Been There, Seen That: A Neural Mechanism for Performing Efficient Visual Search

Abstract

In everyday life, we efficiently find objects in the world by moving our gaze from one location to another. The efficiency of this process is brought about by ignoring items that are dissimilar to the target and remembering which target-like items have already been examined. We trained two animals on a visual foraging task in which they had to find a reward-loaded target among five task-irrelevant distractors and five potential targets. We found that both animals performed the task efficiently, ignoring the distractors and rarely examining a particular target twice. We recorded the single unit activity of 54 neurons in the lateral intraparietal area (LIP) while the animals performed the task. The responses of the neurons differentiated between targets and distractors throughout the trial. Further, the responses marked off targets that had been fixated by a reduction in activity. This reduction acted like inhibition of return in saliency map models; items that had been fixated would no longer be represented by high enough activity to draw an eye movement. This reduction could also be seen as a correlate of reward expectancy; after a target had been identified as not containing the reward the activity was reduced. Within a trial, responses to the remaining targets did not increase as they became more likely to yield a result, suggesting that only activity related to an event is updated on a moment-by-moment bases. Together, our data show that all the neural activity required to guide efficient search is present in LIP. Because LIP activity is known to correlate with saccade goal selection, we propose that LIP plays a significant role in the guidance of efficient visual search.

Predictive remapping gives rise to environmental inhibition of return

“…This finding was later confirmed by a virtual lesion study which abolished environmental IOR by applying TMS to the right intraparietal sulcus (van Koningsbruggen, Gabay, Sapir, Henik, & Rafal, 2009). In visual foraging tasks, IOR is manifested as delayed behavioral responses (e.g., Klein & Macinnes, 1999;Shariat Torbaghan, Yazdi, Mirpour, & Bisley, 2012) or reduced neuronal responses (Mirpour, Arcizet, Ong, & Bisley, 2009) to previous fixated objects (or locations). Mirpour and Bisley (2012) examined LIP neurons that had remapping responses in a foraging task and observed weaker remapping responses for previously fixated items.…”

Brain bases of the automaticity via visual search task

“…Then, we also found changes in the inferior occipital gyrus that could be linked to the PPC. On visual search tasks designed to investigate the priority map function, it has been observed that occipital gyrus neurons do not respond to task demands as the PPC does; the PPC responds more to targets than the occipital gyrus (Ipata et al, 2006;Buschman and Miller, 2007;Thomas and Paré, 2007;Mirpour et al, 2009). The decreased activation in occipital gyrus areas could be explained by repetition suppression mechanisms .…”

“…Supporting this hypothesis, researchers have been observing that maps in early visual areas do not respond to task demands like the PPC does. For example, during visual search tasks, enhanced PPC response was observed more for targets than for distractors (Ipata et al, 2006;Buschman and Miller, 2007;Thomas and Paré, 2007;Mirpour, Arcizet, Ong and Bisley, 2009). It seems that during visual search tasks, the focus of attention is guided through the visual scene using the priority map, where the targets are highlighted and the distractors are suppressed .…”

“…It seems that during visual search tasks, the focus of attention is guided through the visual scene using the priority map, where the targets are highlighted and the distractors are suppressed . Inherited from bottom-up saliency models (Itti and Koch, 2001), it seems that the PPC also engages inhibition of return to suppress already visited locations in the space, making it possible for the visual attention system to progress in the search by dismissing potential objects that eventually do not match the target (Mirpour et al, 2009). …”

“…Supporting this hypothesis, researchers have been observing that maps in early visual areas do not respond to task demands like the PPC does. For example, during visual search tasks, enhanced PPC response was observed more for targets than for distractors (Ipata et al, 2006;Buschman and Miller, 2007;Thomas and Paré, 2007;Mirpour, Arcizet, Ong and Bisley, 2009 seems that during visual search tasks, the focus of attention is guided through the visual scene using the priority map, where the targets are highlighted and the distractors are suppressed . Inherited from bottom-up saliency models (Itti and Koch, 2001), it seems that the PPC also engages inhibition of return to suppress already visited locations in the space, making it possible for the visual attention system to progress in the search by dismissing potential objects that eventually do not match the target (Mirpour et al, 2009).…”