Arcangelo Merla

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.

Contact-Free Measurement of Cardiac Pulse Based on the Analysis of Thermal Imagery

We have developed a novel method to measure human cardiac pulse at a distance. It is based on the information contained in the thermal signal emitted from major superficial vessels. This signal is acquired through a highly sensitive thermal imaging system. Temperature on the vessel is modulated by pulsative blood flow. To compute the frequency of modulation (pulse), we extract a line-based region along the vessel. Then, we apply fast Fourier transform (FFT) to individual points along this line of interest to capitalize on the pulses thermal propagation effect. Finally, we use an adaptive estimation function on the average FFT outcome to quantify the pulse. We have carried out experiments on a data set of 34 subjects and compared the pulse computed from our thermal signal analysis method to concomitant ground-truth measurements obtained through a standard contact sensor (piezo-electric transducer). The performance of the new method ranges from 88.52% to 90.33% depending on the clarity of the vessels thermal imprint. To the best of our knowledge, it is the first time that cardiac pulse has been measured several feet away from a subject with passive means.

Thermal Imaging of Cutaneous Temperature Modifications in Runners During Graded Exercise

In this paper we used high-resolution thermal imaging to visualize the human whole body anterior cutaneous temperature (Tc) variations in well-trained runners during graded exercise. Fifteen male volunteers underwent a graded treadmill test until reaching their individual maximal heart rate. Total body Tc decreased as the subjects started the exercise. Thighs and forearms exhibited the earliest response. A further Tc diminution occurred with the progress of the exercise. At the exercise interruption, Tc values were in average 3–5 °C lower than at baseline. Tc increased during recovery from exercise. Forearms and thighs exhibited the earliest increase, followed by total body Tc increase. Thermal imaging documented the presence of hyperthermal spots (occasionally tree-shaped) due to the presence of muscle perforator vessels during baseline and recovery, but not during exercise. The results we report indicate that thermal infrared imaging permits the quantitative evaluation of specific cutaneous whole body thermal adaptations which occur during and after graded physical activity. Thus providing the basis for evaluating local and systemic cutaneous blood flow adaptation as a function of specific type, intensity and duration of exercise, and helping to determine the ideal conditions (in terms of environment and apparel) in which physical activities should be conducted in order to favor thermal regulatory processes.

Imaging Facial Signs of Neurophysiological Responses

In the present paper, we introduce an integrated framework for detecting peripheral sympathetic responses through purely imaging means. The measurements are performed on three facial areas of sympathetic importance, that is, periorbital, supraorbital, and maxillary. To the best of our knowledge, this is the first time that the sympathetic importance of the maxillary area is analyzed. Because the imaging measurements are thermal in nature and are composed of multiple components of variable frequency (i.e., blood flow, sweat gland activation, and breathing), we chose wavelets as the image analysis framework. The measurements also carry substantial noise due to imperfections in tissue tracking and segmentation. The image analysis is grounded on galvanic skin response (GSR) signals, which are still considered the golden standard in peripheral neurophysiological and psychophysiological studies. The experimental results show that monitoring of the facial channels yields similar detecting power to GSRs. However, detailed quantification of the responses, although feasible in GSR through appropriate modeling, is quite difficult in the facial channels for the moment. Further improvements in facial tissue tracking and segmentation are bound to overcome this limitation. This paper opens a new research area that leads to unobtrusive screening technologies in neurophysiology and psychophysiology.

Thermal infrared imaging in psychophysiology: Potentialities and limits

Functional infrared thermal imaging (fITI) is considered an upcoming, promising methodology in the emotional arena. Driven by sympathetic nerves, observations of affective nature derive from muscular activity subcutaneous blood flow as well as perspiration patterns in specific body parts. A review of 23 experimental procedures that employed fITI for investigations of affective nature is provided, along with the adopted experimental protocol and the thermal changes that took place on selected regions of interest in human and nonhuman subjects. Discussion is provided regarding the selection of an appropriate baseline, the autonomic nature of the thermal print, the experimental setup, methodological issues, limitations, and considerations, as well as future directions.

