Search PubMed⌕ Search
Home/Archive/PubMed

PubMed · 14568093

Expectancy effects on spatial frequency processing.

Paul T Sowden·Emre Ozgen·Philippe G Schyns·Christine Daoutis
View original source ↗Export metadata ↓

Abstract

We explored top-down modulation of spatial frequency (SF) processing. When auditory pre-cueing directed observers' attention to one of two 4-octaves (SF) apart plaid components observers tended to perceive the cued component, suggesting selective attention to the SF channel they expected to carry task relevant information. In agreement, pre-cueing had no effect with components often processed by the same channel (0.5-octaves apart). Further, effects of expectancy were greater than of uncertainty and were SF tuned. Combined our findings suggest top-down modulation of early, cortical, SF processing. We argue this could similarly explain the previously reported influences of categorisation on SF processing.

Explore related subjects

Contrast SensitivityCuesDifferential ThresholdDiscrimination LearningHumansOrientationPattern Recognition, VisualPerceptual MaskingVisual PerceptionJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Paul T Sowden, Emre Ozgen, Philippe G Schyns, Christine Daoutis. 2003. Expectancy effects on spatial frequency processing.. https://doi.org/10.1016/s0042-6989(03)00480-2

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2004

Visual aftereffects: cortical neurons change their tune.

Recent studies of areas V1 and MT in the visual cortex show that exposure to a stimulus can change the contrast sensitivity of cells and shift their peak sensitivity to a new orientation or movement direction. In MT, these shifts can correctly predict illusory changes - visual aftereffects - in movement direction, but in V1, they are more difficult to interpret.

Contrast Sensitivity↗
PubMed2004

Contrast, probability, and saccadic latency; evidence for independence of detection and decision.

Many factors influence how long it takes to respond to a visual stimulus. The lowest-level factors, such as luminance and contrast, determine how easily different elements of a target can be detected. Higher-level factors are to do with whether these elements constitute a stimulus requiring a response; they include prior probability and urgency. It is natural to think of these two processes, detection and decision, as occurring in series, so that overall reaction time is essentially the sum of the contributions of each stage. Here, measurements of saccadic latency to visual targets whose contrast and prior probability are systematically manipulated demonstrate that there are indeed separable stages of detection and decision. Both can be quantitatively described by rise-to-threshold mechanisms; the average rate of rise of the first is a simple logarithmic function of target contrast, whereas the second shows the linear rise characteristic of the LATER model of neural decision making. The implication is that under normal, high-contrast conditions, in which detection is very fast, the random variability that is characteristic of all reaction times is not caused by sensory noise but is gratuitously introduced by the brain itself; paradoxically, by conferring unpredictability it may aid an organism's survival.

Contrast Sensitivity↗
PubMed2004

Contrast sensitivity threshold measured by sweep-visual evoked potential in term and preterm infants at 3 and 10 months of age.

Although healthy preterm infants frequently seem to be more attentive to visual stimuli and to fix on them longer than full-term infants, no difference in visual acuity has been reported compared to term infants. We evaluated the contrast sensitivity (CS) function of term (N = 5) and healthy preterm (N = 11) infants at 3 and 10 months of life using sweep-visual evoked potentials. Two spatial frequencies were studied: low (0.2 cycles per degrees, cpd) and medium (4.0 cpd). The mean contrast sensitivity (expressed in percentage of contrast) of the preterm infants at 3 months was 55.4 for the low spatial frequency (0.2 cpd) and 43.4 for the medium spatial frequency (4.0 cpd). At 10 months the low spatial CS was 52.7 and the medium spatial CS was 9.9. The results for the term infants at 3 months were 55.1 for the low spatial frequency and 34.5 for the medium spatial frequency. At 10 months the equivalent values were 54.3 and 14.4, respectively. No difference was found using the Mann-Whitney rank sum T-test between term and preterm infants for the low frequency at 3 or 10 months or for the medium spatial frequency at 3 or 10 months. The development of CS for the medium spatial frequency was equally fast for term and preterm infants. As also observed for visual acuity, CS was equivalent among term and preterm infants, suggesting that visual experience does not modify the development of the primary visual pathway. An earlier development of synapses in higher cortical visual areas of preterm infants could explain the better use of visual information observed behaviorally in these infants.

Contrast Sensitivity↗