Linear filtering precedes nonlinear processing in early vision

Background: Nonlinearities play a significant role in early visual processing. They are central to the perception of spatial contrast variations, multiplicative transparencies and texture boundaries. This article concerns the stage of processing at which nonlinearities first become significant. Results: Subjects were adapted to a high contrast sinusoidal grating followed by a brief presentation of a contrast modulated test (plaid) pattern. Thresholds for the detection of the contrast modulation (the beat) were measured. Results show that threshold elevation is greatest when the orientation and spatial frequency of the adapting grating are close to the principal Fourier frequency (the carrier) of the test pattern. Adaptation to sinewave-gratings near the frequency of the contrast modulation has relatively little effect. The data also show that the processing of contrast is frequency selective, with a peak tuning frequency near 0.4 cycles per degree. Conclusions: The data are consistent with a model in which the contrast beats are processed in a frequency- specific manner, after an initial stage of frequency-specific and orientation-specific linear filtering

Recognition of Facial Expressions by Cortical Multi-scale Line and Edge Coding

Face-to-face communications between humans involve emotions, which often are unconsciously conveyed by facial expressions and body gestures. Intelligent human-machine interfaces, for example in cognitive robotics, need to recognize emotions. This paper addresses facial expressions and their neural correlates on the basis of a model of the visual cortex: the multi-scale line and edge coding. The recognition model links the cortical representation with Paul Ekman's Action Units which are related to the different facial muscles. The model applies a top-down categorization with trends and magnitudes of displacements of the mouth and eyebrows based on expected displacements relative to a neutral expression. The happy vs. not-happy categorization yielded a. correct recognition rate of 91%, whereas final recognition of the six expressions happy, anger, disgust, fear, sadness and surprise resulted in a. rate of 78%

Cost-effectiveness of replacing versus discarding the nail in children with nail bed injury

Every year in the UK, around 10 000 children need to have operations to mend injuries to the bed of their fingernails. Currently, most children have their fingernail placed back on the injured nail bed after the operation. The NINJA trial found that children were slightly less likely to have an infection if the nail was thrown away rather than being put back, but the difference between groups was small and could have be due to chance. This study looked at whether replacing the nail is cost-effective compared with throwing it away. Using data from the NINJA trial, we compared costs, healthcare use, and quality of life and assessed the cost-effectiveness of replacing the nail. It was found that throwing the nail away after surgery would save the National Health Service (NHS) £75 (€85) per operation compared with placing the nail back on the nail bed. Changing clinical practice could save the NHS in England £720 000 (€819 000) per year