Biomedical subjects

Traian Popa

Publications and source records attributed to Traian Popa.

3 recordsLinked to original sources

PubMed2007

Adaptive changes in postural strategy selection in chronic low back pain.

Chronic low back pain (CLBP) patients achieve postural stability during challenging stance conditions by increasing sway speed. We investigated the mechanisms underlying this behavior, and whether postural strategy selection may be influenced by short-term experience of postural perturbation. Thirteen CLBP patients and thirteen age-matched controls underwent posturography tests. Subjects were asked to stand quietly: (a) with eyes open and eyes closed, and (b) while expecting a series of four backward translations of the support surface. Data from condition (a) was subjected to sway density analysis (SDA). This computes the number of consecutive spaces and respectively time samples during which center of pressure (COP) displacements remained inside a 2.5 mm radius. Three parameters of this analysis were considered: the mean number of peaks (MP), reflecting the time spent by COP in regions of stability, the mean time between peaks (MT) relating to the rate of production of posturographic commands, and the mean spatial distance (MD), reflecting the distance between stable regions. In condition (b) the mean COP positions were analyzed during the time (500 ms) preceding each translation. The MD was significantly increased in the CLBP group as compared to controls (P < 0.01), while the MP and MT did not present any significant difference. The expectation of backward translations initially produced a different COP positioning between the two groups (P < 0.0001) which decreased with repetition of platform translations (controls: PDelta1-4 < 0.002; patients: PDelta1-4 < 0.005). The findings show that the timing and the rate of the balance motor commands is comparable between the two groups. On the other hand, there is greater distance between regions of stability in the patient group. Such modification of motor control patterns might be the consequence of a reweighting of sensory input, possibly due to a deterioration of its reliability. Platform translation findings show that both groups aimed at optimizing their posture selection strategy based on prior testing experience. CLBP patients make use of a different postural motor strategy to maintain quiet stance. This is probably the consequence of an imprecise internal estimate of body sway, due to reduced accuracy in the sensory integration process.

Adaptation, Physiological↗

PubMed2005

Electroencephalographic spectral power in writer's cramp patients: evidence for motor cortex malfunctioning during the cramp.

We investigated cortical activation as reflected in task-related spectral power (TRPow) changes in 8 writer's cramp patients during writing on a digital board and during isometric contraction and compared them to those of 8 age-matched healthy subjects. Scalp EEG was recorded over the contralateral primary sensorimotor area (SM1(c)), and from the ipsilateral sensorimotor area (SM1(i)). The electromyogram (EMG) was recorded from the Extensor Digitorum Communis (Extensor), Flexor Digitorum Superficialis (Flexor), and First Dorsal Interosseous (FDI) muscles. We analyzed (1) handwriting performance, (2) changes in the TRPow confined to alpha and beta band, and (3) the EMG spectral power during both tasks, writing and isometric contraction. During writing, all patients developed writer's cramp. The handwriting in writer's cramp patients was associated with significantly less reduction of the beta-range TRPow and lower frequency of the TRPow reduction compared to controls. No significant differences between patients and controls for the alpha band TRPow reduction during handwriting were observed. During writing, the patients showed higher EMG spectral power than the controls but this difference was at the border of significance. The present results indicate disorder in the motor execution system, in writer's cramp patients, associated with impaired functional beta-network state of the contra- and ipsilateral sensorimotor cortices, most probably due to inadequate modulation of the intracortical inhibition associated with writing.

Adult↗

PubMed2004

Cortico-muscular coupling in a patient with postural myoclonus.

We investigated the cortico-muscular coherence in a patient with posturally induced cortically originating negative myoclonus. We recorded simultaneously 50 channels EEG and EMG from quadriceps and biceps femoris muscles of the left upper leg. Three experimental conditions were investigated with the patient in a seated position: (i) recording during rest (Rest), (ii) recording while the patient had to hold his left leg horizontally stretched out (Postural), and (iii) recording while the patient had to hold his left leg horizontally stretched out against a vertical force (Postural against force). Coherence, phase difference and cumulant density were computed as indicators for cortico-muscular coupling. The cortical component preceding the silent period was shown by averaging and was reconstructed. During postural and postural against force conditions, the EEG over the vertex was significantly coherent with EMG, in alpha (7-15 Hz) and beta range (15-30 Hz). The strongest coherence peak was at 21 Hz. No high-frequency coherence was observed. The phase difference and the cumulant density estimate corresponded to a 32 ms time lag between motor cortex and muscles, with EEG leading. The broadening of the coherence spectrum at which the motor cortex drives the muscles together with the excessive coherence levels and the giant SEP could reflect the hyperexcitability of the sensorimotor cortex. The frequency content of the coherence may be characteristic for this type of myoclonus. The results lend support to the view that the frequency analysis may have some diagnostic potential in cortical myoclonus.

Aged↗