Papers
Spatio-temporal electrical stimuli shape behavior of an embodied cortical network in a goal-directed learning task.
Bakkum, D. J., Chao, Z. C. (Co-First Authors), & Potter, S. M. (2008). Spatio-temporal electrical stimuli shape behavior of an embodied cortical network in a goal-directed learning task. Journal of Neural Engineering, 5, 310-323.
We developed an adaptive training algorithm, whereby an in vitro neocortical network learned to modulate its dynamics and achieve predetermined activity states within tens of minutes through the application of patterned training stimuli using a multi-electrode array. A priori knowledge of functional connectivity was not necessary. Instead, effective training sequences were continuously discovered and refined based on real-time feedback of performance. The short-term neural dynamics in response to training became engraved in the network, requiring progressively fewer training stimuli to achieve successful behavior in a movement task. After 2 h of training, plasticity remained significantly greater than the baseline for 80 min (p-value <0.01). Interestingly, a given sequence of effective training stimuli did not induce significant plasticity (p-value = 0.82) or desired behavior, when replayed to the network and no longer contingent on feedback. Our results encourage an in vivo investigation of how targeted multi-site artificial stimulation of the brain, contingent on the activity of the body or even of the brain itself could treat neurological disorders by gradually shaping functional connectivity.
- 58 Views
-
Like (5)
MEART: The Semi-living Artist.
Bakkum DJ, Gamblen PM, Ben-Ary G, Chao ZC and Potter SM (2007) MEART: The semi-living artist. Front. Neurorobot. (2007) 1:5. doi:10.3389/neuro.12.005.2007
Here, we and others describe an unusual neurorobotic project, a merging of art and science called MEART, the semi-living artist.We built a pneumatically actuated robotic arm to create drawings, as controlled by a living network of neurons from rat cortex grown on a multielectrode array (MEA). Such embodied cultured networks formed a real-time closed-loop system which could now behave and receive electrical stimulation as feedback on its behavior.We used MEART and simulated embodiments, or animats, to study the network mechanisms that produce adaptive, goal-directed behavior. This approach to neural interfacing will help instruct the design of other hybrid neuralrobotic systems we call hybrots. The interfacing technologies and algorithms developed have potential applications in responsive deep brain stimulation systems and for motor prosthetics using sensory components. In a broader context, MEART educates the public about neuroscience, neural interfaces, and robotics. It has paved the way for critical discussions on the future of bio-art and of biotechnology.
http://www.frontiersin.org/neurorobotics/paper/10.3389/neuro.12/005.20
An extremely rich repertoire of bursting patterns during the development of cortical cultures.
Wagenaar, D. A., Pine, J. and Potter, S. M. (2006). An extremely rich repertoire of bursting patterns during the development of cortical cultures. BMC Neuroscience 7:11.
Background: We have collected a comprehensive set of multi-unit data on dissociated cortical cultures. Previous studies of the development of the electrical activity of dissociated cultures of cortical neurons each focused on limited aspects of its dynamics, and were often based on small numbers of observed cultures. We followed 58 cultures of different densities—3000 to 50,000 neurons on areas of 30 to 75 mm2—growing on multi-electrode arrays (MEAs) during the first five weeks of their development. Results: Plating density had a profound effect on development. While the aggregate spike detection rate scaled linearly with density, as expected from the number of cells in proximity to electrodes, dense cultures started to exhibit bursting behavior earlier in development than sparser cultures. Analysis of responses to electrical stimulation suggests that axonal outgrowth likewise occurred faster in dense cultures. After two weeks, the network activity was dominated by population bursts in most cultures. In contrast to previous reports, development continued with changing burst patterns throughout the observation period. Burst patterns were extremely varied, with inter-burst intervals between 1 and 300 s, different amounts of temporal clustering of bursts, and different firing rate profiles during bursts. During certain stages of development bursts were organized into tight clusters with highly conserved internal structure.
- 18 Views
-
Like (1)
Vital imaging: Two photons are better than one
Potter, S. M. (1996) "Vital imaging: Two photons are better than one." Curr. Biol. 6: 1595-1598.
The recently developed technique of two-photon fluorescence microscopy causes much less photodamage than conventional confocal microscopy, expanding the possibilities for imaging living specimens.
- 77 Views
-
Like (4)
Intravital imaging of green fluorescent protein using 2-photon laser-scanning microscopy
Potter, S. M., Wang, C. M., Garrity, P. A. and Fraser, S. E. (1996) "Intravital imaging of green fluorescent protein using 2-photon laser-scanning microscopy." Gene 173: 25-31.
