Maurizio Corbetta

Publications of Maurizio Corbetta

• Large-scale cortical correlation structure of spontaneous oscillatory activity.

  Authors: Joerg F Hipp, David J Hawellek, Maurizio Corbetta, Markus Siegel, Andreas K Engel

  Nature neuroscience. 05/2012;

  Little is known about the brain-wide correlation of electrophysiological signals. We found that spontaneous oscillatory neuronal activity exhibited frequency-specific spatial correlation structure inLittle is known about the brain-wide correlation of electrophysiological signals. We found that spontaneous oscillatory neuronal activity exhibited frequency-specific spatial correlation structure in the human brain. We developed an analysis approach that discounts spurious correlation of signal power caused by the limited spatial resolution of electrophysiological measures. We applied this approach to source estimates of spontaneous neuronal activity reconstructed from magnetoencephalography. Overall, correlation of power across cortical regions was strongest in the alpha to beta frequency range (8-32 Hz) and correlation patterns depended on the underlying oscillation frequency. Global hubs resided in the medial temporal lobe in the theta frequency range (4-6 Hz), in lateral parietal areas in the alpha to beta frequency range (8-23 Hz) and in sensorimotor areas for higher frequencies (32-45 Hz). Our data suggest that interactions in various large-scale cortical networks may be reflected in frequency-specific power envelope correlations.

• Distinct representations for shifts of spatial attention and changes of reward contingencies in the human brain.

  Authors: Annalisa Tosoni, Gordon L Shulman, Anna L W Pope, Mark P McAvoy, Maurizio Corbetta

  Cortex; a journal devoted to the study of the nervous system and behavior. 04/2012;

  Success in a dynamically changing world requires both rapid shifts of attention to the location of important objects and the detection of changes in motivational contingencies that may alter futureSuccess in a dynamically changing world requires both rapid shifts of attention to the location of important objects and the detection of changes in motivational contingencies that may alter future behavior. Here we addressed the relationship between these two processes by measuring the blood-oxygenation-level-dependent (BOLD) signal during a visual search task in which the location and the color of a salient cue respectively indicated where a rewarded target would appear and the monetary gain (large or small) associated with its detection. While cues that either shifted or maintained attention were presented every 4 to 8sec, the reward magnitude indicated by the cue changed roughly every 30sec, allowing us to distinguish a change in expected reward magnitude from a maintained state of expected reward magnitude. Posterior cingulate cortex was modulated by cues signaling an increase in expected reward magnitude, but not by cues for shifting versus maintaining spatial attention. Dorsal fronto-parietal regions in precuneus and frontal eye field (FEF) also showed increased BOLD activity for changes in expected reward magnitude from low to high, but in addition showed large independent modulations for shifting versus maintaining attention. In particular, the differential activation for shifting versus maintaining attention was not affected by expected reward magnitude. These results indicate that BOLD activations for shifts of attention and increases in expected reward magnitude are largely separate. Finally, visual cortex showed sustained spatially selective signals that were significantly enhanced when greater reward magnitude was expected, but this reward-related modulation was not observed in spatially selective regions of dorsal fronto-parietal cortex.

• Functional connectivity and neurological recovery.

  Authors: Maurizio Corbetta

  Developmental psychobiology. 04/2012; 54(3):239-53.

  Modern theories of brain function emphasize the importance of distributed functional networks and synchronized activity within and between networks in mediating cognitive functions. This viewModern theories of brain function emphasize the importance of distributed functional networks and synchronized activity within and between networks in mediating cognitive functions. This view highlights the importance of considering brain-behavior relationships after focsal lesions not only as the result of local structural damage but also as a more widespread alteration of the physiological state of networks connected to the lesion. Recent findings demonstrate coherent activity in large-scale brain networks not only during task performance, but also, surprisingly, at rest in the absence of stimuli, tasks, or overt responses. Moreover, breakdown of coherent activity at rest, even in regions that are structurally intact, correlates with behavioral deficits and with their recovery after injury. This network perspective is fundamental to understand not only healthy brain function, but also the pathophysiology of brain injuries, mechanisms of functional recovery, and the basis for novel interventions for therapy. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 54:239-253, 2012.

