Biomedical subjects

Minna Hong

Publications and source records attributed to Minna Hong.

4 recordsLinked to original sources

PubMed2006

Podokinetic after-rotation in Parkinson disease.

Walking on a rotating platform for 15 min causes healthy subjects to involuntarily turn when walking without vision. This adaptive response, called podokinetic after-rotation (PKAR), uses the same kinematic patterns as voluntary turning suggesting that PKAR and voluntary turning share common mechanisms. The purpose of this study is to determine whether people with Parkinson disease (PD), a condition that produces substantial disability from turning difficulties, can adapt to the rotating platform. Initial testing of people with PD revealed that most were unable to step on the rotating platform for 15 continuous minutes. We thus tested a less intense version of the paradigm in eight healthy people. On one day, subjects walked on the platform for 15 continuous minutes; on another day, they walked on the platform for three 5-minute intervals separated by 5-minute rests. After both sessions, subjects rested for 5 min then walked in place for 30 min without vision, while we recorded rotational velocity of PKAR. Continuous and interval protocols effectively elicited robust PKAR. We then tested eight subjects with PD and matched controls using the 5-minute interval protocol and recorded PKAR responses for 10 min. There were no significant differences between the PD and control groups. We conclude that PD subjects can adapt to the rotating platform and develop PKAR from interval training. Future studies are needed to determine whether the rotating platform may act as a rehabilitative tool to reinforce motor patterns for turning and alleviate turning difficulties in people with PD.

Adaptation, Physiological↗

PubMed2006

Kinematics of podokinetic after-rotation: similarities to voluntary turning and potential clinical implications.

We examined the kinematics of voluntary turning in place at three different speeds and of inadvertent turning in place during attempts to step in place following stepping on a rotating disc (podokinetic after-rotation, PKAR). We hypothesized that voluntary turning in place, like online turning during walking, would be characterized by a top-down sequence of yaw rotations in the direction of the turn, i.e. the head would rotate first, followed by the trunk and then the foot. We also hypothesized that in place PKAR would be characterized by a bottom-up sequence of yaw rotations, i.e. the foot would rotate first, followed by the trunk and the head. The alternative possibility was that PKAR, like voluntary turning, would be initiated by the head and trunk and the foot would rotate last. As expected, voluntary turning in place was characterized by a top-down sequence similar to that noted previously during online turning in the midst of walking. Turning velocity did not alter the sequence of rotations in voluntary turning. In place PKAR was also characterized by a top-down sequence, indicating that PKAR may access the same neural circuits employed during voluntary turning. These data suggest that the rotating treadmill may be a useful training tool for addressing difficulties with turning that are experienced by individuals with Parkinson disease (PD).

Adult↗

PubMed2006

Postural tremor suppression is dependent on thalamic stimulation frequency.

Deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) reduces tremor in people with essential tremor (ET), yet the dependence of tremor suppression on stimulation frequency remains unclear. To address this issue, we tested tremor suppression for three 15-second measurements during a variety of stimulation frequencies in 11 ET patients treated with VIM DBS. Stimulation frequencies at or above 100 Hz produced maximal benefit; higher frequencies provided no additional benefit. If this short-term measure predicts long-term response in routine activities at home, then this stimulation frequency setting will prolong battery half-life compared to higher frequency settings. These findings suggest that ET patients treated with VIM DBS may receive adequate benefit from stimulation frequencies about 100 Hz and this setting compared to commonly used higher settings will prolong battery life of surgically implanted pulse generators.

Aged↗

PubMed2004

Effect of stimulation frequency on tremor suppression in essential tremor.

We sought to determine the effect of deep brain stimulation (DBS) frequency on tremor suppression in essential tremor (ET) patients with deep brain stimulators implanted in the ventral intermediate nucleus (VIM) of the thalamus. A uniaxial accelerometer was used to measure tremor in the right upper extremity of subjects with a diagnosis of ET who had DBS electrodes implanted in the left VIM. The root-mean-square acceleration was used as the index of tremor magnitude and normalized to the OFF DBS condition. There was a highly significant inverse sigmoidal relationship between stimulation frequency and normalized tremor acceleration (X(2)/DoF = 0.42, r(2) = 0.997). Tremor acceleration had a nearly linear response to stimulation frequencies between 45 and 100 Hz with little additional benefit above 100 Hz. These findings have two important implications. Clinically, frequency of thalamic stimulation is an important variable for optimal tremor control with maximal benefit achieved with 100 to 130 Hz in most patients. Second, thalamic DBS provides tremor benefit in a graded manner and is not an all-or-nothing phenomenon.

Adult↗