Imaging a fluorophore in a living tissue presents several unique problems. The fluorescence from the labeled cell@) may be weak, the labeled cells may be buried deep within tissue and the presence of a fluorophore may render the cells photo-sensitive. Two-photon laser-scanning microscopy (TPLSM) offers several advantages in meeting these challenges. We show that TPLSM provides greater sensitivity, better resolution and less photo-bleaching, as compared to confocal laser-scanning microscopy. The dramatically reduced photo-bleaching makes it possible to image cells continuously for long periods of time. Therefore, TPLSM allows a safer and higher-resolution means of imaging living cells labeled with a variety of fluorophores, including green fluorescent protein.
- 5 Views
-
Like
A new approach to neural cell culture for long-term studies
Potter, S.M., DeMarse, T. B. (2001) "A new approach to neural cell culture for long-term studies." J. Neurosci. Methods 110: 17-24.
We have developed a new method for culturing cells that maintains their health and sterility for many months. Using
conventional techniques, primary neuron cultures seldom survive more than 2 months. Increases in the osmotic strength of media due to evaporation are a large and underappreciated contributor to the gradual decline in the health of these cultures. Because of this and the ever-present likelihood of contamination by airborne pathogens, repeated or extended experiments on any given culture have until now been difficult, if not impossible. We surmounted survival problems by using culture dish lids that form a gas-tight seal, and incorporate a transparent hydrophobic membrane (fluorinated ethylene–propylene) that is selectively permeable to oxygen (O2) and carbon dioxide (CO2), and relatively impermeable to water vapor. This prevents contamination and greatly reduces evaporation, allowing the use of a non-humidified incubator. We have employed this technique to grow dissociated cortical cultures from rat embryos on multi-electrode arrays. After more than a year in culture, the neurons still exhibit robust spontaneous electrical activity. The combination of sealed culture dishes with extracellular multi-electrode recording and stimulation enables study of development, adaptation, and very long-term plasticity, across months, in cultured neuronal networks. Membrane-sealed dishes will also be useful for the culture of many other cell types susceptible to evaporation and
contamination
- 24 Views
-
Like (1)
Controlling bursting in cortical cultures with closed-loop multi-electrode stimulation
Wagenaar, D. A. Madhavan, R. Pine, J. and Potter, S. M. (2005) Controlling bursting in cortical cultures with closed-loop multi-electrode stimulation. J. Neuroscience 25: 680-688.
One of the major modes of activity of high-density cultures of dissociated neurons is globally synchronized bursting. Unlike in vivo, neuronal ensembles in culture maintain activity patterns dominated by global bursts for the lifetime of the culture (up to 2 years). We hypothesize that persistence of bursting is caused by a lack of input from other brain areas. To study this hypothesis, we grew small but dense monolayer cultures of cortical neurons and glia from rat embryos on multi-electrode arrays and used electrical stimulation to substitute for afferents. We quantified the burstiness of the firing of the cultures in spontaneous activity and during several stimulation protocols. Although slow stimulation through individual electrodes increased burstiness as a result of burst entrainment, rapid stimulation reduced burstiness. Distributing stimuli across several electrodes, as well as continuously fine-tuning stimulus strength with closed-loop feedback, greatly enhanced burst control. We conclude that externally applied electrical stimulation can substitute for natural inputs to cortical neuronal ensembles in transforming burst-dominated activity to dispersed spiking, more reminiscent of the awake cortex in vivo. This nonpharmacological method of controlling bursts will be a critical tool for exploring the information processing capacities of neuronal ensembles in vitro and has potential applications for the treatment of epilepsy.
Key words: bursting; dissociated culture; cortex; epilepsy; distributed stimulation; multi-electrode array; deep brain stimulation
- 8 Views
-
Like (1)
The Neurally Controlled Animat: Biological Brains Acting with Simulated Bodies
DeMarse, T. B., Wagenaar, D. A., Blau, A. W. and Potter, S. M. (2001). "The Neurally Controlled Animat: Biological Brains Acting with Simulated Bodies." Autonomous Robots 11: 305-310.
