Reading focus
Syllabus: How Does the Nervous System Develop and Change?
Build a short list of biological processes that could influence each structural imaging measure.
Why you’re reading it. This prepares the move from identified spines to aggregate human tissue measurements.
A question to consider. If a scan changed after training, which additional observation would help distinguish a synaptic account from a vascular or myelin-related account?
Why this reading
A scan can reveal a change without identifying what changed at the cellular level. Zatorre, Fields, and Johansen-Berg connect structural imaging findings with plausible biological processes and the comparisons needed to distinguish them. Their review explains why imaging and microscopic evidence are complementary rather than interchangeable.
Before you read
Structural MRI measures signals related to tissue properties. Image-processing methods estimate properties such as regional volume or thickness; diffusion measures are sensitive to water movement within tissue. A voxel is a small three-dimensional image element containing many biological components. Cross-sectional studies compare people at one time, while longitudinal studies follow change within people; neither design automatically identifies a cellular mechanism.
Read for
- Match each imaging measure to several biological changes that might influence it, including neuronal, glial, vascular, and myelin-related processes.
- Compare claims from expert–novice differences with claims from training studies that include baseline measures and comparison groups.
- Follow proposals for combining human imaging with animal experiments, histology, and other measurements. Ask what ambiguity each addition could reduce.
Consider afterwards
- A training group shows an increase in a regional MRI measure. Give two cellular explanations and a measurement that could help distinguish them.
- Why might a decrease, or no net change, in an imaging measure coexist with improved performance?
Editorial context
The review's value is its account of the inference from an aggregate signal to tissue mechanisms. An anatomical difference is not a direct count of new neurons or synapses, and a larger value is not inherently better. The examples describe methods and evidence available in 2012; they do not supply a timeless one-to-one dictionary from MRI signals to cell biology. Interpreting a training effect still requires attention to design, measurement, and its relation to behavior.