Limits...
High-frequency Broadband Modulations of Electroencephalographic Spectra.

Onton J, Makeig S - Front Hum Neurosci (2009)

Bottom Line: High-frequency cortical potentials in electroencephalographic (EEG) scalp recordings have low amplitudes and may be confounded with scalp muscle activities.Multi-dimensional scaling revealed significant but spatially complex relationships between mean broadband brain IM effects and the valence of the imagined emotions.Thus, contrary to prevalent assumption, unitary modes of spectral modulation of frequencies encompassing the beta, gamma, and high gamma frequency ranges can be isolated from scalp-recorded EEG data and may be differentially associated with brain sources and cognitive activities.

View Article: PubMed Central - PubMed

Affiliation: Institute for Neural Computation, University of California San Diego, La Jolla, CA, USA.

ABSTRACT
High-frequency cortical potentials in electroencephalographic (EEG) scalp recordings have low amplitudes and may be confounded with scalp muscle activities. EEG data from an eyes-closed emotion imagination task were linearly decomposed using independent component analysis (ICA) into maximally independent component (IC) processes. Joint decomposition of IC log spectrograms into source- and frequency-independent modulator (IM) processes revealed three distinct classes of IMs that separately modulated broadband high-frequency ( approximately 15-200 Hz) power of brain, scalp muscle, and likely ocular motor IC processes. Multi-dimensional scaling revealed significant but spatially complex relationships between mean broadband brain IM effects and the valence of the imagined emotions. Thus, contrary to prevalent assumption, unitary modes of spectral modulation of frequencies encompassing the beta, gamma, and high gamma frequency ranges can be isolated from scalp-recorded EEG data and may be differentially associated with brain sources and cognitive activities.

No MeSH data available.


Broadband independent modulators of brain and scalp muscle components. Brain and scalp muscle ICs are separately modulated by IMs with similar broadband high-frequency templates (upper rows). The left column shows broadband templates for each IC category (black trace is the mean). The right three columns show equivalent-dipole locations of the affected ICs. A distinct cluster of putative ocular motor IMs, shown in the bottom row, have a peak effect near 50 Hz on ICs many of whose bilaterally symmetric equivalent-dipole models (bottom right panels) are located near the eyes. (ICs whose best-fit equivalent-dipole model comprised two bilaterally symmetrical dipoles are represented with a dotted yellow line connecting the dipole pair). Dipole locations for scalp muscle ICs are outside the brain volume (middle row). Green lines in dipole plots connect ICs co-modulated by the same IM and the colors of the dipole spheres (yellow to red) indicate the relative strength of modulation (yellow = 50%, to red = 100% of maximal). Purple spheres indicate individually modulated ICs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2806183&req=5

Figure 4: Broadband independent modulators of brain and scalp muscle components. Brain and scalp muscle ICs are separately modulated by IMs with similar broadband high-frequency templates (upper rows). The left column shows broadband templates for each IC category (black trace is the mean). The right three columns show equivalent-dipole locations of the affected ICs. A distinct cluster of putative ocular motor IMs, shown in the bottom row, have a peak effect near 50 Hz on ICs many of whose bilaterally symmetric equivalent-dipole models (bottom right panels) are located near the eyes. (ICs whose best-fit equivalent-dipole model comprised two bilaterally symmetrical dipoles are represented with a dotted yellow line connecting the dipole pair). Dipole locations for scalp muscle ICs are outside the brain volume (middle row). Green lines in dipole plots connect ICs co-modulated by the same IM and the colors of the dipole spheres (yellow to red) indicate the relative strength of modulation (yellow = 50%, to red = 100% of maximal). Purple spheres indicate individually modulated ICs.

Mentions: Figure 4 shows that both brain and scalp muscle ICs exhibited monotonic broadband modulations with similar spectral patterns. However, in our data no broadband IM affected both scalp muscle and brain ICs. In the right three columns of Figure 4, spheres represent the estimated positions of equivalent-dipole models of the affected ICs, co- registered to the MNI brain template (Montreal Neurological Institute), their color varying according to the RMS strength of their IM template relative to that IM's highest-RMS IC. Purple spheres represent equivalent dipoles of ICs solely affected by an IM. Green lines connect spheres whose ICs were co-modulated by the same IM.


