Dynamical consequences of lesions in cortical networks

Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana 47405, USA.
Human Brain Mapping (Impact Factor: 5.97). 07/2008; 29(7):802-9. DOI: 10.1002/hbm.20579
Source: PubMed


To understand the effects of a cortical lesion it is necessary to consider not only the loss of local neural function, but also the lesion-induced changes in the larger network of endogenous oscillatory interactions in the brain. To investigate how network embedding influences a region's functional role, and the consequences of its being damaged, we implement two models of oscillatory cortical interactions, both of which inherit their coupling architecture from the available anatomical connection data for macaque cerebral cortex. In the first model, node dynamics are governed by Kuramoto phase oscillator equations, and we investigate the sequence in which areas entrain one another in the transition to global synchrony. In the second model, node dynamics are governed by a more realistic neural mass model, and we assess long-run inter-regional interactions using a measure of directed information flow. Highly connected parietal and frontal areas are found to synchronize most rapidly, more so than equally highly connected visual and somatosensory areas, and this difference can be explained in terms of the network's clustered architecture. For both models, lesion effects extend beyond the immediate neighbors of the lesioned site, and the amplitude and dispersal of nonlocal effects are again influenced by cluster patterns in the network. Although the consequences of in vivo lesions will always depend on circuitry local to the damaged site, we conclude that lesions of parietal regions (especially areas 5 and 7a) and frontal regions (especially areas 46 and FEF) have the greatest potential to disrupt the integrative aspects of neocortical function.

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Available from: Olaf Sporns, Dec 20, 2013
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    • "However, the widespread effect of focal inhibition of M1 was mainly constrained to patterns of connectivity involving the sensorimotor system, whereas excitatory TMS over the primary motor cortex did not significantly change connectivity within the sensorimotor system, or between this system and other systems in the brain. In general, these findings support earlier computational investigations suggesting that damage to highly interconnected regions may have more dramatic effects on brain functions (Honey and Sporns, 2008; Alstott et al., 2009; Warren et al., 2014). "
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    ABSTRACT: The flexible integration of segregated neural processes is essential to healthy brain function. Advances in neuroimaging techniques have revealed that psychiatric and neurological disorders are characterized by anomalies in the dynamic integration of widespread neural populations. Re-establishing optimal neural activity is an important component of the treatment of such disorders. Non-invasive brain stimulation is emerging as a viable tool to selectively restore both local and widespread neural activity in patients affected by psychiatric and neurological disorders. Importantly, the different forms of non-invasive brain stimulation affect neural activity in distinct ways, which has important ramifications for their clinical efficacy. In this review, we discuss how non-invasive brain stimulation techniques influence widespread neural integration across brain regions. We suggest that the efficacy of such techniques in the treatment of psychiatric and neurological conditions is contingent on applying the appropriate stimulation paradigm to restore specific aspects of altered neural integration.
    Neuroscience & Biobehavioral Reviews 09/2015; DOI:10.1016/j.neubiorev.2015.09.010 · 8.80 Impact Factor
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    • "First, similar symptoms may result from lesions in different locations, making localization to specific regions challenging (Chung et al., 2004; Vuilleumier, 2013; Corbetta et al., 2015). Second, symptoms may result from lesion-induced functional alterations in anatomically intact, connected brain regions (Feeney and Baron, 1986; He et al., 2007a; Honey and Sporns, 2008; Bartolomeo, 2011; Catani et al., 2012; Carrera and Tononi, 2014). The fact that lesions have remote functional effects has been appreciated for over a century (Brown- Sequard, 1875; Von Monakow and Harris, 1914); however, it has remained unclear how one might incorporate such effects into traditional lesion mapping. "
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    ABSTRACT: A traditional and widely used approach for linking neurological symptoms to specific brain regions involves identifying overlap in lesion location across patients with similar symptoms, termed lesion mapping. This approach is powerful and broadly applicable, but has limitations when symptoms do not localize to a single region or stem from dysfunction in regions connected to the lesion site rather than the site itself. A newer approach sensitive to such network effects involves functional neuroimaging of patients, but this requires specialized brain scans beyond routine clinical data, making it less versatile and difficult to apply when symptoms are rare or transient. In this article we show that the traditional approach to lesion mapping can be expanded to incorporate network effects into symptom localization without the need for specialized neuroimaging of patients. Our approach involves three steps: (i) transferring the three-dimensional volume of a brain lesion onto a reference brain; (ii) assessing the intrinsic functional connectivity of the lesion volume with the rest of the brain using normative connectome data; and (iii) overlapping lesion-associated networks to identify regions common to a clinical syndrome. We first tested our approach in peduncular hallucinosis, a syndrome of visual hallucinations following subcortical lesions long hypothesized to be due to network effects on extrastriate visual cortex. While the lesions themselves were heterogeneously distributed with little overlap in lesion location, 22 of 23 lesions were negatively correlated with extrastriate visual cortex. This network overlap was specific compared to other subcortical lesions (P < 10(-5)) and relative to other cortical regions (P < 0.01). Next, we tested for generalizability of our technique by applying it to three additional lesion syndromes: central post-stroke pain, auditory hallucinosis, and subcortical aphasia. In each syndrome, heterogeneous lesions that themselves had little overlap showed significant network overlap in cortical areas previously implicated in symptom expression (P < 10(-4)). These results suggest that (i) heterogeneous lesions producing similar symptoms share functional connectivity to specific brain regions involved in symptom expression; and (ii) publically available human connectome data can be used to incorporate these network effects into traditional lesion mapping approaches. Because the current technique requires no specialized imaging of patients it may prove a versatile and broadly applicable approach for localizing neurological symptoms in the setting of brain lesions. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email:
    Brain 07/2015; DOI:10.1093/brain/awv228 · 9.20 Impact Factor
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    • "We used a virtual lesion method ( Honey and Sporns 2008 ; Pestilli et al . 2014 ) to characterize the strength of evidence supporting the VOF . "
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    ABSTRACT: Human visual cortex comprises many visual field maps organized into clusters. A standard organization separates visual maps into 2 distinct clusters within ventral and dorsal cortex. We combined fMRI, diffusion MRI, and fiber tractography to identify a major white matter pathway, the vertical occipital fasciculus (VOF), connecting maps within the dorsal and ventral visual cortex. We use a model-based method to assess the statistical evidence supporting several aspects of the VOF wiring pattern. There is strong evidence supporting the hypothesis that dorsal and ventral visual maps communicate through the VOF. The cortical projection zones of the VOF suggest that human ventral (hV4/VO-1) and dorsal (V3A/B) maps exchange substantial information. The VOF appears to be crucial for transmitting signals between regions that encode object properties including form, identity, and color and regions that map spatial information. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail:
    Cerebral Cortex 03/2015; DOI:10.1093/cercor/bhv064 · 8.67 Impact Factor
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