Biomedical subjects

Francisco Vega-Bermudez

Publications and source records attributed to Francisco Vega-Bermudez.

3 recordsLinked to original sources

PubMed2005

Sawtooth wave density analysis during REM sleep in temporal lobe epilepsy patients.

BACKGROUND AND PURPOSE: This study analyzes sawtooth waves (STW), a characteristic feature of rapid eye movement (REM) sleep, in temporal lobe epilepsy patients in order to test the hypothesis of STW dysfunction in this population. METHODS: Polysomnographic records from 16 patients with temporal lobe epilepsy and 11 controls were scored for density (STW/h of REM sleep), duration (STW duration in s), and frequency of STW (waves/second within each STW complex). These measures were compared between both groups. RESULTS: STW measures were significantly different in control vs. epilepsy patients; respectively, density was 60.8 vs. 20.9 waves/h (P<0.005), average duration was 6.5 vs. 5.4 s (P<0.005 cycles 1-4), and frequency was 2.75 vs. 2.61 Hz (P<0.0005 across all cycles). CONCLUSIONS: Our measurements show a change in the density, duration and frequency of STW in patients with temporal lobe epilepsy compared to controls. Other parameters of REM sleep appear to be similar in both groups. These findings suggest a cortical influence on REM sleep either directly or through limbic-hypothalamic-brainstem connections.

Adolescent↗

PubMed2004

Fingertip skin conformance accounts, in part, for differences in tactile spatial acuity in young subjects, but not for the decline in spatial acuity with aging.

The ability of the skin to conform to the spatial details of a surface or an object is an essential part of our ability to discriminate fine spatial features haptically. In this study, we examined the extent to which differences in tactual acuity between subjects of the same age and between younger and older subjects can be accounted for by differences in the properties of the skin. We did so by measuring skin conformance and tactile spatial acuity in the glabrous skin at the fingertip in 18 younger (19-36 years old) and 9 older (61-69 years old) subjects. Skin conformance was measured as the degree to which the skin invaded the spaces in the psychophysical stimuli. There were several findings. First, skin conformance accounted for 50% of the variance in our measure of tactile spatial acuity (the threshold for grating orientation discrimination) between the younger subjects. The subjects with more compliant skin had substantially lower thresholds than did the subjects with stiffer skin. Second, the skin of the younger subjects was more compliant across than along the skin ridges, and this translated into significantly greater performance when the gratings were oriented along than when oriented across the skin. Third, skin conformance was virtually identical in the younger and the older subjects. Consequently, skin conformance cannot account for the loss of spatial acuity reported in earlier studies and confirmed in this study. We infer that the loss must be neural in origin.

Adult↗

PubMed2002

Spatial acuity after digit amputation.

Digit amputation in human and non-human primates results in reorganization of somatosensory cortex in which the representations of adjacent, intact digits expand to fill the cortical region previously devoted to the amputated digits. Whether this expanded representation results in improved sensory performance has not been determined. Consequently, we measured the ability to recognize small objects (raised letters) with a digit adjacent to the amputation and the same digit on the normal, contralateral hand in 15 amputees. The same digits were also tested in 15 age-matched, amputation-free subjects. There was no significant difference in recognition scores between digits in the amputees or between amputees and control subjects. More detailed analyses of specific confusion patterns and of the improvement with practice showed no significant differences. As far as we could determine, the cortical expansion that is presumed to accompany digit amputation had no effect on tactile pattern recognition performance.

Adult↗