Abstract
BackgroundThe visual cortex of the human brain contains specialized modules for processing different visual features of an object. Confronted with multiple objects, the system needs to attribute the correct features to each object (often referred to as 'the binding problem'). The brain is assumed to integrate the features of perceived objects into object files – pointers to the neural representations of these features, which outlive the event they represent in order to maintain stable percepts of objects over time. It has been hypothesized that a new encounter with one of the previously bound features will reactivate the other features in the associated object file according to a kind of pattern-completion process.MethodsFourteen healthy volunteers participated in an fMRI experiment and performed a task designed to measure the aftereffects of binding visual features (houses, faces, motion direction). On each trial, participants viewed a particular combination of features (S1) before carrying out a speeded choice response to a second combination of features (S2). Repetition and alternation of all three features was varied orthogonally.ResultsThe behavioral results showed the standard partial repetition costs: a reaction time increase when one feature was repeated and the other feature alternated between S1 and S2, as compared to complete repetitions or alternations of these features. Importantly, the fMRI results provided evidence that repeating motion direction reactivated the object that previously moved in the same direction. More specifically, perceiving a face moving in the same direction as a just-perceived house increased activation in the parahippocampal place area (PPA). A similar reactivation effect was not observed for faces in the fusiform face area (FFA). Individual differences in the size of the reactivation effects in the PPA and FFA showed a positive correlation with the corresponding partial repetition costs.ConclusionOur study provides the first neural evidence that features are bound together on a single presentation and that reviewing one feature automatically reactivates the features that previously accompanied it.
Highlights
The visual cortex of the human brain contains specialized modules for processing different visual features of an object
When subjects were asked to respond to the direction of the motion, attention spread from the motion to the object, regardless of which object was moving: Functional magnetic resonance imaging results showed that the parahippocampal place area (PPA) was activated more strongly when the house moved, and the fusiform face area (FFA) was activated more strongly when the face moved
Reactivation effect in the PPA (S1: house moving, S2: face moving) To examine the presence of a reactivation effect in the PPA we contrasted the conditions in which the house in S1 and the face in S2 moved in the same direction versus in different directions (HF = minus HF≠)
Summary
The visual cortex of the human brain contains specialized modules for processing different visual features of an object. The human visual cortex is divided into specialized modules that code a variety of different visual features, like motion in area MT/MST [1,2], faces in the fusiform face area (FFA; [3]) and houses in the parahippocampal place area (PPA; [4]) This division of labor entails a wellknown problem: When confronted with multiple objects, how does the visual system 'know' which features belong together in one object?. This suggests that attending to an event creates some sort of functional link between the representations of its features, whether they are relevant (like the direction of the motion in this example) or irrelevant (like the faces or houses) Further support for this notion comes from a recent fMRI study by Yi et al [8] who found that face-selective regions in the FFA and lateral occipital cortex exhibited significantly less activation when (taskrelevant) faces were repeated in (task-irrelevant) continuous versus discontinuous trajectories. This suggests that attending to a moving object creates an object file in which object identity and spatiotemporal parameters are closely integrated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
