Biomedical subjects

Janniko R Georgiadis

Publications and source records attributed to Janniko R Georgiadis.

6 recordsLinked to original sources

PubMed2008

8-13 Hz fluctuations in rectal pressure are an objective marker of clitorally-induced orgasm in women.

Orgasm is a subjective experience accompanied by involuntary muscle contractions. We hypothesized that orgasm in women would be distinguishable by frequency analysis of a perineal muscle-derived signal. Rectal pressure, an index of perineal muscle activity, was measured continuously in 23 healthy women during different sexual tasks: receiving clitoral stimulation, imitation of orgasm, and attempt to reach orgasm, in which case the women were asked to report whether orgasm had been reached ("orgasm") or not ("failed orgasm attempt"). We performed spectral analysis on the rectal pressure data and calculated the spectral power in the frequency bands delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-13 Hz), and beta (13-25 Hz). The most significant and most important difference in spectral power between orgasm and both control motor tasks (imitation of orgasm and failed orgasm attempt) was found in the alpha band. An objective rule based on spectral power in the alpha band recognized 94% (29/31) of orgasms and correctly labeled 69% (44/64) of all orgasm attempts as either successful or failed. Because outbursts of alpha fluctuations in rectal pressure only occurred during orgasm and not during voluntary imitation of orgasm or failed attempts, we propose that they represent involuntary contractions of muscles in the rectal vicinity. This is the first objective and quantitative measure that has a strong correspondence with the subjective experience of orgasm.

Adult↗

PubMed2006

Regional cerebral blood flow changes associated with clitorally induced orgasm in healthy women.

There is a severe lack of knowledge regarding the brain regions involved in human sexual performance in general, and female orgasm in particular. We used [15O]-H2O positron emission tomography to measure regional cerebral blood flow (rCBF) in 12 healthy women during a nonsexual resting state, clitorally induced orgasm, sexual clitoral stimulation (sexual arousal control) and imitation of orgasm (motor output control). Extracerebral markers of sexual performance and orgasm were rectal pressure variability (RPstd) and perceived level of sexual arousal (PSA). Sexual stimulation of the clitoris (compared to rest) significantly increased rCBF in the left secondary and right dorsal primary somatosensory cortex, providing the first account of neocortical processing of sexual clitoral information. In contrast, orgasm was mainly associated with profound rCBF decreases in the neocortex when compared with the control conditions (clitoral stimulation and imitation of orgasm), particularly in the left lateral orbitofrontal cortex, inferior temporal gyrus and anterior temporal pole. Significant positive correlations were found between RPstd and rCBF in the left deep cerebellar nuclei, and between PSA and rCBF in the ventral midbrain and right caudate nucleus. We propose that decreased blood flow in the left lateral orbitofrontal cortex signifies behavioural disinhibition during orgasm in women, and that deactivation of the temporal lobe is directly related to high sexual arousal. In addition, the deep cerebellar nuclei may be involved in orgasm-specific muscle contractions while the involvement of the ventral midbrain and right caudate nucleus suggests a role for dopamine in female sexual arousal and orgasm.

Adult↗

PubMed2005

Human brain activation during sexual stimulation of the penis.

Penile sensory information is essential for reproduction, but almost nothing is known about how sexually salient inputs from the penis are processed in the brain. We used positron emission tomography to measure regional cerebral blood flow (rCBF) during various stages of male sexual performance. Compared to a passive resting condition (without penile erection), sexual stimulation of the penis increased rCBF in an area of the right hemisphere encompassing the posterior insula and adjacent posterior part of the secondary somatosensory cortex (SII) and decreased rCBF in the right amygdala. No activation was observed in either the thalamus, genital part of primary somatosensory cortex (SI), or hypothalamus. Based on these results we put forward the concept that during sexual performance the salience of the stimulus, represented by activation of the insula and SII, is of greater significance than the exact location of the stimulus, encoded in SI. The absence of activation in the hypothalamus indicates that this region is more important for the onset of sexual arousal than for the resulting sexual performance. Deactivation of the amygdala during sexual stimulation of the penis corresponds with a decrease of vigilance during sexual performance.

Adult↗

PubMed2004

Ultrastructural evidence for a direct excitatory pathway from the nucleus retroambiguus to lateral longissimus and quadratus lumborum motoneurons in the female golden hamster.

