Flexibly switching attentional strategies is crucial for adaptive behavior in changing environments. Depending on the context, task demand employs different degrees of the two fundamental components of attention- attentional selectivity (preferentially attending to one location in visual space) and effort (the total non-selective intensity of attention). Neuronal responses in the visual cortex that show modulation with changes in either selective attention or effort are reported to partially

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... resent motivational aspect of the task context. The relative contributions and interactions of these two components of attention to modulate neuronal signals and their sensitivity to distinct motivational drives are poorly understood. To address this question, we independently controlled monkeys' spatially selective attention and non-selective attentional intensity in the same experimental session during a novel visual orientation change detection task. Attention was controlled either by adjusting the relative difficulty of the orientation changes at the two locations or by the reward associated with stimuli at two locations while simultaneously recording spikes from populations of neurons in area V4. We found that V4 neurons are robustly modulated by either selective attention or attentional intensity. Notably, as attentional selectivity for a neuron's receptive field location decreased, its responses became weaker, despite an increase in the animal's overall attentional intensity. This strong interaction between attentional selectivity and intensity could be identified in single trial spike trains. A simple divisive normalization of spatially distributed attention performances can explain the interaction between attention components well at the single neuron level. The effects of attentional selectivity and attentional intensity on neuronal responses were the same regardless of whether the changes were motivated by reward or task difficulty. These results provide a detailed cellular-level mechanism of how fundamental components of attention integrate and affect sensory processing in varying motivational and stimulus contexts.