Adding a sustained attention task to a physically demanding cycling exercise exacerbates neuromuscular fatigue and impairs cognitive performance in both normoxia and hypoxia.

PURPOSE: Both cognitive motor dual-tasks (CMDT) protocols and hypoxic environments have been associated with significant impairments in cognitive and physical performance. We aimed to determine the effects of hypoxia on cognitive performance and neuromuscular fatigue during a highly physically demanding CMDT. METHODS: Fifteen young adults completed a first session involving a cognitive task (CTLCOG) followed by cycling exercise (CTLEX) in normoxia. After that, they randomly participated in CMDT sessions in normoxia (DTNOR) and hypoxia (DTHYP). The physical exercise consisted of 20 min cycling at a "hard" perceived effort, and the cognitive task consisted of 15 min sustained attention to response time task (SART). Concurrent psycho-physiological measurements included: quadriceps neuromuscular fatigue (peripheral/central components from femoral nerve electrostimulation), prefrontal cortex (PFC) oxygenation by near-infrared spectroscopy, and perception of effort. RESULTS: SART performance significantly decreased in DTNOR (-15.7 ± 15.6%, P < 0.01) and DTHYP (-26.2 ± 16.0%, P < 0.01) compared to CTLCOG (-1.0 ± 17.7%, P = 0.61). Peripheral fatigue similarly increased across conditions, whereas the ability of the central nervous system to activate the working muscles was impaired similarly in DTNOR (-6.1 ± 5.9%, P < 0.001) and DTHYP (-5.4 ± 7.3%, P < 0.001) compared to CTLEX (-1.1 ± 0.2%, P = 0.52). Exercise-induced perception of effort was higher in DTHYP vs. DTNOR and in DTNOR vs. CTLEX. This was correlated with cognitive impairments in both normoxia and hypoxia. PFC deoxygenation was more pronounced in DTHYP compared to DTNOR and CTLEX. CONCLUSION: In conclusion, performing a sustained attention task together with physically challenging cycling exercise promotes central neuromuscular fatigue and impairs cognitive accuracy; the latter is particularly noticeable when the CMDT is performed in hypoxia.

The anterior medial hippocampus contributes to both recall and familiarity-based memory for scenes.

The hippocampus is usually associated with recall memory, whereas its contribution to familiarity-based memory is debated. Growing evidence support the idea that this structure participates to any cognitive process performed on scene representations. In parallel, differences in functional specialisation and cortical connectivity were found across the longitudinal and transverse axes of the hippocampus. Here we reanalysed functional MRI data from 51 participants showing stronger engagement of the hippocampus in recall, familiarity-based recognition and rejection, and visual discrimination, of scenes compared to single objects. A conjunction analysis between these four tasks revealed a set of occipital, medial temporal, posterior cingulate, and parietal regions, matching the scene construction network described in the literature. Crucially, we found that the anterior medial part of the hippocampus was consistently involved in all tasks investigated for scene stimuli. These findings support that the hippocampus can contribute to both recall and familiarity-based memory, depending on stimulus type. More generally, this bolsters the recent proposal that circumscribed regions within the hippocampus may underpin specific cognitive mechanisms.

Neural correlates of the healthiness evaluation processes of food labels.

OBJECTIVES: This fMRI study evaluated the cognitive mechanisms and the cerebral substrates when evaluating the healthiness of food products from nutritional information displayed either with a traffic light (TL) system, a colored nutritional label, or with a guideline daily amount (GDA) system, a numeric label. We postulated that TL label would recruit emotional processes and activation of subjacent cerebral regions (e.g. insula and amygdala). On the contrary, the nutritional information presented in a GDA label, would recruit, due to its numeric format and higher complexity, supplementary cognitive processes and activation of related brain regions (e.g. middle and superior frontal as well as parietal cortices). METHODS: We examined 50 healthy participants during an evaluation task on the healthiness of real food products from nutritional information only. Per total, 60 food products nutritional labels have been presented, with either colored (TL) or numeric (GDA) nutritional information and three levels of complexity of nutritional information. RESULTS: In line with our predictions, evaluations based on GDA recruited prefrontal and parietal regions reported for analytic processes. Contrary to our predictions, the same network has been recruited when evaluations were based on TL. Finally, we found significant correlation between response time and the superior parietal lobule in the GDA condition. DISCUSSION: Our results suggested that TL did not have an effect on the used strategy compared to GDA, based on calculation and arithmetic processes. Correlations between response time and brain activations suggested a significant involvement of the arithmetic mechanisms in the evaluation of food healthiness.

Specific incremental test in elite squash players.

OBJECTIVES: To compare cardiorespiratory responses between incremental treadmill (non-specific) and field (sport specific) tests in elite squash players. METHODS: Seven elite players (ranked 1 to 25 in their national federation including the World number 1) randomly performed an incremental treadmill test (TT) and a squash specific graded test (ST) to exhaustion. The ST consisted of repeated displacements replicating the game of squash, at increasing speed on the court. In both tests, ventilatory variables and heart rate were determined at the ventilatory threshold, respiratory compensation point, and maximal loads (max). RESULTS: Heart rate and percentage maximal oxygen uptake (VO2MAX) at the ventilatory threshold and respiratory compensation point were not different between the ST and TT, whereas VO2MAX was higher in the ST than in the TT (63.6 (3.0) v 54.9 (2.5) ml/kg/min; p < 0.001). Time to exhaustion was not different between the ST and TT (1056 (180) v 962 (71) seconds) but correlated with the ranking of the players only in the ST (r = -0.96, p < 0.001). CONCLUSIONS: VO2MAX values derived from laboratory testing were not relevant for accurately estimating fitness in elite squash players. So the ST may be used as an additional test for determination of training intensity. Improved training advice for prescribing aerobic exercise or perfecting stroke technique may result from these results.

Diurnal variations of tonic electrodermal activity.

Diurnal variability of skin conductance level (SCL) was examined in two complementary experiments, simultaneously with variability of skin temperature (ST) and that of simple reaction time (RT) which was recorded as a behavioural index of arousal. In Experiment I, 6 subjects spent 6 days in the laboratory in homogeneous conditions. Three recording sessions, each lasting 2 h, began, respectively, at 9:00 a.m. (morning), 1:00 p.m. (afternoon) and 5:00 p.m. (evening). Results indicated that SCL increased linearly throughout the day. Experiment II was undertaken to test whether this effect could still be observed in more heterogeneous conditions. Subjects (n = 12) attended to their own activities between the two 30-min sessions beginning, respectively, at 9:30 a.m. and 6:00 p.m. during a single experimental day. Again, SCL was higher in the evening than in the morning. In both experiments the SCL pattern seemed to be asynchronous with ST and RT variations. Taken as a whole, these data bring additional evidence of temporal electrodermal variation, a phenomenon which should be further taken into account in EDA research.

[Atypical cellular blue nevus. Apropos of 1 case]. / Le naevus bleu cellulaire atypique. A propos d'un cas.

We report a new case of a cellular blue nevus with clinicopathologic atypia. It was a large lesion presenting clinically as a vascular tumor located in the middle of the back. It grew for 2 years without skin ulceration. The pathological study suggested a cellular blue nevus with moderate nuclear atypia, without any atypical mitosis and necrosis. The differential diagnosis such as malignant blue nevus and melanoma are discussed in search of a better definition of these rare lesions.