Showing papers in "Journal of Cognitive Neuroscience in 2004"

Sensitive Periods in the Development of the Brain and Behavior

Abstract: Experience exerts a profound influence on the brain and, therefore, on behavior. When the effect of experience on the brain is particularly strong during a limited period in development, this period is referred to as a sensitive period. Such periods allow experience to instruct neural circuits to process or represent information in a way that is adaptive for the individual. When experience provides information that is essential for normal development and alters performance permanently, such sensitive periods are referred to as critical periods. Although sensitive periods are reflected in behavior, they are actually a property of neural circuits. Mechanisms of plasticity at the circuit level are discussed that have been shown to operate during sensitive periods. A hypothesis is proposed that experience during a sensitive period modifies the architecture of a circuit in fundamental ways, causing certain patterns of connectivity to become highly stable and, therefore, energetically preferred. Plasticity that occurs beyond the end of a sensitive period, which is substantial in many circuits, alters connectivity patterns within the architectural constraints established during the sensitive period. Preferences in a circuit that result from experience during sensitive periods are illustrated graphically as changes in a ''stability landscape,'' a metaphor that represents the relative contributions of genetic and experiential influences in shaping the information processing capabilities of a neural circuit. By understanding sensitive periods at the circuit level, as well as understanding the relationship between circuit properties and behavior, we gain a deeper insight into the critical role that experience plays in shaping the development of the brain and behavior.

Reflecting upon Feelings: An fMRI Study of Neural Systems Supporting the Attribution of Emotion to Self and Other

Abstract: Understanding one's own and other individual's emotional states is essential for maintaining emotional equilibrium and strong social bonds. Although the neural substrates supporting ref lection upon one's own feelings have been investigated, no studies have directly examined attributions about the internal emotional states of others to determine whether common or distinct neural systems support these abilities. The present study sought to directly compare brain regions involved in judging one's own, as compared to another individual's, emotional state. Thirteen participants viewed mixed valence blocks of photos drawn from the International Affective Picture System while whole-brain fMRI data were collected. Preblock cues instructed participants to evaluate either their emotional response to each photo, the emotional state of the central figure in each photo, or (in a baseline condition) whether the photo was taken indoors or outdoors. Contrasts indicated (1) that both self and other judgments activated the medial prefrontal cortex (MPFC), the superior temporal gyrus, and the posterior cingulate/precuneus, (2) that self judgments selectively activated subregions of the MPFC and the left temporal cortex, whereas (3) other judgments selectively activated the left lateral prefrontal cortex (including Broca's area) and the medial occipital cortex. These results suggest (1) that self and other evaluation of emotion rely on a network of common mechanisms centered on the MPFC, which has been hypothesized to support mental state attributions in general, and (2) that medial and lateral PFC regions selectively recruited by self or other judgments may be involved in attention to, and elaboration of, internally as opposed to externally generated information.

Maturation of White Matter is Associated with the Development of Cognitive Functions during Childhood

Abstract: In the human brain, myelination of axons continues until early adulthood and is thought to be important for the development of cognitive functions during childhood. We used diffusion tensor MR imaging and calculated fractional anisotropy, an indicator of myelination and axonal thickness, in children aged between 8 and 18 years. Development of working memory capacity was positively correlated with fractional anisotropy in two regions in the left frontal lobe, including a region between the superior frontal and parietal cortices. Reading ability, on the other hand, was only correlated with fractional anisotropy in the left temporal lobe, in the same white matter region where adults with reading disability are known to have lower fractional anisotropy. Both the temporal and the frontal regions were also correlated with age. These results show that maturation of white matter is an important part of brain maturation during childhood, and that maturation of relatively restricted regions of white matter is correlated with development of specific cognitive functions.

Neural Circuits Involved in the Recognition of Actions Performed by Nonconspecifics: An fMRI Study

Abstract: Functional magnetic resonance imaging was used to assess the cortical areas active during the observation of mouth actions performed by humans and by individuals belonging to other species (monkey and dog). Two types of actions were presented: biting and oral communicative actions (speech reading, lip-smacking, barking). As a control, static images of the same actions were shown. Observation of biting, regardless of the species of the individual performing the action, determined two activation foci (one rostral and one caudal) in the inferior parietal lobule and an activation of the pars opercularis of the inferior frontal gyrus and the adjacent ventral premotor cortex. The left rostral parietal focus (possibly BA 40) and the left premotor focus were very similar in all three conditions, while the right side foci were stronger during the observation of actions made by conspecifics. The observation of speech reading activated the left pars opercularis of the inferior frontal gyrus, the observation of lip-smacking activated a small focus in the pars opercularis bilaterally, and the observation of barking did not produce any activation in the frontal lobe. Observation of all types of mouth actions induced activation of extrastriate occipital areas. These results suggest that actions made by other individuals may be recognized through different mechanisms. Actions belonging to the motor repertoire of the observer (e.g., biting and speech reading) are mapped on the observer's motor system. Actions that do not belong to this repertoire (e.g., barking) are essentially recognized based on their visual properties. We propose that when the motor representation of the observed action is activated, the observer gains knowledge of the observed action in a "personal" perspective, while this perspective is lacking when there is no motor activation.

