Salon.com > Mice

Neuroscience’s future: Mice with human brain cells

Thu, 09 May 2013 16:25:00 +0000

Into brains of newborn mice, researchers implanted human “progenitor cells.” These mature into a type of brain cell called astrocytes (see below). They grew into human astrocytes, crowding out mouse astrocytes. The mouse brains became chimeras of human and mouse, with the workhorse mouse brain cells – neurons – nurtured by billions of human astrocytes.

Neuroscience is only beginning to discover what astrocytes do in brains. One job that is known is that they help neurons build connections (synapses) with other neurons. (Firing neurotransmitter molecules across synapses is how neurons communicate.) Human astrocytes are larger and more complex than those of other mammals. Humans’ unique brain capabilities may depend on this complexity.

Human astrocytes certainly inspired the mice. Their neurons did indeed build stronger synapses. (Perhaps this was because human astrocytes signal three times faster than mouse astrocytes do.) Mouse learning sharpened, too. On the first try, for instance, altered mice perceived the connection between a noise and an electric shock (a standard learning test in mouse research). Normal mice need a few repetitions to get the idea. Memories of the doctored mice were better too: they remembered mazes, object locations, and the shock lessons longer.

The reciprocal pulsing of billions of human and mouse brain cells inside a mouse skull is a little creepy. Imagine one of these hybrid mice exploring your living room. Would you feel like a Stone Age tribesman observing a toy robot? Does the thing think?

Neuroscience has no idea – none – of how a mind rises like a genie from the fleshy human brain. It supposes, however, that the magic trick’s spoiler will turn out to reside in physics and chemistry of brain cells. That is the discipline’s fundamental assumption. Nowhere else can the mystery be hiding.

But we have no idea what’s happening as billions of human astrocytes animate rodent awareness inside the tiny skulls. And “awareness” is one quality of “mind.” Do billions of human cells have no effect on mouse awareness? That seems unlikely.

Sorry, but your house is soaked in mouse urine

Sat, 03 Nov 2012 16:00:00 +0000

UNTIL A FEW WEEKS AGO I didn’t have the slightest interest in mouse urine. But after some study I’ve concluded that it is covertly running and ruining the world, strangling small children, and driving the profits of Big Pharma.

I came to know mouse urine, the molecules of which are known as MUPs (Major Urinary Proteins), and specifically as Mus m 1, because the molecules were stubbornly clinging to the studs of a cabin that I recently bought. Though I didn’t yet know the molecular names or weights of my MUPs, I knew they were there. Mice had burrowed through the cabin’s fiberglass insulation, and it looked like a splendid and huge pink ant farm.

Mice sort their food; there were larders of pasta, lentils, acorns, and blue poison crystals in my walls. Looking at the elaborate networks in the walls, it’s easy to imagine that my new-old (built in 1939) cabin’s erstwhile owner was a rustic prisoner who suffered respiratory ailments. The mice operated a space-age metropolitan economy in the walls around him, communicating through sophisticated molecular signaling.

Where does gluttony come from?

Fri, 21 Sep 2012 20:33:00 +0000

How much is too much chocolate? Desperately devouring 5 percent of one's body weight might sound extreme, but scientists tinkering with the brain chemistry of rodents have found it's certainly possible.

Scientists at the University of Michigan (U.M.) have identified how a brain region plays a role in our pursuit of sweet temptations. As they describe in the September 20 issue of Current Biology, a surge of chemical compounds resembling opium in this area can trigger the impulse to gorge on a treat without restraint.

The region in question is the neostriatum. In humans, this area is split into two parts, behind the eyes and below the folds of the cortex near the front of the head. It's just above the brain's well-studied reward circuitry, which includes the ventral striatum and nucleus accumbens. Traditionally, the neostriatum has been studied in movement and habitual motor behaviors. Although no previous research had found a clear causal link between the region and motivation to eat, some human studies with functional magnetic resonance imaging have suggested that the neostriatum is active when an overweight subject looks at food or an addict views a drug of choice.