Academic journal article Perception and Psychophysics

How Attention Enhances Spatial Resolution: Evidence from Selective Adaptation to Spatial Frequency

Academic journal article Perception and Psychophysics

How Attention Enhances Spatial Resolution: Evidence from Selective Adaptation to Spatial Frequency

Article excerpt

In this study, we investigated how spatial resolution and covert attention affect performance in a texture segmentation task in which performance peaks at midperiphery and drops at peripheral and central retinal locations. The central impairment is called the central performance drop (CPD; Kehrer, 1989). It has been established that attending to the target location improves performance in the periphery where resolution is too low for the task, but impairs it at central locations where resolution is too high. This is called the central attention impairment (CAI; Yeshurun & Carrasco, 1998, 2000). We employed a cuing procedure in conjunction with selective adaptation to explore (1) whether the CPD is due to the inhibition of low spatial frequency responses by high spatial frequency responses in central locations, and (2) whether the CAI is due to attention's shifting sensitivity to higher spatial frequencies. We found that adaptation to low spatial frequencies does not change performance in this texture segmentation task. However, adaptation to high spatial frequencies diminishes the CPD and eliminates the CAI. These results indicate that the CPD is primarily due to the dominance of high spatial frequency responses and that covert attention enhances spatial resolution by shifting sensitivity to higher spatial frequencies.

One of the most intriguing areas of current research in visual science concerns the role of attention in information processing. Visual attention allows us to select a certain location or aspect of a scene and grant it priority in processing. Spatial covert attention (hereafter referred to as attention) is the selective processing of visual information at a given location in the absence of eye movements to that location (Posner, 1980). Attention can be either voluntarily allocated to a given location according to goals-sustained attention-or involuntarily (reflexively) allocated in response to a cue that appears suddenly in the visual field-transient attention (Cheal & Lyon, 1991; Jonides, 1981; Nakayama & Mackeben, 1989).

Psychophysical studies using a variety of tasks indicate that attention affects early visual processing, including two basic dimensions of vision-contrast sensitivity (e.g., Cameron, Tai, & Carrasco, 2002; Carrasco, PenpeciTalgar, & Eckstein, 2000; Dosher & Lu, 200Oa, 200Ob; Lee, Itti, Koch, & Braun, 1999; Ling & Carrasco, 2006; Lu & Dosher, 1998, 2000) and spatial resolution. Support for enhanced spatial resolution is provided by studies on visual search (Carrasco & McElree, 2001 ; Carrasco & Yeshurun, 1998), acuity and hyperacuity (Carrasco, Williams, & Yeshurun, 2002; Golla, Ignashchenkova, Haarmeier, & Their, 2004; Shiu & Pashler, 1995; Yeshurun & Carrasco, 1999), and texture segmentation (Talgar & Carrasco, 2002; Yeshurun & Carrasco, 1998,2000). Psychophysical studies on acuity (Yeshurun & Carrasco, 1999) and texture segmentation (Yeshurun & Carrasco, 1998, 2000) lend support and psychological reality to the neurophysiological studies showing that attention increases spatial resolution (Reynolds & Desimone, 1999). Furthermore, other psychophysical studies suggest that attention allows a finer scale analysis. For instance, focusing attention on the target location reduces orientation thresholds through the operation of a smaller-scaled stimulus analyzer (Morgan, Ward, & Castet, 1998). Likewise, an attended line is perceived as shorter because smaller attentional receptive fields mediate the processing of the attended stimulus (Tsal & Shalev, 1996). Recently, it has been shown that transient attention also increases apparent spatial frequency and gap size (Gobell & Carrasco, 2005).

The primary goal of this study was to directly test whether covert attention enhances spatial resolution by shifting sensitivity to higher spatial frequencies. Given that spatial resolution decreases with eccentricity, it follows that performance also decreases with eccentricity in most resolution tasks (see, e. …

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