Limits...
Stimulus-evoked high frequency oscillations are present in neuronal networks on microelectrode arrays.

Hales CM, Zeller-Townson R, Newman JP, Shoemaker JT, Killian NJ, Potter SM - Front Neural Circuits (2012)

Bottom Line: As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away.Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation.Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Center for Neurodegenerative Diseases, Emory University, Atlanta GA, USA.

ABSTRACT
Pathological high frequency oscillations (250-600 Hz) are present in the brains of epileptic animals and humans. The etiology of these oscillations and how they contribute to the diseased state remains unclear. This work identifies the presence of microstimulation-evoked high frequency oscillations (250-400 Hz) in dissociated neuronal networks cultured on microelectrode arrays (MEAs). Oscillations are more apparent with higher stimulus voltages. As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away. Oscillations develop across four weeks in vitro. Oscillations still occur in the presence of tetrodotoxin and synaptic blockers, and they cause no apparent disruption in the ability of oscillation-presenting electrodes to elicit directly evoked action potentials (dAPs) or promote the spread of synaptic activity throughout the culture. Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation. Finally, carbenoxolone significantly reduces or eliminates the high frequency oscillations. Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies. This is the first demonstration of stimulus-evoked high frequency oscillations in dissociated cultures. Unlike current models that rely on complex in vivo recording conditions, this work presents a simple controllable model in neuronal cultures on MEAs to further investigate how the oscillations occur at the molecular level and how they may contribute to the pathophysiology of disease.

No MeSH data available.


Related in: MedlinePlus

Stimulus-evoked dAPs and synaptic activity with oscillations. (A) Detected spikes (.) over 20 trials (y-axis) 100 ms before and after a 0.5 V stimulus (large black arrowhead) only on that electrode. Raster plots are oriented to recording electrode location. Small arrowheads designate dAPs on five of the electrodes although they are present on most electrodes. (B) 100 ms post-stimulation of SALPA filtered traces on all 59 electrodes of a MEA. Synaptic activity evoked on multiple electrodes (small black arrowheads). Representative examples (A, cortical culture age six weeks; B, hippocampal culture age seven weeks) from n = 152 electrodes in six cultures (two cortical and four hippocampal). TTX was not present in the medium.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3351760&req=5

Figure 6: Stimulus-evoked dAPs and synaptic activity with oscillations. (A) Detected spikes (.) over 20 trials (y-axis) 100 ms before and after a 0.5 V stimulus (large black arrowhead) only on that electrode. Raster plots are oriented to recording electrode location. Small arrowheads designate dAPs on five of the electrodes although they are present on most electrodes. (B) 100 ms post-stimulation of SALPA filtered traces on all 59 electrodes of a MEA. Synaptic activity evoked on multiple electrodes (small black arrowheads). Representative examples (A, cortical culture age six weeks; B, hippocampal culture age seven weeks) from n = 152 electrodes in six cultures (two cortical and four hippocampal). TTX was not present in the medium.

Mentions: In addition to oscillations, typical stimulus-evoked activity on MEAs includes evoked spiking activity. Directly evoked action potentials (dAPs), which are detected even in the presence of synaptic blockers, occur first followed by a synaptic wave spreading across the dish (Wagenaar et al., 2006b; Bakkum et al., 2008). dAPs are spikes that occur in the first 0–20 ms after a stimulus and represent a direct depolarization of a cell process or soma by the stimulating electrode. dAPs are best demonstrated on spike raster plots containing multiple stimulus trials because their latency has little variation making them more visible as aligned spikes when plotted on the same graph (Figure 6A). Figure 6A shows that despite evoking a robust oscillation on one electrode, dAPs continued to occur throughout the culture, and this is similar to dAPs produced by electrodes that do not display the evoked oscillation (data not shown). Similarly, there was also no clear disruption of stimulus-evoked synaptic activity (Figure 6B). There were action potentials present on most electrodes within 100 ms of the stimulus.


Stimulus-evoked high frequency oscillations are present in neuronal networks on microelectrode arrays.