Default-Mode Activity during a Passive Sensory Task: Uncoupled from Deactivation but Impacting Activation

Abstract: Deactivation refers to increased neural activity during lowdemand tasks or rest compared with high-demand tasks. Several groups have reported that a particular set of brain regions, including the posterior cingulate cortex and the medial prefrontal cortex, among others, is consistently deactivated. Taken together, these typically deactivated brain regions appear to constitute a default-mode network of brain activity that predominates in the absence of a demanding external task. Examining a passive, block-design sensory task with a standard deactivation analysis (rest epochs vs. stimulus epochs), we demonstrate that the default-mode network is undetectable in one run and only partially detectable in a second run. Using independent component analysis, however, we were able to detect the full default-mode network in both runs and to demonstrate that, in the majority of subjects, it persisted across both rest and stimulus epochs, uncoupled from the task waveform, and so mostly undetectable as deactivation. We also replicate an earlier finding that the default-mode network includes the hippocampus suggesting that episodic memory is incorporated in default-mode cognitive processing. Furthermore, we show that the more a subject's default-mode activity was correlated with the rest epochs (and "deactivated" during stimulus epochs), the greater that subject's activation to the visual and auditory stimuli. We conclude that activity in the default-mode network may persist through both experimental and rest epochs if the experiment is not sufficiently challenging. Time-series analysis of default-mode activity provides a measure of the degree to which a task engages a subject and whether it is sufficient to interrupt the processes—presumably cognitive, internally generated, and involving episodic memory—mediated by the default-mode network

How Would You Feel versus How Do You Think She Would Feel? A Neuroimaging Study of Perspective-Taking with Social Emotions

Abstract: Perspective-taking is a complex cognitive process involved in social cognition. This positron emission tomography (PET) study investigated by means of a factorial design the interaction between the emotional and the perspective factors. Participants were asked to adopt either their own (first person) perspective or the (third person) perspective of their mothers in response to situations involving social emotions or to neutral situations. The main effect of third-person versus first-person perspective resulted in hemodynamic increase in the medial part of the superior frontal gyrus, the left superior temporal sulcus, the left temporal pole, the posterior cingulate gyrus, and the right inferior parietal lobe. A cluster in the postcentral gyrus was detected in the reverse comparison. The amygdala was selectively activated when subjects were processing social emotions, both related to self and other. Interaction effects were identified in the left temporal pole and in the right postcentral gyrus. These results support our prediction that the frontopolar, the somatosensory cortex, and the right inferior parietal lobe are crucial in the process of self/other distinction. In addition, this study provides important building blocks in our understanding of social emotion processing and human empathy.

Reward-related Reversal Learning after Surgical Excisions in Orbito-frontal or Dorsolateral Prefrontal Cortex in Humans

Abstract: Neurophysiological studies in primates and neuroimaging studies in humans suggest that the orbito-frontal cortex is involved in representing the reward value of stimuli and in the rapid learning and relearning of associations between visual stimuli and rewarding or punishing outcomes. In the present study, we tested patients with circumscribed surgical lesions in different regions of the frontal lobe on a new visual discrimination reversal test, which, in an fMRI study (O'Doherty, Kringelbach, Rolls, Hornak, & Andrews, 2001), produced bilateral orbito-frontal cortex activation in normal subjects. In this task, touching one of two simultaneously presented patterns produced reward or loss of imaginary money delivered on a probabilistic basis to minimize the usefulness of verbal strategies. A number of types of feedback were present on the screen. The main result was that the group of patients with bilateral orbito-frontal cortex lesions were severely impaired at the reversal task, in that they accumulated less money. These patients often failed to switch their choice of stimulus after a large loss and often did switch their choice although they had just received a reward. The investigation showed that bilateral lesions were required for this deficit, since patients with unilateral orbito-frontal cortex (or medial prefrontal cortex) lesions were not impaired in the probabilistic reversal task. The task ruled out a simple motor disinhibition as an explanation of the deficit in the bilateral orbito-frontal cortex patients, in that the patients were required to choose one of two stimuli on each trial. A comparison group of patients with dorsolateral prefrontal cortex lesions was in some cases able to do the task, and in other cases, was impaired. Posttest debriefing showed that all the dorsolateral prefrontal patients who were impaired at the task had failed to pay attention to the crucial feedback provided on the screen after each trial about the amount won or lost on each trial. In contrast, all dorsolateral patients who paid attention to this crucial feedback performed normally on the reversal task. Further, it was confirmed that the bilateral orbito-frontal cortex patients had also paid attention to this crucial feedback, but in contrast had still performed poorly at the task. The results thus show that the orbital prefrontal cortex is required bilaterally for monitoring changes in the reward value of stimuli and using this to guide behavior in the task; whereas the dorsolateral prefrontal cortex, if it produces deficits in the task, does so for reasons related to executive functions, such as the control of attention. Thus, the ability to determine which information is relevant when making a choice of pattern can be disrupted by a dorsolateral lesion on either side, whereas the ability to use this information to guide behavior is not disrupted by a unilateral lesion in either the left or the right orbito-frontal cortex, but is severely impaired by a bilateral lesion in this region. Because both abilities are important in many of the tasks and decisions that arise in the course of daily life, the present results are relevant to understanding the difficulties faced by patients after surgical excisions in different frontal brain regions.

