Functional Neurosurgery Unit

Tel Aviv, Israel

Functional Neurosurgery Unit

Tel Aviv, Israel
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Davidesco I.,Hebrew University of Jerusalem | Harel M.,Weizmann Institute of Science | Ramot M.,Hebrew University of Jerusalem | Kramer U.,EEG and Epilepsy Unit | And 10 more authors.
Journal of Neuroscience | Year: 2013

One of the puzzling aspects in the visual attention literature is the discrepancy between electrophysiological and fMRI findings: whereas fMRI studies reveal strong attentional modulation in the earliest visual areas, single-unit and local field potential studies yielded mixed results. In addition, it is not clear to what extent spatial attention effects extend from early to high-order visual areas. Here we addressed these issues using electrocorticography recordings in epileptic patients. The patients performed a task that allowed simultaneous manipulation of both spatial and object-based attention. They were presented with composite stimuli, consisting of a small object (face or house) superimposed on a large one, and in separate blocks, were instructed to attend one of the objects. We found a consistent increase in broadband high-frequency (30 -90 Hz) power, but not in visual evoked potentials, associated with spatial attention starting with V1/V2 and continuing throughout the visual hierarchy. The magnitude of the attentional modulation was correlated with the spatial selectivity of each electrode and its distance from the occipital pole. Interestingly, the latency of the attentional modulation showed a significant decrease along the visual hierarchy. In addition, electrodes placed over high-order visual areas (e.g., fusiform gyrus) showed both effects of spatial and object-based attention. Overall, our results help to reconcile previous observations of discrepancy between fMRI and electrophysiology. They also imply that spatial attention effects can be found both in early and high-order visual cortical areas, in parallel with their stimulus tuning properties. © 2013 the authors.


Ramot M.,Hebrew University of Jerusalem | Fisch L.,Weizmann Institute of Science | Davidesco I.,Hebrew University of Jerusalem | Harel M.,Weizmann Institute of Science | And 10 more authors.
Journal of Neuroscience | Year: 2013

Despite the profound reduction in conscious awareness associated with sleep, sensory cortex remains highly active during the different sleep stages, exhibiting complex interactions between different cortical sites. The potential functional significance of such spatial patterns and how they change between different sleep stages is presently unknown. In this electrocorticography study of human patients, we examined this question by studying spatial patterns of activity (broadband gamma power) that emerge during sleep (sleep patterns) and comparing them to the functional organization of sensory cortex that is activated by naturalistic stimuli during the awake state. Our results show a high correlation (p<10-4, permutation test) between the sleep spatial patterns and the functional organization found during wakefulness. Examining how the sleep patterns changed through the night highlighted a stage-specific difference, whereby the repertoire of such patterns was significantly larger during rapid eye movement (REM) sleep compared with non-REM stages. These results reveal that intricate spatial patterns of sensory functional organization emerge in a stage-specific manner during sleep. © 2013 the authors.


Ramot M.,Hebrew University of Jerusalem | Fisch L.,Weizmann Institute of Science | Harel M.,Weizmann Institute of Science | Kipervasser S.,Tel Aviv Sourasky Medical Center | And 9 more authors.
Journal of Neuroscience | Year: 2012

While research of human cortical function has typically focused on task-related increases in neuronal activity, there is a growing interest in the complementary phenomenon-namely, task-induced reductions. Recent human BOLD fMRI studies have associated such reductions with a specific network termed the default mode network (DMN). However, detailed understanding of the spatiotemporal patterns of task-negative responses and particularly how they compare across different cortical networks is lacking. Here we examined this issue in a large-scale electrocorticography study in patients performing a demanding backward masking task. Our results uncovered rapid (>1 s) task-induced reductions in gamma power, often concomitant with power increase in alpha/beta bands. Importantly, these responses were found both in the DMN and sensory-motor networks. Comparing the task-negative responses across these different networks revealed similar spectral signatures and dynamics. We hypothesize that the task-negative responses may reflect a cortical switching mechanism whose role is to steer activity away from cortical networks, which are inappropriate for the task at hand. © 2012 the authors.


