Communication with “a little smear of brain” The Parliamentary Information Office of the Parliamentary Yearbook report on fascinating research which involves cultivating, monitoring and stimulating disembodied brain cultures in the laboratory. Professor Steve Potter and his research team - the Potter Group - in the Laboratory for Neuroengineering at the Georgia Institute of Technology are developing new neuroscience technologies for studying learning and memory in vitro. The methodology for this research relies on using a cultured neuronal network; a cell culture of neurons that are cultivated, monitored and stimulated with an electrical input as a model to study the central nervous system. The methodology for this research relies on the “multi-electrode array” (MEA). This looks like an traditional laboratory petri culture dish which has been adapted through the addition of a patterned array of electrodes situated on the base of the dish, organised in a transparent substrate used for communication with neurons. The electrical contacts allow two-way communication between the research team and the neurons. Not only can the team listen in and monitor the electrical activity of the neural cells, they can stimulate them using electrical inputs. Mammalian brain cells - typically rat brain cells - are grown in culture on multi-electrode arrays (MEAs) to form a long-term two-way interface between the cultured networks and a computer. This type of methodology allows scientists to investigate neuronal activity in a much more controlled environment than would be possible in a live organism (the research is “in vitro” rather than “in vivo”). The neural cultures contain tens of thousands of cells. Graduate student, Michelle Kuykendal from the Potter Lab, refers to “a little smear of brain”. Professor Potter warns us not to underestimate the cultures. “There are some insects, simpler animals, that have approximately the number of cells we have in our culture dishes”, he said. The process begins with neural cells from rats’ brains being plated in the MEAs. At this point the neurons have no capability, having been reset during their extraction from pre-existing neural tissue. Time-lapse photography through a microscope is used to observe the neurons as they gradually develop tendrils called axons which branch out to connect with other neurons forming connections called synapses. Although the process looks ad hoc, the neurons release chemical signals to help guide their axon tendrils. As an increasing number of axons form synaptic connections, electrical activity across the entire culture becomes evident. Ben Whalley at Reading University conducts similar experiments using cultures grown from human stem cells. He notes that: “It’s like a great mesh, a spider’s web of interconnectivity.” He emphasizes that because it is not a static system it has to be monitored very rapidly. The synaptic development within these cultures is an important process which mirrors what happens in child development. The reconfiguration of the pattern of synapses is traditionally considered to lie at the heart of learning and memory, although this approach is now only one of a number of hypotheses. The benefit of this research is that the process of synaptic growth can be observed as it happens through a microscope and intervention is possible; Potter and Whalley communicate with neuronal cultures using electrical stimulation. “We can watch how specific electrical inputs cause certain connections to be strengthened”, said Professor Potter in an interview with the BBC. He described this is more detail: “We can see the activity flowing in the circuit, we can try to strengthen certain circuits, and to weaken other circuits by the electrical stimulation we give to them.” Cultured neuronal networks can be connected via a computer to a real or simulated robotic component to form what is known as a “hybrot”, a hybrid robot. A hybrot has a robotic body controlled by a cultured network of living brain cells. Both Potter and Whalley have been involved in work with neuron-controlled robotic devices. The Potter Group notably developed the first robotic device whose movements are controlled by a cultured network, capable of adaptive behaviour and learning. Neural activity recorded by the electrodes is transmitted across a two-way communication system and processed in Atlanta and Perth to control a robotic drawing arm. The robotic arm will draw on part of a canvas or choose how many coloured markers to use at one time and which colours to use, depending on neuroelectrical activity from the cultured neuronal network. In similar work, Whalley, working with cyberneticist Slawomir Nasuto at their Brain Embodiment Laboratory in Reading, connects cultures to robots and simulations of robots. The cultured neuronal network “learns” how to control the robot. In this case, it is a simple robot on wheels where the cultured neuronal network acts as a guidance control unit. The neuron control helps the robot to avoid walls. The spontaneous activity of the network directs the movements of the robot, which in turn feeds information about its environment back to the cells. The cells make new connections, making the system a learning machine. The researchers facilitate this “learning” process by adding various chemicals to the cell culture to strengthen some synaptic connections and weaken others. Obstacle avoidance shows clear improvement over time. The researchers at Reading are focusing on the practical issue of learning in cell cultures. The skills of their rat-robot hybrids are very basic. They would like to use more complicated robots which can manipulate objects. Professor Nasuto explained: “So we’ll provide the ability to grasp something, turn it round perhaps, bring it closer and at the same time have some sort of rudimentary visual system.” Their aim is to close the loop and have neural systems with feedbacks to enable the robot to compare the task it has planned with the task it has performed, a trial and error learning approach to reaching and grasping. The goal for Potter’s team is to create computing systems that perform more like the human brain. Central to their work is Potter’s belief that over time the team will be able to establish a living network system that learns like the human brain. This research was the subject of a BBC Radio 4’s Frontier programme, “Build Me a Brain” which was aired on 12th June. parliamentaryyearbook.co.uk Email: [email protected]
Posted on: Thu, 18 Jul 2013 10:48:23 +0000
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