Human Frontal Eye Fields and Spatial Priming of Pop-out
O'Shea, J., Muggleton, N. G., Cowey, A., & Walsh, V. (2007). Human Frontal Eye Fields and Spatial Priming of Pop-out. Journal Of Cognitive Neuroscience, 19(7), 1140-1151
I chose this article because I thought it would be interesting to learn more about implicit memories specifically the priming of implicit memories. Priming of pop-out is described as being able to detect accurately an odd target when shown repeatedly while a distraction or different color target is shown, this compares to the target/ distraction combination that varies each time. Previous research has shown that faster detection is present when there are similar targets in relation to space or features of the targets on both trials. Previous research in a fMRI study showed that target’s showing repetitive features and locations induce suppression bilaterally of blood oxygen levels in the frontal eye fields (FEFs) along with multiple parietal regions. Priming of features showed suppression in the color processing regions of the temporal region and the repeating suppression is shown to reduce neural discharge on the presentation of repeated stimuli that also correlates with priming in other studies. In this study they looked at the role of human frontal eye fields (FEFs) in the priming of color pop-out. They looked at the possible contributions of the FEF’s to the feature or spatial priming of pop-out (PoP). Their hypothesis was that FEF’s play a role in short term memory storage. More specifically that transcrantial magnetic stimulation (TSM) applied over the FEF’s would disrupt the spatial but not the feature of the priming. They also looked at the role of the angular gyrus (AG) in spatial priming. They conducted four experiments that controlled for the task meaning the feature or spatial, the TSM site meaning FEF’s or AGs, the hemisphere meaning left or right, and the TSM timing meaning intertribal interval (ITI) or during search array. There were five participants in this study and were tested in each of the four experiments. During the experiment the subjects were placed in a dim lighted room in front of a screen, they were given an eye movement calibration and two practice blocks consisting of 40 trials each to establish saccadic reaction times (SRTs). There were 12 blocks in each experiment which was 80 trials in each TSM condition. Once the fixation circle and then cross appeared, the search array was presented, they were asked to detect the odd target by making a saccade, which is a rapid jerky eye movement, as quick and accurate as possible. After that the array was removed, a 1500-msec ITI was initiated the circle and cross appeared again signaling a new trial. For the TSM during the Search Array, the TSM was given during the middle of the 500- msec period of the ITI to measure timing. The results of this study found that there was no effect from the TSM on spatial or feature priming. The TSM that was applied over the left FEFs eliminated spatial priming but had no effect on feature priming. Their findings prove that the specialization of function of the left FEFs for spatial priming and also show the differences in the role of target discrimination and eye movement related responses. Overall their findings show that the left FEFs have spatial memory signals shown from the eye movement of saccade in location recently visited by the target. This article was very informative and interesting to find out that our left visual field which correlates with the right side of our brain is responsible in this case for the recognition of the pop-out targets and the spatial memory of those targets.
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