Privman E.,Tel Aviv University | Fisch L.,Weizmann Institute of Science | Neufeld M.Y.,Tel Aviv University | Neufeld M.Y.,EEG and Epilepsy Unit | And 10 more authors.
Cerebral Cortex | Year: 2011

Scalp electroencephalography and magnetoencephalography studies have revealed a rapid evoked potential "adaptation" where one visual stimulus suppresses the event-related potential (ERP) of the second stimulus. Here, we investigated a similar effect revealed in subdural intracranial recordings in humans. Our results show that the suppression of the subdural ERP is not associated with a reduction in the gamma frequency power, considered to reflect the underlying neural activity. Furthermore, the evoked potential suppression (EPS) phenomenon was not reflected in recognition behavior of the patients. Rather, the EPS was tightly linked to the level of gamma activity preceding the event, and this effect was independent of the interstimulus time interval. Analyzing other frequency bands failed to reveal a similar link. Our results thus show a consistent antagonism between subdural ERP and gamma power although both are considered markers for neural activity. We hypothesize that the ERP suppression is due to a desynchronization of neuronal firing resulting from recurrent neural activity in the vicinity of the freshly stimulated neurons and not an attenuation of the overall neural activity. © 2010 The Author.


Mukamel R.,University of California at Los Angeles | Ekstrom A.D.,University of California at Los Angeles | Ekstrom A.D.,University of California at Davis | Kaplan J.,University of California at Los Angeles | And 4 more authors.
Current Biology | Year: 2010

Direct recordings in monkeys have demonstrated that neurons in frontal and parietal areas discharge during execution and perception of actions [1-8]. Because these discharges "reflect" the perceptual aspects of actions of others onto the motor repertoire of the perceiver, these cells have been called mirror neurons. Their overlapping sensory-motor representations have been implicated in observational learning and imitation, two important forms of learning [9]. In humans, indirect measures of neural activity support the existence of sensory-motor mirroring mechanisms in homolog frontal and parietal areas [10, 11], other motor regions [12-15], and also the existence of multisensory mirroring mechanisms in nonmotor regions [16-19]. We recorded extracellular activity from 1177 cells in human medial frontal and temporal cortices while patients executed or observed hand grasping actions and facial emotional expressions. A significant proportion of neurons in supplementary motor area, and hippocampus and environs, responded to both observation and execution of these actions. A subset of these neurons demonstrated excitation during action-execution and inhibition during action-observation. These findings suggest that multiple systems in humans may be endowed with neural mechanisms of mirroring for both the integration and differentiation of perceptual and motor aspects of actions performed by self and others. © 2010 Elsevier Ltd. All rights reserved.


Georgiopoulos M.,Functional Neurosurgery Unit | Katsakiori P.,Functional Neurosurgery Unit | Kefalopoulou Z.,Functional Neurosurgery Unit | Constantoyannis C.,Functional Neurosurgery Unit
Stereotactic and Functional Neurosurgery | Year: 2010

Background/Aims: The purpose of the present article is a systematic review of the proposed medical or surgical treatments in patients in chronic vegetative state (VS) or minimally conscious state (MCS), as well as of their mechanisms of action and limitations. Methods: For this review, we have agreed to include patients in VS or MCS having persisted for over 6 months in posttraumatic cases, and over 3 months in nontraumatic cases, before the time of intervention. Searches were independently conducted by 2 investigators between May 2009 and September 2009 in the following databases: Medline, Web of Science and the Cochrane Library. The electronic search was complemented by cross-checking the references of all relevant articles. Overall, 16 papers were eligible for this systematic review. Results: According to the 16 eligible studies, medical management by dopaminergic agents (levodopa, amantadine), zolpidem and median nerve stimulation, or surgical management by deep brain stimulation, extradural cortical stimulation, spinal cord stimulation and intrathecal baclofen have shown to improve the level of consciousness in certain cases. Conclusion: The treatments proposed for disorders of consciousness have not yet gained the level of 'evidence-based treatments'; moreover, the studies to date have led to inconclusiveness. The published therapeutic responses must be substantiated by further clinical studies of sound methodology. Copyright © 2010 S. Karger AG.


