In praise of tedious anatomy

Abstract

Functional neuroimaging is fundamentally a tool for mapping function to structure, and its success consequently requires neuroanatomical precision and accuracy. Here we review the various means by which functional activation can be localised to neuroanatomy and suggest that the gold standard should be localisation to the individual's or group's own anatomy through the use of neuroanatomical knowledge and atlases of neuroanatomy. While automated means of localisation may be useful, they cannot provide the necessary accuracy, given variability between individuals. We also suggest that the field of functional neuroimaging needs to converge on a common set of methods for reporting functional localisation including a common "standard" space and criteria for what constitutes sufficient evidence to report activation in terms of Brodmann's areas.

Figure 1

Examples of various levels of neuroanatomy. A). Gyral macroanatomy: Probability map of location of middle frontal gyrus and superior temporal gyrus (Shattuck, Hojatkashani, Mirza, Adisetiyo, Salamon, et al., 2006). B). Microanatomy: Brodmann’s (Brodmann, 1909) original map of cytoarchitecturally-distinguished cortical regions, with areas 44 and 45 outlined (Amunts, Schleicher, Burgel, Mohlberg, Uylings, et al., 1999). C). Microanatomy: Microscopic image of cytoarchitecture of Brodmann’s areas 44 and 45 (Amunts, Schleicher, Burgel, Mohlberg, Uylings, et al., 1999); these areas are distinguished by the lack of a clearly visible layer IV, with the arrow noting the point of transition between regions. D) Myeloarchitecture: High-resolution MRI imaging showing the stria of Gennari in the occipital cortex (Clare and Bridge, 2005). E) Connectional architecture: Probability map of the location of the corticospinal tract in 10 individuals, identified from myelin-stained postmortem histological sections (Burgel, Amunts, Hoemke, Mohlberg, Gilsbach, et al., 2006). F) Functional anatomy: Retinotopic visual areas identified using fMRI (Tootell, Mendola, Hadjikhani, Ledden, Liu, et al., 1997).

Figure 2

Example of simultaneous visualzation of group functional activation on population cortical surface (left panel) and averaged anatomy (right panel) using CARET software (Van Essen, 2005). The group statistical map was mapped to the population cortical surface using multifiducial mapping.