Conscious processing of narrative stimuli synchronizes heart rate between individuals.

Heart rate has natural fluctuations that are typically ascribed to autonomic function. Recent evidence suggests that conscious processing can affect the timing of the heartbeat. We hypothesized that heart rate is modulated by conscious processing and therefore dependent on attentional focus. To test this, we leverage the observation that neural processes synchronize between subjects by presenting an identical narrative stimulus. As predicted, we find significant inter-subject correlation of heart rate (ISC-HR) when subjects are presented with an auditory or audiovisual narrative. Consistent with our hypothesis, we find that ISC-HR is reduced when subjects are distracted from the narrative, and higher ISC-HR predicts better recall of the narrative. Finally, patients with disorders of consciousness have lower ISC-HR, as compared to healthy individuals. We conclude that heart rate fluctuations are partially driven by conscious processing, depend on attentional state, and may represent a simple metric to assess conscious state in unresponsive patients.

Event related potentials elicited by violations of auditory regularities in patients with impaired consciousness.

Improving our ability to detect conscious processing in non communicating patients remains a major goal of clinical cognitive neurosciences. In this perspective, several functional brain imaging tools are currently under development. Bedside cognitive event-related potentials (ERPs) derived from the EEG signal are a good candidate to explore consciousness in these patients because: (1) they have an optimal time resolution within the millisecond range able to monitor the stream of consciousness, (2) they are fully non-invasive and relatively cheap, (3) they can be recorded continuously on dedicated individual systems to monitor consciousness and to communicate with patients, (4) and they can be used to enrich patients' autonomy through brain-computer interfaces. We recently designed an original auditory rule extraction ERP test that evaluates cerebral responses to violations of temporal regularities that are either local in time or global across several seconds. Local violations led to an early response in auditory cortex, independent of attention or the presence of a concurrent visual task, while global violations led to a late and spatially distributed response that was only present when subjects were attentive and aware of the violations. In the present work, we report the results of this test in 65 successive recordings obtained at bedside from 49 non-communicating patients affected with various acute or chronic neurological disorders. At the individual level, we confirm the high specificity of the 'global effect': only conscious patients presented this proposed neural signature of conscious processing. Here, we also describe in details the respective neural responses elicited by violations of local and global auditory regularities, and we report two additional ERP effects related to stimuli expectancy and to task learning, and we discuss their relations to consciousness.

Prognosis value of plasma S100B protein levels after subarachnoid aneurysmal hemorrhage.

BACKGROUND: S100B has been described as a biologic marker of neuronal damage. The purpose of this study was to assess its prognostic value in patients with subarachnoid aneurysmal hemorrhage. METHODS: Seventy-four patients (32 men and 42 women; age, 48 +/- 11 yr) admitted within 48 h after subarachnoid hemorrhage onset and treated by surgical clipping or coiling within 2 days after admission were included. World Federation of Neurological Surgeons, Fisher, and Glasgow outcome scores at intensive care unit discharge and at 6 months were evaluated. Blood concentrations of S100B were determined at admission and daily up to day 8. RESULTS: The time course of S100B was increased in patients with high World Federation of Neurological Surgeons and Fisher scores. Patients who underwent surgical clipping had an S100B time course longer than that of those who underwent coiling. This difference remained true after stratification for World Federation of Neurological Surgeons and Fisher scores. The threshold of mean daily value of S100B predicting a poor outcome at 6 months was 0.4 microg/l (sensitivity = 0.50 [95% confidence interval (CI), 0.29-0.71], specificity = 0.87[corrected] [95% CI, 0.76-0.95]). In multivariate analysis, high World Federation of Neurological Surgeons score (odds ratio = 9.5 [95% CI, 3.1-29.4]), mean daily S100B value above 0.4 microg/l (odds ratio = 7.3 [95% CI, 2.3-23.6]), and age (odds ratio = 1.08 per year [95% CI, 1.01-1.15]) were independent predictors of a poor 6-month outcome (Glasgow outcome score 1-3). CONCLUSION: Mean daily value of S100B assessed during the first 8 days is a prognostic tool complementary to initial clinical evaluation in subarachnoid hemorrhage patients.

Intra-arterial nimodipine for the treatment of symptomatic cerebral vasospasm after aneurysmal subarachnoid hemorrhage: preliminary results.

BACKGROUND AND PURPOSE: Cerebral vasospasm remains a major problem in patients recovering from aneurysmal subarachnoid hemorrhage despite advances in medical, surgical, and endovascular care. Our purpose was to assess the efficacy of intra-arterial nimodipine, a calcium-channel blocker acting mainly on cerebral vessels, in preventing delayed neurologic deficits in patients with symptomatic vasospasm. METHODS: Clinical charts of 25 consecutively treated patients were retrospectively reviewed. A multifactorial decision tree was used to determine the indication for angiography and subsequent endovascular treatment. Nimodipine was infused intra-arterially via a diagnostic catheter in the internal carotid artery or vertebral artery at a rate of 0.1 mg/min. Angiographic vasospasm before endovascular treatment, immediate vessel caliber modifications, and short- and long-term clinical efficacy of the procedure were assessed. RESULTS: Thirty procedures were performed in 25 patients. Clinical improvement was observed in 19 (76%), 16 of whom improved after the first endovascular procedure, two after the second intra-arterial treatment, and one after the third. Of these 19 patients, only 12 (63%) had notable vascular dilatation at postprocedural angiography. Dilatation of infused vessels occurred in only 13 (43%) of 30 procedures. After follow-up of 3-6 months, 18 (72%) of 25 patients had a favorable outcome (Glasgow outcome scale score of 1-2 and modified Rankin scale score of 0-2). No complications were observed. CONCLUSION: Intra-arterial nimodipine is effective and safe for the treatment of symptomatic vasospasm after subarachnoid hemorrhage. Further prospective randomized studies of cerebral blood flow are needed to confirm these results.