High-frequency Broadband Modulations of Electroencephalographic Spectra.

Onton J, Makeig S - Front Hum Neurosci (2009)

Broadband independent modulators of brain and scalp muscle components. Brain and scalp muscle ICs are separately modulated by IMs with similar broadband high-frequency templates (upper rows). The left column shows broadband templates for each IC category (black trace is the mean). The right three columns show equivalent-dipole locations of the affected ICs. A distinct cluster of putative ocular motor IMs, shown in the bottom row, have a peak effect near 50 Hz on ICs many of whose bilaterally symmetric equivalent-dipole models (bottom right panels) are located near the eyes. (ICs whose best-fit equivalent-dipole model comprised two bilaterally symmetrical dipoles are represented with a dotted yellow line connecting the dipole pair). Dipole locations for scalp muscle ICs are outside the brain volume (middle row). Green lines in dipole plots connect ICs co-modulated by the same IM and the colors of the dipole spheres (yellow to red) indicate the relative strength of modulation (yellow = 50%, to red = 100% of maximal). Purple spheres indicate individually modulated ICs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2806183&req=5

Figure 4: Broadband independent modulators of brain and scalp muscle components. Brain and scalp muscle ICs are separately modulated by IMs with similar broadband high-frequency templates (upper rows). The left column shows broadband templates for each IC category (black trace is the mean). The right three columns show equivalent-dipole locations of the affected ICs. A distinct cluster of putative ocular motor IMs, shown in the bottom row, have a peak effect near 50 Hz on ICs many of whose bilaterally symmetric equivalent-dipole models (bottom right panels) are located near the eyes. (ICs whose best-fit equivalent-dipole model comprised two bilaterally symmetrical dipoles are represented with a dotted yellow line connecting the dipole pair). Dipole locations for scalp muscle ICs are outside the brain volume (middle row). Green lines in dipole plots connect ICs co-modulated by the same IM and the colors of the dipole spheres (yellow to red) indicate the relative strength of modulation (yellow = 50%, to red = 100% of maximal). Purple spheres indicate individually modulated ICs.
Mentions: Figure 4 shows that both brain and scalp muscle ICs exhibited monotonic broadband modulations with similar spectral patterns. However, in our data no broadband IM affected both scalp muscle and brain ICs. In the right three columns of Figure 4, spheres represent the estimated positions of equivalent-dipole models of the affected ICs, co- registered to the MNI brain template (Montreal Neurological Institute), their color varying according to the RMS strength of their IM template relative to that IM's highest-RMS IC. Purple spheres represent equivalent dipoles of ICs solely affected by an IM. Green lines connect spheres whose ICs were co-modulated by the same IM.

Bottom Line: High-frequency cortical potentials in electroencephalographic (EEG) scalp recordings have low amplitudes and may be confounded with scalp muscle activities.Multi-dimensional scaling revealed significant but spatially complex relationships between mean broadband brain IM effects and the valence of the imagined emotions.Thus, contrary to prevalent assumption, unitary modes of spectral modulation of frequencies encompassing the beta, gamma, and high gamma frequency ranges can be isolated from scalp-recorded EEG data and may be differentially associated with brain sources and cognitive activities.

View Article: PubMed Central - PubMed

Affiliation: Institute for Neural Computation, University of California San Diego, La Jolla, CA, USA.

ABSTRACT
High-frequency cortical potentials in electroencephalographic (EEG) scalp recordings have low amplitudes and may be confounded with scalp muscle activities. EEG data from an eyes-closed emotion imagination task were linearly decomposed using independent component analysis (ICA) into maximally independent component (IC) processes. Joint decomposition of IC log spectrograms into source- and frequency-independent modulator (IM) processes revealed three distinct classes of IMs that separately modulated broadband high-frequency ( approximately 15-200 Hz) power of brain, scalp muscle, and likely ocular motor IC processes. Multi-dimensional scaling revealed significant but spatially complex relationships between mean broadband brain IM effects and the valence of the imagined emotions. Thus, contrary to prevalent assumption, unitary modes of spectral modulation of frequencies encompassing the beta, gamma, and high gamma frequency ranges can be isolated from scalp-recorded EEG data and may be differentially associated with brain sources and cognitive activities.

No MeSH data available.