Standard extinction procedures seem to imply an inhibition of the fear response, but not a modification of the original fear-memory trace, which remains intact (Bouton, 2002, 2004). Typically, the behavioral procedure used to modify this trace is the so-called postretrieval extinction, consisting of fear-memory reactivation followed by extinction applied within the reconsolidation window. However, the application of this technique yields mixed results, probably due to a series of boundary conditions that limit the effectiveness of postretrieval-extinction effects. In this study a number of potential, and hitherto unexplored, moderators of such effects are considered. Using an interval of 48 hr between extinction and re-extinction, the findings show a spontaneous recovery similar to that found in studies that use a 24-hr interval. Also, the use of intervals of 10 and 20 min between reactivation and extinction led to a similar fear return. Finally, the burst of white noise used as an unconditioned stimulus (US) here was shown to be as effective as the electric shock normally used in the study of fear-memory reconsolidation. These findings suggest that postretrieval extinction is an effective behavioral technique for modifying the original fear memory and for the elimination of the fear return. (PsycINFO Database Record

Extinction procedures have been used widely in the study of fear memories, and different positions have been adopted regarding the efficacy of such procedures and the mechanisms involved. It has been argued that extinction may interfere with the consolidation of the fear memory if the procedure is applied with the appropriate timing after acquisition. However, the opposite position is also held, that is, that the extinction does not achieve an elimination of the fear response. The aim of the present study is to test the short-term effects of immediate extinction in fear reduction when this extinction is preceded by a retrieval trial. For this, a procedure similar to that employed by Schiller et al. (Nature 463(7277): 49-53, 2010) was used, but in a single day and with white noise as an aversive unconditioned stimulus. The results indicate that a CS+ single retrieval trial before the extinction procedure after acquisition was more effective in fear reduction than standard immediate extinction.

Among a group of monitoring techniques that estimate ICP non-invasively, the measurement of the optic nerve sheath diameter (ONSD) seems to be the most promising. The prediction threshold to correlate with a high ICP (> 20 mmHg) has been proposed by some authors between 5.7 and 5.9 mm but there is no uniform cut-off point in the literature.Objective: To determine the utility of the ONSD measurement as an estimate of non-invasive ICP; correlating it with invasive measurements and cerebral hemodynamic patterns by transcranial Doppler. Method:The sample consisted of a series of five neurocritical cases admitted to the intensive care unit of the Centro de Investigaciones Médico Quirúrgicas, to which an intraventricular catheter was placed to measure ICP by air bag using the Spiegelberg monitor. Each patient underwent simultaneous measurements of ICP, transcranial Doppler ultrasound and retrobulbar ultrasound to measure ONSD. In total, 16 measurements were made that integrated the data for statistical analysis.Results: The value of ONSD over which there was ICP >20 mmHg was 6.50 mm, constituting the cut-off point. The correlation between mvMCA and ONSD was moderate and inverse, with statistical significance (r = -0.532, p = 0.034). Conclusions: Non-invasive multiparametric monitoring as part of critical ultrasound shows promise in neurocritical patients.Measurement of the Optic Nerve Sheath Diameter and Transcranial Doppler Ultrasound as an Approach to Cerebral Hemodynamics