Professor Randy Bruno began his research career as a PhD student at the University of Pittsburgh School of Medicine, where he investigated the connectivity between the thalamus and different cell types in the cerebral cortex. The cerebral cortex, the largest part of the mammalian brain, is responsible for our higher functions such as thought, emotion, language and memory. The thalamus acts as the gateway, responsible for connecting all the senses to the cortex. As a postdoctoral researcher with Nobel Laureate Berk Sakmann, MD at the Max Planck Institute for Medical Research, Professor Bruno built on this work to measure a single synapse between a single neuron in the thalamus and a single neuron in the cortex. In doing so, he became the first person to measure the strength of an individual synaptic connection between two neurons in a living animal. This enabled the research team to gain a unique insight into how the thalamus codes information for transmission to the cortex and what circuit in the cortex allows it to decode that information.
In 2008, Professor Bruno joined Columbia University to commence his independent line of research. It was here that he discovered that the upper and lower halves of the cerebral cortex operate independently from each other, despite being tightly interconnected. More specifically, he demonstrated that the thalamus is providing a large amount of information to a second target in the cortex – the lower layers – in the same way as it has long been understood to activate the upper half of the cortex. According to Professor Bruno: “Duplicating information in two places suggests there might be two parts of the cortex. We then showed that you could turn off the upper part of the cortex and the deep part kept doing the same thing as if we had done nothing, which suggests that your cortex is really two different structures, even though we think of it as one structure.”
This key finding launched a second line of enquiry for the Bruno lab: what are the computational and behavioural contributions of these different parts and the different cell types in the cerebral cortex? What do the upper and lower parts of the cortex do to our behaviour? Professor Bruno says: “Interestingly, no matter what part of the cerebral cortex we look at, we see the same cell types in the same layered pattern with the same pattern of connections between the different layers, and even across different parts of your whole nervous system. It's like evolution has come up with one solution to many different problems, from vision to touch, from auditory perception to cognitive executive function. What we're trying to do now is understand how does that single stereotyped circuit support all of these different behaviours? What is that stereotypical architecture and how does it improve our behavioural repertoire?”
Having identified a large array of behaviours to investigate, this year, Professor Bruno has joined DPAG to tackle the question of computation of behaviour in each of the cerebral cortex layers. Professor Bruno says: “The mouse brain nominally has six cortical layers, the monkey brain has a few more, and the human has even more layers than the monkey. It looks like evolution keeps adding a new layer to the brain to enhance what we can do in terms of how powerful our thoughts can be and how sophisticated our behaviour can be. We’re going to push on this question of what is the computational contribution of each of these layers? How does it improve information processing? And then how is that information processing improving our ability to discriminate objects, whether they're tactile, visual or speech? How do we learn to recognise them?”
Professor Bruno’s research will ultimately interrogate similar questions that preoccupy DPAG’s neuroscientists, which offers an intriguing opportunity for cooperation and potential new partnerships. “It’s actually very general. It’s the same circuit across the brain. If I learn something about the part of the cortex that controls touch, this will be really useful for those looking at what the auditory or frontal cortex is doing. DPAG has a community that is very interested in how the cortex works, and, because we work on different cortical regions, there are a lot of interesting avenues for collaboration. We share an interest in the same general questions. How does the brain work? How does it solve the problems of our lives? And what is the nature of our existence? How does disease produce psychiatric and neurological disorders?”
“DPAG is a great base for my research program, and it’s also really exciting to be part of the greater neuroscience community in Oxford. I’m looking forward to scientific exchanges with researchers across the university.”