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A cruciAl aspect of neurosurgery within or close to eloquent cortex is the preoperative identification of brain regions involved in a number of cognitive, sensory, or motor tasks. In the presurgical assessment of language, both the localization 38 and lateralization 28,32 of functional areas are essential for the prevention of postoperative deficits such as aphasia and dysarthria. More specifically, assessing language lateralization in patients with epilepsy is challenging and complex because of their atypical language network. Language structure among this group tends to be more variable, 40 less lateralized, 11and more subject to plasticity effects 21 as compared with a healthy population.Until recently, the gold standard procedure for language lateralization has been the Wada test. 7,42 This test determines language and memory lateralization of the cerebral function by suppressing cortical activity in one of the hemispheres, while testing the patient's performance using the other. The test involves the unilateral intra-carotid artery injection of a short-acting barbiturate (amobarbital) that immediately suspends several ipsilateral brain functions, allowing for 5-10 minutes of language or memory tests of the contralateral hemisphere. The Wada test findings represent a categorical classification of left, right, or bilateral hemispheric dominance of language or memory function. However, this invasive procedure has potential clinical abbreviatioNs EPI = echo-planar imaging; fMRI = functional MRI; LDP = language dominance probability; LI = lateralization index; SPGR = spoiled gradient; TASMC = Tel Aviv Sourasky Medical Center. obJective Providing a reliable assessment of language lateralization is an important task to be performed prior to neurosurgery in patients with epilepsy. Over the last decade, functional MRI (fMRI) has emerged as a useful noninvasive tool for language lateralization, supplementing or replacing traditional invasive methods. In standard practice, fMRIbased language lateralization is assessed qualitatively by visual inspection of fMRI maps at a specific chosen activation threshold. The purpose of this study was to develop and evaluate a new computational technique for providing the probability of each patient to be left, right, or bilateral dominant in language processing. methods In 76 patients with epilepsy, a language lateralization index was calculated using the verb-generation fMRI task over a wide range of activation thresholds (from a permissive threshold, analyzing all brain regions, to a harsh threshold, analyzing only the strongest activations). The data were classified using a probabilistic logistic regression method. results Concordant results between fMRI and Wada lateralization were observed in 89% of patients. Bilateral and right-dominant groups showed similar fMRI lateralization patterns differentiating them from the left-dominant group but still allowing classification in 82% of patients. coNclusioNs These findings present the utility of a semi-supervised probabilistic learni...

We report a series of experiments in which we assess depth discrimination performance in adults and children using a disparity-balanced target configuration to avoid the effects of anticipatory vergence eye movements. In our first study we found that children outperformed adults by a substantial margin, and the adults were consistently near chance. This was surprising given that we initially tested naïve adults to provide a benchmark for the children's data, and all observers met the criterion for stereoacuity. In subsequent experiments we recruited groups of inexperienced adult observers and assessed the role of a wide range of spatial and temporal factors in this apparent deficit. We found that the adult performance remained poor in spite of changes to the stimulus layout, exposure duration, and spatial scale. The only manipulations that improved performance were those that limited the binocular disparity to a single sign. We conclude that these data reflect a form of involuntary disparity pooling that makes it difficult for naïve observers to judge depth from disparity from multiple targets. The absence of this effect in children likely reflects the late maturation of global processes and depth cue integration.

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