Safe driving and executive functions in healthy middle-aged drivers.

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.

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.

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 Luria's 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.

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.

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.

A lasting post-stimulus activation on dorsolateral prefrontal cortex is produced when processing valence and arousal in visual affective stimuli.

This paper introduces a new paradigm in the study of emotional processes through functional neuroimaging. We study whether the valence and arousal of visual stimuli influence neuroimaging of the evoked hemodynamic changes. Using functional near-infrared spectroscopy (fNIRS), we investigate evoked-cerebral blood oxygenation (CBO) changes in dorsolateral prefrontal cortex (DLPFC) during direct exposure to different emotion-eliciting stimuli ('on' period), and during the period directly following stimulus cessation ('off' period). We hypothesize that the evoked-CBO, rather than return to baseline after stimulus cessation, would show either overshoot or undershoot. The study includes 30 healthy subjects and a total of 9 stimuli, which consist of video-clips with different emotional content. The total sample of trials studied (270) is classified according to the valence and arousal ratings given by the subjects. Results show a more robust activation in DLPFC during the 'off' period than during the 'on' period, depending on the subjective degree of arousal given to the stimulus. Our findings provide the first fNIRS evidence showing that an increment in subjective arousal leads to activation in DLPFC which persists after stimulus cessation and this does not occur with non-arousing stimuli. Neuroimaging studies must consider the duration and affective dimensions of the stimulus as well as the duration of the scanning to specify how much of the recorded response is analyzed. Not accounting for this difference may contribute to confusion in the data interpretation.

Does dorsolateral prefrontal cortex (DLPFC) activation return to baseline when sexual stimuli cease? The role of DLPFC in visual sexual stimulation.

A fundamental question in human sexuality regards the neural substrate underlying sexually-arousing representations. Lesion and neuroimaging studies suggest that dorsolateral pre-frontal cortex (DLPFC) plays an important role in regulating the processing of visual sexual stimulation. The aim of this Functional Near-Infrared Spectroscopy (fNIRS) study was to explore DLPFC structures involved in the processing of erotic and non-sexual films. fNIRS was used to image the evoked-cerebral blood oxygenation (CBO) response in 15 male and 15 female subjects. Our hypothesis is that a sexual stimulus would produce DLPFC activation during the period of direct stimulus perception ("on" period), and that this activation would continue after stimulus cessation ("off" period). A new paradigm was used to measure the relative oxygenated hemoglobin (oxyHb) concentrations in DLPFC while subjects viewed the two selected stimuli (Roman orgy and a non-sexual film clip), and also immediately following stimulus cessation. Viewing of the non-sexual stimulus produced no overshoot in DLPFC, whereas exposure to the erotic stimulus produced rapidly ascendant overshoot, which became even more pronounced following stimulus cessation. We also report on gender differences in the timing and intensity of DLPFC activation in response to a sexually explicit visual stimulus. We found evidence indicating that men experience greater and more rapid sexual arousal when exposed to erotic stimuli than do women. Our results point out that self-regulation of DLPFC activation is modulated by subjective arousal and that cognitive appraisal of the sexual stimulus (valence) plays a secondary role in this regulation.

Differential time course and intensity of PFC activation for men and women in response to emotional stimuli: a functional near-infrared spectroscopy (fNIRS) study.

Using functional near-infrared spectroscopy (fNIRS) we recorded prefrontal cortex (PFC) activation during positive, negative and neutral film clips, based on affective ratings according to their valence and arousal, to assess gender differences in cerebral activation in 15 male and 15 female volunteers. To record PFC activation, five movie clips were presented on a 17-in. TFT screen. The recordings included a pre-stimulus 5-s local baseline and "on" and "off" segments of data, referring to fNIRS Oxy-Hb levels while stimulation (movie clip) was present and during an inter-stimulus blank screen. Our data showed gender differences in the delay period to initial PFC activation and in the course and intensity of activation produced by affective visual stimuli. During the exposure or "on" period of the stimuli we observed more pronounced overshoot and undershoot in men versus women across the range of emotions elicited. This effect was even more pronounced following stimulus cessation ("off" period). The results indicate that gender and the duration of recordings may affect the results of emotional neuroimaging studies.

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.