The physiological basis for the sensation of gloom: quantitative and qualitative aspects

Diffuse light increases metabolic activity in the lateral geniculate nucleus, visual cortex, and superior colliculus of the cone-dominated ground squirrel visual system

Ground squirrels were monocularly exposed to either steady- or flashing-diffuse light for 45 min following an injection of 14C 2-deoxyglucose (2-DG). Autoradiographic analysis indicated greater metabolic activity in the lateral geniculate nucleus, visual cortex and superior colliculus (SC) of the hemisphere lying contralateral to and receiving input from the diffusely stimulated eye (covered by a white mask), than in the corresponding regions of the other hemisphere receiving input from the occluded eye (black mask). The diffuse light results for the cortex and colliculus of the diurnal ground squirrel are different from those for the nocturnal rat. In the rat visual cortex, there is no difference between metabolic activity under conditions of diffuse light (steady or flashing) and under darkness. In the rat SC, although flashing-diffuse light increases metabolic activity (as is the case for the squirrel), steady-diffuse light decreases it to a level below that which occurs in darkness. The cortex and colliculus differences in 2-DG response to diffuse light between the ground squirrel and rat were attributed to differences in the operations of their respective cone- and rod-dominated visual systems.

Effects of cricket ball colour and illuminance levels on catching behaviour in professional cricketers

In recent years there have been many alterations to equipment and technology in professional cricket, including the introduction of white balls during day-night matches. In the present study simulated slip-catching performance and movement initiation time were examined in professional cricketers when ball colour and illuminance levels differed. Five male professional cricketers (mean age: 27.3 +/- 1.4 years) volunteered to catch a total of 60 cricket balls, 20 (10 red and 10 white) under each of three illuminance levels (571, 1143 and 1714 lux). Balls were projected from a ball machine at 20 m s(-1) (45 mph) over a distance of 8.4 m, to the subject's dominant side. Catching performance was measured using an established catching scale. Movement initiation times for each hand were also calculated for each trial using a motion-analysis system. Data were submitted to separate two-way (ball colour [2] x illuminance level [3]) repeated measures analysis of variance. No significant effects were obtained for ball colour or illuminance levels for either catching performance or movement initiation time. Neither ball colour nor light level (within the range tested) affected slip-catching performance and movement initiation times in professional cricketers. Therefore it was concluded that the changes made to ball colour and light conditions in professional cricket were not detrimental to catching performance.

Bad lights stops play

The visual performance of cricket batsmen is simulated over a wide range of ambient illumination. When illumination falls to the level at which they usually stop batting (the gloom level) a rapid increase in reaction time commences. It is also the level at which office and car sidelights are turned on and the sensation of "gloom" occurs.