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Chaos analysis of EEG during isoflurane-induced loss of righting in rats.

MacIver MB, Bland BH - Front Syst Neurosci (2014)

Bottom Line: Chaotic attractor shape was far better at discerning between these awake-like signals, at loss of responses, than was FFT analysis.Attractors readily discriminated between natural sleep and isoflurane-induced "delta" activity.Chaotic attractor shapes changed gradually through the transition from awake to LORR, indicating that this was not an on/off like transition, but rather a point along a continuum of brain states.

View Article: PubMed Central - PubMed

Affiliation: Neuropharmacology Laboratory, Stanford University School of Medicine Stanford, CA, USA.

ABSTRACT
It has long been known that electroencephalogram (EEG) signals generate chaotic strange attractors and the shape of these attractors correlate with depth of anesthesia. We applied chaos analysis to frontal cortical and hippocampal micro-EEG signals from implanted microelectrodes (layer 4 and CA1, respectively). Rats were taken to and from loss of righting reflex (LORR) with isoflurane and behavioral measures were compared to attractor shape. Resting EEG signals at LORR differed markedly from awake signals, more similar to slow wave sleep signals, and easily discerned in raw recordings (high amplitude slow waves), and in fast Fourier transform analysis (FFT; increased delta power), in good agreement with previous studies. EEG activation stimulated by turning rats on their side, to test righting, produced signals quite similar to awake resting state EEG signals. That is, the high amplitude slow wave activity changed to low amplitude fast activity that lasted for several seconds, before returning to slow wave activity. This occurred regardless of whether the rat was able to right itself, or not. Testing paw pinch and tail clamp responses produced similar EEG activations, even from deep anesthesia when burst suppression dominated the spontaneous EEG. Chaotic attractor shape was far better at discerning between these awake-like signals, at loss of responses, than was FFT analysis. Comparisons are provided between FFT and chaos analysis of EEG during awake walking, slow wave sleep, and isoflurane-induced effects at several depths of anesthesia. Attractors readily discriminated between natural sleep and isoflurane-induced "delta" activity. Chaotic attractor shapes changed gradually through the transition from awake to LORR, indicating that this was not an on/off like transition, but rather a point along a continuum of brain states.

No MeSH data available.


Related in: MedlinePlus

Representative EEG recordings of frontal cortex (CORTEX) and hippocampal CA1 (HIPPOCAMPUS) signals for simultaneously recorded activity. During walking/exploring behavior, low amplitude fast activity is seen in cortex and a theta rhythm is generated in hippocampus. Chaotic attractor plots and FFT magnitude graphs, for these two records are shown below the recordings. Calibration bars = 200 μV and 500 ms. Note that the gain of the hippocampal signal was reduced by 1/3 for the analyses, to maintain scaling with respect to cortex.
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Figure 1: Representative EEG recordings of frontal cortex (CORTEX) and hippocampal CA1 (HIPPOCAMPUS) signals for simultaneously recorded activity. During walking/exploring behavior, low amplitude fast activity is seen in cortex and a theta rhythm is generated in hippocampus. Chaotic attractor plots and FFT magnitude graphs, for these two records are shown below the recordings. Calibration bars = 200 μV and 500 ms. Note that the gain of the hippocampal signal was reduced by 1/3 for the analyses, to maintain scaling with respect to cortex.

Mentions: For both the frontal cortex and hippocampal EEG signals there was a good correlation between ongoing behavior and signal appearance, in agreement with previous studies (Bland and Oddie, 2001). For example, during awake exploring, the frontal cortex generated low amplitude fast activity while the hippocampus produced a theta rhythm (Figure 1). Interestingly, in all thirteen rats, the chaotic attractor associated with this frontal fast activity was spherical, in good agreement with attractors seen in frontal cortical signals recorded from alert humans (Walling and Hicks, 2006). The hippocampal EEG attractor during both theta activity (Figure 1) and large amplitude irregular activity (LIA, not shown) was somewhat flattened compared to cortex. The FFT magnitude graphs associated with these signals showed the typical wideband activity in frontal cortex and a prominent theta peak (4–8 Hz) in the hippocampus (bottom graphs in Figure 1).


