The evolution of brain wiring: Navigating to the neocortex

March 23, 2011, Cell Press

A new study is providing fascinating insight into how projections conveying sensory information in the brain are guided to their appropriate targets in different species. The research, published by Cell Press in the March 24 issue of the journal Neuron, reveals a surprising new evolutionary scenario that may help to explain how subtle changes in the migration of "guidepost" neurons underlie major differences in brain connectivity between mammals and nonmammalian vertebrates.

The (the "new" ) is a brain area that is unique to mammals and plays a central role in cognition, motor behavior, and sensory perception. A deeper brain region, called the thalamus, sends sensory information to the neocortex via a major highway called the internal capsule. As might be expected given the differences in brain anatomy, thalamic projections vary tremendously among , with paths in and birds taking a completely different route than that seen in mammals.

"What controls the differential path-finding of thalamic axons in mammals versus nonmammalian vertebrates and how these essential projections have evolved remains unknown," explains senior study author, Dr. Sonia Garel from Ecole Normale Supérieure in Paris. "We examined how thalamic axons, which constitute the main input to the neocortex, are directed internally to their evolutionarily novel target in mammals, while they follow an external path to other targets in reptiles and birds."

Using a series of comparative and functional studies, Dr. Garel and colleagues observed species-specific differences in the migration and positioning of well-characterized "corridor guidepost" neurons. The researchers went on to show that a protein called Slit2, previously implicated in cell migration and axon guidance, was critical for local positioning of mammalian guidepost cells and functioned as a kind of switch to reroute thalamic axons from the default external route to an internal path to the neocortex.

"Taken together, our results show that minor differences in the positioning of conserved guidepost , which is controlled by Slit2, plays an essential role in the species-specific pathfinding of thalamic , thereby providing a novel framework to understand the shaping and evolution of a novel and major brain projection," concludes Dr. Garel. "Furthermore, our study opens the possibility that changes in cell migration may more generally control the evolution of brain connectivity, particularly the formation of other mammalian-specific tracts. Since an increase in cell migration has participated in the morphogenesis of the neocortex itself, these novel findings reveal that cell migration can be considered as a general player in the evolutionary changes that led to the emergence of the mammalian brain."

Related Stories

Recommended for you

When the eyes move, the eardrums move, too

January 23, 2018
Simply moving the eyes triggers the eardrums to move too, says a new study by Duke University neuroscientists.

Cognitive training helps regain a younger-working brain

January 23, 2018
Relentless cognitive decline as we age is worrisome, and it is widely thought to be an unavoidable negative aspect of normal aging. Researchers at the Center for BrainHealth at The University of Texas at Dallas, however, ...

Lifting the veil on 'valence,' brain study reveals roots of desire, dislike

January 23, 2018
The amygdala is a tiny hub of emotions where in 2016 a team led by MIT neuroscientist Kay Tye found specific populations of neurons that assign good or bad feelings, or "valence," to experience. Learning to associate pleasure ...

Your brain responses to music reveal if you're a musician or not

January 23, 2018
How your brain responds to music listening can reveal whether you have received musical training, according to new Nordic research conducted in Finland (University of Jyväskylä and AMI Center) and Denmark (Aarhus University).

New neuron-like cells allow investigation into synthesis of vital cellular components

January 22, 2018
Neuron-like cells created from a readily available cell line have allowed researchers to investigate how the human brain makes a metabolic building block essential for the survival of all living organisms. A team led by researchers ...

Finding unravels nature of cognitive inflexibility in fragile X syndrome

January 22, 2018
Mice with the genetic defect that causes fragile X syndrome (FXS) learn and remember normally, but show an inability to learn new information that contradicts what they initially learned, shows a new study by a team of neuroscientists. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.