Armando Tartaro

Dynamics of male sexual arousal: distinct components of brain activation revealed by fMRI

The peripheral mechanisms of male sexual arousal are well known. Recently, neuroimaging techniques, such as PET or fMRI, allowed the investigation of the subjacent cerebral mechanisms. In ten healthy subjects, we have simultaneously recorded fMRI images of brain activation elicited by viewing erotic scenes, and the time course of penile tumescence by means of a custom-built MRI-compatible pneumatic cuff. We have compared activation elicited by video clips with a long duration, that led to sexual arousal and penile erection, and activation elicited by briefly presented still images, that did induce sexual arousal without erection. This comparison and the use of the time course of penile tumescence in video clips allowed to perform a time resolved data analysis and to correlate different patterns of brain activation with different phases of sexual response. The activation maps highlighted a complex neural circuit involved in sexual arousal. Of this circuit, only a few areas (anterior cingulate, insula, amygdala, hypothalamus, and secondary somatosensory cortices) were specifically correlated with penile erection. Finally, these areas showed distinct dynamic relationships with the time course of sexual response. These differences might correspond to different roles in the development and appraisal of the sexual response. These findings shed light on the psychophysiology of male sexuality and open new perspectives for the diagnosis, therapy, and possible rehabilitation of sexual dysfunction.

Neural correlates of focused attention and cognitive monitoring in meditation.

Meditation refers to a family of complex emotional and attentional regulatory practices, which can be classified into two main styles - focused attention (FA) and open monitoring (OM) - involving different attentional, cognitive monitoring and awareness processes. In a functional magnetic resonance study we originally characterized and contrasted FA and OM meditation forms within the same experiment, by an integrated FA-OM design. Theravada Buddhist monks, expert in both FA and OM meditation forms, and lay novices with 10 days of meditation practice, participated in the experiment. Our evidence suggests that expert meditators control cognitive engagement in conscious processing of sensory-related, thought and emotion contents, by massive self-regulation of fronto-parietal and insular areas in the left hemisphere, in a meditation state-dependent fashion. We also found that anterior cingulate and dorsolateral prefrontal cortices play antagonist roles in the executive control of the attention setting in meditation tasks. Our findings resolve the controversy between the hypothesis that meditative states are associated to transient hypofrontality or deactivation of executive brain areas, and evidence about the activation of executive brain areas in meditation. Finally, our study suggests that a functional reorganization of brain activity patterns for focused attention and cognitive monitoring takes place with mental practice, and that meditation-related neuroplasticity is crucially associated to a functional reorganization of activity patterns in prefrontal cortex and in the insula.

Human brain activation during passive listening to sounds from different locations: An fMRI and MEG study

Recent animal and human studies indicate the existence of a neural pathway for sound localization, which is similar to the “where” pathway of the visual system and distinct from the sound identification pathway. This study sought to highlight this pathway using a passive listening protocol. We employed fMRI to study cortical areas, activated during the processing of sounds coming from different locations, and MEG to disclose the temporal dynamics of these areas. In addition, the hypothesis of different activation levels in the right and in the left hemispheres, due to hemispheric specialization of the human brain, was investigated. The fMRI results indicate that the processing of sound, coming from different locations, activates a complex neuronal circuit, similar to the sound localization system described in monkeys known as the auditory “where” pathway. This system includes Heschls gyrus, the superior temporal gyrus, the supramarginal gyrus, and the inferior and middle frontal lobe. The MEG analysis allowed assessment of the timing of this circuit: the activation of Heschls gyrus was observed 139 ms after the auditory stimulus, the peak latency of the source located in the superior temporal gyrus was at 156 ms, and the inferior parietal lobule and the supramarginal gyrus peaked at 162 ms. Both hemispheres were found to be involved in the processing of sounds coming from different locations, but a stronger activation was observed in the right hemisphere. Hum. Brain Mapping, 2005.

