Noninvasive remote activation of the ventral midbrain by transcranial direct current stimulation of prefrontal cortex.

The midbrain lies deep within the brain and has an important role in reward, motivation, movement and the pathophysiology of various neuropsychiatric disorders such as Parkinson's disease, schizophrenia, depression and addiction. To date, the primary means of acting on this region has been with pharmacological interventions or implanted electrodes. Here we introduce a new noninvasive brain stimulation technique that exploits the highly interconnected nature of the midbrain and prefrontal cortex to stimulate deep brain regions. Using transcranial direct current stimulation (tDCS) of the prefrontal cortex, we were able to remotely activate the interconnected midbrain and cause increases in participants' appraisals of facial attractiveness. Participants with more enhanced prefrontal/midbrain connectivity following stimulation exhibited greater increases in attractiveness ratings. These results illustrate that noninvasive direct stimulation of prefrontal cortex can induce neural activity in the distally connected midbrain, which directly effects behavior. Furthermore, these results suggest that this tDCS protocol could provide a promising approach to modulate midbrain functions that are disrupted in neuropsychiatric disorders.

Overlaying ultrasonographic images on direct vision.

The objective of this technical advance is to permit in situ visualization of ultrasonographic images so that direct hand-eye coordination can be used during invasive procedures. A method is presented that merges the visual outer surface of a patient with a simultaneous ultrasonographic scan of the patient's interior. The method combines a flat-panel monitor with a half-silvered mirror such that the image on the monitor is reflected precisely at the proper location within the patient. The ultrasonographic image is superimposed in real time on the patient, merging with the operator's hands and any invasive tools in the field of view. Instead of looking away from the patient at an ultrasonographic monitor, the operator sees through skin and underlying tissue as if it were translucent. Two working prototypes have been constructed, demonstrating independence of viewer location and requiring no special apparatus to be worn by the operator. This method could enable needles and scalpels to be manipulated with direct hand-eye coordination under ultrasonographic guidance. Invasive tools would be visible up to where they enter the skin, permitting natural visual extrapolation into the ultrasonographic slice. Biopsy needles would no longer be restricted to lie in the plane of the ultrasonographic scan but could instead intersect it. These advances could lead to increased safety, ease, and reliability in certain invasive procedures.