Talgar, CP, Carrasco, M (2001,
May). The effects of attention in texture segmentation in the lower and
upper visual fields. Vision ScienceS Society, Sarasota, FL. 76-B9.
Introduction. This study is based on two findings: 1) In a texture segmentation
task, attending to the target location improved performance where the
resolution is too low (periphery) but impaired it where resolution is
already too high (central locations) for the task. These results indicate
an enhanced spatial resolution at the attended location (Yeshurun & Carrasco,
1998). 2) In some tasks, performance is better across the horizontal than
the vertical meridian - horizontal vertical anisotropy - and in lower
than upper region of the vertical meridian - vertical meridian asymmetry
(VMA). Whereas some attribute this "performance field" to attentional
effects, Carrasco, Talgar & Cameron (in Press) showed that although transient
attention enhances overall contrast sensitivity, the shape of the performance
field does not change - performance fields are determined by visual factors.
Goal. Is there a VMA for spatial resolution? At equal eccentricities,
does attention enhance spatial resolution to the same degree in the upper
and lower regions of the vertical meridian?
Methods. In a texture segmentation task where performance peaks at mid-peripheral
locations, the central performance drop is attributed to the spatial filters
at the fovea being too small for the scale of the texture. In a 2IFC task
observers were presented with a cue that either indicated the time of
target onset (neutral cue: 50 % of trials) or indicated both time and
location of target onset (peripheral cue: 50% of trials). The target patch
appeared at varying eccentricities in a large texture pattern along the
Results. 1) The central performance drop was larger and performance peaked
at farther eccentricities in the lower than upper visual field. 2) Attention
affected the visual field uniformly.
Conclusion. Resolution was higher on the lower half of the vertical meridian.
The degree of enhanced resolution brought about by transient attention
was constant along the vertical meridian.