Grace Lindsay

Explores the value of describing the machinery of neuroscience using the elegant language of mathematics and reveals in full the remarkable fruits of this endeavour.

How Physics, Engineering and Mathematics Have Shaped Our Understanding of the Brain

Models of the Mind

Eneko Uruñuela

Philip Warren Anderson, an American physicist who won a Nobel Prize working on such phenomena, wrote in a now-famous essay entitled 'More is different' that 'the behaviour of large and complex aggregates of elementary particles, it turns out, is not to be understood in terms of a simple extrapolation of the properties of a few particles'. That is, the collective action of many small particles - organised only through their local interactions can produce a function not directly possible in any of them alone. Physicists have formalised these interactions as equations and successfully used them to explain the behaviour of metals, gases and ice. In the late 1970s, a colleague of Anderson's, John J. Hopfield, saw in these in these mathematical models of magnetism a structure akin to that of the brain. Hopfield used this insight to bring under mathematical control a long-lasting mystery: the question of how neurons make and maintain memories.

Parkinson's disease is a disorder that impacts the firing of neurons in the basal ganglia. Located deep in the brain, the basal ganglia are composed of a variety of regions with elaborate Latin names. When the input to one region the striatum is perturbed by Parkinson's disease, it knocks the rest of the basal ganglia off balance. As a result of changes to the striatum, the subthalamic nucleus (another region of the basal ganglia) starts to fire more, which causes neurons in the globus pallidus external (yet another basal ganglia region) to fire. But those neurons send connections back to the subthalamic nucleus that prevent those neurons from firing more - which also, in turn, shuts down the globus pallidus external itself.

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