Focus of spatial attention during spatial working memory maintenance: Evidence from pupillary light response

Abstract

In this experiment, we demonstrate modulation of the pupillary light response by spatial working memory (SWM). The pupillary light response has previously been shown to reflect the focus of covert attention, as demonstrated by smaller pupil sizes when a subject covertly attends a location on a bright background compared to a dark background. We took advantage of this modulation of the pupillary light response to measure the focus of attention during a SWM delay. Subjects performed two tasks in which a stimulus was presented in the periphery on either the bright or the dark half of a black and white display. Importantly, subjects had to remember the exact location of the stimulus in only one of the two tasks. We observed a modulation of pupil size by background luminance in the delay period, but only when subjects had to remember the exact location. We interpret this as evidence for a tight coupling between spatial attention and maintaining information in SWM. Interestingly, we observed particularly strong modulation of background luminance at the beginning and end of the delay, but not in between. This is suggestive of strategic guidance of spatial attention by the content of spatial working memory when it is task relevant. ARTICLE HISTORY

Tracking working memory maintenance with pupillometry

“…This suggests that participants were unable to sustain attentional effort over the entire delay period. Recently, Fabius et al (2017) reported a similar result when examining the pupillary light response. Specifically, Fabius et al found that the pupillary response tended to decrease after approximately 4,000 ms.…”

“…Wang and Munoz (2015) further suggested that BSC-mediated pupil pathways could provide the substrate required for pupil size modulation by various cognitive processes^(p. 139). Indeed, recent research has found that the pupil (in particular the pupillary light reflex) can be used to track covert shifts of attention during WM maintenance (Fabius et al, 2017;. Additionally, as noted above, Alnaes et al (2014) found that SC activity correlated with pupillary changes as the number of items to be tracked increased.…”

Exploring the interaction between the pupillary light response after exogenous attentional cueing and detection performance

“…To measure the behavioral effect of the cue on perception, we constructed a detection performance time series using a dense sampling, exogenous cueing paradigm (Landau & Fries, 2012). If covert attention influences the PLR, the pupil should relatively dilate if a cue is presented at the dark side of a screen, and constrict if the cue is presented at the bright side of a screen, similar to previous studies (Fabius et al, 2017; Mathôt et al, 2014). Furthermore, we hypothesized that if targets appear at the same side of the screen as the preceding cue early in the time series, these targets would be more likely to be detected compared to targets later in the time series or targets appearing at the other side of the screen (Mulckhuyse & Theeuwes, 2010).…”

“…For instance, when participants fixated on the center of a screen with a bright and dark part, their pupils relatively constricted when they covertly attended to the bright part, and relatively dilated when they covertly attended on the dark part (Binda et al, 2013a; Mathôt et al, 2014, 2013). This phenomenon can be elicited both by endogenous (Binda et al, 2013a; Mathôt et al, 2013) and exogenous cueing (Fabius, Mathôt, Schut, Nijboer, & Van der Stigchel, 2017; Mathôt et al, 2014). Moreover, this effect appeared to reverse after approximately one second: when initially on one of the sides, covert attention shifted to the other side after a period of time, reminiscent of inhibition of return (IOR).…”

Pupillometry: Psychology, Physiology, and Function

“…In one of our experiments, participants memorized a location, which could be either on a dark or a bright background (Fabius, Mathôt, Schut, Nijboer, & Van der Stigchel, 2017; see also Unsworth & Robison, 2016). We found that the pupil was smaller when participants memorized a location on a bright, compared to a dark, background.…”