Hales CM, Zeller-Townson R, Newman JP, Shoemaker JT, Killian NJ, Potter SM - Front Neural Circuits (2012)

Stimulus-evoked dAPs and synaptic activity with oscillations. (A) Detected spikes (.) over 20 trials (y-axis) 100 ms before and after a 0.5 V stimulus (large black arrowhead) only on that electrode. Raster plots are oriented to recording electrode location. Small arrowheads designate dAPs on five of the electrodes although they are present on most electrodes. (B) 100 ms post-stimulation of SALPA filtered traces on all 59 electrodes of a MEA. Synaptic activity evoked on multiple electrodes (small black arrowheads). Representative examples (A, cortical culture age six weeks; B, hippocampal culture age seven weeks) from n = 152 electrodes in six cultures (two cortical and four hippocampal). TTX was not present in the medium.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351760&req=5

Figure 6: Stimulus-evoked dAPs and synaptic activity with oscillations. (A) Detected spikes (.) over 20 trials (y-axis) 100 ms before and after a 0.5 V stimulus (large black arrowhead) only on that electrode. Raster plots are oriented to recording electrode location. Small arrowheads designate dAPs on five of the electrodes although they are present on most electrodes. (B) 100 ms post-stimulation of SALPA filtered traces on all 59 electrodes of a MEA. Synaptic activity evoked on multiple electrodes (small black arrowheads). Representative examples (A, cortical culture age six weeks; B, hippocampal culture age seven weeks) from n = 152 electrodes in six cultures (two cortical and four hippocampal). TTX was not present in the medium.
Mentions: In addition to oscillations, typical stimulus-evoked activity on MEAs includes evoked spiking activity. Directly evoked action potentials (dAPs), which are detected even in the presence of synaptic blockers, occur first followed by a synaptic wave spreading across the dish (Wagenaar et al., 2006b; Bakkum et al., 2008). dAPs are spikes that occur in the first 0–20 ms after a stimulus and represent a direct depolarization of a cell process or soma by the stimulating electrode. dAPs are best demonstrated on spike raster plots containing multiple stimulus trials because their latency has little variation making them more visible as aligned spikes when plotted on the same graph (Figure 6A). Figure 6A shows that despite evoking a robust oscillation on one electrode, dAPs continued to occur throughout the culture, and this is similar to dAPs produced by electrodes that do not display the evoked oscillation (data not shown). Similarly, there was also no clear disruption of stimulus-evoked synaptic activity (Figure 6B). There were action potentials present on most electrodes within 100 ms of the stimulus.

Bottom Line: As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away.Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation.Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Center for Neurodegenerative Diseases, Emory University, Atlanta GA, USA.

ABSTRACT
Pathological high frequency oscillations (250-600 Hz) are present in the brains of epileptic animals and humans. The etiology of these oscillations and how they contribute to the diseased state remains unclear. This work identifies the presence of microstimulation-evoked high frequency oscillations (250-400 Hz) in dissociated neuronal networks cultured on microelectrode arrays (MEAs). Oscillations are more apparent with higher stimulus voltages. As with in vivo studies, activity is isolated to a single electrode, however, the MEA provides improved spatial resolution with no spread of the oscillation to adjacent electrodes 200 μm away. Oscillations develop across four weeks in vitro. Oscillations still occur in the presence of tetrodotoxin and synaptic blockers, and they cause no apparent disruption in the ability of oscillation-presenting electrodes to elicit directly evoked action potentials (dAPs) or promote the spread of synaptic activity throughout the culture. Chelating calcium with ethylene glycol tetraacetic acid (EGTA) causes a temporal prolongation of the oscillation. Finally, carbenoxolone significantly reduces or eliminates the high frequency oscillations. Gap junctions may play a significant role in maintaining the oscillation given the inhibitory effect of carbenoxolone, the propagating effect of reduced calcium conditions and the isolated nature of the activity as demonstrated in previous studies. This is the first demonstration of stimulus-evoked high frequency oscillations in dissociated cultures. Unlike current models that rely on complex in vivo recording conditions, this work presents a simple controllable model in neuronal cultures on MEAs to further investigate how the oscillations occur at the molecular level and how they may contribute to the pathophysiology of disease.

No MeSH data available.


Related in: MedlinePlus