Scientists from the Max Planck Institute for Biological Cybernetics have now developed a novel multimodal methodology called “neural event-triggered functional magnetic resonance imaging” (NET-fMRI) and presented the very first results obtained using it in experiments with both anesthetized and awake, behaving monkeys. The new methodology uses multiple-contact electrodes in combination with functional magnetic resonance imaging (fMRI) of the entire brain to map widespread networks of neurons that are activated by local, structure-specific neural events.
The researchers used so-called neural event triggered functional magnetic resonance imaging (NET-fMRI) in both anesthetized and awake, behaving monkeys to characterize the brain areas that consistently increased or decreased their activity in relationship to a certain type of fast hippocampal oscillations known as ripples. Ripples occur primarily during deep sleep and can be measured with electrophysiological methods. Using intracranial recordings of field potentials, the scientists demonstrated that the short periods of aperiodic, recurrent ripples are closely associated with reproducible cortical activations that occur concurrently with extensive activity suppression in other brain structures.
Interestingly, structures were suppressed whose activities could, in principle, interfere with the hippocampal-cortical dialog. The suppression of activity in the thalamus, for instance, reduces signals related to sensory processing, while the suppression of the basal ganglia, the pontine region and the cerebellar cortex may reduce signals related to other memory systems, such as that underlying procedural learning, for example riding a bicycle.