Examinando por Autor "Tomaz, Carlos A."

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    Nonlinear digital signal processing in mental health : Characterization of major depression using instantaneous entropy measures of heartbeat dynamics
    (2015-03-13) Valenza, Gaetano; García, Ronald G.; Citi, Luca; Scilingo, Enzo P.; Tomaz, Carlos A.; Barbieri, Riccardo
    Nonlinear digital signal processing methods that address system complexity have provided useful computational tools for helping in the diagnosis and treatment of a wide range of pathologies. More specifically, nonlinear measures have been successful this study, we propose the use of instantaneous measures of entropy, namely the inhomogeneous point-process approximate entropy (ipApEn) and the inhomogeneous point-process sample entropy (ipSampEn), to describe a novel characterization of MD patients undergoing affective elicitation. Because these measures are built within a nonlinear point-process model, they allow for the assessment of complexity in cardiovascular dynamics at each moment in time. Heartbeat dynamics were characterized from 48 healthy controls and 48 patients with MD while emotionally elicited through either neutral or arousing audiovisual stimuli. Experimental results coming from the arousing tasks show that ipApEn measures are able to instantaneously track heartbeat complexity as well as discern between healthy subjects and MD patients. Conversely, standard heart rate variability (HRV) analysis performed in both time and frequency domains did not show any statistical significance. We conclude that measures of entropy based on non linear point-process models might contribute to devising useful computational tools for care in mental health
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    Plasma nitrate levels and flow-mediated vasodilation in untreated
    (2011-05) García, Ronald G.; Zarruk, Juan G.; Barrera, Carlos; Pinzón, Alexander; Trillos, Elizabeth; Arenas, William D.; Luengas, Carlos; Tomaz, Carlos A.; Lopez-Jaramillo, Patricio
    Objective: Findings from several studies have revealed that major depression is associated with an increased cardiovascular risk. The physiopathologic mechanisms of this association remain unclear, although recently, it has been hypothesized that a decreased production of nitric oxide could be a potential contributor to vascular dysfunction in depressive patients. The objective of this study was to evaluate nitric oxide production and vascular endothelial function in treatment-naive young healthy adults with a first episode of major depression. Methods: A case-control study in 50 treatment-naive young adults with a first episode of major depression and 50 healthy control subjects was conducted. Plasma levels of nitric oxide metabolites (nitrates/nitrites) were determined using a colorimetric assay based on Griess reaction. Endothelial function was assessed by flow-mediated vasodilation measurements after reactive hyperemia. Results: The mean age of the depressed patients was 22.6 (standard deviation [SD], 4.6) years, whereas the controls were 23.4 (SD, 4.8) years. Sixteen men (32%) and 34 women (68%) were included in each group. The plasma nitrite/nitrate concentrations were significantly lower in depressive subjects compared with healthy controls (17.5 [SD, 4.9] Kmol/L versus 21.6 [SD, 7.0] Kmol/L, p G .001); however, flow-mediated vasodilation values were similar in both groups (13.1% [SD, 4.3%] versus 12.1% [SD, 5.0%], p = .10). Conclusions: Decreased plasma concentrations of nitric oxide metabolites are not associated with vascular endothelial dysfunction in young subjects with a first episode of major depression. Reduced nitrate/nitrite levels could reflect a decreased nitric oxide production in the central nervous system of depressed subjects. Further studies are needed to confirm this hypothesis.
  • Publicación
    Acceso abierto
    Relationship between cardiac vagal activity and mood congruent memory bias in major depression
    (2016-01) García, Ronald G.; Valenza, Gaetano; Tomaz, Carlos A.; Barbieri, Riccardo
    Background Previous studies suggest that autonomic reactivity during encoding of emotional information could modulate the neural processes mediating mood-congruent memory. In this study, we use a point-process model to determine dynamic autonomic tone in response to negative emotions and its influence on long-term memory of major depressed subjects. Methods Forty-eight patients with major depression and 48 healthy controls were randomly assigned to either neutral or emotionally arousing audiovisual stimuli. An adaptive point-process algorithm was applied to compute instantaneous estimates of the spectral components of heart rate variability [Low frequency (LF), 0.04–0.15 Hz; High frequency (HF), 0.15–0.4 Hz]. Three days later subjects were submitted to a recall test. Results A significant increase in HF power was observed in depressed subjects in response to the emotionally arousing stimulus (p=0.03). The results of a multivariate analysis revealed that the HF power during the emotional segment of the stimulus was independently associated with the score of the recall test in depressed subjects, after adjusting for age, gender and educational level (Coef. 0.003, 95%CI, 0.0009–0.005, p=0.008). Limitations These results could only be interpreted as responses to elicitation of specific negative emotions, the relationship between HF changes and encoding/recall of positive stimuli should be further examined. Conclusions Alterations on parasympathetic response to emotion are involved in the mood-congruent cognitive bias observed in major depression. These findings are clinically relevant because it could constitute the mechanism by which depressed patients maintain maladaptive patterns of negative information processing that trigger and sustain depressed mood.