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Marina Pavlovskaya, Yoram Bonneh, Nachum Soroker, Shaul Hochstein; Processing visual scene statistical properties in patients with unilateral spatial neglect. Journal of Vision 2010;10(7):280. doi: https://doi.org/10.1167/10.7.280.
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© ARVO (1962-2015); The Authors (2016-present)
Chong and Treisman (2003, 2005, 2008) found that people judge the mean size of a set of circles as quickly and accurately as that of a single item, suggesting that statistical properties may be processed without focused attention. The lack of awareness of left-side input in cases of Unilateral Spatial Neglect (USN) has been attributed to an inability of focusing attention to the left side, suggesting that the processing of statistical properties may be spared. Five USN patients and five controls compared size of a reference circle to a single circle or to the average size of a briefly presented cloud of circles in either the right or left visual fields or spanning both sides. When spanning both sides, their separate averages were either identical or different (difference from reference in ratio 1:4), with the ‘different’ condition used to assess relative impact of each side in judging the mean. USN patients were able to make comparisons and average size in either hemifield, though their left-side performance was somewhat degraded. In the spanning condition, while the controls indeed averaged across sides, lowering their threshold, patients showed a higher threshold when needing to depend on the left side of the cloud (when the right-side cloud was closer to the reference). However, they did use both sides of the cloud so that their spanning-condition thresholds were intermediate between those of controls and those expected if they attended only to the right side. We conclude that USN patients perform a weighted average across sides, giving double weight to the right side, perhaps due to “extinction”. The ability of USN patients to extract the statistical properties of the visual scene on the neglected side points to a relatively spared spread-attention mechanism serving this operation.
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