| Recent neurophysiological and neuropsychological research provides evidence that supports the existence of two cortical processing streams: One ventral and one dorsal, associated with object identification and object localization, respectively. The current study examined possible parallels between the structure of visuospatial abilities and the organization of the underlying neural systems in both young and older adults. Based on findings obtained from recent neuroscientific research, a battery of six speeded perceptual tasks and a battery of six working memory tasks were developed for the current study to measure visuospatial perceptual abilities and working memory abilities. Within each battery, some of the tasks were constructed to primarily assess the abilities to process and maintain object feature information, whereas other tasks were constructed to primarily assess the abilities to process and maintain spatial location information.; A group of 69 young adults and a group of 49 older adults were tested on these two batteries of tasks. Separate factor analyses of the young and older adults' response times from speeded perceptual tasks revealed evidence suggesting that human visuospatial perceptual abilities can be classified into categories according to the specializations of the ventral and dorsal processing streams. More specifically, the factor structure revealed in the analyses provided evidence to support a two-stream hypothesis in young adults and a dedifferentiation hypothesis (i.e., specific ability factors merge into a general ability factor) in older adults. However, factor analyses of the young and older adults' accuracy scores from the working memory battery did not reveal any evidence indicating that there are two visuospatial ability factors, one associated with maintaining object features and one associated with maintaining spatial locations.; Additionally, effects of domain (i.e., memory for object features or spatial locations), delay, and memory load on older adults' visuospatial working memory were examined in the current study. The results indicated that there was a greater age-related deficit associated with object feature working memory than that associated with spatial location working memory. Regardless of domain (i.e., object features versus spatial locations), increases in memory load affected older adults more than young adults, whereas increases in delay affected older adults and young adults to the same degree. |
