Figure 3.

Example of results suggestive of axonal collateral sprouting (adaptedfrom Skipper-Kallal et al., 2017b). Thirty-nine individuals with chronic left hemisphere stroke were tested using the Philadelphia Naming Test and underwent functional magnetic resonance imaging scanning during a delayed response naming task. The group was divided into those with lesions involving the mouth area of motor cortex in the left hemisphere and those with lesions not involving that region. Because the mouth areas of motor cortex in both hemispheres share axonal targets in the brainstem, the principles of axonal collateral sprouting predict the pattern of findings: (A) The mouth area of motor cortex in the right hemisphere was active only when the left mouth area of motor cortex was lesioned, and (B, C) the activity in the right mouth area of motor cortex related to naming ability only when left motor cortex was lesioned.