Interactions between Surround Suppression and Interocular Suppression in Human Vision

Several types of suppression phenomena have been observed in the visual system. For example, the ability to detect a target stimulus is often impaired when the target is embedded in a high-contrast surround. This contextual modulation, known as surround suppression, was formerly thought to occur only in the periphery. Another type of suppression phenomena is interocular suppression, in which the sensitivity to a monocular target is reduced by a superimposed mask in the opposite eye. Here, we explored how the two types of suppression operating across different spatial regions interact with one another when they simultaneously exert suppressive influences on a common target presented at the fovea. In our experiments, a circular target grating presented to the fovea of one eye was suppressed interocularly by a noise pattern of the same size in the other eye. The foveal stimuli were either shown alone or surrounded by a monocular annular grating. The orientation and eye-of-origin of the surround grating were varied. We found that the detection of the foveal target subjected to interocular suppression was severely impaired by the addition of the surround grating, indicating strong surround suppression in the fovea. In contrast, when the interocular suppression was released by superimposing a binocular fusion ring onto both the target and the dichoptic mask, the surround suppression effect was found to be dramatically decreased. In addition, the surround suppression was found to depend on the contrast of the dichoptic noise with the greatest surround suppression effect being obtained only when the noise contrast was at an intermediate level. These findings indicate that surround suppression and interocular suppression are not independent of each other, but there are strong interactions between them. Moreover, our results suggest that strong surround suppression may also occur at the fovea and not just the periphery

Malunion after midshaft clavicle fractures in adults: The current view on clavicular malunion in the literature

This is an overview of the current literature on malunion after midshaft clavicle fracture. Anatomy, trauma mechanism, classification, incidence, symptoms, prevention, and treatment options are all discussed. The conclusion is that clavicle malunion is a distinct clinical entity that can be treated successfully

The results of coraco-clavicular slings for acromio-clavicular dislocation

Article first published online: 21 JAN 2008Background: Treatment of type 3 acromio-clavicular (A-C) dislocations is controversial. There have been over 60 different surgical procedures as well as a variety of conservative measures used to treat this injury. Methods: The outcome of a coraco-clavicular (C-C) sling for grade 3–4 A-C dislocation was studied. A dissolvable sling of braided 1 polydioxanone (PDS, Ethicon) was used with or without excision of the distal end of the clavicle in six patients. The clinical and radiological outcome of the braid and acromio-clavicular joint were studied by clinical examination, plain and stress radiographs and magnetic resonance imaging (MRI). Results: All patients reported good-excellent results from 6 months after surgery. Radiological examination demonstrated some superior clavicular migration in all patients within 1 month of the procedure, although never more than that seen with a grade 2 dislocation. This migration was clinically evident only in patients with a thin build. At 1 month, the MRI demonstrated partial replacement of the braid by granulation tissue. From 6 months on, the braid was absent and fibrous tissue was noted between the coracoid and the clavicle and the acromion and clavicle. Conclusions: The coraco-clavicular sling did not maintain operative reduction of the dislocated clavicle. This did not diminish the functional result but was a cosmetic complication in patients with a thin buildM. Clayer, J. Slavotinek and J. Krishna