Abstract
It is proposed that feedback signals from the prefrontal cortex (PFC) to extrastriate cortex are essential for goal-directed processing, maintenance, and selection of information in visual working memory (VWM). In a previous study, we found that disruption of PFC function with transcranial magnetic stimulation (TMS) in healthy individuals impaired behavioral performance on a face/scene matching task and decreased category-specific tuning in extrastriate cortex as measured with functional magnetic resonance imaging (fMRI). In this study, we investigated the effect of disruption of left inferior frontal gyrus (IFG) function on the fidelity of neural representations of two distinct information codes: (1) the stimulus category and (2) the goal-relevance of viewed stimuli. During fMRI scanning, subjects were presented face and scene images in pseudo-random order and instructed to remember either faces or scenes. Within both anatomical and functional regions of interest (ROIs), a multi-voxel pattern classifier was used to quantitatively assess the fidelity of activity patterns representing stimulus category: whether a face or a scene was presented on each trial, and goal relevance, whether the presented image was task relevant (i.e., a face is relevant in a “Remember Faces” block, but irrelevant in a “Remember Scenes” block). We found a reduction in the fidelity of the stimulus category code in visual cortex after left IFG disruption, providing causal evidence that lateral PFC modulates object category codes in visual cortex during VWM. In addition, we found that IFG disruption caused a reduction in the fidelity of the goal relevance code in a distributed set of brain regions. These results suggest that the IFG is involved in determining the task-relevance of visual input and communicating that information to a network of regions involved in further processing during VWM. Finally, we found that participants who exhibited greater fidelity of the goal relevance code in the non-disrupted right IFG after TMS performed the task with the highest accuracy.
Highlights
Since the human brain has an inherently limited capacity for information processing and working memory (Cowan et al, 2005), it is crucial that relevant information in the environment be filtered from the myriad of visual details that are unimportant, and often detrimental, to the task at hand (Vogel et al, 2005)
We examined two distinct types of representations: (1) stimulus category—whether a face or a scene was presented on each trial of a face/scene matching task and (2) goal relevance—whether the presented image was task relevant
A growing body of evidence suggests that the prioritized processing and storage of information in visual working memory (VWM) relies on topdown modulation of visual areas by the prefrontal cortex (PFC) (Miller and D’Esposito, 2005; Bressler et al, 2008; Sreenivasan et al, 2014a; D’Esposito and Postle, 2015)
Summary
Since the human brain has an inherently limited capacity for information processing and working memory (Cowan et al, 2005), it is crucial that relevant information in the environment be filtered from the myriad of visual details that are unimportant, and often detrimental, to the task at hand (Vogel et al, 2005). After continuous theta-burst TMS to the left inferior frontal gyrus (IFG) or a control region (left somatosensory cortex), participants underwent MRI scanning while performing a face/scene matching task, in which the relevant stimulus category (faces or scenes) varied by block With this approach, we investigated the effect of frontal cortex disruption on the fidelity, as indexed by decoding accuracy, of two distinct types of visual working memory (VWM) representations: (1) stimulus category: whether a face or a scene was presented on each trial and (2) goal relevance, whether the presented image was task relevant (i.e., a face is relevant in a ‘‘Remember Faces’’ block, but irrelevant in a ‘‘Remember Scenes’’ block). Given that PFC likely maintains a code for goal relevance, we hypothesized that PFC disruption would reduce the fidelity of this information code in this disrupted PFC region, as well as other areas that depend on information from this disrupted region
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
