X. De Boissezon

Distinct frontal systems for response inhibition, attentional capture, and error processing

Stopping an action in response to an unexpected event requires both that the event is attended to, and that the action is inhibited. Previous neuroimaging investigations of stopping have failed to adequately separate these cognitive elements. Here we used a version of the widely used Stop Signal Task that controls for the attentional capture of stop signals. This allowed us to fractionate the contributions of frontal regions, including the right inferior frontal gyrus and medial frontal cortex, to attentional capture, response inhibition, and error processing. A ventral attentional system, including the right inferior frontal gyrus, has been shown to respond to unexpected stimuli. In line with this evidence, we reasoned that lateral frontal regions support attentional capture, whereas medial frontal regions, including the presupplementary motor area (pre-SMA), actually inhibit the ongoing action. We tested this hypothesis by contrasting the brain networks associated with the presentation of unexpected stimuli against those associated with outright stopping. Functional MRI images were obtained in 26 healthy volunteers. Successful stopping was associated with activation of the right inferior frontal gyrus, as well as the pre-SMA. However, only activation of the pre-SMA differentiated stopping from a high-level baseline that controlled for attentional capture. As expected, unsuccessful attempts at stopping activated the anterior cingulate cortex. In keeping with work in nonhuman primates these findings demonstrate that successful motor inhibition is specifically associated with pre-SMA activation.

Default Mode Network Connectivity Predicts Sustained Attention Deficits after Traumatic Brain Injury

Traumatic brain injury (TBI) frequently produces impairments of attention in humans. These can result in a failure to maintain consistent goal-directed behavior. A predominantly right-lateralized frontoparietal network is often engaged during attentionally demanding tasks. However, lapses of attention have also been associated with increases in activation within the default mode network (DMN). Here, we study TBI patients with sustained attention impairment, defined on the basis of the consistency of their behavioral performance over time. We show that sustained attention impairments in patients are associated with an increase in DMN activation, particularly within the precuneus and posterior cingulate cortex. Furthermore, the interaction of the precuneus with the rest of the DMN at the start of the task, i.e., its functional connectivity, predicts which patients go on to show impairments of attention. Importantly, this predictive information is present before any behavioral evidence of sustained attention impairment, and the relationship is also found in a subgroup of patients without focal brain damage. TBI often results in diffuse axonal injury, which produces cognitive impairment by disconnecting nodes in distributed brain networks. Using diffusion tensor imaging, we demonstrate that structural disconnection within the DMN also correlates with the level of sustained attention. These results show that abnormalities in DMN function are a sensitive marker of impairments of attention and suggest that changes in connectivity within the DMN are central to the development of attentional impairment after TBI.

Cognitive Control and the Salience Network: An Investigation of Error Processing and Effective Connectivity

The Salience Network (SN) consists of the dorsal anterior cingulate cortex (dACC) and bilateral insulae. The network responds to behaviorally salient events, and an important question is how its nodes interact. One theory is that the dACC provides the earliest cortical signal of behaviorally salient events, such as errors. Alternatively, the anterior right insula (aRI) has been proposed to provide an early cognitive control signal. As these regions frequently coactivate, it has been difficult to disentangle their roles using conventional methods. Here we use dynamic causal modeling and a Bayesian model evidence technique to investigate the causal relationships between nodes in the SN after errors. Thirty-five human subjects performed the Simon task. The task has two conditions (congruent and incongruent) producing two distinct error types. Neural activity associated with errors was investigated using fMRI. Subjects made a total of 1319 congruent and 1617 incongruent errors. Errors resulted in robust activation of the SN. Dynamic causal modeling analyses demonstrated that input into the SN was most likely via the aRI for both error types and that the aRI was the only region intrinsically connected to both other nodes. Only incongruent errors produced behavioral adaptation, and the strength of the connection between the dACC and the left insulae correlated with the extent of this behavioral change. We conclude that the aRI, not the dACC, drives the SN after errors on an attentionally demanding task, and that a change in the effective connectivity of the dACC is associated with behavioral adaptation after errors.

Distinct Frontal Networks Are Involved in Adapting to Internally and Externally Signaled Errors

Errors trigger changes in behavior that help individuals adapt to new situations. The dorsal anterior cingulate cortex (dACC) is thought to be central to this response, but more lateral frontal regions are also activated by errors and may make distinct contributions. We investigated error processing by studying 2 distinct error types: commission and timing. Thirty-five subjects performed a version of the Simon Task designed to produce large number of errors. Commission errors were internally recognized and were not accompanied by explicit feedback. In contrast, timing errors were difficult to monitor internally and were explicitly signaled. Both types of error triggered changes in behavior consistent with increased cognitive control. As expected, robust activation within the dACC and bilateral anterior insulae (the Salience Network) was seen for commission errors. In contrast, timing errors were not associated with activation of this network but did activate a bilateral network that included the right ventral attentional system. Common activation for both error types occurred within the pars operculari and angular gyri. These results show that the dACC does not respond to all behaviorally salient errors. Instead, the error-processing system is multifaceted, and control can be triggered independently of the dACC when feedback is unexpected.

