Interhemispheric communication during haptic self-perception.

During the haptic exploration of a planar surface, slight resistances against the hand's movement are illusorily perceived as asperities (bumps) in the surface. If the surface being touched is one's own skin, an actual bump would also produce increased tactile pressure from the moving finger onto the skin. We investigated how kinaesthetic and tactile signals combine to produce haptic perceptions during self-touch. Participants performed two successive movements with the right hand. A haptic force-control robot applied resistances to both movements, and participants judged which movement was felt to contain the larger bump. An additional robot delivered simultaneous but task-irrelevant tactile stroking to the left forearm. These strokes contained either increased or decreased tactile pressure synchronized with the resistance-induced illusory bump encountered by the right hand. We found that the size of bumps perceived by the right hand was enhanced by an increase in left tactile pressure, but also by a decrease. Tactile event detection was thus transferred interhemispherically, but the sign of the tactile information was not respected. Randomizing (rather than blocking) the presentation order of left tactile stimuli abolished these interhemispheric enhancement effects. Thus, interhemispheric transfer during bimanual self-touch requires a stable model of temporally synchronized events, but does not require geometric consistency between hemispheric information, nor between tactile and kinaesthetic representations of a single common object.

[Effect of cataract surgery for visual field in glaucoma patients]. / Influenta operatiei de cataracta asupra câmpului vizual la pacientii cu glaucom.

PURPOSE: To study the influence of cataract surgery on the quantitative and qualitative parameters of visual field in patients previously operated for glaucoma. METHOD: Retrospective study that included 42 eyes with primary open angle glaucoma that had been previously subjected to trabeculectomy. The glaucoma was therapeutically controlled in all patients. Then they all underwent cataract extraction and artificial lens implantation. All eyes were evaluated pre- and postoperatively at short intervals to avoid glaucoma progression. Throughout the follow-up period the IOP remained under 21 mmHg, with or without antiglaucoma drugs. RESULTS: After cataract surgery the visual acuity increased significantly (preoperative VA 0.22 +/- 0.15, postoperative VA 0.57 +/- 0.27, p < 0.0001). The parameters used for glaucoma evaluation and follow-up remained unchanged (preoperative IOP 17 +/- 6.71 mmHg, postoperative IOP 17.04 +/- 4.56 mmHg, p = 0.97; preoperative C/D ratio 0.59 +/- 0.26, postoperative C/D ratio 0.62 +/- 0.26, p = 0.69). The quantitative parameters of visual field did not change significantly (preoperative MD -15.52 +/- 8.69, postoperative MD -13.33 +/- 9.97, p = 0.28; preoperative PSD 5.86 +/- 3.25, postoperative PSD 6.11 +/- 3.39, p = 0.79). In about 60% of cases the MD value improved and in 24% it worsened. The PSD was ameliorated in 33% of cases and aggravated in 26% of cases. CONCLUSION: Cataract surgery in patients with previously operated, therapeutically controlled glaucoma does not influence significantly the synthetic parameters of visual field.

[A comparative analysis of standard automated perimetry and short wavelength automated perimetry in early diagnosis of glaucoma]. / Analiza comparativa a perimetriei automate standardizate si a perimetriei "albastru pe galben" in diagnosticul precoce al glaucomului.

PURPOSE: To assess the concordance between standard automated perimetry (SAP) and short wavelength automated perimetry (SWAP). To analyze comparatively the early detection and the extent of visual field defects in glaucoma suspects and in early glaucoma. METHOD: A prospective, randomized study that included 55 patients (107 eyes), glaucoma suspects or with early glaucoma who were randomly subject to both SAP and SWAP; the examinations were repeated at 3 and 6 months in order to establish that the visual field defects were real. The studied parameters were the mean value of MD and PSD in the two techniques, the correlation between the results (global and on patients subgroups), the percentage of patients in which the defects were larger, deeper or new defects were found when examined in SWAP. RESULTS: There was no statistically significant difference in the MD value between the two methods (-3.42 +/- 5.17 dB in SWAP, -2.83 +/- 4.84 dB in SAP, p = 0.14); the PSD value was significantly higher (p < 0.0001) in SWAP (3.63 +/- 1.36 dB) than in SAP (2.66 +/- 1.97 dB). There was a high correlation of the MD and PSD values between the two techniques; the highest correlation appeared in POAG patients. The SWAP test has evidenced visual field defects in 10.1% of eyes with normal SAP tests and also larger and deeper defects in 18.7% of cases. CONCLUSIONS: The SWAP and SAP results were concordant; the visual field defects were earlier detected, appeared larger and deeper in SWAP than in SAP.

[FDT versus automated standard perimetry in healthy subjects]. / FDT vs. perimetria statica automata la voluntari sanatosi.

PURPOSE: To assess the frequency of visual field defects in frequency doubling technology (FDT) perimetry performed in healthy volunteers and the correlations between FDT and standard automated perimetry (SAP). METHOD: A transversal study that included 57 healthy volunteers who were subject to visual field testing in both FDT and SAP (randomly effectuated in the same day). The studied parameters were: the frequency of visual field defects in the two techniques, the correlation of the quantitative parameters (MD, PSD) with the C/D ratio and also between techniques, the test reliability and the test duration. The subjects have been questioned about their preference for one test or another. RESULTS: The frequency of visual field defects was 47.35% in FDT and 22.8% in SAP. The MD values were significantly higher in FDT (MD FDT= -1.45+/-1.91, MD SITA= -0.77+/-1.58, p< 0.0001). Also the PSD values were higher in FDT (PSD FDT= 3.76+/-0.96, PSD SITA= 1.94+/-1.05). The correlation of quantitative parameters between the two techniques was low (r = 0.369 for MD and 0.206 for PSD). The correlation between the PSD value and the C/D ratio was extremely weak in both methods (because the subjects were healthy). The mean duration of a FDT test (4 '29") was significantly lower than that of a SITA test (5'18") - p < 0.00001. The reliability indices (fixation losses, false negative and false positive errors) were significantly better in FDT, and 3/4 of subjects declared that they preferred the FDT test. CONCLUSIONS: In normal subjects the frequency of visual field defects was greater in FDT than in SAP. There was a low correlation of quantitative parameters (MD, PSD) between SAP and FDT, and also with the C/D ratio. Better reliability indices, shorter test duration and better patient compliance are arguments for using FDT as a screening test for glaucoma.