Neural Correlates of First-Person Perspective as One Constituent of Human Self-Consciousness

Abstract: Taking the first-person perspective (1PP) centered upon one's own body as opposed to the third-person perspective (3PP), which enables us to take the viewpoint of someone else, is constitutive for human self-consciousness. At the underlying representational or cognitive level, these operations are processed in an egocentric reference frame, where locations are represented centered around another person's (3PP) or one's own perspective (1PP). To study 3PP and 1PP, both operating in egocentric frames, a virtual scene with an avatar and red balls in a room was presented from different camera viewpoints to normal volunteers (n = 11) in a functional magnetic resonance imaging experiment. The task for the subjects was to count the objects as seen either from the avatar's perspective (3PP) or one's own perspective (1PP). The scene was presented either from a ground view (GV ) or an aerial view (AV ) to investigate the effect of view on perspective taking. The factors perspective (3PP vs. 1PP) and view (GV vs. AV ) were arranged in a two-factorial way. Reaction times were increased and percent correctness scores were decreased in 3PP as opposed to 1PP. To detect the neural mechanisms associated with perspective taking, functional magnetic resonance imaging was employed. Data were analyzed using SPM'99 in each subject and non-parametric statistics on the group level. Activations common to 3PP and 1PP (relative to baseline) were observed in a network of occipital, parietal, and prefrontal areas. Deactivations common to 3PP and 1PP (relative to baseline) were observed predominantly in mesial (i.e., parasagittal) cortical and lateral superior temporal areas bilaterally. Differential increases of neural activity were found in mesial superior parietal and right premotor cortex during 3PP (relative to 1PP), whereas differential increases during 1PP (relative to 3PP) were found in mesial prefrontal cortex, posterior cingulate cortex, and superior temporal cortex bilaterally. The data suggest that in addition to joint neural mechanisms, for example, due to visuospatial processing and decision making, 3PP and 1PP rely on differential neural processes. Mesial cortical areas are involved in decisional processes when the spatial task is solved from one's own viewpoint, whereas egocentric operations from another person's perspective differentially draw upon cortical areas known to be involved in spatial cognition.

Grasping the Intentions of Others: The Perceived Intentionality of an Action Influences Activity in the Superior Temporal Sulcus during Social Perception

Abstract: An explication of the neural substrates for social perception is an important component in the emerging field of social cognitive neuroscience and is relevant to the field of cognitive neuroscience as a whole. Prior studies from our laboratory have demonstrated that passive viewing of biological motion (Pelphrey, Mitchell, et al., 2003; Puce et al., 1998) activates the posterior superior temporal sulcus (STS ) region. Furthermore, recent evidence has shown that the perceived context of observed gaze shifts (Pelphrey, Singerman, et al., 2003; Pelphrey et al., 2004) modulates STS activity. Here, using event-related functional magnetic resonance imaging at 4 T, we investigated brain activity in response to passive viewing of goal- and nongoal-directed reaching-to-grasp movements. Participants viewed an animated character making reaching-to-grasp movements either toward (correct) or away (incorrect) from a blinking dial. Both conditions evoked significant posterior STS activity that was strongly right lateralized. By examining the time course of the blood oxygenation level-dependent response from areas of activation, we observed a functional dissociation. Incorrect trials evoked significantly greater activity in the STS than did correct trials, while an area posterior and inferior to the STS (likely corresponding to the MT/ V5 complex) responded equally to correct and incorrect movements. Parietal cortical regions, including the superior parietal lobule and the anterior intraparietal sulcus, also responded equally to correct and incorrect movements, but showed evidence for differential responding based on the hand and arm (left or right) of the animated character used to make the reaching-to-grasp movement. The results of this study further suggest that a region of the right posterior STS is involved in analyzing the intentions of other people's actions and that activity in this region is sensitive to the context of observed biological motions.

