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M Isabel Vanegas, Behrad Noudoost; Changes in V4 sensory processing after frontal eye fields inactivation. Journal of Vision 2020;20(11):1348. https://doi.org/10.1167/jov.20.11.1348.
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© ARVO (1962-2015); The Authors (2016-present)
Working memory (WM) is the ability to form and keep internal representations to pursuit a behavioral goal. Recent findings have shown that, through direct projections from the frontal eye fields (FEF), a prefrontal cortical area involved in working memory and attention, WM modulates the gain of sensory signals in visual area V4. We investigated the contribution of FEF on the influence of WM on visual sensory processing within V4.
We identified V4 and FEF areas with overlapping response fields (RFs). FEF RFs were confirmed with electrical microstimulation (50μA) and V4 RFs were mapped by assessment of the neuronal firing rate in response to visual stimulus presentation. We pharmacologically inactivated FEF by infusing 0.5-1μL of muscimol (5mg/mL) while recording from overlapping V4 neurons using single electrode and linear array probes. Before and after FEF inactivation, the animal performed a memory guided saccade with a task-irrelevant grating background of varying contrasts and orientations, and a passive fixation task tailored for RF mapping.
Preliminary findings show that before inactivation, WM alters the orientation tuning and contrast response function at the level of single neurons, such that more effective stimuli are more strongly modulated by WM. After inactivation of the FEF, the animal showed striking behavioral deficits in memory guided saccades and increased saccade scatter at the RF location. V4 neurons with overlapping RF with the behavioral scotoma, showed changes in their contrast sensitivity and orientation tuning, indicative of a necessary role for the FEF to exert WM-dependent modulations of visual signals within V4. Furthermore, after FEF inactivation, V4 RFs became larger and less spatially selective, an indication of FEF’s role in shaping the spatial sensitivity of V4.
Behavioral effects confirm previously reported findings. Neural findings show the importance of FEF signal for spatial and featural sensitivity within V4.
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