Zendegi

Nasim picked up her phone and found the menu option for ‘I’m not as sick as I thought, I’m coming in after all.’

Instead of the usual reassuring tone confirming success, there was a disapproving buzz and an alert popped up.

‘AcTrack plug-in disabled,’ it read. ‘Unable to complete this function.’

John Redland’s group had the twelfth floor of Building 46 all to themselves. From her corner of the lab, Nasim could peer across Vassar Street at the Stata Centre, an apparition out of a cartoon fairy-tale with its façade of tilted surfaces intersecting at vertiginous angles. As an architect’s sketch or computer model it must have looked enchanting, but in real life this gingerbread house had developed all manner of leaks, cracks and snow-traps.

Nasim turned back to her computer screen, where a tentative wiring map for part of the brain of a zebra finch was slowly taking form. The map wasn’t based on any individual bird, nor was it the product of any single technique. Some of the finches who’d contributed to it had been genetically engineered so that their neurons fluoresced under UV light, with each cell body glowing in a random colour that made it stand out clearly from its neighbours; that was the famous Lichtman-Livet-Sanes ‘Brainbow’ technique, developed over at Harvard. Others had had their brains bathed in cocktails of synthetic molecules – tagged with distinctive radioisotopes – that were taken up only by cells bearing receptors for particular neurotransmitters. A third cohort had been imaged after selective labelling, with monoclonal antibodies, of the cellular adhesion molecules that bound one neuron to another. And a fourth set of birds had been subject to no chemical interventions at all, and simply had their brains peeled by an ATLUM – an Automatic Tape-collecting Lathe Ultra Microtome – into fine slices which could then be imaged by electron microscopes and reassembled in three dimensions.

Altogether, nearly a thousand finches had lived and died to create the map that lay in front of her. Nasim hadn’t personally touched a feather on their heads, though she’d watched her colleagues operating, injecting and dissecting. None of the procedures carried out on the living birds should have left them in pain, and with decent-sized cages, plenty of food and access to mates, their lives probably hadn’t been much more stressful than they would have been in the wild. Nasim was never sure exactly where she’d draw the line, though. If it had been a thousand chimpanzees instead, for a project equally distant from any urgent human need, she didn’t know if she would have found a way to rationalise it, or if she would have walked away.

The map on her screen described the posterior descending pathway, or PDP, of the birds’ vocalisation system. The contributors had all been adult males, each with a fixed song of their own that was somewhat different from the others’. Redland had chosen the PDP for the sake of those two characteristics: it controlled a single, precisely repeatable behaviour in each individual – the bird’s fixed song – but there was also a known variation between the contributors thrown into the mix: no two birds sang quite the same song. Unless the team’s mapping techniques could cope robustly with that degree of difference, making sense of anything as complex as the brains of rats who’d learnt to run different mazes would be a hopeless task.

Nasim slipped on her headphones and linked the latest draft of the zebra finch map to a software syrinx, a biomechanical model of the bird’s vocal tract. She had plenty of fancier, more quantitative ways to gauge her progress, but listening to the song these virtual neurons created seemed an apt way to judge success. The songs of the individual live birds had been recorded, and Nasim had heard them all; she knew exactly what the fast, rhythmic chirping of an adult zebra finch should sound like. As she tapped the PLAY button on the touchscreen, her shoulders tensed in anticipation.

The song was disorganised, weak and confused, more like an infant finch’s exploratory babbling than anything a confident adult would produce. She glanced at a histogram showing a set of simulated electrical measurements; the statistics confirmed that they were, still, nothing like the signals measured by micro-electrodes in the brains of real adult birds.