Abstract
Orbitofrontal cortex (OFC) is implicated in multiple cognitive processes, including inhibitory control, context memory, recency judgment, and choice behavior. Despite an emerging understanding of the role of OFC in memory and executive control, its necessity for core working memory (WM) operations remains undefined. Here, we assessed the impact of OFC damage on interference effects in WM using a Recent Probes task based on the Sternberg item-recognition task (1966). Subjects were asked to memorize a set of letters and then indicate whether a probe letter was presented in a particular set. Four conditions were created according to the forthcoming response (“yes”/“no”) and the recency of the probe (presented in the previous trial set or not). We compared behavioral and electroencephalography (EEG) responses between healthy subjects (n = 14) and patients with bilateral OFC damage (n = 14). Both groups had the same recency pattern of slower reaction time (RT) when the probe was presented in the previous trial but not in the current one, reflecting the proactive interference (PI). The within-group electrophysiological results showed no condition difference during letter encoding and maintenance. In contrast, event-related potentials (ERPs) to probes showed distinct within-group condition effects, and condition by group effects. The response and recency effects for controls occurred within the same time window (300–500 ms after probe onset) and were observed in two distinct spatial groups including right centro-posterior and left frontal electrodes. Both clusters showed ERP differences elicited by the response effect, and one cluster was also sensitive to the recency manipulation. Condition differences for the OFC group involved two different clusters, encompassing only left hemisphere electrodes and occurring during two consecutive time windows (345–463 ms and 565–710 ms). Both clusters were sensitive to the response effect, but no recency effect was found despite the behavioral recency effect. Although the groups had different electrophysiological responses, the maintenance of letters in WM, the evaluation of the context of the probe, and the decision to accept or reject a probed letter were preserved in OFC patients. The results suggest that neural reorganization may contribute to intact recency judgment and response after OFC damage.
Highlights
Damage confined to the orbitofrontal cortex (OFC) does not typically lead to deficient working memory (WM) performance when assessed with standard neuropsychological tests, it has been reported that OFC lesions can impair performance on tasks involving the coordination of WM maintenance, manipulation, and monitoring processes such as in N-back tasks (Wager and Smith, 2003; Owen et al, 2005; Barbey et al, 2011, 2013) and Delayed match-to-sample tasks (Meunier, 1997; Schon et al, 2008)
These results are in line with functional magnetic resonance imaging studies in healthy subjects where OFC was found to be involved in WM maintenance, interference control, and inhibition during delayed-response tasks (D’Esposito et al, 2000)
We focused on the probe period to examine whether the OFC lesion impacts the resolution of proactive interference (PI) in WM
Summary
The orbitofrontal cortex (OFC) is involved in several high-level cognitive functions such as goal-directed attention (Luu et al, 2000; Badre and Wagner, 2004; Ullsperger and Cramon, 2004; Walton et al, 2004; Hebscher and Gilboa, 2016), inhibitory control (Godefroy et al, 1999; Picton et al, 2007), and decisionmaking (Bechara et al, 1998, 2000; Ernst et al, 2002; Hebscher and Gilboa, 2016). Damage confined to the OFC does not typically lead to deficient WM performance when assessed with standard neuropsychological tests, it has been reported that OFC lesions can impair performance on tasks involving the coordination of WM maintenance, manipulation, and monitoring processes such as in N-back tasks (Wager and Smith, 2003; Owen et al, 2005; Barbey et al, 2011, 2013) and Delayed match-to-sample tasks (Meunier, 1997; Schon et al, 2008) These results are in line with functional magnetic resonance imaging (fMRI) studies in healthy subjects where OFC was found to be involved in WM maintenance, interference control, and inhibition during delayed-response tasks (D’Esposito et al, 2000). OFC has been implicated in recency memory (Shimamura et al, 1990; Incisa della Rocchetta and Milner, 1993; for human studies, and Barker et al, 2007; Devito and Eichenbaum, 2011 for rodent studies)
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