Cerf M.,California Institute of Technology | Cerf M.,University of California at Los Angeles | Cerf M.,New York University | Thiruvengadam N.,California Institute of Technology | And 11 more authors.
Nature | Year: 2010

Daily life continually confronts us with an exuberance of external, sensory stimuli competing with a rich stream of internal deliberations, plans and ruminations. The brain must select one or more of these for further processing. How this competition is resolved across multiple sensory and cognitive regions is not known; nor is it clear how internal thoughts and attention regulate this competition. Recording from single neurons in patients implanted with intracranial electrodes for clinical reasons, here we demonstrate that humans can regulate the activity of their neurons in the medial temporal lobe (MTL) to alter the outcome of the contest between external images and their internal representation. Subjects looked at a hybrid superposition of two images representing familiar individuals, landmarks, objects or animals and had to enhance one image at the expense of the other, competing one. Simultaneously, the spiking activity of their MTL neurons in different subregions and hemispheres was decoded in real time to control the content of the hybrid. Subjects reliably regulated, often on the first trial, the firing rate of their neurons, increasing the rate of some while simultaneously decreasing the rate of others. They did so by focusing onto one image, which gradually became clearer on the computer screen in front of their eyes, and thereby overriding sensory input. On the basis of the firing of these MTL neurons, the dynamics of the competition between visual images in the subject's mind was visualized on an external display. © 2010 Macmillan Publishers Limited. All rights reserved.


Tankus A.,University of California at Los Angeles | Tankus A.,Technion - Israel Institute of Technology | Fried I.,University of California at Los Angeles | Fried I.,Functional Neurosurgery Unit | And 2 more authors.
Nature Communications | Year: 2012

Human speech sounds are produced through a coordinated movement of structures along the vocal tract. Here we show highly structured neuronal encoding of vowel articulation. In medial-frontal neurons, we observe highly specific tuning to individual vowels, whereas superior temporal gyrus neurons have nonspecific, sinusoidally modulated tuning (analogous to motor cortical directional tuning). At the neuronal population level, a decoding analysis reveals that the underlying structure of vowel encoding reflects the anatomical basis of articulatory movements. This structured encoding enables accurate decoding of volitional speech segments and could be applied in the development of brain-machine interfaces for restoring speech in paralysed individuals. © 2012 Macmillan Publishers Limited. All rights reserved.


Andelman F.,Functional Neurosurgery Unit | Hoofien D.,Hebrew University of Jerusalem | Goldberg I.,Tel Aviv Sourasky Medical Center | Aizenstein O.,Neuroradiology Unit | And 2 more authors.
Neurocase | Year: 2010

Mental time travel allows individuals to mentally project themselves backwards and forwards in subjective time. This case report describes a young woman suddenly rendered amnesic as a result of bilateral hippocampal damage following an epileptic seizure and brain anoxia. Her neuropsychological profile was characterized by a high-average general level of cognitive functioning, selective deficit in episodic memory of past events and a significant difficulty to envisage her personal future. This case provides clinical support for the concept of mental time travel with its retrospective and prospective components and for the hippocampus being its critical neural substrate. © 2010 Psychology Press.


Sassi M.,Functional Neurosurgery Unit | Porta M.,Movement Disorders and Tourette Center | Servello D.,Functional Neurosurgery Unit
Acta Neurochirurgica | Year: 2011

Tourette's syndrome is a chronic neurobehavioral disorder that can demonstrate refractoriness to conservative treatments, or to invasive nonsurgical treatments such as botulinum toxin infiltration, or to psychobehavioral treatments. In these cases, the surgical option is often proposed, either with lesional interventions, or more recently with deep brain stimulation (DBS). This latter modality is currently preferred because of its reversibility and modularity. Some relevant issues, however, still persist in terms of appropriate indication to treatment, selection of target, and follow-up evaluation. © 2010 Springer-Verlag.

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