Aram Ter Minassian

Dissociating anticipation from perception: Acute pain activates default mode network.

Few studies have explored the effect of acute pain on attentional networks and on the default mode network. Moreover, these studies convey conflicting results, seemingly caused by design. To reassess this issue, we studied 20 healthy subjects with functional magnetic resonance imaging while delivering painful electric shocks. The design was purposely constructed to separate rest, anticipation, and pain perception. We found that default mode network activity in response to pain was biphasic. It deactivated during anticipation when the dorsal attentional network was activated. During pain perception, the default mode network was activated, as were attentional networks. The left posterior fusiform gyrus showed the same dynamics as the default mode network, and its activity was negatively correlated to the subjects pain intensity rating. The associative pregenual anterior cingulate cortex seemed to play a key role in these coactivations. These results concur with data from the literature showing that enhanced pain perception results in greater default mode network activity and that the anticorrelation between the default mode network and the dorsal attentional network disappears in chronic pain patients. Hum Brain Mapp 34:2228–2243, 2013.

Functional MRI comparison of passive and active movement: possible inhibitory role of supplementary motor area.

Recent studies have hypothesized that the supplementary motor area plays a role in motor inhibition. To study this possible role, we used functional MRI study to compare conditions, which require various level of inhibition of motor patterns. Seventeen healthy participants were scanned while executing – actively or passively – rhythmic opening/closing movements of their right hand, with and without congruent visual information. The contrast passive>active movement in the visual guidance condition which requires inhibition in order ‘not’ to perform the movement, yields to significant activation of areas commonly involved in the inhibitory brain circuitry among which, notably, controlateral supplementary motor area.

Effect of observation of simple hand movement on brain activations in patients with unilateral cerebral palsy: an fMRI study.

The aim of this functional magnetic resonance imaging (fMRI) study was to examine and compare brain activation in patients with unilateral cerebral palsy (CP) during observation of simple hand movement performed by the paretic and nonparetic hand. Nineteen patients with clinical unilateral CP (14 male, mean age 14 years, 7-21 years) participated in the study. Hand motor impairment was assessed using the sequential finger opposition task. Using fMRI block design, brain activation was examined following observation at rest of a simple opening-closing hand movement, performed by either the left or right hand of an actor. Eighteen fMRI dataset were analyzed. Observing hand movement produced large bilateral activations in temporo-parieto-fronto-occipital network, comprising most of the nodes of the well described action-observation network. For either side, observing hand movements recruits the primary motor cortex (M1), contralateral to the viewed hand, as would be expected in healthy persons. Viewing movement performed by an actors hand representing the paretic side of patients activated more strongly ipsilesional M1 than viewing movement performed by an actors hand representing the nonparetic side of patients. Observation of hand movement in patients with CP engaged the motor execution network regardless of the degree of motor impairment.

Feasibility and validity of monitoring subarachnoid hemorrhage by a noninvasive MRI imaging perfusion technique: Pulsed Arterial Spin Labeling (PASL)

BACKGROUND AND PURPOSE To evaluate the validity of pulsed arterial spin labeling (PASL) imaging with cerebral blood flow (CBF) quantification for monitoring subarachnoid hemorrhage (SAH); to describe changes in the perfusion signal in the absence of or following several classic complications. MATERIALS AND METHODS Fifteen patients and 14 healthy volunteers were assigned to SAH and control populations, respectively. ASL imaging was performed three times: between Day 0 (D0, i.e., day of onset of SAH symptoms) and D3, between D7 and D9 and between D12 and D14. ASL points were classified as complicated (symptomatic vasospasm, intraparenchymal hematoma or severe intracranial hypertension) or uncomplicated. Perfusion and CBF maps were generated after automated processing. The inversion time (TI) was fixed at 1800 ms. RESULTS CBF mean value of Day0-3 uncomplicated SAH patients (47 ± 11.7 mL/min/100g) was significantly higher than that of the volunteers (36.5 ± 7.6 mL/min/100g; P=0.014). In a case-by-case analysis, we observed a global or regional hypoperfusion pattern when SAH was complicated by vasospasm or severe intracranial hypertension, particularly at the junctional areas. Furthermore, we have faced major vascular artefacts, visible as serpiginous high signals and related to the retention of labeled protons in arteries concerning by angiographic vasospasm. CONCLUSION PASL is an interesting perfusion technique to non-invasively highlight perfusion changes in complicated SAH and can provide a new element in the decision to perform urgent endovascular treatment. However, the increase in arterial transit time makes the Buxton quantification model inapplicable and leads to false high CBF values in the single-TI PASL technique.

Effect of Motor Imagery in Children with Unilateral Cerebral Palsy: fMRI Study

Background Motor imagery is considered as a promising therapeutic tool for rehabilitation of motor planning problems in patients with cerebral palsy. However motor planning problems may lead to poor motor imagery ability. Aim The aim of this functional magnetic resonance imaging study was to examine and compare brain activation following motor imagery tasks in patients with hemiplegic cerebral palsy with left or right early brain lesions. We tested also the influence of the side of imagined hand movement. Method Twenty patients with clinical hemiplegic cerebral palsy (sixteen males, mean age 12 years and 10 months, aged 6 years 10 months to 20 years 10 months) participated in this study. Using block design, brain activations following motor imagery of a simple opening-closing hand movement performed by either the paretic or nonparetic hand was examined. Results During motor imagery tasks, patients with early right brain damages activated bilateral fronto-parietal network that comprise most of the nodes of the network well described in healthy subjects. Inversely, in patients with left early brain lesion brain activation following motor imagery tasks was reduced, compared to patients with right brain lesions. We found also a weak influence of the side of imagined hand movement. Conclusion Decreased activations following motor imagery in patients with right unilateral cerebral palsy highlight the dominance of the left hemisphere during motor imagery tasks. This study gives neuronal substrate to propose motor imagery tasks in unilateral cerebral palsy rehabilitation at least for patients with right brain lesions.

