In February 2023, researchers announced that they had managed to record brain activity in freely moving octopuses for the first time. The scientists implanted electrodes and a data logger into day octopuses (Octopus cyanea).
Brain activity patterns recorded in the research have not yet been tied to specific behaviors, but if the practice sticks, it may provide more information about the inner workings of the octopus, and specifically how their brain activity corresponds to their movements.
There are ethical questions here, as is the case whenever devices are inserted into animals that cannot express consent. But inserting devices into the animals for science is arguably better than frying and eating them (and persuasively so, in the opinion of this writer).