Pedro Montoya

Activation of Cortical and Cerebellar Motor Areas during Executed and Imagined Hand Movements: An fMRI Study

Brain activation during executed (EM) and imagined movements (IM) of the right and left hand was studied in 10 healthy right-handed subjects using functional magnetic resonance imagining (fMRI). Low electromyographic (EMG) activity of the musculi flexor digitorum superficialis and high vividness of the imagined movements were trained prior to image acquisition. Regional cerebral activation was measured by fMRI during EM and IM and compared to resting conditions. Anatomically selected regions of interest (ROIs) were marked interactively over the entire brain. In each ROI activated pixels above a t value of 2.45 (p < 0.01) were counted and analyzed. In all subjects the supplementary motor area (SMA), the premotor cortex (PMC), and the primary motor cortex (M1) showed significant activation during both EM and IM; the somatosensory cortex (S1) was significantly activated only during EM. Ipsilateral cerebellar activation was decreased during IM compared to EM. In the cerebellum, IM and EM differed in their foci of maximal activation: Highest ipsilateral activation of the cerebellum was observed in the anterior lobe (Larsell lobule H IV) during EM, whereas a lower maximum was found about 2-cm dorsolateral (Larsell lobule H VII) during IM. The prefrontal and parietal regions revealed no significant changes during both conditions. The results of cortical activity support the hypothesis that motor imagery and motor performance possess similar neural substrates. The differential activation in the cerebellum during EM and IM is in accordance with the assumption that the posterior cerebellum is involved in the inhibition of movement execution during imagination.

The cortical somatotopic map and phantom phenomena in subjects with congenital limb atrophy and traumatic amputees with phantom limb pain

The extent of the cortical somatotopic map and its relationship to phantom phenomena was tested in five subjects with congenital absence of an upper limb, four traumatic amputees with phantom limb pain and five healthy controls. Cortical maps of the first and fifth digit of the intact hand, the lower lip and the first toe (bilaterally) were obtained using neuroelectric source imaging. The subjects with congenital upper limb atrophy showed symmetric positions of the left and right side of the lower lip and the first toe, whereas the traumatic amputees with pain showed a significant shift (about 2.4 cm) of the cortical representation of the lower lip towards the hand region contralateral to the amputation side but no shift for the toe representation. In healthy controls, no significant hemispheric differences between the cortical representation of the digits, lower lip or first toe were found. Phantom phenomena were absent in the congenital but extensive in the traumatic amputees. These data confirm the assumption that congenital absence of a limb does not lead to cortical reorganization or phantom limbs whereas traumatic amputations that are accompanied by phantom limb pain show shifts of the cortical areas adjacent to the amputation zone towards the representation of the deafferented body part.

The relationship of phantom limb pain to other phantom limb phenomena in upper extremity amputees

Abstract In thirty‐two unilateral upper extremity amputees with and without phantom limb pain, various phantom limb phenomena were investigated. In general, the incidence of non‐painful phantom limb sensations was higher in patients with phantom limb pain than in pain‐free amputees. Kinesthetic and kinetic phantom limb sensations were reported more frequently than exteroceptive cutaneous sensations. There was a significant positive correlation between phantom limb pain and stump pain. Patients more frequently assigned sensory than affective pain qualities to their phantom limb pain, whereas no differences between pain qualities were observed for stump pain. No support was found for a relationship between the presence of telescoping (i.e., shrinkage of the phantom limb) and phantom limb pain. These findings point to central as well as to peripheral factors contributing to phantom limb pain.

Event-related brain potentials and the processing of cardiac activity

The cortical processing of cardiac afferent input can be studied by means of event-related potentials (ERP), in which characteristic brain waves are seen to accompany rhythmic activity of the heart. In the present paper, results from three studies, investigating the heartbeat-evoked potential are summarized. These studies demonstrated that (a) cardio-afferent input is projected primarily to fronto-cortical areas; (b) typically, this activity is reflected as a broad positive wave form in a range of 300-600 ms after the EKG R-wave; (c) psychological factors such as level of attention and motivation exert influences on the heartbeat-evoked potential which are comparable to effects known from exteroceptive evoked potentials. On the basis of these data we infer that cardio-afferent input is for the most part transmitted along visceral fibers and that the cortical processing of cardiac activity is similar to the processing of external stimuli.

Covariation bias in flight phobics

Covariation estimates (CEs) between fear-relevant (FR) stimuli (slides of airplane crash sites) or fear-irrelevant (FI) stimuli (slides of airplanes in flight or mushrooms) and an aversive outcome (electrical shock) were examined in 15 flight phobics (high-fear participants) and 15 non-flight-phobic individuals (low-fear participants) by means of an illusory correlation experiment. In spite of a random relationship between all slide categories and outcome (illusory correlation), flight phobics exhibited a covariation bias and showed higher CEs for the contingency between FR slides and shocks than for the contingency between FI slides and shocks in a first experimental block. The CEs of flight phobics for FR slides and shocks was significantly higher than that of non-flight-phobic individuals, while high- and low-fear participants did not differ in their CEs for the other slide-shock combinations. However, even high-fear individuals were able to correct their initial covariation bias in subsequent illusory correlation blocks, presumably based on disconfirming situational information.