• Prediction of discharge walking ability from initial assessment in a stroke inpatient rehabilitation facility population.

  Authors: Marghuretta D Bland, Audra Sturmoski, Michelle Whitson, Lisa Tabor Connor, Robert Fucetola, Thy Huskey, Maurizio Corbetta, Catherine E Lang

  Archives of physical medicine and rehabilitation. 03/2012;

  OBJECTIVE: To 1) determine which clinical assessments at admission to an IRF most simply predict discharge walking ability, and 2) identify a clinical decision rule to differentiate household versusOBJECTIVE: To 1) determine which clinical assessments at admission to an IRF most simply predict discharge walking ability, and 2) identify a clinical decision rule to differentiate household versus community ambulators at discharge from an IRF. DESIGN: Retrospective cohort study SETTING: Inpatient Rehabilitation Facility (IRF) PARTICIPANTS: Two samples of participants (n = 110 and 159) admitted with stroke. INTERVENTIONS: A multiple regression determined which variables obtained at admission (age, time from stroke to assessment, Motricity Index, somatosensation, Modified Ashworth Scale, Functional Independence Measure (FIM), Berg Balance Scale, 10 m Walk Speed) could most simply predict discharge walking ability (10 m Walk Speed). A logistic regression determined the likelihood of a participant achieving household (<0.4 m/s) versus community (≥0.4-0.8; >0.8 m/s) ambulation at time of discharge. Validity of the results was evaluated on a second sample of participants. MAIN OUTCOME MEASURE: Discharge 10 m Walk Speed RESULTS: Admission Berg Balance Scale and FIM walk item scores explained the majority of the variance in discharge walk speed. The odds ratio of achieving only household ambulation at discharge was 20 (95%CI: 6-63) for Sample 1 and 32 (95%CI: 10-96) for Sample 2 when the combination of having a Berg Balance Scale score ≤ 20 and a FIM walk item score of 1 or 2 was present. CONCLUSION: A Berg Balance Scale score of ≤ 20 and a FIM walk item score of 1 or 2 at admission indicates that a person with stroke is highly likely to only achieve household ambulation speeds at discharge from an IRF.

• Why use a connectivity-based approach to study stroke and recovery of function?

  Authors: Alex R Carter, Gordon L Shulman, Maurizio Corbetta

  NeuroImage. 03/2012;

  The brain is organized into a set of widely distributed networks. Therefore, although structural damage from stroke is focal, remote dysfunction can occur in regions connected to the area of lesion.The brain is organized into a set of widely distributed networks. Therefore, although structural damage from stroke is focal, remote dysfunction can occur in regions connected to the area of lesion. Historically, neuroscience has focused on local processing due in part to the absence of tools to study the function of distributed networks. In this article we discuss how a more comprehensive understanding of the effects of stroke can be attained using resting state functional connectivity BOLD magnetic resonance imaging (resting state fcMRI). Resting state fcMRI has a number of advantages over task-evoked fMRI for studying brain network reorganization in response to stroke, including the ability to image subjects with a broad range of impairments and the ability to study multiple networks simultaneously. We describe our rationale for using resting state connectivity as a tool for investigating the neural substrates of stroke recovery in a heterogeneous population of stroke patients and discuss the main questions we hope to answer, in particular whether resting state fcMRI measures in the acute phase of stroke can predict subsequent recovery. Early results suggest that disruption of inter-hemispheric connectivity in the somatomotor network and the dorsal attention network is more strongly associated with behavioral impairment in those domains than is intra-hemispheric connectivity within either the lesioned or unaffected hemisphere. We also observe in the somatomotor network an interesting interaction between corticospinal tract damage and decreased inter-hemispheric connectivity that suggests that both processes combine to contribute to neuromotor impairment after stroke. A connectivity-based approach will provide greater insight into network reorganization in the acute and chronic phases after stroke and will contribute to improving prognostic ability and the development of therapeutic interventions.

