
Attentional enhancement in the visual cortex is not a constant top-down process but rather a dynamic mechanism influenced by the similarity between competing stimuli, with a more similar distractor reducing the attentional bias towards the target.


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Visual stimuli compete with each other for cortical processing and attention biases this competition in favor of the attended stimulus. How does the relationship between the stimuli affect the strength of this attentional bias? Here, we used functional MRI to explore the effect of target-distractor similarity in neural representation on attentional modulation in the human visual cortex using univariate and multivariate pattern analyses. Using stimuli from four object categories (human bodies, cats, cars and houses), we investigated attentional effects in the primary visual area V1, the object-selective regions LO and pFs, the body-selective region EBA, and the scene-selective region PPA. We demonstrated that the strength of the attentional bias towards the target is not fixed but decreases with increasing target-distractor similarity. Simulations provided evidence that this result pattern is explained by tuning sharpening rather than an increase in gain. Our findings provide a mechanistic explanation for behavioral effects of target-distractor similarity on attentional biases and suggest tuning sharpening as the underlying mechanism in object-based attention.

### Competing Interest Statement

The authors have declared no competing interest.

Attention Modulates Human Visual Responses to Objects by Tuning Sharpening

the-impact-of-target-distractor-similarity-on-attentional-modulation-in-the-human-visual-cortex


The Impact of Target-Distractor Similarity on Attentional Modulation in the Human Visual Cortex
