Reproduction of End-Location and Distance of Movement in Early and Later Blinded Subjects

Repeatability of position sense measurements in persons with osteoarthritis of the knee: a pilot study

Several reports have described a position sense deficit in persons with osteoarthritis of the knee. For purposes of future comparison, this study determined the agreement between serial measurements of knee position sense conducted over a 10-day period for eight persons of mean age 67.87 ± 7.36 years with stable knee-joint disease. The knee angles used to determine position sense were recorded in the seated position using a potentiometer. The outcome measure was the mean absolute error between five set angles and their matching angles. The intra-class correlation coefficients (ICCS) used to assess reliability of the mean absolute error measurements within and between sessions ranged from 0.57 to 0.52 with an average standard error of measurement of 1.18 degrees. It is concluded that while fairly reliable, clinicians should interpret changes in knee position sense of less than 2.31 degrees carefully in these patients before concluding that a true improvement or deterioration in their knee positioning accuracy has occurred.

Sequential vs simultaneous encoding of spatial information: a comparison between the blind and the sighted

The aim of this research is to assess whether the crucial factor in determining the characteristics of blind people's spatial mental images is concerned with the visual impairment per se or the processing style that the dominant perceptual modalities used to acquire spatial information impose, i.e. simultaneous (vision) vs sequential (kinaesthesis). Participants were asked to learn six positions in a large parking area via movement alone (congenitally blind, adventitiously blind, blindfolded sighted) or with vision plus movement (simultaneous sighted, sequential sighted), and then to mentally scan between positions in the path. The crucial manipulation concerned the sequential sighted group. Their visual exploration was made sequential by putting visual obstacles within the pathway in such a way that they could not see simultaneously the positions along the pathway. The results revealed a significant time/distance linear relation in all tested groups. However, the linear component was lower in sequential sighted and blind participants, especially congenital. Sequential sighted and congenitally blind participants showed an almost overlapping performance. Differences between groups became evident when mentally scanning farther distances (more than 5m). This threshold effect could be revealing of processing limitations due to the need of integrating and updating spatial information. Overall, the results suggest that the characteristics of the processing style rather than the visual impairment per se affect blind people's spatial mental images.

Discrimination of Amount of Spinal Flexion for Movements Made with and without Vision after Lumbar Disc Replacement

Discrimination of differences between small lumbar flexion movements made when standing may differ depending on whether vision is available. Dependence on general vision during trunk movements may be increased following surgery, in which an intervertebral disc is replaced with a prosthetic disc. This study investigated whether the availability of vision changed discrimination of small differences in lumbar forward flexion movement when standing for patients with lumbar disc replacement and healthy peers. 20 volunteers without a history of back pain and 20 with disc replacement undertook a 100-trial sequence of forward flexion movements to a set of physical stops, making an absolute judgement as to the position after each movement. General (nontarget) vision during the movement was available or removed randomly trial by trial. Availability of vision did not affect discrimination of flexion movements of the lumbar spine either in normal healthy individuals or those with disc replacement.

The role of visual experience in mental scanning of actual pathways: evidence from blind and sighted people

In this research we compare blind and normally sighted people in mental scanning of spatial maps using locomotor or visual/locomotor exploration of a real 3-D environment. Different types of visual experience were tested: early (congenital) and late (adventitious) onset of blindness, short-term deprivation (blindfolded-sighted), and full vision (sighted). Participants were asked to learn six positions in a large parking area with movement alone (congenital, adventitious, blindfolded-sighted) or with vision plus movement (sighted), and then to mentally scan between positions in the path. Finally, they had to describe how they imagined scanning the learned pathway. We found a significant linear relation between space and time, ie the classic mental scanning effect, in all tested groups. However, the linear component was lower in blind participants, especially congenital. Instead, short-term visual deprivation had minimal impact on mental scanning. Overall, blind participants had shorter scanning times than both sighted groups, and the effect was particularly evident with farther distances. These results suggest that there is a quantitative rather than a qualitative difference between the blind and the sighted. In addition, the mental scanning strategies reported by participants also affected mental scanning times. The theoretical implications of these findings are discussed.

Effects of visual deprivation on space representation: immediate and delayed pointing toward memorised proprioceptive targets

Congenitally blind, late-blind, and blindfolded-sighted participants performed a pointing task at proximal memorised proprioceptive targets. The locations to be memorised were presented on a sagittal plane by passively positioning the left index finger. A 'go' signal for matching the target location with the right index finger was given 0 or 8 s after left-hand demonstration. Absolute distance errors were smaller in the blind groups, with both delays pooled together; signed distance and direction errors were underestimated with the longer delay, and were overestimated by blind groups, whereas the blindfolded-sighted group underestimated them. Elongation of the scatters was stretched but not affected by delay or group. The surface scatter was greater with the longer delay; and orientation of the main axis of the pointing ellipses shows the use of an egocentric frame of reference by the congenitally blind group for both delays, the use of egocentric (0 s) and exocentric (8 s) frame of reference by the blindfolded-sighted group, with the late-blind group using an intermediate frame of reference for both delays. Therefore, early and late visual-deprivation effects are distinguished from transient visual-deprivation effects as long-term deprivation leads to increased capabilities (absolute distance estimations), unaltered organisation (for surface and elongation), and altered organisation (amplitude and direction estimations, orientation of pointing distribution) of the spatial representation with proprioception. Besides providing an extensive exploration of pointing ability and mechanisms in the visually deprived population, the results show that cross-modal plasticity applies not only to neural bases but extends to spatial behaviour.

Texture information in tactual space perception

The significance of texture as a source of information in tactual space perception was studied using a linear positioning task. A spatial texture gradient, whose elements changed with position and distance, a homogeneous raised-element pattern and a smooth surface were used. Participants had to reproduce locations and distances on these surfaces under various conditions. In active conditions, participants moved their indexfinger across the surface. In passive conditions, the texture was moved beneath the indexfinger of the participant. In conditions with equal movement speed, movement speeds' of criterion and reproduction phase were matched, in conditions with unequal movement speed, they did not match. The largest errors were obtained for the combined passive movement-unequal movement speed conditions. In these conditions, differences between textures were visible for signed and unsigned errors, indicating that textures may differ in the cutaneous specification of distance and location.

Proprioceptive sensibility in women with normal and osteoarthritic knee joints

The objective of this study was to quantify the effect of degenerative joint change on the proprioceptive acuity of women with osteoarthritis (OA) of the knee. Middle-aged women with OA of the knee, age-matched healthy women, and younger healthy women were studied. Tests examined the ability of subjects to correctly reproduce knee angles in weightbearing and non-weightbearing situations. The knee angles were photographed and measured in degrees. The absolute error (AE) of each matching test was calculated and the mean AE of two tests was used as the criterion variable in a three-way analysis of variance (ANOVA). The relationship between the reproduction error and the osteoarthritic subjects' self-paced walking speed was also examined. Under both test conditions the AE of the osteoarthritic subjects was greater than that of the healthy subjects (p < .05). There was, however, no significant relationship between the AE measurements of the patients and their walking speed. These data indicate that while women with OA may have poorer proprioception than healthy controls, this impairment may not affect their walking ability.

Memory for Movement in Blind Children

The role of previous visual experience in the reproduction of a criterion movement was examined in sighted, late-blinded, and congenitally blind children. Results showed that the congenitally blind reproduce movements at a low level of accuracy compared with the other two groups. Detailed analysis showed that although the congenitally blind could reproduce the extent of the movement accurately, the movement was poorly reproduced in terms of its orientation to the criterion movement and its orientation from a reference point. The role of prior vision in establishing a frame of reference is discussed.