Changes in physical symptoms, blood pressure and quality of life over 30 days

The existence of subjective symptoms arising from high blood pressure (BP) remains controversial. Few studies have been performed which compare symptoms of hypertensives and normotensives. The results of these studies are inconsistent. The present study investigates the intensities and prevalences of symptoms of hypertensives and normotensives and the relationship between symptoms and BP for both groups. During a 30-day period, 45 patients with primary hypertension and 45 normotensive controls documented BPs and intensities of 13 symptoms daily as well as mood and life satisfaction weekly. Starting on day 3 hypertensives received beta-blocker therapy (bopindolol, 1 mg/day). The BP values of the hypertensives normalized during the study, while the BPs of the normotensives did not change. At the beginning, hypertensives showed higher prevalences and intensities of the symptoms and poorer mood and life satisfaction. After normalization of BP, hypertensives attained scores similar to those of normotensives in all measured categories. Calculating within-S correlations between symptom intensities and systolic BPs, 70% of the hypertensives, but only 27% of the normotensives, showed at least one significant correlation. The differences observed between untreated hypertensives and the normotensive control group with respect to the prevalence and intensity of symptoms provide convincing evidence that untreated hypertensives are by no means symptom-free. The within-S correlations of the present study documented well the close relationship between symptoms and actual BP for a percentage of hypertensives.

On-line and A Posteriori Covariation Estimates in Panic-Prone Individuals: Effects of a High Contingency of Shocks Following Fear-Irrelevant Stimuli

This study replicates previous findings of a covariation bias in high-fear (panic-prone) individuals. High-fear, but not low-fear participants markedly overestimated the contingency between fear-relevant stimuli (FR, emergency situations) and an aversive outcome (electric shock) as long as contingencies were objectively random. However, the experience of a high contingency of shocks following fear-irrelevant (FI) stimuli (83%) together with a low contingency of shocks following FR stimuli (17%) abolished the group difference. Return of contingencies to random led to comparable bias-free covariation estimates in both high- and low-fear participants. In a previous study by the authors a high contingency of shocks following FR stimuli induced a covariation bias, even in low-fear participants. The present findings suggest that the experience of high contingency between FI stimuli and shock is less likely to induce a covariation bias than the same high contingency between FR stimuli and shock.

Differential β- and α-adrenergic activation during psychological stress

Abstract The responsivity of several cardiovascular indices to a computerized mental arithmetic stress and a cold pressor stress were investigated in 22 healthy adult subjects. The major findings were that the largely β-adrenergically driven T-wave amplitude, pre-ejection period, R-wave to pulse interval, and left ventricular ejection time values responded only to mental arithmetic; a significant decrease in cardiac output and increase in peripheral resistance were elicited during the cold pressor test; inter-beat-interval and subjective stress ratings responded significantly to both stresses compared to baseline levels, but more intensely to mental arithmetic than the cold pressor test; blood pressure, stroke volume and the maximum of the first derivative of the raw impedance signal responded unspecifically to both stresses. These findings support the idea that cardiovascular responses to psychological challenge depend on the level of cognitive processing required for the task. In addition, the superfluity of multiple variable measurements to study cardiovascular reactivity in such situations is discussed.

Speaking from the heart: cardiovascular components of stress rating changes and the relative reactivity of physiological and psychological variables

The first part of the experiment compared the relative reactivity of various cardiovascular measurements and self-reported assessment of mental arithmetic, an active coping stress task. It was found that the self-reported stres rating was more responsive (students t=9.4) than the physiological measurements. Among the cardiovascular indices, heart rate was the most responsive (students t=6.5), followed by the interval between R-wave and the maximal systolic pressure (students t=5.0). The second part of the study used a multiple regression to examine the cardiovascular components of change in stres rating following mental arithmetic. Both resting (psychophysiological “trait” varibles) and change under stress (psychophysiological “state” variables) were used to predict change in stress rating. Stress rating increase were associated with greater maximal systolic pressure rate of rise (finger dP/dt) at baseline and less heart rate increase during mental arithmetic, yielding a multiple r of 0.67. The dual autonomic nature of active coping stress response is discussed. The shortcomings of using a correlate of a correlate are noted.

Vibration based shearing technique (vibro-shearing) versus rolling technique in terms of tissue hydration, stiffness, elasticity, and thermography: A double controlled, standardized study

METHODS: Sixty (60) male athletes were nonrandomized into two groups for performing a myofascial self-help treatment on the quadriceps muscle (QM) and the iliotibial band (ITB): The Shearing Group (N=30) used the Fascia-ReleaZer® tool (a myofascial release tool combined with a vibrational oscillation) and the Rolling Group (N=30) utilized a conventional pin roller. Both groups treated their right thighs only for eight minutes. Both thighs were assessed before and after the intervention with the nontreated left thigh serving as an additional control condition. Position, posture and treatment protocols were standardized in both groups. The objective parameters of stiffness, elasticity (MyotonPRO) and hydration (BIA 101 Anniversary SE) were measured before and after the brief interventions. Statistical analysis included the paired t-test, Wilcoxon signed rank test and Cohen’s d-test.