Relationship between somatosensory deficit and brain somatosensory system after early brain lesion: A morphometric study.

Cerebral Palsy (CP) is a group of permanent motor disorders due to non-progressive damage to the developing brain. Poor tactile discrimination is common in children with unilateral CP. Previous findings suggest the crucial role of structural integrity of the primary (S1) and secondary (S2) somatosensory areas located in the ipsilesional hemisphere for somatosensory function processing. However, no focus on the relationship between structural characteristics of ipsilesional S1 and S2 and tactile discrimination function in paretic hands has been proposed. Using structural MRI and a two-point discrimination assessment (2 PD), we explore this potential link in a group of 21 children (mean age 13 years and 7 months) with unilateral CP secondary to a periventricular white matter injury (PWMI) or middle cerebral artery infarct (MCA). For our whole sample there was a significant negative correlation between the 2 PD and the gray matter volume in the ipsilesional S2 (rho = -0.50 95% confidence interval [-0.76, -0.08], one-tailed p-value = 0.0109) and in the ipsilesional S1 (rho = -0.57, 95% confidence interval [-0.81, -0.19], one-tailed p-value = 0.0032). When studying these relationships with regard to the lesion types, we found these correlations were non-significant in the patients with PWMI but stronger in patients with MCA. According to our results, the degree of sensory impairment is related to the spared gray matter volume in ipsilesional S1 and S2 and is marked after an MCA stroke. Our work contributes to a better understanding of why some patients with CP have variable somatosensory deficit following an early brain lesion.

Right Hemisphere Cognitive Functions: From Clinical and Anatomic Bases to Brain Mapping During Awake Craniotomy Part I: Clinical and Functional Anatomy

The nondominant hemisphere (usually the right) is responsible for primary cognitive functions such as visuospatial and social cognition. Awake surgery using direct electric stimulation for right cerebral tumor removal remains challenging because of the complexity of the functional anatomy and difficulties in adapting standard bedside tasks to awake surgery conditions. An understanding of semiology and anatomic bases, along with an analysis of the available cognitive tasks for visuospatial and social cognition per operative mapping allow neurosurgeons to better appreciate the functional anatomy of the right hemisphere and its relevance to tumor surgery. In this article, the first of a 2-part review, we discuss the anatomic and functional basis of right hemisphere function. Whereas part II of the review focuses primarily on semiology and surgical management of right-sided tumors under awake conditions, this article provides a comprehensive review of knowledge underpinning awake surgery on the right hemisphere.

Using a Virtual Reality Social Network During Awake Craniotomy to Map Social Cognition: Prospective Trial

Background In awake craniotomy, it is possible to temporarily inactivate regions of the brain using direct electrical stimulation, while the patient performs neuropsychological tasks. If the patient shows decreased performance in a given task, the neurosurgeon will not remove these regions, so as to maintain all brain functions. Objective The objective of our study was to describe our experience of using a virtual reality (VR) social network during awake craniotomy and discuss its future applications for perioperative mapping of nonverbal language, empathy, and theory of mind. Methods This was a single-center, prospective, unblinded trial. During wound closure, different VR experiences with a VR headset were proposed to the patient. This project sought to explore interactions with the neuropsychologist’s avatar in virtual locations using a VR social network as an available experience. Results Three patients experienced VR. Despite some limitations due to patient positioning during the operation and the limitation of nonverbal cues inherent to the app, the neuropsychologist, as an avatar, could communicate with the patient and explore gesture communication while wearing a VR headset. Conclusions With some improvements, VR social networks can be used in the near future to map social cognition during awake craniotomy. Trial Registration ClinicalTrials.gov NCT03010943; https://clinicaltrials.gov/ct2/show/NCT03010943 (Archived at WebCite at http://www.webcitation.org/70CYDil0P)

Right Hemisphere Cognitive Functions: From Clinical and Anatomical Bases to Brain Mapping During Awake Craniotomy. Part II: Neuropsychological Tasks and Brain Mapping

The nondominant hemisphere (usually right) is determinant for main cognitive functions such as visuospatial and social cognitions. Awake surgery using direct electrical stimulation for right cerebral tumor removal remains challenging due to the complexity of the functional anatomy and the difficulties in adapting the classical bedside tasks for awake surgery conditions. An understanding of semiology, anatomical bases, and an analysis of the available cognitive tasks for visuospatial and social cognition per operative mapping will allow neurosurgeons to better appreciate the functional anatomy of the right hemisphere and its application to tumor surgery. In this second review of 2 parts, we discuss the pertinence of the neuropsychological tests available for the study of nondominant hemisphere functions for the surgery on right-sided tumors in awake surgery conditions. In conjunction with part I of the review, which focuses primarily on the anatomical, functional, and semiological basis of the right hemisphere function, this article provides a comprehensive review of current knowledge supporting the awake surgery in the right hemisphere.