Details

Autor(en) / Beteiligte

• Anderson, Elaine J.
• Dakin, Steven C.
• Schwarzkopf, D. Samuel
• Rees, Geraint
• Greenwood, John A.

Titel

The Neural Correlates of Crowding-Induced Changes in Appearance

Ist Teil von

• Current biology, 2012-07, Vol.22 (13), p.1199-1206

Ort / Verlag

England: Elsevier Inc

Erscheinungsjahr

2012

Quelle

MEDLINE

Beschreibungen/Notizen

• Object recognition in the peripheral visual field is limited by crowding: the disruptive influence of nearby clutter [1, 2]. Despite its severity, little is known about the cortical locus of crowding. Here, we examined the neural correlates of crowding by combining event-related fMRI adaptation with a change-detection paradigm [3]. Crowding can change the appearance of objects, such that items become perceptually matched to surrounding objects; we used this change in appearance as a signature of crowding and measured brain activity that correlated with the crowded percept. Observers adapted to a peripheral patch of noise surrounded by four Gabor flankers. When crowded, the noise appears oriented and perceptually indistinguishable from the flankers. Consequently, substitution of the noise for a Gabor identical to the flankers (“change-same”) is rarely detected, whereas substitution for an orthogonal Gabor (“change-different”) is rarely missed. We predicted that brain areas representing the crowded percept would show repetition suppression in change-same trials but release from adaptation in change-different trials. This predicted pattern was observed throughout cortical visual areas V1–V4, increasing in strength from early to late visual areas. These results depict crowding as a multistage process, involving even the earliest cortical visual areas, with perceptual consequences that are increasingly influenced by later visual areas. ► Crowding influences brain activity throughout the early retinotopic cortex ► Modulation increases from early (V1/V2) to late (V3/V4) visual areas ► The progressive influence of crowding parallels the increase in receptive-field size ► These findings suggest crowding is a multistage process