Localization of sources of brain alpha/theta/delta activity and the influence of the mode of spontaneous mentation

Abstract

A method is described that accounts for multichannel brain field data (EEG) epochs, after transformation into the frequency domain, by a single oscillating dipole source in terms of phase angles. The method produces a potential distribution for each frequency point ('FFT dipole approximation'). These maps can be subjected to conventional equivalent dipole source fittings in terms of amplitudes. We studied the equivalent source locations for the different temporal EEG frequency bands (delta/theta/alpha) in 12 normal subjects during the collection of reports of spontaneous thoughts. Some of the thought reports were classed into two modes, 'visual imagery' and 'abstract', and the associated equivalent source locations during the 2 s immediately prior to these reports were computed. Different equivalent source locations were found for the different spectral components of the EEG, implying that different neural generator populations generate the different frequencies. Further, the different types of spontaneous thought, i.e. different modes of cortical functioning, were found to be associated with the activity of different neuronal generator sources that operated at the same frequency at different source locations.

Persistent QEEG Abnormality in Crack Cocaine Users at 6 Months of Drug Abstinence

“…However, multiply replicated adult norms indicate that 20 to 30% of the total EEG power in central and anterior leads in awake humans is in the delta frequency band (Matous k and Petersén 1973; Gasser et al 1982;Jonkman et al 1985;Alvarez et al 1987;Harmony et al 1987;John et al 1989) and there is a substantial qEEG literature relating delta power to higher order mental functions in normal awake humans. Increased delta activity has been observed in normal subjects performing calculations (Fernandez et al 1995), reaction time tasks (Van Dijk et al 1992), abstract thought (Michel et al 1993), or an omitted stimulus paradigm (Basar-Eroglu et al 1992), and to covary positively with P300 amplitude (Basar et al 1984;Intriligator and Polich 1994). A functional role has been suggested for delta in facilitating "inner concentration" by suppressing extraneous cortical inputs in order to maximize the allocation of attention to tasks involving internal representation (Fernandez et al 1995).…”

“…Studies utilizing dipole modeling (Michel et al 1992(Michel et al , 1993 and the correlation of positron emission tomography and the EEG (Alper et al , 1998 estimate the location of the major site of delta generation in midline and anterior frontal cortex, which corresponds with the location of the main cortical terminal field of the mesotelencephalic DA projection. Cortical layer V contains the pyramidal cells that are thought to generate the delta rhythm (McCormick 1992;Steriade et al 1990), as well as high density of DA teru e minals whose synaptic architecture and laminar distribution appear specifically adapted to the horizontal integration necessary to modulate the wide field, global delta rhythm (Berger 1994;Silberstein 1995).…”

Correlation of qEEG with PET in Schizophrenia

“…However, approximately 20-30% of the voltage of awake normal humans in anterior leads is in delta as revealed by multiple replicated studies [17][18][19][20][21][22]. Increased delta activity has been correlated with a number of presumably metabolically activating states in normal awake humans such as the performance of calculations [25], reaction time tests [26], abstract thought [27] or an omitted stimulus paradigm [28]. The frontal localization of the apparently positive correlation between delta and PET also may be regarded as consistent with the contention that this may be a valid reflection of physiology and not accidental artifact.…”

“…The frontal localization of the apparently positive correlation between delta and PET also may be regarded as consistent with the contention that this may be a valid reflection of physiology and not accidental artifact. Such a contention receives support from the putative role of the forebrain in the normal generation of delta power and from studies utilizing dipole analysis that place the site of maximum delta generation in normals in the frontal cortex [27,29].…”

Short-Term EEG Spectral Pattern as a Single Event in EEG Phenomenology~!2009-11-10~!2010-02-22~!2010-09-08~!

“…Therefore, two source of generation of delta activity can be outlined: (a) cortical which includes anterior medial frontal cortex [127] and distributed cortico-cortical interactions [128][129][130] and (b) subcortical which includes the common brainstem system [131], the nucleus accumbens [132], the ventral pallidum [133], and dopaminergic neurons in the ventral tegmental area [134].…”