Precise Functional Localization of the Foveolar Representation in Anesthetized Macaque Visual Cortex
- 1Nathan S. Kline Institute for Psychiatric Research
Abstract
The foveola-the central ~1{degrees} of the visual field-supports the highest-acuity spatial vision, yet localizing its cortical representation is technically demanding, particularly under anesthesia where gaze cannot be behaviorally controlled. Here we describe a hierarchical, meridian-based 7T BOLD fMRI strategy for sub-degree localization of the foveolar representation in anesthetized macaques. Drifting grating bars presented at three successively finer scales (4.5{degrees}, 1.5{degrees}, 0.5{degrees}) independently refined the vertical and horizontal meridian representations, each identified by a characteristic activation signature: bilateral convergence at the V1/V2 border for the vertical meridian, and simultaneous dorsal and ventral V2/V3 activation at the fundus of the calcarine sulcus for the horizontal. Their functional intersection defined candidate foveolar coordinates, which were refined using 0.2{degrees} spot stimuli. Surface-based rendering resolved discrete foveolar loci at the lateral end of the V1/V2, V2/V3, V3/V4 and V4/TEO borders, together delimiting the previously described 'foveolar core'. Pooling these with awake data, we place the loci in a common stereotaxic frame, yielding a first anatomical atlas of the core. Intrinsic-signal optical imaging further shows that this territory lacks the ocular-dominance and orientation columns of surrounding cortex. The approach provides a reproducible framework for locating and targeting foveolar cortex in anesthetized primates.
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BibTeX
@misc{qian2026precise,
title = {{Precise Functional Localization of the Foveolar Representation in Anesthetized Macaque Visual Cortex}},
author = {M. Qian and M. Chen and A. Barczak and X. Zhang and P. Li and A. W. Roe},
howpublished = {bioRxiv},
year = {2026},
month = aug,
doi = {10.64898/2026.08.16.744304},
url = {https://www.biorxiv.org/content/10.64898/2026.08.16.744304v2},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Precise Functional Localization of the Foveolar Representation in Anesthetized Macaque Visual Cortex
AU - M. Qian
AU - M. Chen
AU - A. Barczak
AU - X. Zhang
AU - P. Li
AU - A. W. Roe
PY - 2026
DA - 2026/08/16
PB - bioRxiv
DO - 10.64898/2026.08.16.744304
UR - https://www.biorxiv.org/content/10.64898/2026.08.16.744304v2
AB - The foveola-the central ~1{degrees} of the visual field-supports the highest-acuity spatial vision, yet localizing its cortical representation is technically demanding, particularly under anesthesia where gaze cannot be behaviorally controlled. Here we describe a hierarchical, meridian-based 7T BOLD fMRI strategy for sub-degree localization of the foveolar representation in anesthetized macaques. Drifting grating bars presented at three successively finer scales (4.5{degrees}, 1.5{degrees}, 0.5{degrees}) independently refined the vertical and horizontal meridian representations, each identified by a characteristic activation signature: bilateral convergence at the V1/V2 border for the vertical meridian, and simultaneous dorsal and ventral V2/V3 activation at the fundus of the calcarine sulcus for the horizontal. Their functional intersection defined candidate foveolar coordinates, which were refined using 0.2{degrees} spot stimuli. Surface-based rendering resolved discrete foveolar loci at the lateral end of the V1/V2, V2/V3, V3/V4 and V4/TEO borders, together delimiting the previously described 'foveolar core'. Pooling these with awake data, we place the loci in a common stereotaxic frame, yielding a first anatomical atlas of the core. Intrinsic-signal optical imaging further shows that this territory lacks the ocular-dominance and orientation columns of surrounding cortex. The approach provides a reproducible framework for locating and targeting foveolar cortex in anesthetized primates.
ER -