ArticlesMagnetic resonance imaging of anatomic and vascular characteristics in a canine model of human aging
Section snippets
Subjects
MRI examination was performed on 18 beagle dogs from the animal facility at the Lovelace Respiratory Research Institute in Albuquerque, NM. The dogs consisted of 9 males and 9 females ranging in age from 4–15 years and weighing between 4 and 15 kg. All dogs had undergone cognitive testing during a 2-year period prior to the imaging study (14).
Cognitive testing
The test apparatus and cognitive tasks have been described in more detail elsewhere 14, 22. All cognitive testing took place in a modified Wisconsin
Results
Aged canines were impaired on a size-discrimination learning task but only a subset of old dogs performed poorly during object- approach learning and object-discrimination learning (14). Old dogs learned as well as younger dogs during reward approach learning, reversal learning and in the long-term retention test. The average test scores obtained from young (5 years and younger), middle aged (5–10 years) and old (10 years and older) dogs as a function of cognitive task are shown in Table 1.
Discussion
MRI was used to study changes in anatomical and vascular characteristics of the canine brain as a function of age. The quality of the anatomical images acquired by the 3D SPGR pulse sequence allowed us to clearly differentiate CSF from gray and white matter (Fig. 2). In old dogs, we observed pronounced ventricular enlargement and severe cortical atrophy, which is similar to age changes seen in humans. The size of the lateral ventricles increased slowly until the age of 10 years and progressed
Conclusion
We demonstrate that anatomical and vascular characteristics of canine brain can be simultaneously studied within a single MRI session. As in humans, ventricular enlargement was the most pronounced feature in aged dogs. The relationship between ventricle size and age was not linear, rather it was stable before age 10 and progressed very rapidly thereafter. The old dogs also exhibited deep gyri and widened sulci, indicating cortical atrophy. Vascular volume was not correlated with age however,
Acknowledgements
This work was supported in part by National Institute on Aging Grant No. AG05142 and D/AG12694–02S1 and a fellowship to M.-Y. Su from University of California at Irvine-Markey Program in Human Neurobiology. The authors thank Dr. Mary Berry and Marjorie A. Billau for their assistance in the animal study, and Benito Montoya for his assistance in image acquisition.
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