Anticipating Words and Their Gender: An Event-related Brain Potential Study of Semantic Integration, Gender Expectancy, and Gender Agreement in Spanish Sentence Reading

Abstract: Recent studies indicate that the human brain attends to and uses grammatical gender cues during sentence comprehension. Here, we examine the nature and time course of the effect of gender on word-by-word sentence reading. Event-related brain potentials were recorded to an article and noun, while native Spanish speakers read medium- to high-constraint Spanish sentences for comprehension. The noun either fit the sentence meaning or not, and matched the preceding article in gender or not; in addition, the preceding article was either expected or unexpected based on prior sentence context. Semantically anomalous nouns elicited an N400. Gender-disagreeing nouns elicited a posterior late positivity (P600), replicating previous findings for words. Gender agreement and semantic congruity interacted in both the N400 window—with a larger negativity frontally for double violations—and the P600 window—with a larger positivity for semantic anomalies, relative to the prestimulus baseline. Finally, unexpected articles elicited an enhanced positivity (500–700 msec post onset) relative to expected articles. Overall, our data indicate that readers anticipate and attend to the gender of both articles and nouns, and use gender in real time to maintain agreement and to build sentence meaning.

Representation of Number in Animals and Humans: A Neural Model

Abstract: This article addresses the representation of numerical information conveyed by nonsymbolic and symbolic stimuli. In a first simulation study, we show how number-selective neurons develop when an initially uncommitted neural network is given nonsymbolic stimuli as input (e.g., collections of dots) under unsupervised learning. The resultant network is able to account for the distance and size effects, two ubiquitous effects in numerical cognition. Furthermore, the properties of the network units conform in detail to the characteristics of recently discovered number-selective neurons. In a second study, we simulate symbol learning by presenting symbolic and nonsymbolic input simultaneously. The same number-selective neurons learn to represent the numerical meaning of symbols. In doing so, they show properties reminiscent of the originally available number-selective neurons, but at the same time, the representational efficiency of the neurons is increased when presented with symbolic input. This finding presents a concrete proposal on the linkage between higher order numerical cognition and more primitive numerical abilities and generates specific predictions on the neural substrate of number processing.

Contextual Modulation of Amygdala Responsivity to Surprised Faces

Abstract: We recently demonstrated a functional relationship between fMRI responses within the amygdala and the medial prefrontal cortex based upon whether subjects interpreted surprised facial expressions positively or negatively. In the present fMRI study, we sought to assess amygdala–medial prefrontal cortex responsivity when the interpretations of surprised faces were determined by contextual experimental stimuli, rather than subjective judgment. Subjects passively viewed individual presentations of surprised faces preceded by either a negatively or positively valenced contextual sentence (e. g., She just found d500 vs. She just lost d500). Negative and positive sentences were carefully matched in terms of length, situations described, and arousal level. Negatively cued surprised faces produced greater ventral amygdala activation compared to positively cued surprised faces. Responses to negative versus positive sentences were greater within the ventrolateral prefrontal cortex, whereas responses to positive versus negative sentences were greater within the ventromedial prefrontal cortex. The present study demonstrates that amygdala response to surprised facial expressions can be modulated by negatively versus positively valenced verbal contextual information. Connectivity analyses identified candidate cortical–subcortical systems subserving this modulation.

Direct Current Stimulation over V5 Enhances Visuomotor Coordination by Improving Motion Perception in Humans

Abstract: The primary aim of this study was to determine the extent to which human MT+/V5, an extrastriate visual area known to mediate motion processing, is involved in visuomotor coordination. To pursue this we increased or decreased the excitability of MT+/V5, primary motor, and primary visual cortex by the application of 7 min of anodal and cathodal transcranial direct current stimulation (tDCS) in healthy human subjects while they were performing a visuomotor tracking task involving hand movements. The percentage of correct tracking movements increased specifically during and immediately after cathodal stimulation, which decreases cortical excitability, only when V5 was stimulated. None of the other stimulation conditions affected visuomotor performance. We propose that the improvement in performance caused by cathodal tDCS of V5 is due to a focusing effect on to the complex motion perception conditions involved in this task. This hypothesis was proven by additional experiments: Testing simple and complex motion perception in dot kinetograms, we found that a diminution in excitability induced by cathodal stimulation improved the subject's perception of the direction of the coherent motion only if this was presented among random dots (complex motion perception), and worsened it if only one motion direction was presented (simple movement perception). Our data suggest that area V5 is critically involved in complex motion perception and identification processes important for visuomotor coordination. The results also raise the possibility of the usefulness of tDCS in rehabilitation strategies for neurological patients with visuomotor disorders.