Chaos analysis of EEG during isoflurane-induced loss of righting in rats.

MacIver MB, Bland BH - Front Syst Neurosci (2014)

Representative EEG recordings of frontal cortex (CORTEX) and hippocampal CA1 (HIPPOCAMPUS) signals for simultaneously recorded activity. During walking/exploring behavior, low amplitude fast activity is seen in cortex and a theta rhythm is generated in hippocampus. Chaotic attractor plots and FFT magnitude graphs, for these two records are shown below the recordings. Calibration bars = 200 μV and 500 ms. Note that the gain of the hippocampal signal was reduced by 1/3 for the analyses, to maintain scaling with respect to cortex.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4199270&req=5

Figure 1: Representative EEG recordings of frontal cortex (CORTEX) and hippocampal CA1 (HIPPOCAMPUS) signals for simultaneously recorded activity. During walking/exploring behavior, low amplitude fast activity is seen in cortex and a theta rhythm is generated in hippocampus. Chaotic attractor plots and FFT magnitude graphs, for these two records are shown below the recordings. Calibration bars = 200 μV and 500 ms. Note that the gain of the hippocampal signal was reduced by 1/3 for the analyses, to maintain scaling with respect to cortex.
Mentions: For both the frontal cortex and hippocampal EEG signals there was a good correlation between ongoing behavior and signal appearance, in agreement with previous studies (Bland and Oddie, 2001). For example, during awake exploring, the frontal cortex generated low amplitude fast activity while the hippocampus produced a theta rhythm (Figure 1). Interestingly, in all thirteen rats, the chaotic attractor associated with this frontal fast activity was spherical, in good agreement with attractors seen in frontal cortical signals recorded from alert humans (Walling and Hicks, 2006). The hippocampal EEG attractor during both theta activity (Figure 1) and large amplitude irregular activity (LIA, not shown) was somewhat flattened compared to cortex. The FFT magnitude graphs associated with these signals showed the typical wideband activity in frontal cortex and a prominent theta peak (4–8 Hz) in the hippocampus (bottom graphs in Figure 1).

Bottom Line: Chaotic attractor shape was far better at discerning between these awake-like signals, at loss of responses, than was FFT analysis.Attractors readily discriminated between natural sleep and isoflurane-induced "delta" activity.Chaotic attractor shapes changed gradually through the transition from awake to LORR, indicating that this was not an on/off like transition, but rather a point along a continuum of brain states.

View Article: PubMed Central - PubMed

Affiliation: Neuropharmacology Laboratory, Stanford University School of Medicine Stanford, CA, USA.

ABSTRACT
It has long been known that electroencephalogram (EEG) signals generate chaotic strange attractors and the shape of these attractors correlate with depth of anesthesia. We applied chaos analysis to frontal cortical and hippocampal micro-EEG signals from implanted microelectrodes (layer 4 and CA1, respectively). Rats were taken to and from loss of righting reflex (LORR) with isoflurane and behavioral measures were compared to attractor shape. Resting EEG signals at LORR differed markedly from awake signals, more similar to slow wave sleep signals, and easily discerned in raw recordings (high amplitude slow waves), and in fast Fourier transform analysis (FFT; increased delta power), in good agreement with previous studies. EEG activation stimulated by turning rats on their side, to test righting, produced signals quite similar to awake resting state EEG signals. That is, the high amplitude slow wave activity changed to low amplitude fast activity that lasted for several seconds, before returning to slow wave activity. This occurred regardless of whether the rat was able to right itself, or not. Testing paw pinch and tail clamp responses produced similar EEG activations, even from deep anesthesia when burst suppression dominated the spontaneous EEG. Chaotic attractor shape was far better at discerning between these awake-like signals, at loss of responses, than was FFT analysis. Comparisons are provided between FFT and chaos analysis of EEG during awake walking, slow wave sleep, and isoflurane-induced effects at several depths of anesthesia. Attractors readily discriminated between natural sleep and isoflurane-induced "delta" activity. Chaotic attractor shapes changed gradually through the transition from awake to LORR, indicating that this was not an on/off like transition, but rather a point along a continuum of brain states.

No MeSH data available.


Related in: MedlinePlus