In terms of anatomical resolution, we can dichotomize all imaging into techniques that have a macroscopic resolution versus those that have a microscopic resolution. Microscopic, by definition, means anything less than a millimeter, so you can consider submillimeter versus super-millimeter resolution.
Many imaging techniques can look at large swatches of the neocortex, parts of the basal ganglia, the whole hippocampus, the whole cerebellum. In some cases this is helpful and in some it is not, and we will be reviewing each modality according to the scheme.
Microscopic resolution is required if you really want to look at the basic neuronal populations of a circuit. It is worth emphasizing that the basic functional unit of the brain is not a Brodmann's area, it is not the cerebellum, it is not a single cell. It is really a cluster of neurons. If you want to understand the cerebellum, you need to look not just at the whole cerebellum, or have an electrode in a single neuron; you want to look at the different nuclei that make up the cerebellar circuit and the different nuclei that make up the basal ganglia, giving rise to movement disorders. The region of the brain that we are most interested in, the hippocampal formation—and I will come back to this again and again throughout my talk—itself is made up of different subregions. The issue of anatomical resolution can be simplified into thinking of microscopic versus macroscopic resolution.
What about the physiological source? Here, too, people have tried to force a dichotomy. The terms we often hear about are structural imaging versus functional imaging, and I list the prototypical modalities that most easily fit into these categories. I should quickly add that this dichotomy is forced, and it leads to confusion when one talks about functional versus structural imaging. Worse, it leads to misuses of the terms, and we are trying to dissuade people from using these terms.
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