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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

Development of stimulus-induced oscillations. (A) Average power spectrum at 11, 18, and 27 DIV with 0.5 V stimulus (large black arrowhead; four cultures) (two cortical and two hippocampal; n = 26 electrodes). (B) The number of active electrodes with the stimulus-evoked oscillation increases as cultures age. (*p < 0.001; n = 7 cultures; median total active electrodes per culture = 59). 1 μM TTX was present in the medium. Error bars: standard deviation.
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Figure 5: Development of stimulus-induced oscillations. (A) Average power spectrum at 11, 18, and 27 DIV with 0.5 V stimulus (large black arrowhead; four cultures) (two cortical and two hippocampal; n = 26 electrodes). (B) The number of active electrodes with the stimulus-evoked oscillation increases as cultures age. (*p < 0.001; n = 7 cultures; median total active electrodes per culture = 59). 1 μM TTX was present in the medium. Error bars: standard deviation.

Mentions: Cultures on MEAs mature as neurons progress from a dissociated state to highly connected neuronal networks with millions of synapses (Wagenaar et al., 2006b). If the stimulus-evoked high frequency oscillations were caused by single cells, then the activity may be more readily apparent very early in development. However, if the oscillations developed and strengthened over time, then this could suggest dependency on network connections. The power spectrum at 11 DIV showed limited development of the 250–400 Hz oscillations, however, high frequency oscillations are present by 18 DIV and persist through 27 DIV (Figure 5A, average power spectra from 26 electrodes, four cultures). The number of electrodes with this stimulus-evoked oscillation varied between cultures (n = 7) and increased from no clear oscillations at 1.5 weeks, to 8.71 ± 7.59% of electrodes with the oscillation at three weeks, and 31.25 ± 10.13% of electrodes with the oscillation at six weeks (Figure 5B). Results in Figure 5B were calculated based on increasing amplitudes, however, the power spectrum in Figure 5A suggests that subtle findings of the oscillation are even becoming apparent at Day 11.


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)

Development of stimulus-induced oscillations. (A) Average power spectrum at 11, 18, and 27 DIV with 0.5 V stimulus (large black arrowhead; four cultures) (two cortical and two hippocampal; n = 26 electrodes). (B) The number of active electrodes with the stimulus-evoked oscillation increases as cultures age. (*p < 0.001; n = 7 cultures; median total active electrodes per culture = 59). 1 μM TTX was present in the medium. Error bars: standard deviation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Development of stimulus-induced oscillations. (A) Average power spectrum at 11, 18, and 27 DIV with 0.5 V stimulus (large black arrowhead; four cultures) (two cortical and two hippocampal; n = 26 electrodes). (B) The number of active electrodes with the stimulus-evoked oscillation increases as cultures age. (*p < 0.001; n = 7 cultures; median total active electrodes per culture = 59). 1 μM TTX was present in the medium. Error bars: standard deviation.
Mentions: Cultures on MEAs mature as neurons progress from a dissociated state to highly connected neuronal networks with millions of synapses (Wagenaar et al., 2006b). If the stimulus-evoked high frequency oscillations were caused by single cells, then the activity may be more readily apparent very early in development. However, if the oscillations developed and strengthened over time, then this could suggest dependency on network connections. The power spectrum at 11 DIV showed limited development of the 250–400 Hz oscillations, however, high frequency oscillations are present by 18 DIV and persist through 27 DIV (Figure 5A, average power spectra from 26 electrodes, four cultures). The number of electrodes with this stimulus-evoked oscillation varied between cultures (n = 7) and increased from no clear oscillations at 1.5 weeks, to 8.71 ± 7.59% of electrodes with the oscillation at three weeks, and 31.25 ± 10.13% of electrodes with the oscillation at six weeks (Figure 5B). Results in Figure 5B were calculated based on increasing amplitudes, however, the power spectrum in Figure 5A suggests that subtle findings of the oscillation are even becoming apparent at Day 11.

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