commentary here:

“From an evolutionary perspective, it must be added that MSR [mirror self recognition] seems hardly interesting. It cannot be an important adaptation, since animals lacking this capacity have no trouble with reflective surfaces, such as standing pools of water. Animals certainly do not need to recognize themselves to survive. The importance of the mirror test rather resides in what it may tell us about how animals perceive themselves in relation to their environment, including their social partners. In other words, the mirror test is interesting not because it shows that an animal has the capacity for self-recognition but because of the cognitive abilities that are associated with MSR.

It has been speculated that MSR coincides with advanced social relationships, including the capacity to look at the world from another’s viewpoint. Gallup already speculated about this connection, and more recently this idea has been connected to the various levels of empathy reached by mammals. The higher levels of empathy require individuals to grasp the situation in which another finds itself, hence looking at the situation from another’s perspective. The same capacity may be reflected in MSR. This is known as the “co-emergence hypothesis,” according to which the capacities for MSR and perspective-taking appear in tandem during both evolution and development.

With regards to human development, this hypothesis is well-supported. Children begin to show perspective-taking abilities at around the same time that they first pass the mirror mark test, even after age has been controlled for. In the future, researchers may be able to address this issue more directly through neural investigation. In humans, for example, the right inferior parietal cortex, at the temporoparietal junction, underpins advanced empathy by helping distinguish between self- and other-produced actions. If mirror responses tap into the same self–other distinction, the mark test is obviously more than it appears.2

References:
1. Prior H, Schwarz A, Güntürkün O (2008) Mirror-Induced Behavior in the Magpie (Pica pica): Evidence of Self-Recognition . PLoS Biol 6(8): e202 doi:10.1371/journal.pbio.0060202
2. de Waal FBM (2008) The Thief in the Mirror. PLoS Biol 6(8): e201 doi:10.1371/journal.pbio.0060201

On Rodent Parkinsons

The cover of the journal Brain

Therapies based on stem cells rely heavily on our ability to coax these blank-cellular-slates into taking on specific forms. Stem cells are exciting as possible sources of medicinal therapy because they have the potential to become any type of cell in the body, but in order for their utility to be realized, we must be able to reliably effect their fates. The process of turning a stem cell into a specific cell type is called, logically, differentiation. With the exception of the immune system, the brain has more cell-types than any other organ, not to mention some of the most differentiated (exotic or distinct) types. Thus, many scientists are busily engaged in the activity of deducing molecular algorithms for deterministic control of their cellular end-state.

One disease where there seems to be a clear connection between cell-type-specific disfunction and pathology is Parkinson’s Disease. In this debilitating condition, the afflicted progressively loose motor function due to a lack of stimulation of their motor corticies (the area responsible for directing movement in the human brain) by dopaminergic neurons found in the amygdala (another brain region associated with emotion and reward). Further, it appears to be the case that the reason for this lack of stimulation is simply a lack of production of dopamine by these dopaminergic amygdalar neurons. The cell-type specificity of the disease makes it an an excellent candidate for treatment by replacing the existing hypoactive neurons with newly differentiated stem cell versions of their kind, which should have normal dopamine production abilities.

A recent paper appearing in the journal Brain reports the results of a study in which the researchers have achieved just such a therapeutic cell-type replacement in rats with a “model” of human Parkinson’s disease (ref. 1). They report that motor function was restored by this approach, and further that the longevity of the differentiated cells was related to their restorative efficacy. Further examples of work like this promise to revolutionize the treatment of a host of diseases.

References:
1. Sanchez-Pernaute R, Lee H, Patterson M, Reske-Nielsen C, Yoshizaki T, Sonntag KC, Studer L, Isacson O. (2008) Parthenogenetic dopamine neurons from primate embryonic stem cells restore function in experimental Parkinson’s disease. Brain.