During mating, the female golden hamster displays a stereotyped specific receptive posture, characterized by lordosis of the back, elevation of the tail, and extension of the legs. Muscles involved in this posture are thought to be iliopsoas, cutaneus trunci, lateral longissimus (LL), and quadratus lumborum (QL). Lesion studies in rats suggest that mating behavior is controlled by the mesencephalic periaqueductal gray (PAG). The PAG does not project directly to the motoneurons innervating the muscles involved in mating, but is thought to make use of the nucleus retroambiguus (NRA) as relay. The NRA is located ventrolaterally in the most caudal medulla, and projects directly to iliopsoas and cutaneus trunci motoneuronal cell groups. The question is whether this is also true for LL and QL muscles. Retrograde HRP tracing experiments revealed that LL and QL motoneurons are located medially in the ventral horn of the T12-L6 and T13-L4 segments, respectively. A subsequent ultrastructural study combined wheatgerm agglutinin-conjugated horseradish peroxidase injections in the NRA with cholera-toxin B-subunit injections in LL and QL muscles. The results revealed monosynaptic contacts between anterogradely labeled NRA-fiber terminals with retrogradely labeled dendrites of both LL and QL motoneurons. Almost all these terminals had asymmetrical synapses and contained spherical vesicles, suggesting an excitatory function of this NRA-motoneuronal pathway. These results correspond with the hypothesis that in hamster the PAG-NRA-motoneuronal projection not only involves motoneurons of iliopsoas and cutaneus trunci but also of LL and QL.

Animals↗

PubMed2004

The emotional brain: neural correlates of cat sexual behavior and human male ejaculation.

The organization of virtually all basic survival mechanisms in the central nervous system (CNS) is within the most central regions of the mesencephalon and the rostrally adjoining diencephalon; in particular, the mesencephalic periaqueductal gray (PAG) and hypothalamus. The PAG sends specific pathways to the caudal brainstem where neurons are located that, in turn, control nociception, blood pressure, heart rate, and micturition. Via projections to the nucleus retroambiguus (NRA) in the most caudal part of the medulla, the PAG controls the intra-abdominal pressure associated with vocalization, vomiting, and parturition. In cats, the PAG also controls sexual posture via NRA projections to motoneurons in the lumbosacral cord. These NRA-lumbosacral motoneuronal pathways are almost nine times stronger in the estrous vs. non-estrous female cat. While neuronal activity in specific CNS pathways is now known to control sexual behavior in the cat, how is it organized in the human? PET-scan results on human ejaculation have revealed that the meso-diencephalic transition zone is particularly and strongly activated. This region includes the so-called ventral tegmental area that is also known as a "reward area." For example, it is also activated during a heroin rush. Other strongly activated structures during sexual activity include the cerebellum and lateral part of the corpus striatum. At the level of the cerebral cortex, areas in the prefrontal and parietal cortex are also activated, but exclusively on the right side. Further study of these structures should certainly lead to better insight into human sexual behavior and provide the possibility to improve sexual activity in those who suffer from problems in this area.

Animals↗

PubMed2003

Brain activation during human male ejaculation.

Brain mechanisms that control human sexual behavior in general, and ejaculation in particular, are poorly understood. We used positron emission tomography to measure increases in regional cerebral blood flow (rCBF) during ejaculation compared with sexual stimulation in heterosexual male volunteers. Manual penile stimulation was performed by the volunteer's female partner. Primary activation was found in the mesodiencephalic transition zone, including the ventral tegmental area, which is involved in a wide variety of rewarding behaviors. Parallels are drawn between ejaculation and heroin rush. Other activated mesodiencephalic structures are the midbrain lateral central tegmental field, zona incerta, subparafascicular nucleus, and the ventroposterior, midline, and intralaminar thalamic nuclei. Increased activation was also present in the lateral putamen and adjoining parts of the claustrum. Neocortical activity was only found in Brodmann areas 7/40, 18, 21, 23, and 47, exclusively on the right side. On the basis of studies in rodents, the medial preoptic area, bed nucleus of the stria terminalis, and amygdala are thought to be involved in ejaculation, but increased rCBF was not found in any of these regions. Conversely, in the amygdala and adjacent entorhinal cortex, a decrease in activation was observed. Remarkably strong rCBF increases were observed in the cerebellum. These findings corroborate the recent notion that the cerebellum plays an important role in emotional processing. The present study for the first time provides insight into which regions in the human brain play a primary role in ejaculation, and the results might have important implications for our understanding of how human ejaculation is brought about, and for our ability to improve sexual function and satisfaction in men.

Adult↗