Juan Manuel Barroso y Martín

Epidemiology of Traumatic Brain Injury and Subarachnoid Hemorrhage

Incidence rates of traumatic brain injury are high in both industrialized and non-industrialized countries and have been estimated variously to be between 150–250 cases per 100,000 population per year. The estimated incidence rates for subarachnoid hemorrhage (SAH) are between 10 to 25 cases per 100,000 population per year. Seasonal variation in the occurrence of subarachnoid hemorrhage has been reported in studies from different countries, with significant seasonal variations and peak periods for aneurysmal SAH differing widely. A differential racial distribution for SAH has been found as well as a higher mortality rate for women than for men. The cognitive and behavioral consequences of TBI and SAH are significant and affect the quality of life of patients and their families. Recent publications have informed of hypopituitary deficits in patients sustaining TBI or SAH. It is not clear whether the cognitive deficits found in these patients are due to the consequences of the brain injury itself or are related to the hypopituitary deficits. There is a need for research distinguishing the differential cognitive and behavioral effects of the brain injury and the endocrinological deficits in these patients, and for developing adequate treatment.

The hemodynamics of cognitive control: The level of concentration of oxygenated hemoglobin in the superior prefrontal cortex varies as a function of performance in a modified Stroop task

The purpose of this study was to establish the relationship between the hemodynamic response of prefrontal cortex (PFC) and individual differences in cognitive control, as measured by a color-word interference task. Twenty-five healthy volunteers were observed through functional near infrared spectroscopy (fNIRS) while performing a modified Stroop paradigm. Mean concentration levels of oxygenated hemoglobin (oxy-Hb) were correlated with behavioral performance in the conflict task. Those with shorter reaction times had higher levels of oxy-Hb concentration in superior dorsolateral PFC. Our results are the first to show a positive correlation between behavioral performance and oxy-Hb levels in superior dorsolateral PFC in a cognitive conflict task. These results suggest that the availability of oxygen in the superior PFC, possibly linked to an increase in metabolism, may be related to attention level and effectiveness of cognitive control.

Delta–alpha ratio correlates with level of recovery after neurorehabilitation in patients with acquired brain injury

OBJECTIVE To explore the relationship between three QEEG global indexes and their association with functional outcome after neurorehabilitation in non-acute acquired brain injury (ABI) patients (traumatic brain injury and stroke). METHODS Twenty-one adult ABI patients in post-acute phase were studied. Delta-alpha ratio (DAR), Power Ratio Index (PRI) and Mean Brain Symmetry Index (mBSI) were calculated from resting-state EEG taken at admission. These indexes and other clinical variables were correlated with functional recovery achieved after six months of neurorehabilitation. RESULTS DAR showed the highest strength of association with the functional outcome measure (rho=-0.65, P=0.002). The other QEEG indexes and clinical variables showed modest non-significant correlations. A posteriori group analysis showed higher DAR in patients with poor recovery as compared to good recovery patients. CONCLUSIONS Functional recovery after neurorehabilitation appears to be associated with a number of clinical and neurophysiological variables. Among the latter, the ratio between delta and alpha may play a significant role in predicting and monitoring functional rehabilitation outcome. SIGNIFICANCE Neurophysiological assessment of ABI patients may be an important tool in monitoring and predicting outcomes after neurorehabilitation.

Efficient learning produces spontaneous neural repetition suppression in prefrontal cortex.

Our study focuses on the physiological effects of repetition on learning and working memory using an adaptation of Lurias Memory Word-Task (LMWT). We assess the hemodynamic response in dorsolateral prefrontal cortex (DLPFC) of 13 healthy subjects while completing LMWT. Free word recalls were acquired at the beginning, middle and end of the task. Behavioral results showed that all subjects could recall the complete word list by the 10th trial, which was considered as successful task accomplishment. We observed an attenuation of stimulus-evoked neural activity in prefrontal neurons. Our findings show that the temporal integration of efficient verbal learning is mediated by a mechanism known as neural repetition suppression (NRS). This mechanism facilitates cortical deactivation in DLPFC once learning is successfully completed. This cortical reorganization is interpreted as a progressive optimization of neural responses to produce a more efficient use of neural circuits. NRS could be considered one of the natural mechanisms involved in the processes of memory learning.

A QEEG index of level of functional dependence for people sustaining acquired brain injury: The Seville Independence Index (SINDI)

Primary objective: To find an easy-to-use, valid and reliable tool for evaluating the level of functional dependence of an individual with brain damage who seeks a diagnosis of his/her functional dependence in daily activities. Methods: Eighty-one patients with acquired brain injury (ABI) in post-acute phase, 40 traumatic brain injury (TBI) and 41 cerebral vascular accident (CVA), were assessed using quantitative electroencephalography (QEEG) and grouped according to the FIM + FAM scale. Discriminant analysis was performed on QEEG variables to obtain a discriminant function with the best discriminative capacity between functionality groups. Results: Discriminant analysis showed classification accuracy of 100% in the training set sample and 75% in an external cross-validation sample; 100% sensitivity and 100% specificity were reached. Coherence measures were the most numerous variables in the function. Conclusions: These results point out that the discriminant function may be a useful tool in objective evaluations of patients seeking a diagnosis of their level of dependence and that it could be included in current functionality assessment protocols.

Recovery of cognitive function during comprehensive rehabilitation after severe traumatic brain injury.

OBJECTIVE To explore the course and timing of functional recovery in patients who have emerged from coma after undergoing severe traumatic brain injury. METHODS An observational study involving 19 patients with traumatic brain injury recovered from coma who underwent holistic, intensive and multidisciplinary neurorehabilitation. Daily performance in each cognitive function (long-term memory, short-term memory, orientation, calculation, attention, mental control, automation, and planning) was clinically scored and compared at admission and discharge. RESULTS The course of cognitive recovery after post-traumatic coma is not uniform, offering a curve with many ups, downs and plateaus. To achieve a good response and outcome nearing normalcy, a patient needs over 300 h of intensive rehabilitation. CONCLUSION The consolidation of functional recovery in patients with traumatic brain injury requires time and adequate training, and discharge is not recommended until cognitive improvement is established.

Safe Driving and Executive Functions in Healthy Middle-Aged Drivers.

ABSTRACT The introduction of the point system driver’s license in several European countries could offer a valid framework for evaluating driving skills. This is the first study to use this framework to assess the functional integrity of executive functions in middle-aged drivers with full points, partial points or no points on their driver’s license (N = 270). The purpose of this study is to find differences in executive functions that could be determinants in safe driving. Cognitive tests were used to assess attention processes, processing speed, planning, cognitive flexibility, and inhibitory control. Analyses for covariance (ANCOVAS) were used for group comparisons while adjusting for education level. The Bonferroni method was used for correcting for multiple comparisons. Overall, drivers with the full points on their license showed better scores than the other two groups. In particular, significant differences were found in reaction times on Simple and Conditioned Attention tasks (both p-values < 0.001) and in number of type-III errors on the Tower of Hanoi task (p = 0.026). Differences in reaction time on attention tasks could serve as neuropsychological markers for safe driving. Further analysis should be conducted in order to determine the behavioral impact of impaired executive functioning on driving ability.