Brain Activity during Episodic Retrieval of Autobiographical and Laboratory Events: An fMRI Study using a Novel Photo Paradigm

Abstract: Functional neuroimaging studies of episodic memory retrieval generally measure brain activity while participants remember items encountered in the laboratory (''controlled laboratory condition'') or events from their own life (''open autobiographical condition''). Differences in activation between these conditions may reflect differences in retrieval processes, memory remoteness, emotional content, retrieval success, self-referential processing, visual/spatial memory, and recollection. To clarify the nature of these differences, a functional MRI study was conducted using a novel ''photo paradigm,'' which allows greater control over the autobiographical condition, including a measure of retrieval accuracy. Undergraduate students took photos in specified campus locations (''controlled autobiographical condition''), viewed in the laboratory similar photos taken by other participants (controlled laboratory condition), and were then scanned while recognizing the two kinds of photos. Both conditions activated a common episodic memory network that included medial temporal and prefrontal regions. Compared with the controlled laboratory condition, the controlled autobiographical condition elicited greater activity in regions associated with self-referential processing (medial prefrontal cortex), visual/spatial memory (visual and parahippocampal regions), and recollection (hippocampus). The photo paradigm provides a way of investigating the functional neuroanatomy of real-life episodic memory under rigorous experimental control.

Implicit and Explicit Evaluation: fMRI Correlates of Valence, Emotional Intensity, and Control in the Processing of Attitudes

Abstract: Previous work suggests that explicit and implicit evaluations (good–bad) involve somewhat different neural circuits that process different dimensions such as valence, emotional intensity, and complexity. To better understand these differences, we used functional magnetic resonance imaging to identify brain regions that respond differentially to such dimensions depending on whether or not an explicit evaluation is required. Participants made either good–bad judgments (evaluative) or abstract–concrete judgments (not explicitly evaluative) about socially relevant concepts (e. g., ''murder,'' ''happiness,'' ''abortion,'' ''welfare''). After scanning, participants rated the concepts for goodness, badness, emotional intensity, and how much they tried to control their evaluation of the concept. Amygdala activation correlated with emotional intensity and right insula activation correlated with valence in both tasks, indicating that these aspects of stimuli were processed by these areas regardless of intention. In contrast, for the explicitly evaluative good–bad task only, activity in the anterior cingulate, frontal pole, and lateral areas of the orbital frontal cortex correlated with ratings of control, which in turn were correlated with a measure of ambivalence. These results highlight that evaluations are the consequence of complex circuits that vary depending on task demands.

Musical Training Enhances Automatic Encoding of Melodic Contour and Interval Structure

Abstract: In music, melodic information is thought to be encoded in two forms, a contour code (up/down pattern of pitch changes) and an interval code (pitch distances between successive notes). A recent study recording the mismatch negativity (MMN) evoked by pitch contour and interval deviations in simple melodies demonstrated that people with no formal music education process both contour and interval information in the auditory cortex automatically. However, it is still unclear whether musical experience enhances both strategies of melodic encoding. We designed stimuli to examine contour and interval information separately. In the contour condition there were eight different standard melodies (presented on 80% of trials), each consisting of five notes all ascending in pitch, and the corresponding deviant melodies (20%) were altered to descending on their final note. The interval condition used one five-note standard melody transposed to eight keys from trial to trial, and on deviant trials the last note was raised by one whole tone without changing the pitch contour. There was also a control condition, in which a standard tone (990.7 Hz) and a deviant tone (1111.0 Hz) were presented. The magnetic counterpart of the MMN (MMNm) from musicians and nonmusicians was obtained as the difference between the dipole moment in response to the standard and deviant trials recorded by magnetoencephalography. Significantly larger MMNm was present in musicians in both contour and interval conditions than in nonmusicians, whereas MMNm in the control condition was similar for both groups. The interval MMNm was larger than the contour MMNm in musicians. No hemispheric difference was found in either group. The results suggest that musical training enhances the ability to automatically register abstract changes in the relative pitch structure of melodies.

Decomposing Components of Task Preparation with Functional Magnetic Resonance Imaging

Abstract: It is widely acknowledged that the prefrontal cortex plays a major role in cognitive control processes. One important experimental paradigm for investigating such higher order cognitive control is the task-switching paradigm. This paradigm investigates the ability to switch flexibly between different task situations. In this context, it has been found that participants are able to anticipatorily prepare an upcoming task. This ability has been assumed to reflect endogenous cognitive control. However, it is difficult to isolate task preparation process from task execution using functional magnetic resonance imaging (fMRI). In the present study, we introduce a new experimental manipulation to investigate task preparation with fMRI. By manipulating the number of times a task was prepared, we could demonstrate that the left inferior frontal junction (IFJ) area (near the junction of inferior frontal sulcus and inferior precentral sulcus), the right inferior frontal gyrus, and the right intraparietal sulcus are involved in task preparation. By manipulating the cue-task mapping, we could further show that this activation is not related to cue encoding but to the updating of the relevant task representation. Based on these and previous results, we assume that the IFJ area constitutes a functionally separable division of the lateral prefrontal cortex. Finally, our data suggest that task preparation does not differ for switch and repetition trials in paradigms with a high proportion of switch trials, casting doubt on the assumption that an independent task set reconfiguration process takes place in the preparation interval.