• Individual variability in functional connectivity predicts performance of a perceptual task.

  Authors: Antonello Baldassarre, Christopher M Lewis, Giorgia Committeri, Abraham Z Snyder, Gian Luca Romani, Maurizio Corbetta

  Proceedings of the National Academy of Sciences of the United States of America. 02/2012; 109(9):3516-21.

  People differ in their ability to perform novel perceptual tasks, both during initial exposure and in the rate of improvement with practice. It is also known that regions of the brain recruited byPeople differ in their ability to perform novel perceptual tasks, both during initial exposure and in the rate of improvement with practice. It is also known that regions of the brain recruited by particular tasks change their activity during learning. Here we investigate neural signals predictive of individual variability in performance. We used resting-state functional MRI to assess functional connectivity before training on a novel visual discrimination task. Subsequent task performance was related to functional connectivity measures within portions of visual cortex and between visual cortex and prefrontal association areas. Our results indicate that individual differences in performing novel perceptual tasks can be related to individual differences in spontaneous cortical activity.

• Interspecies activity correlations reveal functional correspondence between monkey and human brain areas.

  Authors: Dante Mantini, Uri Hasson, Viviana Betti, Mauro G Perrucci, Gian Luca Romani, Maurizio Corbetta, Guy A Orban, Wim Vanduffel

  Nature methods. 01/2012; 9(3):277-82.

  Evolution-driven functional changes in the primate brain are typically assessed by aligning monkey and human activation maps using cortical surface expansion models. These models use putativeEvolution-driven functional changes in the primate brain are typically assessed by aligning monkey and human activation maps using cortical surface expansion models. These models use putative homologous areas as registration landmarks, assuming they are functionally correspondent. For cases in which functional changes have occurred in an area, this assumption prohibits to reveal whether other areas may have assumed lost functions. Here we describe a method to examine functional correspondences across species. Without making spatial assumptions, we assessed similarities in sensory-driven functional magnetic resonance imaging responses between monkey (Macaca mulatta) and human brain areas by temporal correlation. Using natural vision data, we revealed regions for which functional processing has shifted to topologically divergent locations during evolution. We conclude that substantial evolution-driven functional reorganizations have occurred, not always consistent with cortical expansion processes. This framework for evaluating changes in functional architecture is crucial to building more accurate evolutionary models.

• The brain recovery core: building a system of organized stroke rehabilitation and outcomes assessment across the continuum of care.

  Authors: Catherine E Lang, Marghuretta D Bland, Lisa Tabor Connor, Robert Fucetola, Michelle Whitson, Jeff Edmiaston, Clayton Karr, Audra Sturmoski, Jack Baty, Maurizio Corbetta

  Journal of neurologic physical therapy : JNPT. 12/2011; 35(4):194-201.

  This Special Interest article describes a multidisciplinary, interinstitutional effort to build an organized system of stroke rehabilitation and outcomes measurement across the continuum of care.This Special Interest article describes a multidisciplinary, interinstitutional effort to build an organized system of stroke rehabilitation and outcomes measurement across the continuum of care. This system is focused on a cohort of patients who are admitted with the diagnosis of stroke to our acute facility, are discharged to inpatient and/or outpatient rehabilitation at our free-standing facility, and are then discharged to the community. This article first briefly explains the justification, goals, and purpose of the Brain Recovery Core system. The next sections describe its development and implementation, with details on the aspects related to physical therapy. The article concludes with an assessment of how the Brain Recovery Core system has changed and improved delivery of rehabilitation services. It is hoped that the contents of this article will be useful in initiating discussions and potentially facilitating similar efforts among other centers.

• Increased functional connectivity indicates the severity of cognitive impairment in multiple sclerosis.

