Abstract
This beautifully illustrated atlas is the first to combine T1-weighted magnetic resonance (MR) images, histologic sections in color, and labeled topographic maps of the rhesus monkey brain in both horizontal and coronal orientation. There are five chapters in the atlas. Chapter 1 describes the methodologies that were used in preparing the atlas and provides an overview of its organization. Chapter 2 discusses terminology and methods used to classify brain regions by cytoarchitectonic and chemoarchitectonic features. The bulk of the atlas is devoted to Chapter 3 (horizontal hemi-brain sections) and Chapter 4 (coronal hemi-brain sections). [Note: In preparing this atlas, the left side of the brain was used for the horizontal sections and the right side for the coronal sections. However, the plates and figures are arranged so that they appear to be from the same side of the brain.] There are 47 horizontal and 76 coronal levels (taken at 1-mm intervals) included. In addition, Chapter 5 presents 33 selected cortical and subcortical regions in three different MRI planes (horizontal, coronal, and sagittal).
Two adjacent pages are devoted to each of the horizontal and coronal brain levels presented in Chapters 3 and 4. When the atlas is opened to lay flat, the even-numbered page on the left side has either four or five images—a computerized reconstruction of the brain in situ that includes a line showing the plane of orientation of the section, anMR image with a superimposed box outlining the location of the histologic images, and either two or three scanned low-power histologic sections in color. For the horizontal slices, these sections are stained with Nissl, parvalbumin, and SMI-32 (a neurofilament protein). For the coronal sections, parvalbumin- and SMI-32–stained images are shown. The images are all of high quality. A nice feature of this atlas—particularly for general pathologists—is that nonabbreviated labels have been applied to major neuroanatomic regions within the stained sections. This feature should prove to be particularly helpful to microscopists who may not have strong foundations in neuroanatomy.
For each plate of horizontal or coronal brain sections, the facing odd-numbered page includes a topographic figure of the same brain level as in the histologic sections. Within this topographic figure, neuroanatomic regions are labeled in greater detail. Abbreviations are used in this more detailed figure, with the majority of the abbreviations being listed just to the left of each topograph. Although the font used for this abbreviation list is smaller than I would have liked, a complete list of abbreviations in a much larger font size is present at the back of the atlas. A nice feature of the topographic section drawings in this atlas is that certain related neuroanatomic regions (e.g., caudate nucleus and putamen, internal and external portions of the globus pallidus) are color coordinated. The addition of color also improves the visual appeal of the topographic drawings. Also present on the pages bearing the horizontal or coronal topographic drawings are line drawings depicting both the medial and lateral surfaces of a hemi-brain. Within these line drawings, those sulci that are present within the brain slices from the same level are labeled, thus allowing for correlation between the location of sulci in the histologic sections and on the brain surface. In addition to the various topographic drawings, this same page includes an MR image (similar to the one on the facing page but smaller in size) that is located within a grid that also shows the interaural line. This figure assists the reader in determining section size at the relevant level. [Note: section levels in this atlas are based on the distance rostral and caudal to the interaural line or superior and inferior to “ear bar zero” (a horizontal plane passing through the interaural line and the infraorbital ridge). Distances from Bregma (the point of juncture of the coronal and sagittal sutures of the skull) are not used in this atlas.]
Although the atlas under review will stand on its own merits, it is appropriate to draw some comparisons between this new atlas and the current “standard” rhesus monkey brain atlas by Paxinos et al. (Paxinos, G., Huang, X.-F., and Toga, A.W. The Rhesus Monkey Brain in Stereotaxic Coordinates, Academic Press, Orlando, Florida, 2000). Many pathologists and neuroscientists will already own or have access to the latter atlas, so the question may arise as to which of the two atlases might be preferable and/or whether the reader should purchase both. The advantages of the atlas by Saleem and Logothetis include the inclusion of MR images in various orientations (important for investigators using MR or positron emission tomography imaging technologies) and the color plates of histologic stains with full-text labeling of major neuroanatomic sites. The presentation of images in both horizontal and coronal planes will also be of importance to many investigators. In the Paxinos et al. atlas, only coronal sections (with correlative coronal topographic drawings) are presented. On the other hand there are twice as many coronal levels in the Paxinos atlas (151 coronal sections versus 76 in the atlas under review), with the inter-section distance being 400 μm rather than 1 mm. While the histologic images in the Paxinos atlas are monochrome, these images are much larger in size than those in the new atlas (as are the corresponding labeled topographic drawings). Distances from Bregma (as well as from the interaural line) are also included in the Paxinos et al. atlas. Finally, the Paxinos et al. atlas presents greater neuroanatomic detail within a number of brain regions (e.g., within the hypothalamus, brain stem and cerebellum [as discussed in the following paragraph]). In summary, the two brain atlases are quite different and will fulfill different needs. I feel that they complement each other well.
My only disappointment with this new atlas by Saleem and Logothetis is the dearth of labeling of neuroanatomic regions within the caudal brain stem (i.e., caudal midbrain, pons, medulla oblongata) and cerebellum. This deficiency is particularly striking within brain stem regions caudal to the level of the superior colliculus. For example, the cerebellar cortex is merely labeled as “cerebellum.” No labels are present for many important structures such as the deep cerebellar nuclei, vestibular nuclei, olivary nuclei, facial and cochlear nuclei, etc. This limits the value of this atlas to pathologists as a sole source of monkey brain anatomy. Although most pathologists may not require the level of neuroanatomic detail present in the Paxinos et al. rhesus monkey brain atlas, some brain stem nuclei are quite important from both neurochemical and neuropathologic standpoints (e.g., the various raphe nuclei, locus ceruleus, etc.).
In summary, the new rhesus monkey brain atlas by Saleem and Logothetis is beautifully illustrated and should prove to be quite useful to pathologists and neuroscientists, particularly those using MR imaging. However, for neuroanatomic detail within caudal levels of the brain stem and cerebellum, the atlas by Paxinos et al. will still be essential. Laboratories performing studies on macaques should undoubtedly have both of these fine atlases on hand for reference.