Foveal

About: Foveal is a research topic. Over the lifetime, 2652 publications have been published within this topic receiving 94120 citations.

Simple forms and fluctuations of the line of sight: Implications for motor theories of form processing

Abstract: A contact lens optical Jever was used to measure two-dimensional fixation characteristics when experienced Ss fixated at various positions within simple forms small enough to fall entirely on the foveal floor (<80 min). Fixation stability and the average direction of the line of sight were not markedly or systematically affected by the shape of the fixation stimulus. Similar results were obtained when all saccades were suppressed and the line of sight maintained exclusively by means of slow control. These results cast doubt on motor theories of form perception.

The foveal absolute visual threshold for short flashes and small fields.

Abstract: It has been argued (Bouman & van der Velden, 1948; Bouman & Walraven, 1957) that the condition for the detection of a brief foveal stimulus is the absorption of two quanta within any small area of the fovea, it being left undetermined whether the required small area is a single cone or a small group ofcones. The present paper, by examining foveal frequencyof-seeing curves, disproves this hypothesis and proves that if there are independent units in the central fovea such that the excitation of any one suffices for vision, then at least 5 quanta must be absorbed within an independent unit to excite it.

Affective priming of emotional pictures in parafoveal vision: Left visual field advantage

Abstract: This study investigated whether stimulus affective content can be extracted from visual scenes when these appear in parafoveal locations of the visual field and are foveally masked, and whether there is lateralization involved. Parafoveal prime pleasant or unpleasant scenes were presented for 150 msec 2.5° away from fixation and were followed by a foveal probe scene that was either congruent or incongruent in emotional valence with the prime. Participants responded whether the probe was emotionally positive or negative. Affective priming was demonstrated by shorter response latencies for congruent than for incongruent prime-probe pairs. This effect occurred when the prime was presented in the left visual field at a 300-msec prime-probe stimulus onset asynchrony, even when the prime and the probe were different in physical appearance and semantic category. This result reveals that the affective significance of emotional stimuli can be assessed early through covert attention mechanisms, in the absence of overt eye fixations on the stimuli, and suggests that right-hemisphere dominance is involved.

The human motion onset VEP as a function of stimulation area for foveal and peripheral vision.

Abstract: We studied amplitude of the wave N200 of the motion-onset VEP by varying the side length of a square stimulation field between 0.5 and 7 degrees. A significant increase in amplitude was obtained between 0.5 and 1 degree of side length in central stimulation and between 0.5 and 5 degrees in 10-degree peripheral stimulation. Variations of spatial frequency between 0.34 and 6.8 c/deg did not modify the amplitude size, ie, no tuning effect could be found. The results of simultaneous and separate stimulation of foveal and parafoveal regions support the observation that the stimulation field size is a minor influence. Features of motion-sensitive cortical neurons, such as those found in monkeys, could account for this behavior.