The somatosensory representation of the human clitoris: An fMRI study
Institute of Functional Neurosurgery, University Hospital, Zurich, Switzerland. NeuroImage
(Impact Factor: 6.36).
08/2009; 49(1):177-84. DOI: 10.1016/j.neuroimage.2009.07.024
We studied the central representation of pudendal afferents arising from the clitoral nerves in 15 healthy adult female subjects using electrical dorsal clitoral nerve stimulation and fMRI. As a control body region, we electrically stimulated the right hallux in eight subjects. In a block design experiment, we applied bilateral clitoral stimulation and unilateral (right) hallux stimulation. Activation maps were calculated for the contrasts 'electrical dorsal clitoral nerve stimulation versus rest' and 'electrical hallux stimulation versus rest'. A random-effect group analysis for the clitoral stimulation showed significant activations bilateral in the superior and inferior frontal gyri, insulae and putamen and in the postcentral, precentral and inferior parietal gyri (including the primary and secondary somatosensory cortices). No activation was found on the mesial surface of the postcentral gyrus. For the hallux, activations occurred in a similar neuronal network but the activation in the primary somatosensory cortex was localized in the inter-hemispheric fissure. The results of this study demonstrate that the central representation of pudendal afferents arising from the clitoral nerves and sensory inputs from the hallux can be studied and distinguished from each other by fMRI. From the somatotopic order described in the somatosensory homunculus one would expect for electrical clitoral nerve stimulation activation of the mesial wall of the postcentral gyrus. In contrast, we found activations on the lateral surface of the postcentral gyrus.
Available from: Weibo Chen
- "The current study showed that a cognitive decline was associated with connectivity alteration in eleven brain regions including the bilateral hippocampi and related limbic system. The limbic cortex played an important role in memory encoding and the recognition of scenes  . In our earlier study suggested that the right hippocampus developed abnormalities later than the left side, supported by increased water diffusivity appearing first in the left hippocampal areas in aMCI patients and extending to bilateral hippocampi in AD subjects when compared with normal controls . "
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ABSTRACT: Mean diffusivity (MD) derived from diffusion tensor imaging has shown its ability to assess the microscopic structural integrity damage of gray matter in amnestic mild cognitive impairment (aMCI), a prodromal stage of Alzheimer's disease (AD). However, little is known about the small world topology networks constructed by cortical MD in cognitive disease. In this work, we measured the cortical MD in the entire brain in patients with aMCI (n = 30) and AD (n = 30) compared with cognitive-normal (CNs) controls (n = 30), and then constructed the cortical diffusivity network by using graph-theoretical analysis. Compared with CNs, patients with aMCI and AD showed abnormal small-world property of cortical diffusivity networks (higher degree of clustering and longer path length), reflecting a less optimal topological organization. Moreover, the mean degree of connections of network in aMCI patients was characterized by lower than CNs but higher than AD. In addition, 11 hub regions were identified by negative correlations between MD and the score of Montreal Cognitive Assessment after multiple regression analysis, including bilateral hippocampi and related limbic system. Among those hub regions, the connectivity of the right olfactory cortex and middle orbital gyrus to the rest of brain regions were disrupted earlier than the other 9 regions in aMCI when compared to CN. In conclusion, the change of cortical diffusivity in topological network organization, mean degree of connections, and disrupted hub regions in aMCI may serve to identify patients in the prodromal stage of AD and reflect microstructural deterioration of neurodegeneration.
Available from: Leorra Newman
- "A representation of the vagina also exists in S2 (Pukall et al. 2005). In addition, the insula has also been widely implicated as a potential accessory region for the female somatosensory map (Kern et al. 2001; Komisaruk et al. 2004; Komisaruk and Whipple 2005; Komisaruk et al. 2011; Eickhoff et al. 2006; Georgiadis et al. 2009; Michels et al. 2010) (Fig. 2, Table 1). As Figure 2 makes clear, current female-specific somatotopic mappings focus fairly exclusively on the genitalia and sexual function of women, and a static one at that. "
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ABSTRACT: The representation of the body in the brain, the homunculus, was posited by Wilder Penfield based on his studies of patients with intractable epilepsy. While he mapped both male and female patients, Penfield reports little about the females. The now iconic illustration of the map is clearly male with testicles, penis, and no breasts. In order to bring attention to this omission and to stimulate studies of female somatosensory cortex (SS), we discuss what is known about the map of the female body in the brain, including Penfield's findings in his female patients and subsequent work by others exploring the human female SS. We reveal that there is much we do not know about how the entire female body is represented in the brain or how it might change with different reproductive life stages, hormones, and experiences. Understanding what is and is not currently known about the female SS is a first step toward fully understanding neurological and physiological sex differences, as well as producing better-informed treatments for pain conditions related to mastectomy, hysterectomy, vulvodynia, and fibromyalgia. We suggest that the time is ripe for a full mapping of the female brain with the production of a hermunculus.
Available from: PubMed Central
- "Most of the evidence supports a distinct dorsolateral location on the postcentral gyrus (primary somatosensory cortex, SI) for both penis and clitoris, regardless of whether the stimulation happened in an intentionally erotic context (Georgiadis et al., 2006, 2010) or not (Kell, von Kriegstein, Rosler, Kleinschmidt, & Laufs, 2005; Michels, Mehnert, Boy, Schurch, & Kollias, 2010). The secondary somatosensory cortex (SII), located in the parietal operculum, is also readily activated by stimulation of (nerves of) the external genitalia (Georgiadis et al., 2006, 2010; Georgiadis & Holstege, 2005; Kell et al., 2005; Komisaruk et al., 2011; Mäkelä et al., 2003; Michels et al., 2010; Pukall et al., 2005), and this activation gains strength when stimulation becomes more salient (e.g. painful, see, e.g. "
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ABSTRACT: We like to think about sexual activity as something fixed, basic and primal. However, this does not seem to fully capture reality. Even when we relish sex, we may be capable of mentalizing, talking, voluntarily postponing orgasm, and much more. This might indicate that the central control mechanisms of sexual activity are quite flexible and susceptible to learning mechanisms, and that cortical brain areas play a critical part.
This study aimed to identify those cortical areas and mechanisms most consistently implicated in sexual activity.
A comprehensive review of the human functional neuroimaging literature on sexual activity, i.e. genital stimulation and orgasm, is made.
Genital stimulation recruits the classical somatosensory matrix, but also areas far beyond that. The posterior insula may be particularly important for processing input from the engorged penis and coordinating penile responses. Extrastriate visual cortex tracks sexual arousal and responds to genital stimulation even when subjects have their eyes closed. The ventromedial prefrontal cortex is also tightly coupled to sexual arousal, but low activity in this area predicts high sexual arousal.
This review has indicated cortical sites where activity is moderated by tactile genital inflow and high sexual arousal. Behavioral implications are discussed and where possible the relevance for learning mechanisms is indicated. Overall, it is clear that the cerebral cortex has something to say about sexual activity.
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