Replication of Reduced Pattern Electroretinogram Amplitudes in Depression With Improved Recording Parameters

Background: The retina has gained increasing attention in non-ophthalmological research in recent years. The pattern electroretinogram (PERG), a method to evaluate retinal ganglion cell function, has been used to identify objective correlates of the essentially subjective state of depression. A reduction in the PERG contrast gain was demonstrated in patients with depression compared to healthy controls with normalization after remission. PERG responses are not only modulated by stimulus contrast, but also by check size and stimulation frequency. Therefore, the rationale was to evaluate potentially more feasible procedures for PERG recordings in daily diagnostics in psychiatry.Methods: Twenty-four participants (12 patients with major depression (MDD) and 12 age- and sex-matched healthy controls) were examined in this pilot study. We investigated PERG amplitudes for two steady-state pattern reversal frequencies (12.5/18.75 rps) and four sizes of a checkerboard stimulus (0.8°, 1.6°, 3.2°, and 16°) to optimize the PERG recordings in MDD patients.Results: Smaller PERG amplitudes in MDD patients were observed for all parameters, whereby the extent of the reduction appeared to be stimulus-specific. The most pronounced decline in the PERG of MDD patients was observed at the higher stimulation frequency and the finest pattern, whilst responses for the largest check size were less affected. Following the PERG ratio protocol for early glaucoma, where similar stimulus dependent modulations have been reported, we calculated PERG ratios (0.8°/16°) for all participants. At the higher frequency (18.75 rps), significantly reduced ratios were observed in MDD patients.Conclusion: The “normalization” of the PERG responses—via building a ratio—appears to be a very promising approach with regard to the development of an objective biomarker of the depressive state, facilitating inter-individual assessments of PERG recordings in patients with psychiatric disorders.

Cortical Contrast Processing in Retinitis Pigmentosa: Evidence of PVEPs Spatial Functions

Objective: To study the effect of check width size of the stimuli on the amplitude and latency of the P100 component of visual evoked potentials recorded in patients with retinitis pigmentosa (RP). Methods: Pattern reversal visual evoked potentials (PVEPs) were recorded in 16 RP patients and 20 visually normal subjects. Pattern reversal stimuli with five different check widths and 100% of contrast were projected in the right eye of both patients and control subjects. PVEPs induced by stimuli with 78%, 16%, and 6% of contrast were also recorded in 10 of the control subjects. Results: In RP patients, the amplitude of P100 was smaller than controls in all check sized used and the peak P100 amplitude was obtained with a larger check width than in controls. P100 was also delayed in RP patients in all check sizes studied. The P100 amplitude- and latency-check size functions of RP patients were like those found in control subjects with low contrast stimuli of 16% and 6%. Conclusion: The PVEPs spatial functions of RP patients show quantitative and qualitative changes, suggesting disease induced alteration in the neural processing of stimulus contrast.

At Your Service on the Table: Impact of Tabletop Technology on Restaurant Performance

Some industries, such as healthcare and financial services, have reported significant productivity gains from introduction of new technologies. However, other more traditional, labor-intensive industries are lagging behind. We use granular data to examine the impact of a customer-facing technology (a tabletop device that facilitates the table service process) on the check size and meal duration aspects of restaurant performance. The restaurant chain in our study implemented tabletop devices in a staggered manner, offering us a quasi-experimental setting in which to apply a difference-in-difference technique and identify the causal effect of the technology. We find that the tabletop technology is likely to improve average sales per check by approximately 1% (95% confidence interval is from 0.8% to 1.02%), and reduce the meal duration by close to 10% (95% confidence interval ranges from −9.94% to −9.54%). The combination of these two effects increases the sales per minute or sales productivity by approximately 11%. Various robustness checks of our empirical strategy and post hoc analyses find that tabletop technology allows low-ability waiters to improve their performance more significantly than high-ability waiters. In addition, the technology does not change the staffing level. Overall, our results indicate great potential for introducing tabletop technology in a large service industry that currently lacks digitalization. This paper was accepted by Vishal Gaur, operations management.

Differential Effects of the Valence and Volume of Online Reviews on Customer Share of Visits: The Case of US Casual Dining Restaurant Brands

Online customer reviews increasingly influence customer purchase decisions. Indeed, many customers have highlighted the significance of online reviews as an influential source of information. This study reports an investigation of the differential effects of online reviews, such as valence and volume, on the customer share of visits. Our findings suggest that valence (i.e., star rating) had more effect, giving a higher average check size to restaurants on the share of visits, while number reviews (volume) did not drive the share of visits to restaurants regardless of the average check size. Therefore, the ideal for casual dining restaurant brands would be to manage highly positive ratings to retain their customers.

