Observation of brain activity in the awake state is of great interest to scientists, particularly those studying progressive neurological disorders. Marmosets, small primates inhabiting South America, are very useful animal model for neuroscience research because of ease of handling with a small body size and high reproductive rate, but until recently it has proven difficult to image animal brains in awake state.Yoshifumi Matsumoto and co-workers at Kawasaki's Central Institute for Experimental Animals, in association with RIKEN in Japan, have demonstrated a novel imaging methodology suitable for carrying out neuronal imaging in awake marmosets. The team designed a novel device to fix a marmoset's body under two kinds of microscopes such as epifluorescence and 2-photon microscopy and systematic acclimation training to the device.
These methods minimized the motion artefact on the images, which can affect the clarity of macroscopic and cellular features. Subjected marmosets were mounted a cranial window, and areas of the brain sensitive to sensory stimulation were injected with a neuron-targeting virus carrying a Ca2+ indicator, which emits a fluorescent signal when neural activity occurs.
The team investigated the responses evoked by tactile stimulation to the foot, leg or tails under awake state and clearly indicated the differences of responsive area called "somatotopic map". They further uncovered significant differences between anesthetized and awake condition in the brain activity and the spatial pattern of sensory responses.
They succeeded in chronic imaging of brain activity in response to tactile stimulation over several weeks. Their breakthrough holds significant implication for studying of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease.
More information: Yoshiyuki Yamada et al. Chronic multiscale imaging of neuronal activity in the awake common marmoset, Scientific Reports (2016). DOI: 10.1038/srep35722
Journal reference: Scientific Reports
Provided by: Kawasaki City