老年人活动需求视角下老旧住区街道开放空间优化

老旧住区是老年人主要的居住场所,老旧住区街道开放空间也是老年人户外活动的重要场所.选取南京市锁金村住区街道中10处开放空间为研究对象,综合运用行为注记法和问卷访谈法,分析了老年人户外活动的需求、空间的环境和使用特征,并且选取5种参与人数最多的活动与街道开放空间要素进行关联研究,分析每种活动与各空间要素之间的关联性,得出影响老年人使用开放空间的相关要素.在此基础上,从老年人活动需求角度提出老旧住区街道开放空间的优化建议.     

The motor side of depth vision

To achieve stereoscopic vision, the brain must search for corresponding image features on the two retinas. As long as the eyes stay still, corresponding features are confined to narrow bands called epipolar lines. But when the eyes change position, the epipolar lines migrate on the retinas. To find the matching features, the brain must either search different retinal bands depending on current eye position, or search retina-fixed zones that are large enough to cover all usual locations of the epipolar lines. Here we show, using a new type of stereogram in which the depth image vanishes at certain gaze elevations, that the search zones are retina-fixed. This being the case, motor control acquires a crucial function in depth vision: we show that the eyes twist about their lines of sight in a way that reduces the motion of the epipolar lines, allowing stereopsis to get by with smaller search zones and thereby lightening its computational load.     

Non-commutativity in the brain.

In non-commutative algebra, order makes a difference to multiplication, so that a x b not equal to b x a. This feature is necessary for computing rotary motion, because order makes a difference to the combined effect of two rotations. It has therefore been proposed that there are non-commutative operators in the brain circuits that deal with rotations, including motor circuits that steer the eyes, head and limbs, and sensory circuits that handle spatial information. This idea is controversial: studies of eye and head control have revealed behaviours that are consistent with non-commutativity in the brain, but none that clearly rules out all commutative models. Here we demonstrate non-commutative computation in the vestibulo-ocular reflex. We show that subjects rotated in darkness can hold their gaze points stable in space, correctly computing different final eye-position commands when put through the same two rotations in different orders, in a way that is unattainable by any commutative system.     

Optimal transsaccadic integration explains distorted spatial perception

We scan our surroundings with quick eye movements called saccades, and from the resulting sequence of images we build a unified percept by a process known as transsaccadic integration. This integration is often said to be flawed, because around the time of saccades, our perception is distorted and we show saccadic suppression of displacement (SSD): we fail to notice if objects change location during the eye movement. Here we show that transsaccadic integration works by optimal inference. We simulated a visuomotor system with realistic saccades, retinal acuity, motion detectors and eye-position sense, and programmed it to make optimal use of these imperfect data when interpreting scenes. This optimized model showed human-like SSD and distortions of spatial perception. It made new predictions, including tight correlations between perception and motor action (for example, more SSD in people with less-precise eye control) and a graded contraction of perceived jumps; we verified these predictions experimentally. Our results suggest that the brain constructs its evolving picture of the world by optimally integrating each new piece of sensory or motor information.