  Authors: David J Hawellek, Joerg F Hipp, Christopher M Lewis, Maurizio Corbetta, Andreas K Engel

  Proceedings of the National Academy of Sciences of the United States of America. 11/2011; 108(47):19066-71.

  Correlations in spontaneous brain activity provide powerful access to large-scale organizational principles of the CNS. However, making inferences about cognitive processes requires a detailedCorrelations in spontaneous brain activity provide powerful access to large-scale organizational principles of the CNS. However, making inferences about cognitive processes requires a detailed understanding of the link between these couplings and the structural integrity of the CNS. We studied the impact of multiple sclerosis, which leads to the severe disintegration of the central white matter, on functional connectivity patterns in spontaneous cortical activity. Using a data driven approach based on the strength of a salient pattern of cognitive pathology, we identified distinct networks that exhibit increases in functional connectivity despite the presence of strong and diffuse reductions of the central white-matter integrity. The default mode network emerged as a core target of these connectivity modulations, showing enhanced functional coupling in bilateral inferior parietal cortex, posterior cingulate, and medial prefrontal cortex. These findings imply a complex and diverging relation of anatomical and functional connectivity in early multiple sclerosis and, thus, add an important observation for understanding how cognitive abilities and CNS integrity may be reflected in the intrinsic covariance of functional signals.

• Upstream dysfunction of somatomotor functional connectivity after corticospinal damage in stroke.

  Authors: Alex R Carter, Kevin R Patel, Serguei V Astafiev, Abraham Z Snyder, Jennifer Rengachary, Michael J Strube, Anna Pope, Joshua S Shimony, Catherine E Lang, Gordon L Shulman, Maurizio Corbetta

  Neurorehabilitation and neural repair. 07/2011; 26(1):7-19.

  Recent studies have shown that focal injuries can have remote effects on network function that affect behavior, but these network-wide repercussions are poorly understood. This study tested theRecent studies have shown that focal injuries can have remote effects on network function that affect behavior, but these network-wide repercussions are poorly understood. This study tested the hypothesis that lesions specifically to the outflow tract of a distributed network can result in upstream dysfunction in structurally intact portions of the network. In the somatomotor system, this upstream dysfunction hypothesis predicted that lesions of the corticospinal tract might be associated with functional disruption within the system. Motor impairment might then reflect the dual contribution of corticospinal damage and altered network functional connectivity. A total of 23 subacute stroke patients and 13 healthy controls participated in the study. Corticospinal tract damage was quantified using a template of the tract generated from diffusion tensor imaging in healthy controls. Somatomotor network functional integrity was determined by resting state functional connectivity magnetic resonance imaging. The extent of corticospinal damage was negatively correlated with interhemispheric resting functional connectivity, in particular with connectivity between the left and right central sulcus. Although corticospinal damage accounted for much of the variance in motor performance, the behavioral impact of resting connectivity was greater in subjects with mild or moderate corticospinal damage and less in those with severe corticospinal damage. Our results demonstrated that dysfunction of cortical functional connectivity can occur after interruption of corticospinal outflow tracts and can contribute to impaired motor performance. Recognition of these secondary effects from a focal lesion is essential for understanding brain-behavior relationships after injury, and they may have important implications for neurorehabilitation.

• Differential contribution of right and left parietal cortex to the control of spatial attention: a simultaneous EEG-rTMS study.

  Authors: Paolo Capotosto, Claudio Babiloni, Gian Luca Romani, Maurizio Corbetta

  Cerebral cortex (New York, N.Y. : 1991). 06/2011; 22(2):446-54.

