Applications of manganese‐enhanced magnetic resonance imaging (MEMRI) to image brain plasticity in song birds

Abstract

The song control system of song birds is an excellent model for studying brain plasticity and has thus far been extensively analyzed by histological and electrophysiological methods. However, these approaches do not provide a global view of the brain and/or do not allow repeated measures, which are necessary to establish correlations between alterations in neural substrate and behavior. Application of in vivo manganese-enhanced MRI enabled us for the first time to visualize the song control system repeatedly in the same bird, making it possible to quantify dynamically the volume changes in this circuit as a function of seasonal and hormonal influences. In this review, we introduce and explore the song control system of song birds as a natural model for brain plasticity to validate a new cutting edge technique, which we called 'repeated dynamic manganese enhanced MRI' or D-MEMRI. This technique is based on the use of implanted permanent cannulaefor accurate repeated manganese injections in a defined target area-and the subsequent MRI acquisition of the dynamics of the accumulation of manganese in projection brain targets. A compilation of the D-MEMRI data obtained thus far in this system demonstrates the usefulness of this new method for studying brain plasticity. In particular it is shown to be a perfect tool for long-term studies of morphological and functional responses of specific brain circuits to changes in endocrine conditions. The method was also successfully applied to obtain quantitative measures of changes in activity as a function of auditory stimuli in different neuronal populations of a same nucleus that project to different targets. D-MEMRI, combined with other MRI techniques, clearly harbors potential for unraveling seasonal, hormonal, pharmacological or even genetically driven changes in a neuronal circuit, by simultaneously measuring changes in morphology, activity and connectivity.

Manganese-Enhanced MRI of Brain Plasticity in Relation to Functional Recovery after Experimental Stroke

“…In conclusion, in line with studies on the bird song control system (Van der Linden et al, 2004) and mossy fiber sprouting in a rat epilepsy model (Nairismagi et al, 2006), our results show the unique potential of MEMRI for in vivo detection of structural plasticity in the brain. Our MEMRI data on spatiotemporal changes in neuroanatomical connectivity after stroke suggest that remodeling of intraand interhemispheric neuronal networks effectively contributes to poststroke functional recovery.…”

“…Mean lateral coordinates were 2.4±0.7, 2.2±0.6, 2.3 ± 0.6, and 2.6 ± 0.5 mm for Groups S-2w, S-4w, S-10w, and C-4w, respectively. As shown in our previous study, such small variation in lateral position of the injection site does not result in significant differences in the pattern of manganese enhancement in subcortical regions of the sensorimotor network (van der Zijden et al, 2007).…”

“…Thus, each container consisted of 10 to 15 slices covering the whole brain. Free-floating sections were processed for immunohistochemical detection of WGA-HRP using goat anti-WGA (Vector Laboratories, Burlingame, CA, USA) as a primary antibody and development using a diaminobenzidine peroxidase substrate kit (Vector Laboratories) as described before (van der Zijden et al, 2007).…”

“…We and others have recently shown that changes in neuronal connectivity after experimental stroke can be assessed in vivo with manganese-enhanced magnetic resonance imaging (MEMRI) (Allegrini and Wiessner, 2003;van der Zijden et al, 2007). Upon intracerebral injection, the paramagnetic ion manganese (Mn 2 + ) acts as a neuronal tracer, as it enters neurons through Ca 2 + channels and moves along axons (Pautler et al, 1998;Sloot and Gramsbergen, 1994).…”

Temperature dependence of 1H NMR chemical shifts and its influence on estimated metabolite concentrations

“…Recently, the use of alternative animal models for in vivo MR studies in experimental medicine or in comparative physiology have gained increasing interest, including those that use birds [25], lower vertebrates such as amphibians [26], fishes [27], and invertebrates [28]. The body temperatures of these organisms are usually far away from 37 °C or depend on their environmental temperature (ectothermic animals) that can range from very low temperatures around the freezing point of water [29] up to 40 °C and higher in insects [30].…”