Working Memory Representations in Visual Cortex Mediate the Effects of Distraction

Abstract

Although the contents of working memory (WM) can be decoded from activity in visual cortex, these representations may play a limited role if they are not robust to distraction. Here, we used model-based fMRI to estimate the impact that a distracting visual task had on WM representations in several visual field maps in visual and frontoparietal association cortex. Distraction caused the fidelity of WM representations in all maps to briefly dip when both the memorandum and distractor were jointly encoded by the population activities. Moreover, distraction induced small biases in memory errors which were predicted by biases in neural decoding in early visual cortex, but not other regions. Although distraction briefly disrupts WM representations, the widespread redundancy with which WM information is encoded may protect against catastrophic loss. In early visual cortex, nonetheless, the neural representation of information in WM and behavioral performance were intertwined, solidifying its importance in memory.

Joint representation of working memory and uncertainty in human cortex

“…We defined four retinotopic visual (V1, V2, V3 and V3AB), four parietal (IPS0, IPS1, IPS2 and IPS3) and two frontal areas (iPCS and sPCS) as regions of interest (ROIs) using population receptive field mapping techniques 48,49 . Similar to previous studies using other decoding methods 16,23,25,28,50 , we found that the remembered stimulus location could be decoded from the delay period BOLD responses in retinotopic visual, parietal, and frontal cortex. First, we plotted a distribution of the trial-wise decoding error (decoded location minus target location; Fig.…”

Persistent Activity during Working Memory from Front to Back

“…Measuring neural activity with fMRI while humans perform spatial WM tasks, including memory-guided saccade WM tasks like those used to initially study the macaque PFC (Funahashi et al, 1989), we find that fMRI is perfectly sensitive to WM representations of single items (Curtis et al, 2004; Curtis and D’Esposito, 2006; Schluppeck et al, 2006; Srimal and Curtis, 2008; Tark and Curtis, 2009; Jerde et al, 2012; Sprague et al, 2014; Saber et al, 2015; Rahmati et al, 2020; Hallenbeck et al, 2021). However, in none of the above cited studies did we find evidence that neural activity persists in the human dorsolateral PFC during simple spatial WM tasks.…”

“…Hypothesis 1: These monkey data predict that lesions to human dlPFC will impair spatial WM performance, including the accuracy of memory-guided saccades. However, human neuroimaging studies typically find persistent activity or multivoxel decoding of information restricted to the PCS, posterior to the likely homolog of the monkey principal sulcus in the dlPFC (Li et al; Courtney et al, 1998; Srimal and Curtis, 2008; Jerde et al, 2012; Sprague et al, 2014; Hallenbeck et al, 2021). Hypothesis 2: These data predict that lesions to human PCS, not dlPFC, will impair WM performance.…”

“…Utilizing the same logic, advances in population receptive field (pRF) mapping (Dumoulin and Wandell 2008; Mackey et al 2017; Wandell and Winawer 2015) allow researchers to compare BOLD estimates of persistent activity between trials in which the memoranda fall within and outside of a voxel’s pRF. In Figure 3, the time courses of BOLD activity during a memory-guided saccade task are shown for ten visual field maps (Rahmati et al, 2020; Hallenbeck et al, 2021). Each visual field map contains either an upright or inverted representation of the contralateral visual field.…”

“…For each ROI, we show a timecourse of reconstructed representations (each row is a single timepoint; average of reconstructions for all experimental trials aligned to the remembered location), along with the average channel response profile over the final 1.5 s of the delay period (red line). Data adapted from Hallenbeck et al, (Hallenbeck et al, 2021) (A-B; all ROIs except SC) and Rahmati et al, (Rahmati et al, 2020) (B; SC). This Figure depicts the same data shown in Fig.…”