Differential responsiveness of the right parahippocampal region to electrical stimulation in fixed human brains: Implications for historical surgical stimulation studies?

Rouleau, Nicolas; Persinger, Michael A.

doi:10.1016/j.yebeh.2016.04.028

Cited by 9 publications

(24 citation statements)

References 32 publications

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“…A coaxial cable coupled to an electronic breadboard jumper cable by an alligator clip served as a stimulating probe which was inserted into the tissue. The voltage equivalent at the level of the needle probe positioned within ~2 mm adjacent to the stimulating probe, 2 μV, was measured directly by the electrophysiological recording device [12]. …”

Section: Methodsmentioning

confidence: 99%

When Is the Brain Dead? Living-Like Electrophysiological Responses and Photon Emissions from Applications of Neurotransmitters in Fixed Post-Mortem Human Brains

et al. 2016

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The structure of the post-mortem human brain can be preserved by immersing the organ within a fixative solution. Once the brain is perfused, cellular and histological features are maintained over extended periods of time. However, functions of the human brain are not assumed to be preserved beyond death and subsequent chemical fixation. Here we present a series of experiments which, together, refute this assumption. Instead, we suggest that chemical preservation of brain structure results in some retained functional capacity. Patterns similar to the living condition were elicited by chemical and electrical probes within coronal and sagittal sections of human temporal lobe structures that had been maintained in ethanol-formalin-acetic acid. This was inferred by a reliable modulation of frequency-dependent microvolt fluctuations. These weak microvolt fluctuations were enhanced by receptor-specific agonists and their precursors (i.e., nicotine, 5-HTP, and L-glutamic acid) as well as attenuated by receptor-antagonists (i.e., ketamine). Surface injections of 10 nM nicotine enhanced theta power within the right parahippocampal gyrus without any effect upon the ipsilateral hippocampus. Glutamate-induced high-frequency power densities within the left parahippocampal gyrus were correlated with increased photon counts over the surface of the tissue. Heschl’s gyrus, a transverse convexity on which the primary auditory cortex is tonotopically represented, retained frequency-discrimination capacities in response to sweeps of weak (2μV) square-wave electrical pulses between 20 Hz and 20 kHz. Together, these results suggest that portions of the post-mortem human brain may retain latent capacities to respond with potential life-like and virtual properties.

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Section: Methodsmentioning

confidence: 99%

When Is the Brain Dead? Living-Like Electrophysiological Responses and Photon Emissions from Applications of Neurotransmitters in Fixed Post-Mortem Human Brains

et al. 2016

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“…A similar procedure has been previously applied to human tissue [3]. Microvolt fluctuations within brains were measured by insertion of 1/3 of the needle probe (6.6 mm) into the dorsal or ventral surface of the left and right hemispheres of the rat cerebrum (Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Functional neuroimaging tools such as quantitative electroencephalography (QEEG), however, are used exclusively in living subjects. Rouleau and Persinger [3] have recently demonstrated that a modified QEEG technique using needle electrodes and a vascular electrical reference can be used to identify intrinsic laterality of frequency-dependent microvolt fluctuation power in coronal sections of human brain tissue. The experiments also demonstrated that select areas including the parahippocampal gyrus could be “reactivated” by frequency-modulated 2 μV pulsed current applied directly to the brain.…”

Section: Introductionmentioning

confidence: 99%

“…We hypothesized that structural changes at the level of the cerebrum would be paired with quantifiable fluctuations of electric potential differences within the fixed tissue samples. If, as Rouleau and Persinger [3] demonstrated, the normal human brain’s regional structure is intimately tied to unique, spatially-specific microvolt potential fluctuations, the pathological rat brains should display an equivalent structural-electrical relationship. Here we present evidence that long after brains have been removed and fixed there are residual, site-specific electrophysiological anomalies that reflect the history of the animals.…”

Section: Introductionmentioning

confidence: 99%

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Functional neuroimaging of post-mortem tissue: lithium-pilocarpine seized rats express reduced brain mass and proportional reductions of left ventral cerebral theta spectral power

