The effect of spatial frequency on peripheral collinear facilitation

Abstract

The detection of a Gabor patch (target) can be decreased or improved by the presence of co-oriented Gabor patches (flankers) having the same spatial frequency as the target. These phenomena are thought to be mediated by lateral interactions. Depending on the distance between target and flankers, commonly defined as a multiple of the wavelength (λ) of the carrier, flankers can increase or decrease a target's detectability. Studies with foveal presentation showed that for target-to-flankers distances<2λ contrast thresholds for the central target increase, while for target-to-flankers distances>3λ contrast thresholds decrease. Earlier studies on collinear facilitation at the near-periphery of the visual field (4° of eccentricity) showed inconsistent facilitation (Shani & Sagi, 2005, Vision Research, 45, 2009-2024) whereas more recent studies showed consistent facilitation for larger separations (7-8λ) (Maniglia et al., 2011, PLoS ONE, 6, e25568; Lev & Polat, 2011, Vision Research, 51, 2488-2498). However, all of these studies used medium-to-high spatial frequencies (3-8 cpd). In this study we tested lower spatial frequencies (1, 2, and 3 cpd) with different target-to-flankers distances. The rationale was that near-peripheral vision is tuned for lower spatial frequencies and this could be reflected in collinear facilitation. Results show consistent collinear facilitation at 8λ for all the spatial frequencies tested, but also show collinear facilitation at shorter target-to-flanker distance (6λ) for the lowest spatial frequencies tested (1 cpd). Additionally, collinear facilitation decreases as spatial frequency increases; opposite to the findings of Polat (2009, Spatial Vision, 22, 179-193) in the fovea, indicating a different spatial frequency tuning between foveal and peripheral lateral interactions.

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“…PL with collinear configuration increases facilitation, reduces suppression (Polat & Sagi, 1994b) and transfers to untrained, higher-level visual abilities such as VA and CSF (see Polat, 2009 for a review). In addition, there is recent psychophysical evidence of collinear facilitation in the near periphery of the visual field (4° of eccentricity), at a target-to-flankers distance larger than in the fovea (between 7λ and 8λ) (Maniglia et al, 2011;Maniglia, Pavan, & Trotter, 2015), suggesting that the spatial range of facilitatory lateral interactions is increased in the near periphery. Moreover, peripheral collinear suppression appears to be modulated by PL.…”

The spatial range of peripheral collinear facilitation

“…In particular, there are no studies on the extent of the range of collinear interactions (expressed as multiples of the stimulus wavelength) in near periphery. Maniglia and colleagues39 tested up to 8λ, while earlier investigations did not test beyond 7λ3641.…”

“…Therefore, physiological evidence seem to indicate that collinear facilitation should be present also for near peripheral presentation of the stimuli. Indeed, a series of recent studies363839 showed that collinear facilitation can be observed in the near-periphery of the visual field (4° of eccentricity), with some differences with respect to the foveal vision: a) it emerges at a target-to-flankers relative distance of 6–8λ3638, approximately 2–3 times the minimum separation for eliciting collinear facilitation in fovea (3λ); b) it shows a preference for lower spatial frequencies39, consistently with the contrast sensitivity function measured in peripheral vision40; c) it is present from a target-to-flankers relative distance of 6λ for stimuli with a spatial frequency of 1 cpd (corresponding to an angular distance of 8 deg), whereas for higher spatial frequencies collinear facilitation emerged at 8λ (corresponding to an angular distance of 4°, 2° and 1.33° for 2, 4 and 6 cpd, respectively39; d) the difference in contrast sensitivity between collinear and orthogonal condition at the critical relative distance of 8λ decreases as spatial frequency increases39, the opposite of what found in fovea where the magnitude of collinear facilitation (measured at the critical relative distance of 3λ) increases as spatial frequency increases6 (differences are summarized in Table 1). However, apart for these few recent studies, collinear facilitation with stimuli presentation in the near-periphery of the visual field has not been properly investigated.…”

“…The third hypothesis, based on Maniglia et al 39, proposed that different spatial frequencies might show different facilitation curves. In particular, low spatial frequencies might have either an overall larger facilitatory range, starting from 6λ and decaying at the same target-to-flankers distance as for higher spatial frequencies; or it could be shifted leftwards with respect to the higher spatial frequencies, decaying at shorter relative distances.…”

“…In order to obtain a reliable baseline measurement, we measured contrast thresholds also in the orthogonal condition; with flankers orthogonally oriented to the target, a configuration that does not elicit collinear interactions311 and is commonly used as baseline condition for measuring collinear facilitation383941.…”