Contributions and complexities from the use of in-vivo animal models to improve understanding of human neuroimaging signals.

Many of the major advances in our understanding of how functional brain imaging signals relate to neuronal activity over the previous two decades have arisen from physiological research studies involving experimental animal models. This approach has been successful partly because it provides opportunities to measure both the hemodynamic changes that underpin many human functional brain imaging techniques and the neuronal activity about which we wish to make inferences. Although research into the coupling of neuronal and hemodynamic responses using animal models has provided a general validation of the correspondence of neuroimaging signals to specific types of neuronal activity, it is also highlighting the key complexities and uncertainties in estimating neural signals from hemodynamic markers. This review will detail how research in animal models is contributing to our rapidly evolving understanding of what human neuroimaging techniques tell us about neuronal activity. It will highlight emerging issues in the interpretation of neuroimaging data that arise from in-vivo research studies, for example spatial and temporal constraints to neuroimaging signal interpretation, or the effects of disease and modulatory neurotransmitters upon neurovascular coupling. We will also give critical consideration to the limitations and possible complexities of translating data acquired in the typical animals models used in this area to the arena of human fMRI. These include the commonplace use of anaesthesia in animal research studies and the fact that many neuropsychological questions that are being actively explored in humans have limited homologues within current animal models for neuroimaging research. Finally we will highlighting approaches, both in experimental animals models (e.g. imaging in conscious, behaving animals) and human studies (e.g. combined fMRI-EEG), that mitigate against these challenges

BDNF: A Key Factor with Multipotent Impact on Brain Signalingand Synaptic Plasticity

Abstract Brain-derived neurotrophic factor (BDNF) isone of the most widely distributed and extensively studiedneurotrophins in the mammalian brain. Among its prominentfunctions, one can mention control of neuronal andglial development, neuroprotection, and modulation ofboth short- and long-lasting synaptic interactions, whichare critical for cognition and memory. A wide spectrum ofprocesses are controlled by BDNF, and the sometimescontradictory effects of its action can be explained basedon its specific pattern of synthesis, comprising severalintermediate biologically active isoforms that bind to differenttypes of receptor, triggering several signaling pathways.The functions of BDNF must be discussed in closerelation to the stage of brain development, the differentcellular components of nervous tissue, as well as themolecular mechanisms of signal transduction activatedunder physiological and pathological conditions. In thisreview, we briefly summarize the current state of knowledgeregarding the impact of BDNF on regulation ofneurophysiological processes. The importance of BDNFfor future studies aimed at disclosing mechanisms of activationof signaling pathways, neuro- and gliogenesis, aswell as synaptic plasticity is highlighted.Keywords BDNF Cognition Development Neurotrophin Synaptic plasticit