An example of the experimental design.

<p>The experiment consisted of six runs. In each run ¼ of the trials were viewing trials (were participants watched a centrally presented picture), ¾ were tracking trials. Familiar and unfamiliar runs were intertwined. Presented stimuli throughout a run were either buildings, objects or faces. In a familiar trial both targets and distractors remained the same from trial to trial, whereas in an unfamiliar run target-identities changed from trial to trial. Familiar runs consisted of 96 trials, unfamiliar runs of 36 trials. These 6 runs were followed by a localizer task, in which the participant watched faces, buildings or objects.</p

A side, sliced and top-view of four points in the brain: Blue shows the areas that are more active during the familiar condition and red those areas that are more active during the unfamiliar condition.

<p>Center of gravity coordinates (MNI reference system) are shown below each slice. The left picture shows the side view of the brain (s indicates the top of the brain, I the bottom, p the back, and a the front). The middle picture shows a sliced view of the brain (r denotes the rights side of the brain, l the left side). The right picture shows a top view of the brain. For more brain slices: see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042929#pone.0042929.s001" target="_blank">Appendix S1</a>.</p

This is a clockwise depiction of a tracking trial.

<p>First highlights indicated what the targets are. Then all objects move around for 2–6 seconds. Then all objects are masked, one masked item is highlighted, and the subject indicates if the highlighted item is the same as the centrally depicted probe.</p

A similar overview as in Table 2, but now of the regions that are more active during familiar trials.

<p>A similar overview as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0042929#pone-0042929-t002" target="_blank">Table 2</a>, but now of the regions that are more active during familiar trials.</p

An overview of the regions that are more active during unfamiliar trials.

<p>Coordinates are in mm. One voxel is 2×2×3 mm. Names are based on the Harvard-Oxford cortical structural atlas. LOC stands for lateral occipital cortex.</p

Behavioral data showing that subjects performed significantly better, with regards to identity accuracy, on familiar trials.

<p>On the y-axis percentage correct is indicated.</p

Tracking Moving Identities: After Attending the Right Location, the Identity Does Not Come for Free

<div><p>Although tracking identical moving objects has been studied since the 1980's, only recently the study into tracking moving objects with <em>distinct</em> identities has started (referred to as Multiple Identity Tracking, MIT). So far, only behavioral studies into MIT have been undertaken. These studies have left a fundamental question regarding MIT unanswered, is MIT a one-stage or a two-stage process? According to the one-stage model, after a location has been attended, the identity is released without effort. However, according to the two-stage model, there are two effortful stages in MIT, attending to a location, and attending to the identity of the object at that location.</p> <p> In the current study we investigated this question by measuring brain activity in response to tracking familiar and unfamiliar targets. Familiarity is known to automate effortful processes, so if attention to identify the object is needed, this should become easier. However, if no such attention is needed, familiarity can only affect other processes (such as memory for the target set). Our results revealed that on unfamiliar trials neural activity was higher in both attentional networks, and visual identification networks. These results suggest that familiarity in MIT automates attentional identification processes, thus suggesting that attentional identification is needed in MIT. This then would imply that MIT is essentially a two-stage process, since after attending the location, the identity does not seem to come for free.</p> </div