  We have recently shown that interference with repetitive transcranial magnetic stimulation (rTMS) of right posterior intraparietal sulcus (IPS) cortex during the allocation of spatial attention leadsWe have recently shown that interference with repetitive transcranial magnetic stimulation (rTMS) of right posterior intraparietal sulcus (IPS) cortex during the allocation of spatial attention leads to abnormal desynchronization of anticipatory (pretarget) electroencephalographic alpha rhythms (8-12 Hz) in occipital-parietal cortex and the detection of subsequently presented visual targets (Capotosto et al. 2009). Since lesion data suggest that lesions of the right frontoparietal cortices produce more severe and long-lasting deficits of visual spatial attention than lesions of the left hemisphere, here, we used the mentioned rTMS-electroencephalographic procedure to test if the control of anticipatory alpha rhythms by IPS is asymmetrically organized in the 2 hemispheres. Results showed that interference with either left or right IPS during covert spatial attention equally disrupted the normally lateralized anticipatory modulation of occipital visual cortex, with stronger alpha desynchronization contralaterally to the attended visual field. In contrast, only interference with right IPS induced a paradoxical pretarget synchronization of alpha rhythms and bilateral deficits of target identification. These results suggest that the control of spatial topography of anticipatory alpha rhythms in occipital-parietal cortex is shared between left and right IPS cortex, but that right IPS uniquely contributes to a bilateral prestimulus activation of occipital visual cortex.

• The effect of age on human motor electrocorticographic signals and implications for brain-computer interface applications.

  Authors: Jarod Roland, Kai Miller, Zac Freudenburg, Mohit Sharma, Matthew Smyth, Charles Gaona, Jonathan Breshears, Maurizio Corbetta, Eric C Leuthardt

  Journal of neural engineering. 06/2011; 8(4):046013.

  Electrocorticography (ECoG)-based brain-computer interface (BCI) systems have emerged as a new signal platform for neuroprosthetic application. ECoG-based platforms have shown significant promise forElectrocorticography (ECoG)-based brain-computer interface (BCI) systems have emerged as a new signal platform for neuroprosthetic application. ECoG-based platforms have shown significant promise for clinical application due to the high level of information that can be derived from the ECoG signal, the signal's stability, and its intermediate nature of surgical invasiveness. However, before long-term BCI applications can be realized it will be important to also understand how the cortical physiology alters with age. Such understanding may provide an appreciation for how this may affect the control signals utilized by a chronic implant. In this study, we report on a large population of adult and pediatric invasively monitored subjects to determine the impact that age will have on surface cortical physiology. We evaluated six frequency bands--delta (<4 Hz), theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz), low gamma band (30-50 Hz), and high gamma band (76-100 Hz)--to evaluate the effect of age on the magnitude of power change, cortical area of activation, and cortical networks. When significant trends are evaluated as a whole, it appears that the aging process appears to more substantively alter thalamocortical interactions leading to an increase in cortical inefficiency. Despite this, we find that higher gamma rhythms appear to be more anatomically constrained with age, while lower frequency rhythms appear to broaden in cortical involvement as time progresses. From an independent signal standpoint, this would favor high gamma rhythms' utilization as a separable signal that could be maintained chronically.

• Neurological principles and rehabilitation of action disorders: computation, anatomy, and physiology (CAP) model.

  Authors: Scott H Frey, Leonardo Fogassi, Scott Grafton, Nathalie Picard, John C Rothwell, Nicolas Schweighofer, Maurizio Corbetta, Susan M Fitzpatrick

  Neurorehabilitation and neural repair. 06/2011; 25(5 Suppl):6S-20S.

  This chapter outlines the basic computational, anatomical, and physiological (CAP) principles underlying upper-limb actions, such as reaching for a cup and grasping it or picking up a key, insertingThis chapter outlines the basic computational, anatomical, and physiological (CAP) principles underlying upper-limb actions, such as reaching for a cup and grasping it or picking up a key, inserting it into a lock, and turning it.

• Neural rehabilitation: action and manipulation.

  Authors: Maurizio Corbetta, Susan M Fitzpatrick

  Neurorehabilitation and neural repair. 06/2011; 25(5 Suppl):3S-5S.

• Neurological principles and rehabilitation of action disorders: common clinical deficits.

