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Koorosh Mirpour, Wei Song Ong, James Bisley; Biasing attentional priority by microstimulation of LIP. Journal of Vision 2010;10(7):161. doi: https://doi.org/10.1167/10.7.161.
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People can find objects hidden in a cluttered scene quickly and efficiently. This cannot be done unless there is a prioritizing algorithm, which optimizes the choice of the goal of the next eye movement. It has been suggested that the lateral intraparietal area (LIP) acts as a priority map, which incorporates both bottom-up sensory and top-down cognitive inputs in order to find stimuli similar to the target of the visual search. An eye movement is then made toward the most behaviorally important location in the scene, represented by the highest activity in LIP. In this study, we investigated whether increasing the activity of the LIP priority map can bias saccade goal selection during a visual foraging task.
Two animals were trained to perform a free-viewing visual foraging task in which they searched through 5 potential targets (T) and 5 distractors (+) to find the target that was loaded with reward. To get the reward they had to fixate the target for 500 ms within 8 s. After training, both animals performed the task with a high degree of efficiency by avoiding Ts that had been previously fixated and distractors. On microstimulation trials, a 350 ms burst of 20 μA peak-to-peak biphasic pulses at 200 Hz was injected into LIP 150 ms after the third saccade. We found that on stimulation trials, the animals were more likely to make their next saccade to stimuli that were in the stimulated receptive field than on non-stimulation trials. The strength of this bias was consistent for all visual stimuli, regardless of behavioral relevance. These results demonstrate that the activity of LIP neurons is causally related to a strategy that guides efficient visual search.
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