Recruitment pattern of sympathetic muscle neurons during premature ventricular contractions in heart failure patients and controls.

Premature ventricular contractions (PVC) elicit larger bursts of multiunit muscle sympathetic nerve activity (MSNA), reflecting the ability to increase postganglionic axonal recruitment. We tested the hypothesis that chronic heart failure (CHF) limits the ability to recruit postganglionic sympathetic neurons as a response to PVC due to the excessive sympathetic activation in these patients. Sympathetic neurograms of sufficient signal-to-noise ratio were obtained from six CHF patients and from six similarly aged control individuals. Action potentials (APs) were extracted from the multiunit sympathetic neurograms during sinus rhythm bursts and during the post-PVC bursts. These APs were classified on the basis of the frequency per second, the content per burst, and the peak-to-peak amplitude, which formed the basis of binning the APs into active clusters. Compared with controls, CHF had higher APs per burst and higher number of active clusters per sinus rhythm burst (P < 0.05). Compared with sinus rhythm bursts, both groups increased AP frequency and the number of active clusters in the post-PVC burst (P < 0.05). However, compared with controls, the increase in burst integral, AP frequency, and APs per burst during the post-PVC burst was less in CHF patients. Nonetheless, the PVC-induced increase in active clusters per burst was similar between the groups. Thus, these CHF patients retained the ability to recruit larger APs but had a diminished ability to increase overall AP content.

Evaluation of neuroanatomical training using a 3D visual reality model.

As one of the more difficult components of any curricula, neuroanatomy poses many challenges to students - not only because of the numerous discrete structures, but also due to the complicated spatial relations between them, which must be learned. Traditional anatomical education uses 2D images with a focus on dissection. This approach tends to underestimate the cognitive leaps required between textbook, lecture, and dissection cases. With reduced anatomical teaching time available, and varying student spatial abilities, new techniques are needed for training. The goal of this study is to assess the improvement of trainee understanding of 3D brain anatomy, orientation, visualization, and navigation through the use of digital training regimes in comparison with current methods. Two subsets of health science and medical students were tested individually after being given a group lecture and either a pre- or post-dissection digital lab. Results suggest that exposure to a 3D digital lab may improve knowledge acquisition and understanding by the students, particularly for first time learners.