Contrast thresholds for the pattern electroretinogram (PERG) were measured using lock-in amplifier retrieval of the retinal signal and a swept contrast display. Contrast sensitivity functions (CSF) developed from these PERG contrast thresholds were compared with those established psychophysically under identical stimulus conditions. Whereas the PERG CSF showed a band-pass characteristic across ...

To assess the role of second-order channels in symmetry perception we measured the effects of check size, spatial frequency content, eccentricity and grey scale range on the detection of symmetrical and anti-symmetrical patterns. Thresholds for symmetrical stimuli were only moderately affected by these manipulations. Anti-symmetrical stimuli composed of large black and white checks elicited low...

Preliminary results on a way to reduce terms for text categorization are presented. We have used the transition point; a frequency which splits the words of a text into high frequency words and low frequency words. Thresholds outcoming from document frequency of terms, Information Gain and χ were tested in combination with the transition point. A text categorization experiment based on Rocchio’...

Observers detected briefly pulsed sine-wave gratings presented with various asynchronies before, during or after a 700 msec conditioning flash. Although the conditioning flash raised increment thresholds for detection of both low and high spatial frequency gratings, shapes of the masking curves differed. Curves for low spatial frequency gratings exhibited peaks at the conditioning field on and ...

Introduction Abnormal neural impulses in the nervous system may lead to various diseases and disabilities. High frequency alternating currents (HFAC) has been used to block the propagation of such impulses and improve the symptoms or disabilities. The technique is safe, reversible, and relatively selective, and its reliability, the optimum stimulation parameters, and elimination of the onset re...