Tressan's Brain

Today, at exactly 4 weeks old, Tressan has a new trick: he can track movement with his eyes. It might seem like a basic thing, but I feel like I can interact with him more deeply than I could yesterday. It turns out that at 4 weeks, visual cortex begins to compete with more ancient, subcortical visual structures to control gaze (2). Right on schedule, T!

I've been watching Tressan's brain since he was 12 weeks gestational age. In that ultrasound, where we could see his several inch body kicking vigorously, his brain didn't even fill up his apricot-sized skull. By 24 weeks gestation, his brain looked roughly like the macaque and human brains that I have studied, at least at an ultrastructural level. But those grainy black and white images were deceptive- his brain was just starting to develop into a functional system.

Now we watch Tressan face to face, kissing his little head and gently touching his fontanelle, that precarious allowance for a larger brain at birth. Underneath, things continue at a rapid pace: between birth and age 2 months, Tressan will double the number of synapses in his cortex (1). This comes out to an addition of something like 1.8 million new synapses every second (2)!

As a scientist, I am amazed by the rapidity (and nearly fail-safe-ness) of this developmental period. As Tressan's mother, I think more about what this means for his mind. What might it be like to be him? How can we possibly know? No one remembers what it is like to be a newborn.  Yet I will hazard a couple of guesses.

The precipitous rate at which synapses are added during the first months (indeed, the first year) combined with Tressan's relative lack of sensory experience before birth might make sensation (and emotion and volition?) so changeable as to be unrecognizable from one time to the next. In other words, maybe for Tressan the same painting looks different, the same flower smells different, the same voice sounds different today than it did last week.  Some perceptions are remembered of course- my smell, for instance- but even there, we cannot know whether that smell is the same for Tressan from day to day, or merely familiar enough to be recognized. 

He has so little context that dividing experiences into different sensory modes might not make any sense at all. How do you know if two things smell the same or different if you have never smelled anything? In a study where infants were presented with a visual stimulus, many sensory areas beyond visual cortex "lit up" with activity.  Fernyhough suggests that this might mean infants experience the world in the way synesthetes do: tasting music, smelling voices, hearing colors (2). 

Of course, these are just guesses. It's fun to try to imagine what it is like to be Baby T, and I hope it makes me a little more sympathetic. When he is fussing and there is no discernible reason for it, I try to remember how disordered and dynamic and vibrant the world probably seems to him. It's easy to imagine that something pleasurable could easily turn the corner into painful or at least unpleasant, just by being a bit too intense, or not intense enough.  We try not to overstimulate his little mind, but it's hard to find that sweet spot sometimes. 

1. Huttenlocher, PR.  Neuropsychologia 28(6):517-527 (1990)
2. Fernyhough, C. A Thousand Days of Wonder (2008)

 

Tressan looks suspiciously up at us...