Effect of Motor State on Postactivation Depression of the Soleus H-Reflex in Parkinson's Disease During Deep Brain Stimulation and Dopaminergic Medication Treatment: A Pilot Study.

Purpose: Postactivation depression of the Hoffmann reflex is reduced in Parkinson's disease (PD), but how the recovery is influenced by the state of the muscle is unknown. The present pilot study examined postactivation depression in PD at rest and during a voluntary contraction while patients were off treatment and while receiving medications and/or deep brain stimulation.

Methods: The authors recruited nine patients with PD treated with implanted deep brain stimulation and examined postactivation depression under four treatment conditions.

Intraoperative changes in the H-reflex pathway during deep brain stimulation surgery for Parkinson's disease: A potential biomarker for optimal electrode placement.

Background: Deep Brain Stimulation (DBS) targeting the subthalamic nucleus (STN) and globus pallidus interna (GPi) is an effective treatment for cardinal motor symptoms and motor complications in Parkinson's Disease (PD). However, malpositioned DBS electrodes can result in suboptimal therapeutic response.

Objective: We explored whether recovery of the H-reflex-an easily measured electrophysiological analogue of the stretch reflex, known to be altered in PD-could serve as an adjunct biomarker of suboptimal versus optimal electrode position during STN- or GPi-DBS implantation.

Characterizing the effect of low intensity transcranial magnetic stimulation on the soleus H-reflex at rest.

Modulation of a Hoffmann (H)-reflex following transcranial magnetic stimulation (TMS) has been used to assess the nature of signals transmitted from cortical centers to lower motor neurons. Further characterizing the recruitment and time-course of the TMS-induced effect onto the soleus H-reflex adds to the discussion of these pathways and may improve its utility in clinical studies. In 10 healthy controls, TMS was used to condition the soleus H-reflex using TMS intensities from 65 to 110% of the resting motor threshold (RMT).

Effects of Deep Brain Stimulation and Dopaminergic Medication on Excitatory and Inhibitory Spinal Pathways in Parkinson Disease.

Purpose: Abnormal activity within the corticospinal system is believed to contribute to the motor dysfunction associated with Parkinson disease. However, the effect of treatment for parkinsonian motor symptoms on dysfunctional descending input to the motor neuron pool remains unclear.

Methods: We recruited nine patients with PD treated with deep brain stimulation and examined the time course of interaction between a conditioning pulse from transcranial magnetic stimulation and the soleus H-reflex.

Intraoperative spinal cord monitoring using low intensity transcranial stimulation to remove post-activation depression of the H-reflex.

Objective: To investigate whether low intensity transcranial electrical stimulation (TES) can be used to condition post-activation depression of the H-reflex and simultaneously monitor the integrity of spinal motor pathways during spinal deformity correction surgery.

Methods: In 20 pediatric patients undergoing corrective surgery for spinal deformity, post-activation depression of the medial gastrocnemius H-reflex was initiated by delivering two pulses 50-125ms apart, and the second H-reflex was conditioned by TES.

Results: Low intensity TES caused no visible shoulder or trunk movements during 19/20 procedures and the stimulation reduced post-activation depression of the H-reflex.

Reduced postactivation depression of soleus H reflex and root evoked potential after transcranial magnetic stimulation.

Postactivation depression of the Hoffmann (H) reflex is associated with a transient period of suppression following activation of the reflex pathway. In soleus, the depression lasts for 100-200 ms during voluntary contraction and up to 10 s at rest. A reflex root evoked potential (REP), elicited after a single pulse of transcutaneous stimulation to the thoracolumbar spine, has been shown to exhibit similar suppression.

Post-activation depression in the human soleus muscle using peripheral nerve and transcutaneous spinal stimulation.

Transcutaneous stimulation of the human lumbar spine can be used to elicit root-evoked potentials (REPs). These sensory-motor responses display notable similarities to the monosynaptic H-reflex. The purpose of this study was to compare post-activation depression of the soleus REP to that of the H-reflex, when conditioned by either an H-reflex or an REP.

Associations compete directly in memory.

Associations are confusable when they share an item. For example, double-function pairs (with the form AB, BC) are harder to remember than control pairs. Although ambiguous pairs are more difficult on average, it is not clear whether memories for associations compete directly with one another (associative competition hypothesis), as assumed by models that incorporate associative symmetry (bidirectional associations).

Blood ordering from the operating room: turnaround time as a quality indicator.

Background: Quality indicators in transfusion medicine are necessary for patient safety and customer satisfaction. The turnaround time (TAT) of issuing red blood cells (RBCs) has emerged as a quality indicator but is not an established benchmark. We examined the TAT for issuing RBCs from the blood bank to the operating rooms (ORs) at Vanderbilt University Medical Center (VUMC) and Stanford University Medical Center (SUMC).