Assessing explicit processes does not influence the magnitude of implicit processes.

Implicit (unconscious) and explicit (strategy) processes have been shown to contribute to visuomotor adaptation. Current methods, such as the Process Dissociation Procedure (PDP) and the Verbal Report Framework (VRF), simultaneously evaluate both implicit and explicit contributions to visuomotor adaptation. It is unclear whether the act of assessing explicit adaptation leads to variations in the magnitude of implicit adaptation observed. To address this question, four groups of participants adapted their reaches to a 40° clockwise visuomotor rotation. Implicit and explicit adaptation were assessed in a PDP-IE group and a VRF-IE group following 3 blocks of rotated reach training trials. In contrast, only implicit adaptation was assessed at the same time points for a PDP-I group and VRF-I group. Results indicated a similar magnitude of implicit adaptation regardless of whether explicit adaptation was assessed or not. Thus, assessing explicit adaptation simultaneously with implicit adaptation following reach adaptation does not influence the magnitude of implicit adaptation established via the PDP and VRF methods.

Assessing and defining explicit processes in visuomotor adaptation.

The Process Dissociation Procedure (PDP) and Verbal Report Framework (VRF) reveal that both explicit (conscious) and implicit (unconscious) processes contribute to visuomotor adaptation. We looked to determine whether these two assessment methods establish similar processes underlying visuomotor adaptation by comparing the magnitude of explicit and implicit adaptation over time between the two assessments and to post-experiment assessments of awareness of the visuomotor distortion. Three groups of participants (PDP, VRF, VRF No-Cursor) completed three blocks of reach training in a virtual environment with a cursor rotated 40° clockwise relative to hand motion. Explicit and implicit adaptations were assessed immediately following each block, and again 5 min later. The VRF No-Cursor group completed the same assessment trials as the VRF group, but no visual feedback was presented during explicit and implicit assessment. Finally, participants completed a post-experiment questionnaire and a drawing task to assess their awareness of the visuomotor rotation and changes in reaches at the end of the experiment, respectively. We found that all groups adapted their reaches to the rotation. Averaged across participants, the magnitude and retention of explicit and implicit adaptations were similar between the PDP group and VRF group, with the VRF group demonstrating greater implicit adaptation than the VRF No-Cursor group. Furthermore, the magnitude of explicit adaptation established in the VRF group was not related to participant's post-experiment awareness of the visuomotor distortion nor how they had changed their reaches, as observed in the PDP group and VRF No-Cursor group. Together, these results indicate that, explicit adaptation established via typical VRF methods does not reflect one's awareness of the visuomotor distortion at the end of the experiment, and hence the established processes underlying visuomotor adaptation are dependent on method of assessment (i.e., PDP versus VRF).

Imaging-based characterization of convective tissue properties.

Convective transport is an important phenomenon for nanomedicine delivery. We present an imaging-based approach to recover tissue properties that are significant in the accumulation of nanoparticles delivered via systemic methods. The classical pharmacokinetic analysis develops governing equations for the particle transport from a first principle mass balance. Fundamentally, the governing equations for compartmental mass balance represent a spatially invariant mass transport between compartments and do not capture spatially variant convection phenomena. Further, the parameters recovered from this approach do not necessarily have direct meaning with respect to the governing equations for convective transport. In our approach, a framework is presented for directly measuring permeability in the sense of Darcy flow through porous tissue. Measurements from our approach are compared to an extended Tofts model as a control. We demonstrate that a pixel-wise iterative clustering algorithm may be applied to reduce the parameter space of the measurements. We show that measurements obtained from our approach are correlated with measurements obtained from the extended Tofts model control. These correlations demonstrate that the proposed approach contains similar information to an established compartmental model and may be useful in providing an alternative theoretical framework for parameterizing mathematical models for treatment planning and diagnostic studies involving nanomedicine where convection dominated effects are important.

High intensity focused ultrasound: The fundamentals, clinical applications and research trends.

Diagnostic ultrasound has been clinically used for decades. More recently, high intensity focused ultrasound (HIFU) has been developed for therapeutic use as a non-invasive technique for tissue ablation. HIFU is also being investigated for advanced applications at the cellular level. Under guidance by magnetic resonance or ultrasound imaging, HIFU can achieve precise biological effects in tissue with a high safety profile. In this article, we discuss the basic principles, advantages and limitations of HIFU. We will also address the food and drug administration (FDA) approved clinical applications in the United States and highlight active HIFU research with promising clinical outcomes.