Reading focus
Syllabus: How Does the Nervous System Develop and Change?
Trace one developmental process from cellular conditions through connections to a possible functional consequence.
Why you’re reading it. This supplies the assembly framework that later examples of timing and plasticity need.
A question to consider. Choose a developing neural pathway and explain how the history of its cells and a signal from their surroundings could jointly affect its organization.
Why this reading
Explaining development requires more than saying that a brain grows. Stiles and Jernigan connect the production, movement, differentiation, and interaction of cells with the emergence of organized neural systems. Their overview makes genes, cellular conditions, and experience parts of a developmental process rather than competing explanations of the finished brain.
Before you read
A progenitor cell can divide to produce further cells. Migration is movement to a developing location; differentiation is the acquisition of more specialized properties. Axons carry signals toward other cells, and synapses are sites of communication. Gene expression produces functional RNA and, for protein-coding genes, proteins. Myelin insulates many axons and affects signal transmission. These processes unfold on different schedules and influence one another.
Read for
- Trace how a cell's developmental history and signals in its surroundings jointly affect its fate, movement, and connections.
- Distinguish cell production, synapse formation, elimination, and myelination. Ask why a decrease in one biological measure need not mean a loss of functioning.
- Follow the movement between animal experiments, human tissue and imaging. Identify where a developmental timetable is measured directly and where it is inferred.
Consider afterwards
- What observations could distinguish a change in the number of cells from a change in their connections?
- Why would development before ordinary sensory experience still involve interactions with an environment?
Editorial context
This 2010 review supplies a broad framework rather than a current catalogue of every molecular mechanism. Its account acknowledges uncertainty in human developmental timing and the use of evidence from other species. One introductory simplification needs care: gene expression does not always end in a protein, because some genes produce functional RNAs, as the NHGRI gene definition explains. Developmental regularity also does not supply an exact timetable for an individual child.