Different Contribution of the Monkey Prefrontal and Premotor Dorsal Cortex in Decision Making During a Transitive Inference Task.

Several studies have reported similar neural modulations between brain areas of the frontal cortex, such as the dorsolateral prefrontal (DLPFC) and the premotor dorsal (PMd) cortex, in tasks requiring encoding of the abstract rules for selecting the proper action. Here we compared the neuronal modulation of the DLPFC and PMd of monkeys trained to choose the higher rank from a pair of abstract images (target item), selected from an arbitrarily rank-ordered set (A > B > C > D > E > F) in the context of a transitive inference task. Once acquired by trial-and-error, the ordinal relationship between pairs of adjacent images (i.e., A > B; B > C; C > D; D > E; E > F), monkeys were tested in indicating the ordinal relation between items of the list not paired during learning. During these decisions, we observed that the choice accuracy increased and the reaction time decreased as the rank difference between the compared items enhanced. This result is in line with the hypothesis that after learning, the monkeys built an abstract mental representation of the ranked items, where rank comparisons correspond to the items' position comparison on this representation. In both brain areas, we observed higher neuronal activity when the target item appeared in a specific location on the screen with respect to the opposite position and that this difference was particularly enhanced at lower degrees of difficulty. By comparing the time evolution of the activity of the two areas, we observed that the neural encoding of target item spatial position occurred earlier in the DLPFC than in the PMd.

A 4-year implementation strategy of aggressive post-resuscitation care and temperature management after cardiac arrest.

BACKGROUND: target temperature management (TTM) not only improves neurological outcome and survival but has given momentum to a more aggressive and comprehensive treatment after resuscitation. Yet, implementation issues represent the main obstacle to systematic treatment with TTM and aggressive post-resuscitation care. We devised a strategy to introduce, monitor and improve the quality of aggressive treatment after resuscitation, including TTM. METHODS: standard operative procedures on aggressive post-resuscitation care, written jointly by physicians and nurses, were introduced in November 2004. Data of all resuscitated patients admitted to the ICU were prospectively acquired for 4 years. Periodic audits (every 16 months) were programmed, leading to three equally long periods. Several critical issues were identified after each audit and addressed subsequently, leading to a growing complexity of care. Moreover, after 2 years we introduced an educational programme with medical credits for all staff attending critically ill patients. Neurological outcome and survival at hospital discharged were compared to historical controls of the preceding 22 months. RESULTS: 129 consecutively resuscitated patients were admitted to the ICU in the 4-year study period. Of these, 96 (74%) were treated with TTM and aggressive post-resuscitation care. Favourable neurological recovery among patients discharged alive significantly improved in the 4-year intervention period (81% vs. 50% in historical controls, p<0.01). A composite endpoint of mortality and poor neurological outcome also improved (64% vs. 82% respectively, p<0.05). Overall survival increased throughout the 4 years, leading to a significant improvement in the 3rd period compared to historical controls (60% vs. 35%; p<0.05). CONCLUSIONS: we propose a strategy to successfully introduce and implement TTM and aggressive post-resuscitation care via standard operative procedures, periodic audits and feedback. Continuous education among other factors contributed to a significant improvement in neurological outcome and a progressive increase in survival.

Left ventricular performance in the early stages of systemic hypertension. HARVEST Study Group. Hypertension and Ambulatory Recording Venetia Study.

