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Abstract

Electrical stimulation (ES) of the brain has been performed for over 100 years, and although some might say it is a crude technique for understanding the detailed mechanisms underlying
different neural computations, microstimulation has made significant contributions to our
knowledge in both basic and clinical research. Recently there has been resurgence in its use in
the context of electrotherapy and neural prostheses. For example, ES has made it possible to
at least partially restore hearing to deaf patients by delivering pulses via implanted electrodes
to different regions of the cochlea. Stimulation of the basal ganglia is remarkably effective in
restoring motor function to Parkinson’s patients, and microstimulation of the geniculostriate
visual pathway is regarded by some as a very promising (future) method for making the blind
see again.
Yet, the methodology still suffers from at least two fundamental problems; (a) we do not always
know exactly what is being stimulated when we pass currents through the tissue; and
(b) stimulation causes activation in a large number of areas even outside the stimulation site,
making it difficult to isolate and evaluate the behavioral effects of the stimulated area itself.
Microstimulation during fMRI (esfMRI) could provide a unique opportunity to visualize the networks
underlying electrostimulation-induced behaviors, to map neuromodulatory systems, or
to develop electrotherapy and neural prosthetic devices. Moreover esfMRI is an excellent tool
for the study of the effects of regional synaptic plasticity, e.g. LTP in hippocampus, on cortical
connectivity. Last but not least, esfMRI can offer important insights into the functional
neurovascular coupling. In my talk, I shall discuss findings from recent and on-going work on
signal propagation during electrical stimulation, as well as data related to effective connectivity.