Introducing a “humanized” version of a language-linked gene into mice accelerates their learning, according to a study.
The gene, called Foxp2, is of a type known as transcription factor—a gene that controls the activity of other genes. It has also been linked to the development of human speech and language. The gene is found in both humans and mice, in slightly different forms.
In the new study, researchers created mice whose version of the Foxp2 gene had changes in two key amino acids—somewhat equivalent to two “letters” of its genetic code. The changes were designed to make the gene more similar to human Foxp2.
The study aimed at learning “how genetic changes might have adapted the nervous system” to language and speech, wrote the scientists, Ann Graybiel of the Massachusetts Institute of Technology and colleagues. The report appeared Sept. 15 online in the journal Proceedings of the National Academy of Sciences.
The report, however, didn’t address what some scientists have described as ethical questions posed by the mixing of human and animal genes. One concern, for example, is that humanity might eventually have to confront the weighty issue of whether an animal with some human genes deserves human rights.
Graybiel and colleagues found that the two-“letter” change affected a part of the mouse brain known as the striatum and related circuits called the cortico-basal ganglia. These areas are “known to be essential for motor and cognitive behaviors such as speech and language capabilities in humans,” explained a summary of the report issued by the journal.
Different portions of the striatum underlie two modes of learning considered crucial for speech and language, the researchers said. One is a conscious form of learning called declarative learning; the other, a non-conscious form called procedural learning.
In a series of maze experiments, mice with the “humanized” gene learned stimulus-response associations more rapidly than regular mice when both declarative and procedural forms of learning were engaged, the investigators reported.
Parts of the striatum associated with these two modes of learning were found to respond differently in the mice, as judged by levels of dopamine, a messenger chemical in the brain; by gene activity patterns; and by changeability in the strength of brain connections, known as synaptic plasticity. The findings suggest that the humanized gene differently influences how different regions of the striatum contribute to learning, said the researchers, who speculate that these effects may have contributed to the emergence of human language.
Source : www.world-science.net/