  Authors: K Sathian, Laurel J Buxbaum, Leonardo G Cohen, John W Krakauer, Catherine E Lang, Maurizio Corbetta, Susan M Fitzpatrick

  Neurorehabilitation and neural repair. 06/2011; 25(5 Suppl):21S-32S.

  In this chapter, the authors use the computation, anatomy, and physiology (CAP) principles to consider the impact of common clinical problems on action. They focus on 3 major syndromes: paresis,In this chapter, the authors use the computation, anatomy, and physiology (CAP) principles to consider the impact of common clinical problems on action. They focus on 3 major syndromes: paresis, apraxia, and ataxia. They also review mechanisms that could account for spontaneous recovery, using what is known about the best-studied clinical dysfunction--paresis--and also ataxia. Together, this and the previous chapter lay the groundwork for the third chapter in this series, which reviews the relevant rehabilitative interventions.

• Neurological principles and rehabilitation of action disorders: rehabilitation interventions.

  Authors: Valerie Pomeroy, Salvatore M Aglioti, Victor W Mark, Dennis McFarland, Cathy Stinear, Steven L Wolf, Maurizio Corbetta, Susan M Fitzpatrick

  Neurorehabilitation and neural repair. 06/2011; 25(5 Suppl):33S-43S.

  This third chapter discusses the evidence for the rehabilitation of the most common movement disorders of the upper extremity. The authors also present a framework, building on the computation,This third chapter discusses the evidence for the rehabilitation of the most common movement disorders of the upper extremity. The authors also present a framework, building on the computation, anatomy, and physiology (CAP) model, for incorporating some of the principles discussed in the 2 previous chapters by Frey et al and Sathian et al in the practice of rehabilitation and for discussing potentially helpful interventions based on emergent neuroscience principles.

• Episodic memory retrieval, parietal cortex, and the default mode network: functional and topographic analyses.

  Authors: Carlo Sestieri, Maurizio Corbetta, Gian Luca Romani, Gordon L Shulman

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 03/2011; 31(12):4407-20.

  The default mode network (DMN) is often considered a functionally homogeneous system that is broadly associated with internally directed cognition (e.g., episodic memory, theory of mind,The default mode network (DMN) is often considered a functionally homogeneous system that is broadly associated with internally directed cognition (e.g., episodic memory, theory of mind, self-evaluation). However, few studies have examined how this network interacts with other networks during putative "default" processes such as episodic memory retrieval. Using functional magnetic resonance imaging, we investigated the topography and response profile of human parietal regions inside and outside the DMN, independently defined using task-evoked deactivations and resting-state functional connectivity, during episodic memory retrieval. Memory retrieval activated posterior nodes of the DMN, particularly the angular gyrus, but also more anterior and dorsal parietal regions that were anatomically separate from the DMN. The two sets of parietal regions showed different resting-state functional connectivity and response profiles. During memory retrieval, responses in DMN regions peaked sooner than non-DMN regions, which in turn showed responses that were sustained until a final memory judgment was reached. Moreover, a parahippocampal region that showed strong resting-state connectivity with parietal DMN regions also exhibited a pattern of task-evoked activity similar to that exhibited by DMN regions. These results suggest that DMN parietal regions directly supported memory retrieval, whereas non-DMN parietal regions were more involved in postretrieval processes such as memory-based decision making. Finally, a robust functional dissociation within the DMN was observed. Whereas angular gyrus and posterior cingulate/precuneus were significantly activated during memory retrieval, an anterior DMN node in medial prefrontal cortex was strongly deactivated. This latter finding demonstrates functional heterogeneity rather than homogeneity within the DMN during episodic memory retrieval.

• A signal-processing pipeline for magnetoencephalography resting-state networks.

  Authors: Dante Mantini, Stefania Della Penna, Laura Marzetti, Francesco de Pasquale, Vittorio Pizzella, Maurizio Corbetta, Gian Luca Romani

  Brain connectivity. 01/2011; 1(1):49-59.