The brain is perhaps the most advanced and robust computation system known. We are creating a method to study how information is processed and encoded in living cultured neuronal networks by interfacing them to a computer-generated animal, the Neurally-Controlled Animat, within a virtual world. Cortical neurons from rats are dissociated and cultured on a surface containing a grid of electrodes (multi-electrode arrays, or MEAs) capable of both recording and stimulating neural activity. Distributed patterns of neural activity are used to control the behavior of the Animat in a simulated environment. The computer acts as its sensory system providing electrical feedback to the network about the Animat’smovement within its environment. Changes in the Animat’s behavior due to interaction with its surroundings are studied in concert with the biological processes (e.g., neural plasticity) that produced those changes, to understand how information is processed and encoded within a living neural network. Thus, we have created a hybrid real-time processing engine and control system that consists of living, electronic, and simulated components. Eventually this approach may be applied to controlling robotic devices, or lead to better real-time silicon-based information processing and control algorithms that are fault tolerant and can repair themselves.
Keywords: MEA, multi-electrode arrays, rat cortex, prosthetics, hybrid system, cybernetics
- 11 Views
-
Like
Persistent dynamic attractors in activity patterns of cultured neuronal networks
Wagenaar, D. A., Nadasdy, Z., & Potter, S. M. (2006). Persistent dynamic attractors in activity patterns of cultured neuronal networks. Physical Review E 73:51907.1-8.
Three remarkable features of the nervous system—complex spatiotemporal patterns, oscillations, and persistent activity—are fundamental to such diverse functions as stereotypical motor behavior, working memory, and awareness. Here we report that cultured cortical networks spontaneously generate a hierarchical structure of periodic activity with a strongly stereotyped population-wide spatiotemporal structure demonstrating all three fundamental properties in a recurring pattern. During these “superbursts,” the firing sequence of the culture periodically converges to a dynamic attractor orbit. Precursors of oscillations and persistent activity have previously been reported as intrinsic properties of the neurons. However, complex spatiotemporal patterns that are coordinated in a large population of neurons and persist over several hours—and thus are capable of representing and preserving information—cannot be explained by known oscillatory properties of isolated neurons. Instead, the complexity of the observed spatiotemporal patterns implies large-scale self-organization of neurons interacting in a precise temporal order even in vitro, in cultures usually considered to have random connectivity
- 8 Views
-
Like
Precisely timed spatiotemporal patterns of neural activity in dissociated cortical cultures
Rolston, J. D., Wagenaar, D. A., & Potter, S. M. (2007). Precisely timed spatiotemporal patterns of neural activity in dissociated cortical cultures. Neuroscience, 148, 294-303
Recurring patterns of neural activity, a potential substrate of both information transfer and transformation in cortical networks, have been observed in the intact brain and in brain slices. Do these patterns require the inherent cortical microcircuitry of such preparations or are they a general property of self-organizing neuronal networks? In networks
of dissociated cortical neurons from rats—which lack evidence of the intact brain’s intrinsic cortical architecture—we have observed a robust set of spontaneously repeating spatiotemporal patterns of neural activity, using a template matching algorithm that has been successful both in vivo and in brain slices. The observed patterns in cultured monolayer networks are stable over minutes of extracellular recording, occur throughout the culture’s development, and are temporally precise within milliseconds. The identification of these patterns in dissociated cultures opens a powerful methodological avenue for the study of such patterns, and their persistence despite the topological and morphological rearrangements of cellular dissociation is further evidence that precisely timed patterns are a universal emergent feature of self-organizing neuronal networks.
Key words: multielectrode array, activity pattern, neural network, spontaneous activity, attractor, synfire chain.
- 3 Views
-
Like (2)
Long-term activity-dependent plasticity of action potential propagation delay and amplitude in cortical networks.
Bakkum, D. J., Chao, Z. C., & Potter, S. M. (2008). Long-term activity-dependent plasticity of action potential propagation delay and amplitude in cortical networks. PLoS One, 3(5), e2088.
Background
The precise temporal control of neuronal action potentials is essential for regulating many brain functions. From the viewpoint of a neuron, the specific timings of afferent input from the action potentials of its synaptic partners determines whether or not and when that neuron will fire its own action potential. Tuning such input would provide a powerful mechanism to adjust neuron function and in turn, that of the brain. However, axonal plasticity of action potential timing is counter to conventional notions of stable propagation and to the dominant theories of activity-dependent plasticity focusing on synaptic efficacies.
Methodology/Principal Findings
Here we show the occurrence of activity-dependent plasticity of action potential propagation delays (up to 4 ms or 40% after minutes and 13 ms or 74% after hours) and amplitudes (up to 87%). We used a multi-electrode array to induce, detect, and track changes in propagation in multiple neurons while they adapted to different patterned stimuli in controlled neocortical networks in vitro. The changes did not occur when the same stimulation was repeated while blocking ionotropic gabaergic and glutamatergic receptors. Even though induction of changes in action potential timing and amplitude depended on synaptic transmission, the expression of these changes persisted in the presence of the synaptic receptor blockers.
