Persistent Spatial Information in the Frontal Eye Field during Object-Based Short-Term Memory

Department of Neurobiology and Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, California 94305, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 08/2012; 32(32):10907-14. DOI: 10.1523/JNEUROSCI.1450-12.2012
Source: PubMed


Spatial attention is known to gate entry into visual short-term memory, and some evidence suggests that spatial signals may also play a role in binding features or protecting object representations during memory maintenance. To examine the persistence of spatial signals during object short-term memory, the activity of neurons in the frontal eye field (FEF) of macaque monkeys was recorded during an object-based delayed match-to-sample task. In this task, monkeys were trained to remember an object image over a brief delay, regardless of the locations of the sample or target presentation. FEF neurons exhibited visual, delay, and target period activity, including selectivity for sample location and target location. Delay period activity represented the sample location throughout the delay, despite the irrelevance of spatial information for successful task completion. Furthermore, neurons continued to encode sample position in a variant of the task in which the matching stimulus never appeared in their response field, confirming that FEF maintains sample location independent of subsequent behavioral relevance. FEF neurons also exhibited target-position-dependent anticipatory activity immediately before target onset, suggesting that monkeys predicted target position within blocks. These results show that FEF neurons maintain spatial information during short-term memory, even when that information is irrelevant for task performance.

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    • "Noudoost and Moore (2011b) examined the long-range effects of altering prefrontal DA signaling on visual responses in extrastriate area V4. V4, like much of visual cortex, receives direct projections from the Frontal Eye Field (FEF) part of the PFC, an area strongly implicated in controlling spatial attention (Moore and Fallah, 2004; Armstrong et al., 2009; Clark et al., 2012), and it is believed that these projections may be the source of the changes in activity observed in V4 during the deployment of covert attention (Moore and Armstrong, 2003; Awh et al., 2006; Noudoost et al., 2010, 2014; Squire et al., 2013; Clark et al., 2014). Noudoost and Moore examined the effects of manipulating either D1Rs or D2Rs on V4 visual responses during a passive fixation task, and their effect on saccadic target selection in a free-choice task (Noudoost and Moore, 2011a,b). "
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    PLoS ONE 04/2013; 8(4):e60804. DOI:10.1371/journal.pone.0060804 · 3.23 Impact Factor
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    • "For example, neurons in the frontal eye fields respond to target stimuli even when a saccade is directed in the opposite direction [79], for targets rather than distractors [80], or when the monkey is rewarded for not making a saccade to the target [68]. However, recent findings show that neurons in this region maintain spatial information during WM tasks even when it is irrelevant to the task [70], suggesting that the frontal eye fields may inevitably maintain spatial coordinates of stimuli. Finally, there is electrophysiological evidence showing that object feature information, such as shape, in addition to spatial information, is represented in the frontal eye fields [81e83]. "
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