Post-stroke hemiplegia rehabilitation: evolution of the concepts.

Stroke rehabilitation has undergone a revolution over the last three decades. Cohort studies have consistently reinforced the importance of post-stroke rehabilitation to stimulate recovery, but the concepts of empirical methods originally proposed by therapists to rehabilitate these patients have not withstood clinical analysis. Functional neuroimaging and animal models have unveiled the mechanisms underlying functional recovery and helped teams understand its limitations and improvement modalities. These neuroscience discoveries constitute the grounds needed to understand the emergence of new technologies: robotics and virtual reality. The objective of this review of the literature was to select key works in this field to better understand current therapeutic possibilities.

Feasibility of the cognitive assessment scale for stroke patients (CASP) vs. MMSE and MoCA in aphasic left hemispheric stroke patients.

INTRODUCTION Post-stroke aphasia makes it difficult to assess cognitive deficiencies. We thus developed the CASP, which can be administered without using language. Our objective was to compare the feasibility of the CASP, the Mini Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) in aphasic stroke patients. MATERIAL AND METHODS All aphasic patients consecutively admitted to seven French rehabilitation units during a 4-month period after a recent first left hemispheric stroke were assessed with CASP, MMSE and MoCA. We determined the proportion of patients in whom it was impossible to administer at least one item from these 3 scales, and compared their administration times. RESULTS Forty-four patients were included (age 64±15, 26 males). The CASP was impossible to administer in eight of them (18%), compared with 16 for the MMSE (36%, P=0.05) and 13 for the MoCA (30%, P=0.21, NS). It was possible to administer the CASP in all of the patients with expressive aphasia, whereas the MMSE and the MoCA could not be administered. Administration times were longer for the CASP (13±4min) than for the MMSE (8±3min, P<10(-6)) and the MoCA (11±5min, P=0.23, NS). CONCLUSION The CASP is more feasible than the MMSE and the MoCA in aphasic stroke patients.

The Cognitive Assessment scale for Stroke Patients (CASP) vs. MMSE and MoCA in non-aphasic hemispheric stroke patients

INTRODUCTION CASP specifically assesses post-stroke cognitive impairments. Its items are visual and as such can be administered to patients with severe expressive aphasia. We have previously shown that the CASP was more suitable than the Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) in aphasic patients. Our objective was to compare the above scales in non-aphasic stroke patients, and assess to what extent the solely visual items of the CASP were problematic in cases of neurovisual impairments. METHODS Fifty non-aphasic patients admitted to Physical Medicine and Rehabilitation (PM&R) units after a recent left- or right-hemisphere stroke were evaluated with the CASP, MMSE and MoCA. We compared these three scales in terms of feasibility, concordance, and influence of neurovisual impairments on the total score. RESULTS Twenty-nine men and 21 women were included (mean age 63 ± 14). For three patients, the MoCa was impossible to administer. It took significantly less time to administer the CASP (10 ± 5 min) than the MoCA (11 ± 5 min, P=0.02), yet it still took more time than MMSE administration (7 ± 3 min, P<10(-6)). Neurovisual impairments affected equally the total scores of the three tests. Concordance between these scores was poor and only the CASP could specifically assess unilateral spatial neglect. CONCLUSION The sole visual format of the CASP scale seems suitable for administration in post-stroke patients.

A Step Forward for Mirror Neurons? Investigating the Functional Link between Action Execution and Action Observation in Limb Apraxia

Increasing evidence suggests that action execution and action observation are encoded by the same brain regions. This renders motor events central to the question of self and nonself discrimination ([Georgieff and Jeannerod, 1998][1]). In humans, it is widely assumed that mirror neurons link action

Communication disabilities after right hemispheric stroke: Impact of a pluridisciplinary group rehabilitation based on an acting course

© 201 difference in treatment outcome to j90. However, the treated group communication book is changing faster. Each shows a significant improvement in communication through the use of the C.COM, the communication test with the six tasks being managed by it in 85% of all patients at the end of follow-up period compared to 31% inclusion. Our results show the impact of the C.COM in pragmatic communication, but do not demonstrate the interest of a patient specific training, probably for lack of power related to the reduced number of patients and the effect of spontaneous important recovery in this a group of people with aphasia.

Surgical management of pressure sores in neurological patients

© 201 CO18-005-e Surgical management of pressure sores in neurological patients A. Andre *, X. de Boissezon , J.-L. Grolleau , J.-P. Chavoin a a Service de chirurgie plastique et reconstructive, hôpital Rangueil, CHU Toulouse, TSA 50032, 31059 Toulouse cedex 9, France b Service de MPR, hôpital Rangueil, CHU Toulouse, 31059 Toulouse cedex 9, France *Corresponding author. E-mail address: andre.a@chu-toulouse.fr.