De amore libri tres

No verso da anteportada consta: "Tiratge especial de 25 exemplars sobre paper de fil "Gvarro"No verso da anteportada: "Tiratge especial de 25 exemplars sobre paper de fil"Gvarro"Texto paralelo en catalán e latí

Caloric vestibular stimulation reveals discrete neural mechanisms for coherence rivalry and eye rivalry: a meta-rivalry model

Binocular rivalry is an extraordinary visual phenomenon that has engaged investigators for centuries. Since its first report, there has been vigorous debate over how the brain achieves the perceptual alternations that occur when conflicting images are presented simultaneously, one to each eye. Opposing high-level/stimulus-representation models and low-level/eye-based models have been proposed to explain the phenomenon, recently merging into an amalgam view. Here, we provide evidence that during viewing of Dı´az-Caneja stimuli, coherence rivalry—in which aspects of each eye’s presented image are perceptually regrouped into rivalling coherent images—and eye rivalry operate via discrete neural mechanisms. We demonstrate that high-level brain activation by unilateral caloric vestibular stimulation shifts the predominance of perceived coherent images (coherence rivalry) but not half-field images (eye rivalry). This finding suggests that coherence rivalry (like conventional rivalry according to our previous studies) is mediated by interhemispheric switching at a high level, while eye rivalry is mediated by intrahemispheric mechanisms, most likely at a low level. Based on the present data, we further propose that Dı´az-Caneja stimuli induce ‘meta-rivalry’ whereby the discrete high- and low-level competitive processes themselves rival for visual consciousness

Vestibular modulation of somatosensory perception

Functional imaging studies show that vestibular and somatosensory projections overlap in the human brain. However, it remains unclear whether and how vestibular inputs affect somatosensory function. To address this issue, we studied the effects of left caloric vestibular stimulation (CVS) on detection of near-threshold somatosensory stimuli delivered to the left and right hands of healthy volunteers. To investigate whether these effects were somatosensory specific, or supramodal, we also tested CVS modulation of visual contrast detection. Signal detection analyses showed increased somatosensory perceptual sensitivity immediately after CVS, both ipsilaterally and contralaterally. No statistically reliable effects on visual contrast sensitivity were found. These findings suggest that vestibular stimulation has a specific facilitatory effect on somatosensory detection, distinct from non-specific arousal and spatial attentional effects of CVS. Thus, the overlap in brain activations for vestibular and somatosensory inputs is not simply an anatomical curiosity, but may reflect a functional cross-modal perceptual interaction

How the vestibular system modulates tactile perception in normal subjects: a behavioural and physiological study

Caloric vestibular stimulation (CVS) is a physiological technique demonstrated to transiently improve hemianaesthesia in right brain-damaged patients (Bottini et al. in Exp Brain Res 99(1):164–169, 1994, Nature 376:778–781, 1995, Neurology 65(8):1278–1283, 2005). Recent studies suggest that these effects are based on the anatomical overlapping between vestibular and tactile projections (Bottini et al. in Nature 376:778–781, 1995) in the human brain. However, much less is known about behavioural effects of this manipulation on normal subjects. We aimed to explore tactile perception during left ear CVS in normal subjects. We administered seventeen right-handed normal subjects with different types of tactile stimuli (above and below threshold) during left ear CVS. To further ensure standardized procedure, tactile stimulation was delivered through a tool-developed ad hoc for the experiment. The experiment was divided in 3 conditions: (1) Baseline, (2) PostCVS and (3) Delayed CVS. We found a main effect of stimulus type (F (2,32) = 907.712; P = 0.000) and condition (F (2,32) = 55.505; P = 0.000). Moreover, post hoc comparisons revealed that below threshold stimuli are most affected by CVS (t (16) = −11.213; P = 0.000). Left ear CVS modulates tactile perception also in normal subjects. Moreover, this modulation seems to be selective for below threshold stimuli and not caused by attentive processes. A multisensory phenomenon is possibly the best explanation for this interaction between touch and vestibular systems, corroborated also by the anatomical evidence and by the previous knowledge about interaction with the environment