As people find their way through their environment, objects at navigationally relevant locations can serve as crucial landmarks. The parahippocampal gyrus has previously been shown to be involved in object and scene recognition. In the present study, we investigated the neural representation of navigationally relevant locations. Healthy human adults viewed a route through a virtual museum with objects placed at intersections (decision points) or at simple turns (non-decision points). Event-related functional magnetic resonance imaging (fMRI) data were acquired during subsequent recognition of the objects in isolation. Neural activity in the parahippocampal gyrus reflected the navigational relevance of an object's location in the museum. Parahippocampal responses were selectively increased for objects that occurred at decision points, independent of attentional demands. This increase occurred for forgotten as well as remembered objects, showing implicit retrieval of navigational information. The automatic storage of relevant object location in the parahippocampal gyrus provides a part of the neural mechanism underlying successful navigation.Studies on the neural basis of navigation have consistently shown the hippocampus to be crucially involved in the creation of an allocentric spatial representation of our environment 1-12 . The parahippocampal gyrus, a brain region highly interconnected with the hippocampus, has been implicated in the encoding of objects-in-place during navigation 5,6,13 , as well as in the processing of spatial visual scenes 14,15 . Successful navigation is facilitated by the presence of objects, or landmarks, at different locations along a route [16][17][18] . Not all objects along a route, however, are equally relevant for navigation. Whereas objects at intersections convey information about which of the possible paths is the correct one, objects placed at simple turns in the road are of much less significance. Behavioral studies have reported that objects placed at decision points (that is, intersections) are more likely to be remembered later than objects placed at non-decision points 17 . They are also regarded as more important when participants evaluate the quality of a route description 19 . How this distinction between navigationally relevant and irrelevant objects is stored and maintained in the brain is still unknown. To date, all studies have focused on the neural correlates of encoding spatial information during navigation. To find one's way back in a surrounding, however, the information about relevant locations needs to be available at a later moment in time. Therefore, it is likely that spatial information that is crucial for pathfinding is encoded and stored differently than information that is of less importance. Here we report event-related fMRI evidence for differential representation of objects in the parahippocampal gyrus as a function of their navigational relevance in a large-scale environment.In the study phase of the experiment, twenty healthy, right-handed human adu...

Does our ability to visually identify everyday objects rely solely on access to information about their appearance or on a more distributed representation incorporating other object properties? Using functional magnetic resonance imaging, we addressed this question by having subjects visually match pictures of novel objects before and after extensive training to use these objects to perform specific tool-like tasks. After training, neural activity emerged in regions associated with the motion (left middle temporal gyrus) and manipulation (left intraparietal sulcus and premotor cortex) of common tools, whereas activity became more focal and selective in regions representing their visual appearance (fusiform gyrus). These findings indicate that this distributed network is automatically engaged in support of object identification. Moreover, the regions included in this network mirror those active when subjects retrieve information about tools and their properties, suggesting that, as a result of training, these previously novel objects have attained the conceptual status of "tools."

The temporal properties of semantic and phonological processes in speech production were investigated in a new experimental paradigm using movement-related brain potentials. The main experimental task was picture naming. In addition, a 2-choice reaction go/no-go procedure was included, involving a semantic and a phonological categorization of the picture name. Lateralized readiness potentials (LRPs) were derived to test whether semantic and phonological information activated motor processes at separate moments in time. An LRP was only observed on no-go trials when the semantic (not the phonological) decision determined the response hand. Varying the position of the critical phoneme in the picture name did not affect the onset of the LRP but rather influenced when the LRP began to differ on go and no-go trials and allowed the duration of phonological encoding of a word to be estimated. These results provide electrophysiological evidence for early semantic activation and later phonological encoding.

In normal conversation, speakers translate thoughts into words at high speed. To enable this speed, the retrieval of distinct types of linguistic knowledge has to be orchestrated with millisecond precision. The nature of this orchestration is still largely unknown. This report presents dynamic measures of the real-time activation of two basic types of linguistic knowledge, syntax and phonology. Electrophysiological data demonstrate that during noun-phrase production speakers retrieve the syntactic gender of a noun before its abstract phonological properties. This two-step process operates at high speed: the data show that phonological information is already available 40 milliseconds after syntactic properties have been retrieved.

Cognitive control includes the ability to formulate goals and plans of action and to follow these while facing distraction. Previous neuroimaging studies have shown that the presence of conflicting response alternatives in Stroop-like tasks increases activity in dorsal anterior cingulate cortex (ACC), suggesting that the ACC is involved in cognitive control. However, the exact nature of ACC function is still under debate. The prevailing conflict detection hypothesis maintains that the ACC is involved in performance monitoring. According to this view, ACC activity reflects the detection of response conflict and acts as a signal that engages regulative processes subserved by lateral prefrontal brain regions. Here, we provide evidence from functional MRI that challenges this view and favors an alternative view, according to which the ACC has a role in regulation itself. Using an arrow-word Stroop task, subjects responded to incongruent, congruent, and neutral stimuli. A critical prediction made by the conflict detection hypothesis is that ACC activity should be increased only when conflicting response alternatives are present. Our data show that ACC responses are larger for neutral than for congruent stimuli, in the absence of response conflict. This result demonstrates the engagement of the ACC in regulation itself. A computational model of Stroop-like performance instantiating a version of the regulative hypothesis is shown to account for our findings.action regulation ͉ cognitive control ͉ neuroimaging ͉ performance monitoring G oals dominate human thinking and behavior. We feel able to exercise control over our thoughts and actions, and yet, we experience limitations to that control. ''I can resist everything except temptation,'' a character in an Oscar Wilde play once said. In general, we are good but not perfect at dealing with distraction. This fundamental truth is exploited in investigations of cognitive control. Cognitive control refers to the regulative processes that ensure that our thinking, memory retrieval, planning, and actions are in accordance with our goals. In this way, cognitive control helps us to resist temptations to satisfy other goals. Another important aspect of cognitive control concerns performance monitoring, or assessing whether the planning and action are consistent with intent.A classic task that uses distraction in studying cognitive control is the color-word Stroop task (1, 2), which is among the most frequently used tasks in the cognitive and brain sciences. In this task, subjects are asked to name the ink color of written color words (e.g., say red to the word blue written in red ink). Results have consistently shown that people are much slower in naming the ink color of incongruent color words than in naming the ink color of a row of neutral xs, and people are often, but not always, faster when color and word are congruent (e.g., say red to the word red in red ink) than in the neutral condition. The finding that only a few errors are made on incongruent trials shows that people ...