Functional magnetic resonance imaging (fMRI) in animal models provides an opportunity for more extensive investigation of drug effects, manipulations, and underlying physiological mechanisms than is possible in humans.

Activation of the primary (SI) and secondary (SII) somatosensory cortex of an isoflurane anesthetised rat following electrical forepaw stimulation.

The Theta Rhythm

Coherent oscillatory activity of neuronal populations plays a major role in cerebral functions across species. By examining oscillatory systems over multiple frequency bands, it will be possible to bridge the gap between the activity of single neurons and that of neural assemblies aiding in the task of truly elucidating functional brain mechanisms. The theta rhythm of the rat is a 4-10 Hz oscillatory electrical activity found in the hippocampus and related structures and is suggested to participate in sensorimotor integration, spatial navigation, and memory. Using functional magnetic resonance imaging (fMRI) we will be able to study the spatial extent of the brain associated with the theta state. Simultaneous EEG-fMRI combines the superior spatial resolution of the blood-oxygenation-level dependent (BOLD) signal with the high temporal resolution of EEG.

Brain activation associated with an electrically induced theta oscillation. Recordings were made simultaneously with electroencephalography at 9.4T.

Resting State fMRI

fMRI studies are now examining the changes in brain activity during rest. Using resting state analysis it is possible to determine functionally correlated and connected brain regions. As well, some networks only activated during this period. It has been also shown that different pathologies, such as epilepsy, schizophrenia, and Alzheimer’s disease may adversely affect these resting state networks and therefore, may be used as a diagnostic tool. Previously, most studies define regions of interest in an a priori fashion to determine these functional networks. An emerging trend is the use of independent component analysis (ICA) which allows the blind separation of underlying spatial and temporal signals without the use of a model.

A spatially and temporally  distinct hippocampal network of the  rat brain during rest and its associated time course.