Functional topography of the secondary somatosensory cortex for nonpainful and painful stimuli: an fMRI study

The regional activity of the contralateral primary (SI) and the bilateral secondary (SII) somatosensory areas during median nerve stimulations at five intensity levels (ranging from nonpainful motor threshold to moderate pain) was studied by means of functional magnetic resonance imaging (fMRI). The aim was to characterize the functional topography of SII compared to SI as a function of the stimulus intensity. Results showed that the galvanic stimulation of the median nerve activated the contralateral SI at all stimulus intensities. When considered as a single region, SII was more strongly activated in the contralateral than in the ipsilateral hemisphere. When a finer spatial analysis of the SII responses was performed, the activity for the painful stimulation was localized more posteriorly compared to that for the nonpainful stimulation. This is the first report on such a SII segregation for transient galvanic stimulations. The activity (relative signal intensity) of this posterior area increased with the increase of the stimulus intensity. These results suggest a spatial segregation of the neural populations that process signals conveyed by dorsal column-medial lemniscus (nonpainful signals) and neospinothalamic (painful signals) pathways. Further fMRI experiments should evaluate the functional properties of these two SII subregions during tasks involving sensorimotor integration, learning, and memory demands.

Diagnostic utility of an echo-contrast agent in patients with synovitis using power Doppler ultrasound: a preliminary study with comparison to contrast-enhanced MRI

Abstract The purpose of this study was to first evaluate Levovist (Schering, Berlin, Germany), an echo-contrast agent, during power Doppler sonography (PDS) in patients with synovitis using asymptomatic joints as controls. Then we evaluated the accuracy of this technique against contrast-enhanced MRI. Forty patients (19 men and 21 women; mean age 40 years) were enrolled on the basis of clinical signs, laboratory tests, and radiographic findings positive for articular inflammatory disease. They were examined with conventional ultrasonography (US) and PDS techniques before and after intravenous contrast medium injection. Fourteen patients then underwent MRI with and without contrast medium 8–14 days after PDS studies. Three expert readers independently evaluated each examination. After contrast medium, synovium in inflammatory arthritis enhanced on PDS compared with normal joints in the same patient. Power Doppler sonography after contrast medium and MRI were concordant in all cases. Power Doppler sonography with contrast medium showed a qualitative increase in signal from synovial vessels, the first sign of synovial changes in inflammatory diseases.

Topographic organization of the human primary and secondary somatosensory cortices: comparison of fMRI and MEG findings

We studied MEG and fMRI responses to electric median and tibial nerve stimulation in five healthy volunteers. The aim was to compare the results with those of a previous study using only fMRI on the primary and secondary somatosensory cortices in which the somatotopic organization of SII was observed with fMRI. In the present work we focus on the comparison between fMRI activation and MEG equivalent current dipole (ECD) localizations in the SII area. The somatotopic organization of SII was confirmed by MEG, with the upper limb areas located more anteriorly and more inferiorly than the lower limb areas. In addition a substantial consistency of the ECD locations with the areas of fMRI activation was observed, with an average mismatch of about 1 cm. MEG ECDs and fMRI activation areas showed comparable differences in SI.

Human secondary somatosensory cortex is involved in the processing of somatosensory rare stimuli: An fMRI study

In the human somatosensory system, the contralateral primary somatosensory cortex (SI) is presumed to process and encode type and intensity of the sensory inputs, whereas the bilateral secondary somatosensory cortex (SII) is believed to perform higher order functions including sensorimotor integration, integration of information from the two body halves, attention, learning and memory. In this fMRI study we investigated the effect of attention on the activation of SI and SII, as induced by nonpainful and painful rare deviant electric stimuli during somatosensory oddball tasks. The working hypothesis is of stronger effects of attention on SII with respect to SI. Four runs were acquired according to an oddball scheme. Frequent nonpainful electrical stimuli were delivered to the ulnar nerve at motor threshold, whereas rare/deviant stimuli were delivered to median nerve in four conditions (one condition per run): nonpainful, painful, counting nonpainful, and counting painful. Results showed a statistically significant fMRI activation in bilateral SII but not in contralateral SI when the rare/deviant median nerve stimuli were delivered at nonpainful and painful levels as well as at the two levels of attention considered (i.e., associated with counting and non-counting tasks). Furthermore, fMRI activation in SII did not differ across the different levels of stimulus intensity (nonpainful, painful) and attention (non-counting, counting). These results corroborate the notion that SII is the target of independent pathways for the processing and integration of nonpainful and painful somatosensory stimuli salient for further high-order elaborations.