Conclusions/Significance
We conclude that, along with changes in synaptic efficacy, propagation plasticity provides a cellular mechanism to tune neuronal network function in vitro and potentially learning and memory in the brain.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.000
Long-term activity-dependent plasticity of action potential propagation delay and amplitude in cortical networks.
Bakkum, D. J., Chao, Z. C., & Potter, S. M. (2008). Long-term activity-dependent plasticity of action potential propagation delay and amplitude in cortical networks. PLoS One, 3(5), e2088.
Background
The precise temporal control of neuronal action potentials is essential for regulating many brain functions. From the viewpoint of a neuron, the specific timings of afferent input from the action potentials of its synaptic partners determines whether or not and when that neuron will fire its own action potential. Tuning such input would provide a powerful mechanism to adjust neuron function and in turn, that of the brain. However, axonal plasticity of action potential timing is counter to conventional notions of stable propagation and to the dominant theories of activity-dependent plasticity focusing on synaptic efficacies.
Methodology/Principal Findings
Here we show the occurrence of activity-dependent plasticity of action potential propagation delays (up to 4 ms or 40% after minutes and 13 ms or 74% after hours) and amplitudes (up to 87%). We used a multi-electrode array to induce, detect, and track changes in propagation in multiple neurons while they adapted to different patterned stimuli in controlled neocortical networks in vitro. The changes did not occur when the same stimulation was repeated while blocking ionotropic gabaergic and glutamatergic receptors. Even though induction of changes in action potential timing and amplitude depended on synaptic transmission, the expression of these changes persisted in the presence of the synaptic receptor blockers.
Conclusions/Significance
We conclude that, along with changes in synaptic efficacy, propagation plasticity provides a cellular mechanism to tune neuronal network function in vitro and potentially learning and memory in the brain.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.000
Shaping Embodied Neural Networks for Adaptive Goal-directed Behavior. PLoS Computational Biology
Chao, Z. C., Bakkum, D. J., & Potter, S. M. (2008). Shaping Embodied Neural Networks for Adaptive Goal-directed Behavior. PLoS Computational Biology, 4(3): e1000042.
The acts of learning and memory are thought to emerge from the modifications of synaptic connections between neurons, as guided by sensory feedback during behavior. However, much is unknown about how such synaptic processes can sculpt and are sculpted by neuronal population dynamics and an interaction with the environment. Here, we embodied a simulated network, inspired by dissociated cortical neuronal cultures, with an artificial animal (an animat) through a sensory-motor loop consisting of structured stimuli, detailed activity metrics incorporating spatial information, and an adaptive training algorithm that takes advantage of spike timing dependent plasticity. By using our design, we demonstrated that the network was capable of learning associations between multiple sensory inputs and motor outputs, and the animat was able to adapt to a new sensory mapping to restore its goal behavior: move toward and stay within a user-defined area. We further showed that successful learning required proper selections of stimuli to encode sensory inputs and a variety of training stimuli with adaptive selection contingent on the animat's behavior. We also found that an individual network had the flexibility to achieve different multi-task goals, and the same goal behavior could be exhibited with different sets of network synaptic strengths. While lacking the characteristic layered structure of in vivo cortical tissue, the biologically inspired simulated networks could tune their activity in behaviorally relevant manners, demonstrating that leaky integrate-and-fire neural networks have an innate ability to process information. This closed-loop hybrid system is a useful tool to study the network properties intermediating synaptic plasticity and behavioral adaptation. The training algorithm provides a stepping stone towards designing future control systems, whether with artificial neural networks or biological animats themselves.
http://dx.plos.org/10.1371/journal.pcbi.1000042
High-speed CCD movie camera with random pixel selection, for neurobiology research
Potter, S. M., Mart, A. N. and Pine, J. (1997) High-speed CCD movie camera with random pixel selection, for neurobiology research. SPIE Proceedings 2869: 243-253.
We have designed and built a CCD camera capable of producing movies at over 1000 frames per second. For maximum frame rate, we have incorporated the ability to digitize only the pixels of interest, user-selectable from a custom LabView interface. With a resolution of 64x64 pixels, the system is intended to bridge the gap between fast, small photodiode arrays, and slow, high-resolution scientific CCD cameras. The system was designed for imaging neurons labeled with voltage-sensitive dyes, to allow the simultaneous recording of neural activity in a large number of neurons, or to probe the membrane voltage at many different points of a single neuron.
- 35 Views
-
Like
Add Comment