Monday, March 8, 2010
Accessibility Level: Intermediate-Advanced
What changes in the brain as children mature? Are there patterns in the way the changes occur? Do some regions mature more quickly than others?
Last time, we talked about a paper by Schlaggar et al that examined brain differences between children and adults during a word generation task. A study published in Cerebral Cortex by Brown and colleagues extends that study, looking at changes in more detail.
The authors scanned children and adults aged 7-32 while performing a word generation task. Participants were given a word, either visually or aurally, and had to say a response based on an instruction ("opposite" for example). The authors then looked for the regions that differed in activation between the youngest (7-8) and oldest groups (23-32). For more details on this, and how they controlled for performance differences, see the entry on the Shlaggar et al paper.
The authors found many regions that either increased or decreased in activation between ages 8 and 23. That’s not surprising. It’s a lot of years and a lot of development. They did notice a few patterns though.
1. Posterior regions, generally involved in sensory processing, tended to decrease in activation with age. Frontal regions, generally involved in controlling and modifying the activity of the lower level regions, tended to increase with age.
2. The posterior and frontal regions differed not only in direction of change, but in speed of change. The frontal regions became more adult-like first, with the posterior regions maturing later.
The authors propose a model explaining the results. In this model, children first use lower level, sensory regions to perform a task. Because they are unskilled, their brains are less efficient and activate more. Then, as the children mature, frontal control regions develop and kick in, at which point they help fine-tune the posterior regions. The posterior sensory regions then become more efficient, and activation in these regions decreases.
This is an interesting model, and it will be interesting to see whether future developmental studies confirm it.
Brown, T. (2004). Developmental Changes in Human Cerebral Functional Organization for Word Generation Cerebral Cortex, 15 (3), 275-290 DOI: 10.1093/cercor/bhh129