As demonstrated in this thesis, there are clear differences in resting-state brain activity between awake and anesthetized rats, and anesthesia can modulate brain activity even over the long-term. Although some anesthetics can be said to preserve brain activity such that it resembles the conscious state, each anesthetic agent has its unique modulatory effect on brain function and connectivity. In addition, as these effects are further modulated by anesthesia, specific long-term functional changes, the interpretations drawn from preclinical fMRI studies using anesthetized animals can be complicated and compromised. If anesthesia is used, one needs to be careful
invasive and potentially unpleasant procedures, it is important to consider the above-mentioned factors.
However, when studying the brain functional networks at the whole-brain level, with the aim of exploring cognition, awareness, memory and behavior etc., there are justifiable reasons for utilizing fully awake animals. Indeed, there has been a growing interest in conducting awake animal fMRI imaging. Even though there have been and still are certain limitations in awake animal imaging, which are mainly related to animal motion and stress, improved MRI sequences, post-processing techniques, and imaging and habituation applications have been developed and there are several active research projects aiming to reduce these obstacles. The usage of fully conscious animals opens many exciting possibilities for incorporation into a variety of different fMRI study schemes, such as in the assessment of animal behavior. By broadening fMRI study design possibilities, preclinical fMRI can hopefully even further increase its translational value in the future. It can also be predicted that multimodal neuroimaging techniques where fMRI imaging techniques are combined with various forms of stimulation (e.g.
deep brain electrical, optogenetic or transcranial magnetic stimulation) or other brain measuring techniques (e.g. calcium and ultrasound imaging, microelectrode arrays) will become increasingly popular in the near future.
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