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In activo

In activo is a neologism (made-up word) used to distinguish a scientific result obtained from the brain in an awake behaving state, versus the broader in vivo term which specifies an intact living organism, but critically does not distinguish between the anesthetized and awake, behaving states.

Many neuroscience results obtained in vivo have failed to generalize to the in activo state, so it is critical to make this distinction in understanding the relevance of a given finding to the actual neural mechanisms driving awake, behaving cognitive function, which is what we ultimately care about here.

Furthermore, many studies are done in the in vitro preparation, using slices or cultures of neurons extracted from the brain and analyzed in a dish under a microscope, which enables much more detailed and sophisticated analyses of individual neural functions to be studied. However, these conditions are even further removed from the in activo state, and thus are even more susceptible to a failure to generalize to that state.

There are a large number of neuromodulatory and systems-level connectivity differences between an awake, behaving brain and one that is under a state of anaesthesia. For example, in the anesthetized brain, neural activity in the neocortex is generally much more synchronous and there is typcically less overall activity. This has implications for the mechanisms of neural adaptation for example, because it turns out that ongoing neural activity in the awake, behaving state results in persistent synaptic depression, which otherwise has been widely discussed as an important functional property of different neuron types (Abbott et al., 1997). See the adaptation page and Borst (2010) in particular for details.

In general, as Borst (2010) notes, the behavior of the awake brain tends to be more linear overall, with less short-term plasticity and less bursting. This is the behavior that we capture in our Axon neurons, which we verify through extensive larger-scale simulations produce the best overall computational results.

List of phenomena that do not generalize to the in activo state