Right temporoparietal junction activation by a salient contextual cue facilitates target discrimination

Abstract

The right temporoparietal junction (R TPJ) is involved in stimulus-driven attentional control in response to the appearance of an unexpected target or a distractor that shares features with a task-relevant target. An unresolved question is whether these responses in R TPJ are due simply to the presence of a stimulus that is a potential target, or instead responds to any task-relevant information. Here, we addressed this issue by testing the sensitivity of R TPJ to a perceptually salient, non-target stimulus - a contextual cue. Although known to be a non-target, the contextual cue carried probabilistic information regarding the presence of a target in the opposite visual field. The contextual cue was therefore always of potential behavioral relevance, but only sometimes paired with a target. The appearance of the contextual cue alone increased activation in R TPJ, but more so when it appeared with a target. There was also greater connectivity between R TPJ and a network of attentional control and decision areas when the contextual cue was present. These results demonstrate that R TPJ is involved in the stimulus-driven representation of task-relevant information that can be used to engage an appropriate behavioral response.

Figure 1

Illustration of experimental conditions. Standard stimuli were presented in rapid bilateral visual streams. The central fixation indicated which stimulus stream targets would appear in and whether the target discrimination would be easy or hard (e.g, the right-sided blue rectangle at fixation in the illustration above instructed subjects to attend to the right-sided stream for easy targets). There were three event types of interest within each block: 1) target alone trials in which a target appeared in the attended stream and a standard in the unattended stream; 2) target + contextual cue trials in which a target and a contextual cue appeared simultaneously; and 3) contextual cue alone trials in which the stimulus in the unattended stream increased in luminance and a standard stimulus appeared in the attended location.

Figure 2

Eye-position data from all 12 conditions plotted as the proportion of trials in each condition at each distance in degrees of visual angle from central fixation.

Figure 3

Behavioral data from trials with correct target detection showing interactions between contextual cue presence and target discrimination difficulty. ‘*’ signifies statistically significant differences. A) RTs were shorter when the contextual cue was present and the difference was bigger when detection was hard; B) sensitivity (d′) was greater for easy targets overall, but amongst hard targets, sensitivity was greater when the contextual cue was present; and C) the decision criterion (c) was more liberal in the presence of a contextual cue, particularly when target discrimination was hard. Error bars are standard error of the mean.

Figure 4

A) TPJ and precuneus regions activated by contrast of target + contextual cue minus target alone. B) Parameter estimates for left and right TPJ ROIs in each of the three conditions of interest.

Figure 5

PPI results from whole brain using R TPJ as the seed region. There was greater connectivity between R TPJ and these attentional control and decision areas when the target appeared with a contextual cue compared to a standard in the unattended visual stream.