To investigate whether and how frequently left ventricular (LV) systolic performance assessed with endocardial and midwall measurement is depressed in young subjects with mild systemic hypertension, we studied 722 borderline to mild hypertensive patients (mean age +/- SEM 33 +/- 0.3 years, mean office blood pressure (BP) 146 +/- 0.4/94 +/- 0.2 mm Hg) enrolled in the Hypertension and Ambulatory Recording Venetia Study and 50 normotensive controls with similar age and sex distribution. BP was measured with 24-hour ambulatory monitoring. LV dimensional and functional indexes were assessed by M-mode echocardiography and sympathetic activity from 24-hour urinary catecholamines. In 64 hypertensive subjects (8.9%) the LV midwall shortening-stress relation was < 95% of the confidence interval in 50 normotensive controls. Subjects with depressed LV myocardial function had age, duration of hypertension, and LV mass similar to those of hypertensives with normal performance, and greater relative wall thickness (0.42 vs 0.37, p < 0.001). Stroke volume and cardiac output were lower (p < 0.001) in the former group. Among these 64 subjects, endocardial performance was depressed in 35 (group 1) and normal in 29 (group 2). Group 2 subjects had greater posterior wall (10.0 vs 9.5 mm, p = 0.03), ventricular septum (10.6 vs 10.1 mm, p = 0.05), and relative wall (0.44 vs 0.40, p < 0.001) thicknesses than group 1 subjects. Urinary norepinephrine was 50% higher in group 2 subjects (106 vs 70 g/24 hours, p = 0.03). Stroke volume and cardiac output were similar in both groups. In conclusion, these results show that LV contractility may be depressed in young subjects with borderline to mild hypertension.

Supernormal left ventricular performance in young subjects with mild hypertension: an alerting response to the echocardiographic procedure?

1. To assess the clinical significance of supernormal left ventricular systolic function in the initial phase of hypertension, 635 never-treated 18-45-year-old borderline to mild hypertensive subjects (477 males, 158 females) were studied. All subjects underwent echocardiography, 24 h ambulatory blood pressure monitoring and 24 h urine collection for catecholamine dosage. 2. Subjects whose left ventricular shortening-stress relationship was above the 95% confidence intervals of 50 normotensive subjects of similar age and sex distribution were defined as having supernormal function. 3. Age, duration of hypertension and left ventricular mass were similar in the hypertensive subjects with normal (85%) and supernormal (15%) ejective performance. Subjects with supernormal function showed higher office systolic blood pressure (P < 0001), office heart rate (P = 0.03) and cardiac index (P < 0001). Conversely, 24 h systolic blood pressure, 24 h heart rate and 24 h catecholamine output did not differ according to left ventricular function. 4. In conclusion, the greater white-coat effect and the normal baseline sympathetic tone exhibited by the patients with increased performance suggest that supernormal left ventricular pump function is only a marker of the alerting reaction elicited by the echocardiographic examination.

Endocardial versus midwall measurement of left ventricular function in mild hypertension: an insight from the Harvest Study.

OBJECTIVE: To compare endocardial and midwall measurement of left ventricular fractional shortening in assessing cardiac systolic function in hypertension. SETTING: Seventeen hypertension clinics in northeast Italy. MAIN OUTCOME MEASURES: Left ventricular endocardial fractional shorteningcircumferential stress relationship versus midwall shortening-stress relationship in the subjects divided according to relative wall thickness (RWT) and left ventricular mass indexed by body surface area. PATIENTS: Borderline-to-mild hypertensives [n = 635, aged 33 +/- 0.3 years (mean +/- SEM), office blood pressure 146 +/- 0.4/94 +/- 0.2 mmHg (means +/- SEM)] in the Harvest Study and 50 normotensive controls with similar age and sex distributions. METHODS: Blood pressure was measured by 24 h ambulatory monitoring. Left ventricular dimensional and functional indices were assessed by M-mode echocardiography. RESULTS: In the subjects divided into quintiles of RWT, the left ventricular shortening-stress relationship was increased in a parallel fashion when calculated by endocardial and by midwall measurements for RWT < or = 0.35. Instead, for greater RWT values (> or = 0.37) endocardial measurement constantly gave large values than did midwall measurement. Both the endocardial and the midwall shortening-stress relationships progressively decreased with increasing RWT. However, the endocardial shortening-stress relationship remained greater than normal at any RWT, whereas the midwall shortening-stress relationship was decreased for RWT > or = 0.37. In a multiple-regression analysis RWT was the most potent predictor of the endocardialmidwall shortening difference, left ventricular mass and 24 h systolic blood pressure being the second and third most potent predictors. CONCLUSIONS: We found a parallel increase in indices of cavity emptying and of myocardial contractility in mild hypertensive subjects with normal left ventricular geometry. When the RWT is increased, ejection phase indices may be normal in the presence of decreased myocardial contractility.