Presented for the first time with a human's internal organs, an alien neuroscientist might not grasp right away that the brain is the seat of human consciousness.
Outwardly, a brain looks somewhat like other large, blobby organs. And unlike a computer's central processing unit, the brain's ability to calculate, imagine, and perform other tasks resides not in a few thousand neatly arranged and simply connected components but in 1011 interconnected brain cells that come in just two broad types—neurons and glial cells.
As for determining how the brain works, the alien neuroscientist would probably do what human biologists do: try to find out how the brain cells' operation, organization, and connectivity manifest consciousness.
The tools and techniques available to alien neuroscientists are unknown. Human neuroscientists, however, are using an increasingly sophisticated set of tools, some of which physicists devised. Physicists are also engaged in interpreting data gathered from brains and neurons.
A recent paper in Nature exemplifies both trends. Michael Long and Michale Fee of MIT and Dezhe Jin of the Pennsylvania State University built and deployed tiny sensors in the heads of male zebra finches that recorded neural activity as the birds sang.
Long, Fee, and Jin started their paper by noting that complex behavior is possible because of the brain's ability to step through a sequence of neural states. A male zebra finch's song, being made up of recognizable repeated motifs, is one such complex behavior and is among the easiest to study.
Neuroscientists already know which parts of the bird's brain control song. The question that the three scientists set out to answer was how the neurons that control singing fire in the correct sequence.
Two models have been proposed to explain the sequencing. In the synaptic chain model, the individual neurons responsible for each note (not quite the right word, but it will do) are linked to each other head to toe—or dendrite to axon—in a chain.
In the ramp-to-threshold model, the neurons lie next to each other in the same sequence but aren't in direct, synaptic contact with each other. Rather, they fire in sequence when a wave of excitatory or inhibitory stimulus washes over them one after the other.
The ramp-to-threshold model's wave would show up as a change in membrane potential from one neuron to the next. The sensors implanted in the finches didn't record such a change—quite the opposite, in fact. The membrane potentials of the neurons remained constant when the finches sang their strings of notes, supporting the synaptic chain model.
Biophysical ethics
For the experiment to succeed, the finches had to be happy enough to sing. Evidently, the implantation and operation of the recording devices was not too traumatic for them. The finches were, however, killed after recordings were made. To be sure they had recorded signals from the correct neurons, the experimenters removed, sliced, and wired up the finches' brains.
I have no reason to suspect that the finches suffered during the experiment. The paper's methods summary includes the line, "All animal procedures were reviewed and approved by the MIT committee on animal care."
However, despite the line's reassuring tone, I was unable to find out what criteria the committee applies to evaluate experiments on live animals. MIT's division of comparative medicine, which administers the criteria, doesn't make them publicly available on its website.
I was also unable to find any statement about the ethical treatment of animals issued by two professional organizations that biophysicists in the US belong to: the Biophysical Society and the American Physical Society's division of biological physics. Given that US labs and universities, such as MIT, have committees that oversee animal welfare, it's not necessary, for the animals' sake, that the two societies have any policy on experiments on animals.
It might, however, be desirable for the humans' sake. If I were a biophysicist like Long, Fee, and Jin, trying to figure out how brains work (or don't work in the case of brain disorders), I'd like to belong to an organization that officially values the welfare of zebra finches and other lab animals.