ELEVATED RESPONSE OF HUMAN AMYGDALA TO NEUTRAL STIMULI IN MILD POST TRAUMATIC STRESS DISORDER: NEURAL CORRELATES OF GENERALIZED EMOTIONAL RESPONSE

Previous evidence from functional magnetic resonance imaging (fMRI) studies has shown that amygdala responses to emotionally neutral pictures are exaggerated at a group level in patients with severe post-traumatic stress disorder (PTSD) [Hendler T, Rotshtein P, Yeshurun Y, Weizmann T, Kahn I, Ben-Bashat D, Malach R, Bleich A (2003) Neuroimage 19(3):587-600]. The present fMRI study tested the hypothesis that amygdala responses are elevated not only in response to negative pictures but also to neutral pictures as a function of disease severity in patients with mild symptoms and in subjects who did not develop symptoms. To this end, fMRI scans were performed in 10 patients with mild PTSD and 10 healthy controls (both victims of a bank robbery), during the execution of a visuo-attentional task in which they were asked to observe emotionally negative or neutral pictures. Control subjects showed enhanced amygdala responses to emotionally negative stimuli compared to neutral stimuli. On the contrary, PTSD patients were characterized by high amygdala responses to both neutral and emotional pictures, with no statistically significant difference between the two classes of stimuli. In the entire group, we found correlations among the severity of the PTSD symptoms, task performance, and amygdala activation during the processing of neutral stimuli. Results of this study suggest that amygdala responses and the selectivity of the emotional response to neutral stimuli are elevated as a function of disease severity in PTSD patients with mild symptoms.

Thermal Signatures of Emotional Arousal: A Functional Infrared Imaging Study

Functional infrared imaging was used to study the facial thermal signatures of three fundamental emotional conditions: stress, fear and pleasure arousal. Facial cutaneous temperature and its topographic distribution exhibited specific features clearly correlated to emotional arousal and concomitant measures of standard physiological signals of the sympathetic activity. The results of this study indicate functional infrared imaging as an alternative, touch less, non invasive method for assessing individuals emotional arousal in psychophysiology.

Infrared functional imaging applied to Raynaud's phenomenon

Presents an approach that allows simultaneous assessment of thermal properties of multiple fingers on both hands. It is a novel approach to the estimation of Raynauds phenomenon based on infrared functional imaging assessments. Q, which represents the total amount of stored heat by the finger during the rewarming processes and is evaluated by means of the area under the time-temperature curve, seems to be particularly effective in order to describe the thermal recovery capabilities of the finger, also in terms of thermal efficiency. Q clearly highlights the difference between primary Raynauds phenomenon and secondary scleroderma patients, and between patients and normal as well, and provides useful information about the abnormalities of their thermoregulatory finger properties.

Imaging the cardiovascular pulse

We have developed a novel method to measure human cardiac pulse at a distance. It is based on the information contained in the thermal signal emitted from major superficial vessels. This signal is acquired through a highly sensitive thermal imaging system. Temperature on the vessel is modulated by pulsative blood flow. To compute the frequency of modulation (pulse), we extract a line-based region along the vessel. Then, we apply Fast Fourier Transform (FFT) to individual points along this line of interest to capitalize on the pulse propagation effect. Finally, we use an adaptive estimation function on the average FFT outcome to quantify the pulse. We have tested the accuracy of our method on 5 subjects with highly successful results. The technology is expected to find applications among others in sustained physiological monitoring of cardiopulmonary diseases, sport training, sleep studies, and psychophysiology (polygraph).

The Autonomic Signature of Guilt in Children: A Thermal Infrared Imaging Study

So far inferences on early moral development and higher order self conscious emotions have mostly been based on behavioral data. Emotions though, as far as arguments support, are multidimensional notions. Not only do they involve behavioral actions upon perception of an event, but they also carry autonomic physiological markers. The current study aimed to examine and characterise physiological signs that underlie self-conscious emotions in early childhood, while grounding them on behavioral analyses. For this purpose, the “mishap paradigm” was used as the most reliable method for evoking feelings of “guilt” in children and autonomic facial temperature variation were detected by functional Infrared Imaging (fIRI). Fifteen children (age: 39–42 months) participated in the study. They were asked to play with a toy, falsely informed that it was the experimenters “favourite”, while being unaware that it was pre-planned to break. Mishap of the toy during engagement caused sympathetic arousal as shown by peripheral nasal vasoconstriction leading to a marked temperature drop, compared to baseline. Soothing after the mishap phase induced an increase in nose temperature, associated with parasympathetic activity suggesting that the childs distress was neutralized, or even overcompensated. Behavioral analyses reported signs of distress evoked by the paradigm, backing up the thermal observation. The results suggest that the integration of physiological elements should be crucial in research concerning socio-emotional development. fIRI is a non invasive and non contact method providing a powerful tool for inferring early moral emotional signs based on physiological observations of peripheral vasoconstriction, while preserving an ecological and natural context.