Analysis of Least Significant Bit Method Using Sequential Encoding-Decoding in Steganography Digital Image

The method of steganography commonly used to hide data or information is Least Significant Bit (LSB) method. One of the relevant research is LSB using sequential Encoding - Decoding by David Pipkorn and Preston Weisbrot. In this research, an analysis of the LSB method using Sequential Encoding - Decoding by doing some testing. The tests are on the aspect of message security using tools StegSpy and enhanced LSB algorithm, testing on image quality by calculating the Peak Signal to Noise Ratio (PSNR) value and see the image histogram, testing on robustness of message by doing some image processing operations on stego image, like cropping, rotating, and etc, and then testing on capacity to check size of cover image and stego image and calculates the maximum size of data that can be hidden. From the testing process, we know that there are deficiencies in the aspects of security, robustness and capacity of a message. And then in this research we try to change the location of messages that are hidden in the image bits, which previous research used the 8th bit of each bytes, changed to the 7th bit. To be able to correct deficiencies in the security aspect. After repairing and testing like before, obtained better results in the security aspect. This can be seen from the image of the enhanced LSB algorithm process, the message is not detected, but unfortunately the image quality is reduced, with the low PSNR value generated.

NILAI NORMAL LATENSI DAN AMPLITUDO GELOMBANG VISUAL EVOKED POTENTIAL PADA USIA DEWASA

NORMATIVE VALUES OF VISUAL EVOKED POTENTIALS` LATENCIES AND AMPLITUDES IN ADULTSABSTRACTIntroduction: Visual evoked potentials (VEP) is used to assess the visual pathway through the optic nerves and brain. VEP wave can be affected by physiological and non-physiological factors; some of which can be controlled, while others cannot. Thus, each VEP laboratory needs its own set of normative values. A normal VEP response to a stimulus is a positive occipital peak that occurs at a mean latency of 100ms. Most of the published normal value originated from abroad where demographical and environment condition are considered less appropriate with Indonesian population.Aims: To established normal value of adult VEP latency and amplitude in Clinical Naeurophysiology Laboratori- um, Neurology Clinic Dr. Cipto Mangunkusumo Hospital, Jakarta.Method: A cross-sectional study on healthy subject between 18 to 55 years old. The anthropometric parameters including age, height, weight, body mass index and head circumference were recorded in all the subjects. VEP was record- ed with a Caldwell Sierra Summit machine and standard silver-silver chloride disc electrodes. A VEP monitor displaying checker board was used to give the pattern reversal stimulus. The VEP parameters recorded were latencies to P100 waves.Results: P100 latencies on 110 subjects, 55 male, and 55 female upon recording at 32’ check size were 117ms in male and 119 ms in female. Upper normal limit of interocular latency difference values in recording at the same size were 10,96ms in male and 10,2ms in female. No significant differences of P100 latencies between male and female were found, but there were significant differences in amplitudes.Discussion: In our population, gender is an important factor affecting P100 amplitudes but not P100 latencies.Keywords: Amplitude, latency, P100, visual evoked potentialABSTRAKPendahuluan: Visual evoked potentials (VEP) digunakan untuk menilai jaras visual dari nervus optikus hingga korteks visual. Gelombang VEP dapat dipengaruhi oleh berbagai faktor fisiologis dan non-fisiologis yang tidak semua dapat dikontrol, sehingga diperlukan referensi nilai normal latensi dan amplitudo gelombang VEP untuk di setiap laborato- rium. Sejauh ini mayoritas referensi berasal dari studi di luar negeri yang secara demografi maupun kondisi setempat dapat kurang sesuai dengan populasi di Indonesia.Tujuan: Mengetahui nilai normal latensi dan amplitudo gelombang VEP pada subjek dewasa di Laboratorium Neurofisiologi Klinik, Poliklinik Saraf RSUPN Dr. Cipto Mangunkusumo, Jakarta, sebagai referensi pemeriksaan VEP di kemudian hari.Metode: Studi potong lintang pada subjek sehat berusia antara 18 hingga 55 tahun. Subjek diukur antropometri, seperti usia, tinggi badan, berat badan, indeks massa tubuh, dan lingkar kepala. Perekaman VEP menggunakan alat Cald- well Sierra Summit, dan elektroda elektroensefalografi (EEG) standar. Stimulus VEP menggunakan layar berpola dan metode transient pattern reversal. Parameter VEP yang direkam adalah latensi dan amplitudo P100.Hasil: Pada perekaman terhadap 110 subjek yang terdiri dari 55 subjek laki-laki dan 55 subjek perempuan dengan ukuran kotak 32’, nilai batas atas latensi gelombang P100 adalah 117ms pada laki-laki dan 119ms pada perempuan. Nilai batas atas perbedaan latensi interokular pada perekaman dengan ukuran kotak yang sama adalah 10,96ms untuk laki-laki dan 10,2ms untuk perempuan. Tidak ada perbedaan bermakna antara latensi gelombang P100 pada kelompok laki-laki dan perempuan, tetapi terdapat perbedaan amplitudo P100 yang bermakna antara kelompok laki-laki dan perempuan.Diskusi: Terdapat perbedaan yang bermakna pada rerata amplitudo P100 antara subjek laki-laki dan perempuan pada perekaman dengan ukuran kotak 16’ maupun 32’.Kata kunci: Amplitudo, latensi, P100, visual evoked potentials