Understanding Intentions in Social Interaction: The Role of the Anterior Paracingulate Cortex

Abstract: Neuroimaging studies have identified the anterior paracingulate cortex (PCC) as the key prefrontal region subserving theory of mind. We adopt an evolutionary perspective hypothesizing that, in response to the pressures of social complexity, a mechanism for manipulating information concerning social interaction has emerged in the anterior PCC. To date, neuroimaging studies have not properly distinguished between intentions of persons involved in social interactions and intentions of an isolated person. In two separate fMRI experiments, we demonstrated that the anterior PCC is not necessarily involved in the understanding of other people's intentions per se, but primarily in the understanding of the intentions of people involved in social interaction. Moreover, this brain region showed activation when a represented intention implies social interaction and therefore had not yet actually occurred. This result suggests that the anterior PCC is also involved in our ability to predict future intentional social interaction, based on an isolated agent's behavior. We conclude that distinct areas of the neural system underlying theory of mind are specialized in processing distinct classes of social stimuli.

Frontal and Temporo-Parietal Lobe Contributions to Theory of Mind: Neuropsychological Evidence from a False-Belief Task with Reduced Language and Executive Demands

Abstract: A model of the functional and anatomical basis of belief reasoning is essential for understanding the relationship between belief reasoning and other cognitive processes in both normal development and pathology. Studies of brain-damaged patients can give valuable insights into the nature of belief processing but pose unique methodological problems. The current study addresses these problems by using a nonlinguistic belief-reasoning task with substantially reduced executive demands. A case series of 12 brain-damaged patients is presented. The belief-reasoning errors of four patients with damage to the prefrontal cortex appeared to arise from these patients' executive function problems. The belief-reasoning errors of three patients with damage to the temporo-parietal junction could not easily be accounted for in this way, raising the possibility that this brain region has a necessary role in representing beliefs, rather than handling the executive demands of belief-reasoning tasks. We discuss the importance of gaining empirical evidence about the scope of ''theory of mind'' impairments, and the important role for neuropsychological studies in this project.

Reference Frames for Spatial Cognition: Different Brain Areas are Involved in Viewer-, Object-, and Landmark-Centered Judgments About Object Location

Abstract: Functional magnetic resonance imaging was used to compare the neural correlates of three different types of spatial coding, which are implicated in crucial cognitive functions of our everyday life, such as visuomotor coordination and orientation in topographical space. By manipulating the requested spatial reference during a task of relative distance estimation, we directly compared viewer-centered, object-centered, and landmark-centered spatial coding of the same realistic 3-D information. Common activation was found in bilateral parietal, occipital, and right frontal premotor regions. The retrosplenial and ventromedial occipital–temporal cortex (and parts of the parietal and occipital cortex) were significantly more activated during the landmark-centered condition. The ventrolateral occipital–temporal cortex was particularly involved in object-centered coding. Results strongly demonstrate that viewer-centered (egocentric) coding is restricted to the dorsal stream and connected frontal regions, whereas a coding centered on external references requires both dorsal and ventral regions, depending on the reference being a movable object or a landmark.

Orienting Attention to Locations in Perceptual Versus Mental Representations

Abstract: Extensive clinical and imaging research has characterized the neural networks mediating the adaptive distribution of spatial attention. In everyday behavior, the distribution of attention is guided not only by extrapersonal targets but also by mental representations of their spatial layout. We used event-related functional magnetic resonance imaging to identify the neural system involved in directing attention to locations in arrays held as mental representations, and to compare it with the system for directing spatial attention to locations in the external world. We found that these two crucial aspects of spatial cognition are subserved by extensively overlapping networks. However, we also found that a region of right parietal cortex selectively participated in orienting attention to the extrapersonal space, whereas several frontal lobe regions selectively participated in orienting attention within on-line mental representations.

The Faces of Development: A Review of Early Face Processing over Childhood

Abstract: The understanding of the adult proficiency in recognizing and extracting information from faces is still limited despite the number of studies over the last decade. Our knowledge on the development of these capacities is even more restricted, as only a handful of such studies exist. Here we present a combined reanalysis of four ERP studies in children from 4 to 15 years of age and adults (n = 424, across the studies), which investigated face processing in implicit and explicit tasks. We restricted these analyses to what was common across studies: early ERP components and upright face processing across all four studies and the inversion effect, investigated in three of the studies. These data demonstrated that processing faces implicates very rapid neural activity, even in young children— at the P1 component—with protracted age-related change in both P1 and N170, that were sensitive to the different task demands. Inversion produced latency and amplitude effects on the P1 from the youngest group, but on N170 only starting in mid childhood. These developmental data suggest that there are functionally different sources of the P1 and N170, related to the processing of different aspects of faces.