  Abstract To study functional connectivity using magnetoencephalographic (MEG) data, the high-quality source-level reconstruction of brain activity constitutes a critical element. MEG resting-stateAbstract To study functional connectivity using magnetoencephalographic (MEG) data, the high-quality source-level reconstruction of brain activity constitutes a critical element. MEG resting-state networks (RSNs) have been documented by means of a dedicated processing pipeline: MEG recordings are decomposed by independent component analysis (ICA) into artifact and brain components (ICs); next, the channel maps associated with the latter ones are projected into the source space and the resulting voxel-wise weights are used to linearly combine the IC time courses. An extensive description of the proposed pipeline is provided here, along with an assessment of its performances with respect to alternative approaches. The following investigations were carried out: (1) ICA decomposition algorithm. Synthetic data are used to assess the sensitivity of the ICA results to the decomposition algorithm, by testing FastICA, INFOMAX, and SOBI. FastICA with deflation approach, a standard solution, provides the best decomposition. (2) Recombination of brain ICs versus subtraction of artifactual ICs (at the channel level). Both the recombination of the brain ICs in the sensor space and the classical procedure of subtracting the artifactual ICs from the recordings provide a suitable reconstruction, with a lower distortion using the latter approach. (3) Recombination of brain ICs after localization versus localization of artifact-corrected recordings. The brain IC recombination after source localization, as implemented in the proposed pipeline, provides a lower source-level signal distortion. (4) Detection of RSNs. The accuracy in source-level reconstruction by the proposed pipeline is confirmed by an improved specificity in the retrieval of RSNs from experimental data.

• A behavioral analysis of spatial neglect and its recovery after stroke.

  Authors: Jennifer Rengachary, Biyu J He, Gordon L Shulman, Maurizio Corbetta

  Frontiers in human neuroscience. 01/2011; 5:29.

  In a longitudinal study of recovery of left neglect following stroke using reaction time computerized assessment, we find that lateralized spatial deficits of attention and perception to be moreIn a longitudinal study of recovery of left neglect following stroke using reaction time computerized assessment, we find that lateralized spatial deficits of attention and perception to be more severe than disturbance of action. Perceptual-attention deficits also show the most variability in the course of recovery, making them prime candidates for intervention. In an anatomical analysis of MRI findings, ventral frontal cortex damage was correlated with the most severe neglect, reflecting impaired fronto-parietal communication.

• False Belief vs. False Photographs: A Test of Theory of Mind or Working Memory?

  Authors: Alicia Callejas, Gordon L Shulman, Maurizio Corbetta

  Frontiers in psychology. 01/2011; 2:316.

  Theory of mind (ToM), the ability to reason about other people's thoughts and beliefs, has been traditionally studied in behavioral and neuroimaging experiments by comparing performance in "falseTheory of mind (ToM), the ability to reason about other people's thoughts and beliefs, has been traditionally studied in behavioral and neuroimaging experiments by comparing performance in "false belief" and "false photograph" (control) stories. However, some evidence suggests that these stories are not matched in difficulty, complicating the interpretation of results. Here, we more fully evaluated the relative difficulty of comprehending these stories and drawing inferences from them. Subjects read false belief and false photograph stories followed by comprehension questions that probed true ("reality" questions) or false beliefs ("representation" questions) appropriate to the stories. Stories and comprehension questions were read and answered, respectively, more slowly in the false photograph than false belief conditions, indicating their greater difficulty. Interestingly, accuracy on representation questions for false photograph stories was significantly lower than for all other conditions and correlated positively with participants' working memory span scores. These results suggest that drawing representational inferences from false photo stories is particularly difficult and places heavy demands on working memory. Extensive naturalistic practice with ToM reasoning may enable a more flexible and efficient mental representation of false belief stories, resulting in lower memory load requirements. An important implication of these results is that the differential modulation of right temporal-parietal junction (RTPJ) during ToM and "false photo" control conditions may reflect the documented negative correlation of RTPJ activity with working memory load rather than a specialized involvement in ToM processes.