Topographic organization of the human primary and secondary somatosensory areas: an fMRI study.

The topographical organization of SI and SII somatosensory areas was investigated using fMRI at 1.5 T and electrical sensory stimulation. Electrical stimuli were delivered unilaterally to the median nerve at the wrist and to the tibial nerve at the medial malleolus, during a block paradigm study. In all subjects, activation was observed, contralaterally to the stimulated side, in the post-central gyrus, in the posterior parietal cortex, in the mesial pre-frontal region and, bilaterally, in the supratemporal region at the level of the Sylvian fissure. The latter region, corresponding presumably to SII, showed a rough but clearcut topographical organization, with the median nerve areas located more posteriorly. In addition, weaker activations were observed in some subjects in the ipsilateral mesial prefrontal region and in the ipsilateral posterior parietal cortex. Information contained in the present study represent an interesting database for future investigations on the effects of sensorimotor learning in normal individuals on plastic reorganization following a lesion of the primary sensorimotor centers, i.e. in stroke patients, on the topography and balance between upper and lower limb representations in primary and secondary somatosensory cortices.

Default network is not hypoactive in dementia with fluctuating cognition: an Alzheimer disease/dementia with Lewy bodies comparison.

Default mode network resting state activity in posterior cingulate cortex is abnormally reduced in Alzheimer disease (AD) patients. Fluctuating cognition and electroencephalogram abnormalities are established core and supportive elements respectively for the diagnosis of dementia with Lewy bodies (DLB). Our aim was to assess whether patients with DLB with both of these features have different default mode network patterns during resting state functional magnetic resonance imaging compared with AD. Eighteen patients with DLB, 18 AD patients without fluctuating cognition, and 15 control subjects were selected after appropriate matching and followed for 2-5 years to confirm diagnosis. Independent component analysis with functional connectivity (FC) and Granger causality approaches were applied to isolate and characterize resting state networks. FC was reduced in AD and DLB patients compared with control subjects. Posterior cingulate cortex activity was lower in AD than in control subjects and DLB patients (p < 0.05). Right hemisphere FC was reduced in DLB patients in comparison with control subjects but not in patients with AD, and was correlated with severity of fluctuations (ρ = -0.69; p < 0.01). Causal flow analysis showed differences between patients with DLB and AD and control subjects.

Functional connectivity MR imaging of the language network in patients with drug-resistant epilepsy.

BACKGROUND AND PURPOSE: Subtle linguistic dysfunction and reorganization of the language network were described in patients with epilepsy, suggesting the occurrence of plasticity changes. We used resting state FC-MRI to investigate the effects induced by chronic epilepsy on the connectivity of the language-related brain regions and correlated it with language performance. MATERIALS AND METHODS: FC-MRI was evaluated in 22 right-handed patients with drug-resistant epilepsy (11 with LE and 11 with RE) and in 12 healthy volunteers. Neuropsychological assessment of verbal IQ was performed. Patients and controls underwent BOLD fMRI with a verb-generation task, and language function was lateralized by an LI. Intrinsic activity fluctuations for FC analysis were extracted from data collected during the task. Six seeding cortical regions for speech in both hemispheres were selected to obtain a measure of the connectivity pattern among the language networks. RESULTS: Patients with LE presented atypical language lateralization and an overall reduced connectivity of the language network with respect to controls. In patients with both LE and RE, the mean FC was significantly reduced within the left (dominant) hemisphere and between the 2 hemispheres. In patients with LE, there was a positive correlation between verbal IQ scores and the left intrahemispheric FC. CONCLUSIONS: In patients with intractable epilepsy, FC-MRI revealed an overall reduction and reorganization of the connectivity pattern within the language network. FC was reduced in the left hemisphere regardless of the epileptogenic focus side and was positively correlated with linguistic performance only in patients with LE.