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Michael Arcaro, Stephanie McMains, Sabine Kastner; Phase-encoded attention tasks reveal topographic maps in posterior parahippocampal cortex. Journal of Vision 2008;8(6):1001. doi: 10.1167/8.6.1001.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies have demonstrated two retinotopically organized areas, VO-1 and VO-2, in human ventral occipital cortex adjacent to hV4 (see Wandell et. al., Neuron, 2007 for review). In the present study, we extend these findings by examining topographic organization in the areas adjacent to the VO complex in human posterior parahippocampal cortex using a cognitive mapping approach.
Data were collected using a phased array coil with a functional in-plane resolution of 2x2 mm2. While maintaining fixation, subjects were required to allocate attention towards a rotating wedge of moving dots. Subjects detected changes in the direction of motion for the majority of dots. In a second scan session, subjects attended an expanding/contracting ring filled with bouncing balls while maintaining fixation. Subjects detected when one of the balls dimmed. Subjects performed both tasks around 75% accuracy. In a third scan session, responses evoked by object, scene, face, and color stimuli were probed.
We identified two topographic areas that have not previously been described in the human. The new regions are located along the collateral sulcus in the posterior portion of parahippocampal cortex with the first new region being adjacent to VO-2. Both regions contain a complete representation of the contralateral visual field with boundaries defined by a phase reversal. Eccentricity mapping revealed a representation of the fovea and periphery organized perpendicular to the polar angle maps. These two additional topographic areas show selectivity for scenes as compared to objects and faces. We are currently comparing this topographic organization to that obtained with typical retinotopic mapping methods.
Using an attention-demanding task, we revealed topographic organization not previously reported with typical retinotopic mapping methods. These new topographically organized regions overlap with the functionally defined place area, PPA, and show strong preference for scenes in both the foveal and peripheral representations.
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