# Neural Mechanisms of Visual Crowding

> **NIH NIH R01** · YALE UNIVERSITY · 2022 · $417,609

## Abstract

Project Summary
Visual perception is an active process of information selection. Two critical components of this selection
process are the mechanisms of spatial attention and saccadic eye-movements. Attention allows us to deploy
limited neural resources for privileged processing of salient stimuli; saccades allow us to bring stimuli of
interest to the center of gaze for detailed inspection. The dynamic interplay of attention and saccades is
particularly prominent in peripheral vision where inappropriate integration of contextual information has been
proposed as one of the underlying mechanisms of visual crowding. Visual crowding is the inability to identify
stimuli amidst clutter and is a fundamental bottleneck to object recognition in peripheral vision. It is particularly
detrimental in the case of patients with central vision loss such as macular degeneration (MD), since these
individuals rely on a peripheral retinal locus (PRL) for object recognition tasks. Crowding zones, the area in
visual space over which distractors affect target identification, are markedly elongated along the radial axis
aligned with the fovea in normal vision. Crowding zones undergo systematic reorganization in MD patients with
an elongated component along the radial PRL axis. Despite decades of research, the neural underpinnings of
crowding and that of the elongated shape of crowding zones remain unknown. In this proposal we will bridge
these knowledge gaps in the context of the activity of six neural sub-populations – two cell classes (inhibitory
and excitatory neurons) in three layers (superficial, input, deep) – that are fundamental components of the
sensory laminar cortical circuit. Our broad hypothesis is that sub-population specific activity dynamics form the
substrate for contextual interactions underlying crowding and for the formation and re-organization of crowding
zones. We propose to answer several key questions regarding this hypothesis. What are the laminar
mechanisms of contextual modulation in crowding zones (Aim 1)? What the spatio-temporal dynamics of peri-
saccadic activity in the laminar cortical circuit (Aim 2)? What are the neural mechanisms of crowding zone
reorganization following central vision zone (Aim 3)? We will achieve these aims using high-density laminar
neural recordings in visual area V4 of awake non-human primates. V4, a critical node in the object recognition
pathway, that also receives strong attention related and oculomotor signals, is ideally suited for these
investigations. The results of these investigations will uncover the neural mechanisms of crowding, provide a
broad framework for visual form processing in the periphery and inform possible future intervention studies in
central vision loss.

## Key facts

- **NIH application ID:** 10365136
- **Project number:** 1R01EY032555-01A1
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Anirvan S. Nandy
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $417,609
- **Award type:** 1
- **Project period:** 2022-01-01 → 2026-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10365136

## Citation

> US National Institutes of Health, RePORTER application 10365136, Neural Mechanisms of Visual Crowding (1R01EY032555-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10365136. Licensed CC0.

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