The early processing of visual sexual stimuli shows signs of automaticity. Moreover, there is evidence for sex-specific patterns in cognitive and physiological responding to erotica. However, little is known about the time course of rapid pupillary responses to sexual stimuli and their correspondence with other measures of autonomic activity in women and men. To study pupil dilation as an implicit measure of sexual arousal at various stages of picture processing, we presented 35 heterosexual participants with pictures showing either erotic couples or single (male/female) erotic nudes, contrasted with people involved in everyday situations. Brightness-adjusted grayscale pictures were shown for a duration of 2,500 ms within the central visual field, alternating with perceptually matched patches. Left pupil diameter was recorded at 500 Hz using a video-based eye tracker. Skin conductance and heart rate were coregistered and correlated with latent components of pupil dilation (dissociated by temporal PCA). Whereas stimulus-evoked changes in pupil size indicated virtually no initial constriction, a rapid effect of appetence emerged (dilation to erotica within 500 ms). Responses at early stages of processing were remarkably consistent across both sexes. In contrast, later phases of pupil dilation, subjective ratings, and skin conductance responses showed a sex-specific pattern. Moreover, evidence for an association of early-onset pupil dilation and heart rate acceleration was found, suggestive of parasympathetic inhibition, whereas the late component was mainly related to sympathetically mediated skin conductance. Taken together, our results indicate that different temporal components of pupil responses to erotic stimuli may reflect divergent underlying neural mechanisms.

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Cardiac-cycle-time effects are attributed to variations in baroreceptor (BR) activity and have beenshown to impinge on subcortical as well as cortical processes. However, cognitive and sensorimotor processes mediating voluntary responses seem to be differentially affected. We sought to disentangle cardiac-cycle-time effects on subcortical and cortical levels as well as sensorimotor and cognitive processes within a spatial stimulus-response-compatibility paradigm employing startling stimuli of different modalities. Air-puffs and white noise-bursts were presented unilaterally during either cardiac systole or diastole while bilateral startle eMG responses were recorded. Modality, laterality and cardiaccycle-time were randomly varied within-subjects. cognitive and sensorimotor stimulus-responsecompatibility was orthogonally varied between-subjects: Participants (N = 80) responded to the stimuli via left/right button-push made with either the contra-or ipsilateral hand (sensorimotor compatibility) on either the ipsi-or contralateral button (cognitive compatibility). We found that sensorimotor compatible reactions were speeded during systole whereas sensorimotor incompatible ones were prolonged. This effect was independent of cognitive compatibility and restricted to auditory stimuli. Startle was inhibited during systole irrespective of modality or compatibility. our results demonstrate how differential cardiac-cycle-time effects influence performance in conflict tasks and further suggest that stimulus-response-compatibility paradigms offer a viable method to uncover the complex interactions underlying behavioral BR effects.The ability to flexibly adapt our behavior according to changes in bodily states is crucial to survival, promoting adequate actions e.g. in times of illness and stress. This ability is mediated by signaling pathways that convey information about peripheral events to the central nervous system, thereby influencing brain activity and potentially psychological state 1 . Beside humoral transmission of messengers essential to the immune and endocrine systems, neural projections originating from organ receptors located in the periphery contribute to altered brain activity. The cardiovascular system is a major source of variations in such viscero-afferent traffic and arterial baroreceptors (BR), mechanoreceptors expressed mainly within the carotid sinus and the aortic arch, are responsible for relaying cardiovascular events to the brain 2 . These stretch-sensitive receptors increase their firing rate in response to tension on the vessel walls and are essential for the homeostatic control of blood pressure and heart rate 3,4 . Afferent fibers project to the nucleus tractus solitarius (NTS) and determine the output of autonomic brain stem centers, thereby regulating cardiac activity and vascular contraction via sympathetic as well as parasympathetic efferents 5,6 . However, baroafferent signals do not remain at the brainstem level but are relayed by the NTS to the reticular formation and higher-order structu...

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