Task context modulates the selectivity of macaque Superior Temporal Sulcus neurons for partially occluded bodies

Most single-unit studies of animate object processing in the primate ventral visual stream rely on passive fixation, leaving it unclear whether neuronal selectivity for socially relevant stimuli depends on behavioral context. Here, we tested whether task demands alter the selectivity of neurons in the ventral bank of the superior temporal sulcus (STS) for body pose or viewpoint. Male rhesus monkeys viewed identical body stimuli (monkey avatars) under two conditions: a task in which body pose was behaviorally relevant, and a condition in which the same stimuli were irrelevant for obtaining a reward. Task context modulated STS responses: neuronal responses were stronger and more selective when stimuli were task-relevant, yielding improved decoding performance compared to the task-irrelevant condition. These effects were most pronounced for partially occluded bodies, indicating that task demands enhance processing under challenging visual conditions. Despite these modulations, the overall impact of task context was modest relative to the neurons' intrinsic selectivity, and stimulus preference rankings remained largely stable across tasks. For partially occluded bodies, task-dependent effects were observed in both middle and anterior STS, with a tendency for earlier modulation in middle STS, consistent with hierarchical processing. These findings suggest that STS neurons maintain largely stable body selectivity across behavioral contexts, while task relevance enhances response gain and selectivity, particularly when visual information is degraded. More generally, this study helps reconcile previous conflicting reports of task context modulations in macaque inferior temporal cortex by showing that task effects are present but relatively subtle and depend on stimulus conditions.Significance statement Whether neuronal selectivity in the primate ventral stream for social stimuli depends on behavioral context remains unclear, because most previous single-unit studies used passive fixation. By recording from the Superior Temporal Sulcus (STS) of macaques viewing body stimuli under task-relevant versus task-irrelevant conditions, we show that task demands enhance response strength and selectivity, improving decoding performance-especially for partially occluded bodies. Task effects tended to emerge earlier in middle than anterior STS, consistent with hierarchical processing. These data suggest that the body representation in the STS is largely robust to changes in task context and reconcile conflicting reports of task context effects in the macaque inferior temporal cortex by demonstrating that task modulation is mainly present for partially occluded stimuli.