Scientists have long known that brains need neural activity to mature and that sensory input is most important during a specific window of time called the 'critical period' when the brain is primed for aggressive learning. Vision, hearing and touch all develop during such critical periods, while other senses, such as the olfactory system, maintain lifelong plasticity.

A new study focusing on the molecular roots of plasticity has found that visual stimulus turns up the expression of some genes and turns down the expression of others, somewhat like a conductor cueing the members of an orchestra. The study also found that during different stages of life in rodents, distinct sets of genes spring into action in response to visual input. These gene sets may work in concert to allow synapses and neural circuits to respond to visual activity and shape the brain.

The investigators' identification of many distinct sets of activity-dependent genes follows a shift in neuroscience research toward a more holistic view of the role of genes in neural development and plasticity.

First author Marta Majdan and co-author Carla Shatz, and Nathan Marsh Pusey, studied rodents during the critical period in which visual input stimulates aggressive plasticity, shaping the mesh of neural connections in the cortex and tuning the strengths of messages relayed by synapses. In mice, this period begins shortly after they open their eyes and begin to see. Previous research had determined that visual activity changes the level of expression of, or regulates, individual genes.

The researchers found other sets of genes superimposed on this core pathway, but these sets are turned on and off by vision at specific ages before, during and after the critical period and into adulthood.

"This suggests that sensory experience regulates different genes in your brain depending on your age and past experience," said Shatz. "Thus, nurture, our experience of the world via our senses, acts through nature, sets of genes, to alter brain circuits."

This study helps explain why it is that children learn so quickly and easily, and it lends credence to the idea that, in adults, mental activity leads to mental agility.

"It is amazing that, even in our oldest mice we saw genes regulated by vision. Genes in the brain change with experience at every age, forming a basis for our ability to learn and remember even in adulthood," said Shatz. >from *Research Shows How Visual Stimulation Turns Up Genes to Shape the Brain* . May 1, 2006

related context
> brain is a dynamic network. 'brain is not a huge fixed network, as had been previously thought, but a dynamic, changing network that adapts continuously.' october 15, 2003
> synaptic plasticity: how experiences rewire the brain. 'rewiring of the brain involves the formation and elimination of synapses, the connections between neurons. the traditional view of neural development has been that when animals mature, the formation of synapses ceases.' january 23, 2003
> neurogenesis observed in human adult brain. 'new cells in the adult brain grow and mature over time. this landmark study upset long-held dogma that stated we are born with a full supply of brain cells that steadily diminish throughout our lives.' march 6, 2002
> how genes affect brain structure. 'brain mapping researchers have created the first images to show how an individual's genes influence their brain structure and intelligence. the amount of gray matter in frontal brain regions was strongly inherited, and also predicted an individual's iq score.' november 4, 2001

imago
> gen expandable orchestra

sonic flow
> activity-dependent genes [stream]
activity-dependent genes [download]