Rouleau

Reive

Persinger

2016

Heliyon

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Structural imaging tools can be used to identify neuropathology in post-mortem tissue whereas functional imaging tools including quantitative electroencephalography (QEEG) are thought to be restricted for use in living subjects. We are not aware of any study which has used electrophysiological methods decades after death to infer pathology. We therefore attempted to discriminate between chemically preserved brains which had incurred electrical seizures and those that did not using functional imaging. Our data indicate that modified QEEG technology involving needle electrodes embedded within chemically fixed neural tissue can be used to discriminate pathology. Forty (n = 40) rat brains preserved in ethanol-formalin-acetic acid (EFA) were probed by needle electrodes inserted into the dorsal and ventral components of the left and right cerebral hemispheres. Raw microvolt potentials were converted to spectral power densities within classical electroencephalographic frequency bands (1.5 Hz to 40 Hz). Brain mass differences were shown to scale with left hemispheric ventral theta-band spectral power densities in lithium-pilocarpine seized rats. This relationship was not observed in non-seized rats. A conspicuous absence of pathological indicators within dorsal regions as inferred by microvolt fluctuations was expected given the known localization of post-ictal damage in lithium-pilocarpine seized rats. Together, the data demonstrate that post-mortem neuroimaging is both possible and potentially useful as a means to identify neuropathology without structural imaging techniques or dissection.

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“…The anterior, middle, and posterior cerebral arteries were intact and partially affixed to the cerebrum and brainstem. This was important as previous electrophysiological measurements involving post-mortem fixed human brain tissue has involved the use of vasculature as the electrical reference point [22,23].…”

Section: Human Brain Tissuementioning

confidence: 99%

Neural Tissues Filter Electromagnetic Fields: Investigating Regional Processing of Induced Current in Ex vivo Brain Specimens

Rouleau¹,

Persinger²

2017

Biol Med (Aligarh)

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As has been demonstrated experimentally, the living brain responds to pulsatile electromagnetic fields. Our aim was to investigate the capacities of ex vivo neural tissue to process and filter induced current generated by naturally occurring and laboratory-controlled electromagnetic fields. Microvolt potentials within the chemically fixed postmortem brains were collected throughout the field exposures. During strong geomagnetic storms there was a significant increase in power spectra within the 7.5 Hz to 14 Hz range within the right but not the left parahippocampal gyrus compared to days with relatively quiet geomagnetic activity. This finding indicated that ambient electromagnetic fluctuations from natural sources were processed differentially as a function of subsections of the postmortem tissue. Exposing a whole, fixed human brain to two physiologically patterned magnetic fields that have been associated with powerful subjective experiences reported by hundreds of human volunteers in the laboratory setting elicited increased power within the 7.5 Hz to 20 Hz range. The effects required 10 to 20 s to emerge and were primarily represented within tissue subsections of the right amygdala and orbitofrontal gyri. Other fields such as simple sine-wave (20 Hz) patterns of comparable intensity (2 to 10 μT) did not elicit the same configuration of changes. The results indicate that neural tissues filter electromagnetic fields non-randomly.

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Differential responsiveness of the right parahippocampal region to electrical stimulation in fixed human brains: Implications for historical surgical stimulation studies?

Cited by 9 publications

References 32 publications

When Is the Brain Dead? Living-Like Electrophysiological Responses and Photon Emissions from Applications of Neurotransmitters in Fixed Post-Mortem Human Brains

When Is the Brain Dead? Living-Like Electrophysiological Responses and Photon Emissions from Applications of Neurotransmitters in Fixed Post-Mortem Human Brains

Functional neuroimaging of post-mortem tissue: lithium-pilocarpine seized rats express reduced brain mass and proportional reductions of left ventral cerebral theta spectral power

Neural Tissues Filter Electromagnetic Fields: Investigating Regional Processing of Induced Current in Ex vivo Brain Specimens

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