Pattern reversal visual evoked potentials in adults: variability with age

Purpose: Pattern reversal visual evoked potential (PRVEP) is an electrophysiological test for evaluating the visual pathway. This study measured the changes in the latencies and amplitudes of the PRVEP with age and gender in normal subjects. Methods: Healthy participants (n=81; 162 total eyes), between the ages of 20 and 92 years were recruited for the study. Stimulation was performed monocularly with a high-contrast (>50%) black-white checkerboard pattern with a check size of 30° at a reversal rate of 2 Hz, a band-pass of 1-100 Hz, a sweep of 250 msec and an average of 150 stimulations in a dark room. Mean and standard deviations for three latencies (N75, P100 and N145) and the amplitude (N75-P100) for each decade were measured. Results: There was a linear trend by age for all three latencies, indicating that the higher age groups had longer latencies. The latencies decreased in the 5th decade before increasing in the higher age groups. The amplitude of N75-P100 decreased with age. The P100 latencies were longer in males than females in all age groups and the difference increased with increasing age.

Pattern Visual Evoked Potential Changes in Diabetic Patients without Retinopathy

Purpose.To assess the different check sizes of pattern visual evoked potential (PVEP) in diabetic patients without retinopathy according to HbA1c levels and diabetes duration.Methods.Fifty-eight eligible patients with type 2 diabetes mellitus and 26 age- and sex-matched healthy controls were included in the study. Only the right eye of each patient was analyzed. All of the patients underwent a comprehensive ophthalmic examination, and the PVEPs were recorded.Results.There was a statistically significant difference in P100 latency in 1-degree check size and in N135 latency in 2-degree check size between controls and patient groups which have different HbA1c levels. There were statistically significant, positive, and weak correlations with diabetes duration and P100 latency in 7-minute and 15-minute check sizes and N135 latency in 15-minute check size.Conclusions.It was showed that there were prolongations in P100 latency only in 1-degree check size and in N135 only in 2-degree check size in diabetic patients without retinopathy. There was statistically significant correlation between diabetes duration and P100 and N135 latencies in different check sizes.

Pattern ERG as a predictor in ocular hypertensive

Purpose: To report the repeatability of Pattern Electrotretinogram (PERG) and its findings in ocular hypertension (OHT) and normal eyes.Methods: A cross-sectional study where PERG responses were compared between the study group comprising of 80 eyes of 80 patients with intraocular pressure (IOP)>21 mmHg and the control group with 80 eyes of 80 normal individuals (IOP≤21mmHg). The optic disc and the visual fields were normal with a visual acuity of ≥ 0.8 in both groups. PERG was recorded twice for each individual in the control group by a single operator on 2 consecutive days to assess the repeatability.Results: The mean age in the study and control groups was 50.05±10.03 and 54.8±7.66 years(p=0.44) respectively. The mean IOP was 26.55±3.9 mmHg for the study group as opposed to 14.45±2.9 mmHg for the controls (p<0.001). The central corneal thickness and the cup-disc ratio was similar between the groups (p>.05). The P50-N95 amplitude (p=0.01) and the P50 latency (p<0.001) was statistically significantly different between both the groups. The intra-class correlation coefficient (ICC) showed poor agreement for all parameters except for N35-P50 0.8 to 16 degree check size amplitude ratio (PERG ratio).Conclusion: Increase in P50 latency emerges as a new candidate for early glaucoma indicator in addition to reduction in P50-N95 amplitude. PERG parameters suffer from high test-retest variability. Deterioration in PERG recordings should be interpreted with caution. The variability is lesser for the PERG ratio which maybe more meaningful while monitoring for change over time.