Processing Objects at Different Levels of Specificity

Abstract: How objects are represented and processed in the brain is a central topic in cognitive neuroscience. Previous studies have shown that knowledge of objects is represented in a feature-based distributed neural system primarily involving occipital and temporal cortical regions. Research with nonhuman primates suggest that these features are structured in a hierarchical system with posterior neurons in the inferior temporal cortex representing simple features and anterior neurons in the perirhinal cortex representing complex conjunctions of features (Bussey & Saksida, 2002; Murray & Bussey, 1999). On this account, the perirhinal cortex plays a crucial role in object identification by integrating information from different sensory systems into more complex polymodal feature conjunctions. We tested the implications of these claims for human object processing in an event-related fMRI study in which we presented colored pictures of common objects for 19 subjects to name at two levels of specificity - basic and domain. We reasoned that domain-level naming requires access to a coarser-grained representation of objects, thus involving only posterior regions of the inferior temporal cortex. In contrast, basic-level naming requires finer-grained discrimination to differentiate between similar objects, and thus should involve anterior temporal regions, including the perirhinal cortex. We found that object processing always activated the fusiform gyrus bilaterally, irrespective of the task, whereas the perirhinal cortex was only activated when the task required finer-grained discriminations. These results suggest that the same kind of hierarchical structure, which has been proposed for object processing in the monkey temporal cortex, functions in the human.

Modulation of Motor Excitability during Speech Perception: The Role of Broca's Area

Abstract: Studies in both human and nonhuman primates indicate that motor and premotor cortical regions participate in auditory and visual perception of actions. Previous studies, using transcranial magnetic stimulation (TMS), showed that perceiving visual and auditory speech increased the excitability of the orofacial motor system during speech perception. Such studies, however, cannot tell us which brain regions mediate this effect. In this study, we used the technique of combining positron emission tomography with TMS to identify the brain regions that modulate the excitability of the motor system during speech perception. Our results show that during auditory speech perception, there is increased excitability of motor system underlying speech production and that this increase is significantly correlated with activity in the posterior part of the left inferior frontal gyrus (Broca's area). We propose that this area ''primes'' the motor system in response to heard speech even when no speech output is required and, as such, operates at the interface of perception and action.

The Functional Neuroanatomy of Episodic and Semantic Autobiographical Remembering: A Prospective Functional MRI Study

Abstract: Autobiographical memory comprises episodic and semantic components mediated by dissociable states of consciousness, one promoting the experience of the self at a specific moment in the past, and the other involving self-knowledge that does not require ''mental time travel.'' These components can be difficult to dissociate using retrospective autobiographical stimuli collection. In this study, we manipulated the episodic/semantic distinction within prospectively collected autobiographical stimuli. Over several months, participants made recordings documenting specific episodes, repeated episodes, and world knowledge. These recordings were later played back to participants during scanning with functional MRI. The results indicated overlapping but distinct patterns of brain activity corresponding to episodic and semantic autobiographical memory. Both episodic and semantic autobiographical memory engaged the left anteromedial prefrontal cortex associated with self-reference, but the episodic condition did so to a greater degree. The episodic condition uniquely engaged the medial temporal, posterior cingulate, and diencephalic regions associated with remote memory recovery. Whereas the episodic condition engaged the right temporo-parietal cortex involved in reconstruction of spatial context and attentional orienting, the semantic condition engaged the left temporo-parietal and parieto-frontal systems involved in egocentric spatial processing and topdown attentional control. Episodic recollection was also associated with suppression of emotional paralimbic regions. These findings support a functional neuroanatomical dissociation between episodic and semantic autobiographical memory, providing concordance to amnesic syndromes with disproportionate impairment in one of these two forms of autobiographical memory.

Motor Sequence Complexity and Performing Hand Produce Differential Patterns of Hemispheric Lateralization

Abstract: Studies in brain damaged patients conclude that the left hemisphere is dominant for controlling heterogeneous sequences performed by either hand, presumably due to the cognitive resources involved in planning complex sequential movements. To determine if this lateralized effect is due to asymmetries in primary sensorimotor or association cortex, whole-brain functional magnetic resonance imaging was used to measure differences in volume of activation while healthy right-handed subjects performed repetitive (simple) or heterogeneous (complex) finger sequences using the right or left hand. Advanced planning, as evidenced by reaction time to the first key press, was greater for the complex than simple sequences and for the left than right hand. In addition to the expected greater contralateral activation in the sensorimotor cortex (SMC), greater left hemisphere activation was observed for left, relative to right, hand movements in the ipsilateral left superior parietal area and for complex, relative to simple, sequences in the left premotor and parietal cortex, left thalamus, and bilateral cerebellum. No such volumetric asymmetries were observed in the SMC. Whereas the overall MR signal intensity was greater in the left than right SMC, the extent of this asymmetry did not vary with hand or complexity level. In contrast, signal intensity in the parietal and premotor cortex was greater in the left than right hemisphere and for the complex than simple sequences. Signal intensity in the caudal anterior cerebellum was greater bilaterally for the complex than simple sequences. These findings suggest that activity in the SMC is associated with execution requirements shared by the simple and complex sequences independent of their differential cognitive requirements. In contrast, consistent with data in brain damaged patients, the left dorsal premotor and parietal areas are engaged when advanced planning is required to perform complex motor sequences that require selection of different effectors and abstract organization of the sequence, regardless of the performing hand.

Evidence of Developmental Differences in Implicit Sequence Learning: An fMRI Study of Children and Adults

Abstract: Prevailing theories of implicit or unaware learning propose a developmental invariance model, with implicit function maturing early in infancy or childhood despite prolonged improvements in explicit or intentional learning and memory systems across childhood. Neuroimaging studies of adult visuomotor sequence learning have associated fronto-striatal brain regions with implicit learning of spatial sequences. Given evidence of continued development in these brain regions during childhood, we compare implicit sequence learning in adults and 7- to 11-year-old children to examine potential developmental differences in the recruitment of fronto-striatal circuitry during implicit learning. Participants performed a standard serial reaction time task. Stimuli alternately followed a fixed 10-step sequence of locations or were presented in a pseudorandom order of locations. Adults outperformed children, achieving a significantly larger sequence learning effect and showing learning more quickly than children. Age-related differences in activity were observed in the premotor cortex, putamen, hippocampus, inferotemporal cortex, and parietal cortex. We observed differential recruitment of cortical and subcortical motor systems between groups, presumably reflecting age differences in motor response execution. Adults showed greater hippocampal activity for sequence trials, whereas children demonstrated greater signal during random trials. Activity in the right caudate correlated significantly with behavioral measures of implicit learning for both age groups, although adults showed greater signal change than children overall, as would be expected given developmental differences in sequence learning magnitude. These results challenge the idea of developmental invariance in implicit learning and instead support a view of parallel developments in implicit and explicit learning systems.

Cortical Regions for Judgments of Emotions and Personality Traits from Point-light Walkers

Abstract: Humans are able to use nonverbal behavior to make fast, reliable judgments of both emotional states and personality traits. Whereas a sizeable body of research has identified neural structures critical for emotion recognition, the neural substrates of personality trait attribution have not been explored in detail. In the present study, we investigated the neural systems involved in emotion and personality trait judgments. We used a type of visual stimulus that is known to convey both emotion and personality information, namely, point-light walkers. We compared the emotion and personality trait judgments made by subjects with brain damage to those made by neurologically normal subjects and then conducted a lesion overlap analysis to identify neural regions critical for these two tasks. Impairments on the two tasks dissociated: Some subjects were impaired at emotion recognition, but judged personality normally; other subjects were impaired on the personality task, but normal at emotion recognition. Moreover, these dissociations in performance were associated with damage to specific neural regions: Right somatosensory cortices were a primary focus of lesion overlap in subjects impaired on the emotion task, whereas left frontal opercular cortices were a primary focus of lesion overlap in subjects impaired on the personality task. These findings suggest that attributions of emotional states and personality traits are accomplished by partially dissociable neural systems.

Development of Brain Mechanisms for Processing Orthographic and Phonologic Representations

Abstract: Developmental differences in the neurocognitive networks for lexical processing were examined in 15 adults and 15 children (9- to 12-year-olds) using functional magnetic resonance imaging (fMRI). The lexical tasks involved spelling and rhyming judgments in either the visual or auditory modality. These lexical tasks were compared with nonlinguistic control tasks involving judgments of line patterns or tone sequences. The first main finding was that adults showed greater activation than children during the cross-modal lexical tasks in a region proposed to be involved in mapping between orthographic and phonologic representations. The visual rhyming task, which required conversion from orthography to phonology, produced greater activation for adults in the angular gyrus. The auditory spelling task, which required the conversion from phonology to orthography, also produced greater activation for adults in the angular gyrus. The greater activation for adults suggests they may have a more elaborated posterior heteromodal system for mapping between representational systems. The second main finding was that adults showed greater activation than children during the intra-modal lexical tasks in the angular gyrus. The visual spelling and auditory rhyming did not require conversion between orthography and phonology for correct performance but the adults showed greater activation in a system implicated for this mapping. The greater activation for adults suggests that they have more interactive convergence between representational systems during lexical processing.

A Comparison of the Electroencephalogram between Institutionalized and Community Children in Romania

Abstract: Electroencephalographic (EEG) data were collected from a sample of institutionalized infants and young children in Bucharest, Romania, and were compared with EEG data from age-matched children from the local community who had never been institutionalized and who were living with their families in the Bucharest area. Compared with the never-institutionalized group, the institutionalized group showed a pattern of increased low-frequency (theta) power in posterior scalp regions and decreased high-frequency (alpha and beta) power, particularly at frontal and temporal electrode sites. This finding is consistent with EEG studies of children facing environmental adversity and children with learning disorders. The institutionalized group also showed less marked hemispheric EEG asymmetries than the never-institutionalized group, particularly in the temporal region. The results are discussed in the context of two models: that the pattern of EEG in the institutionalized children reflects a maturational lag in nervous system development, or that it reflects tonic cortical hypoactivation.