Joelle Mast

A new statistic for steady-state evoked potentials ☆

Steady-state evoked potentials are often characterized by the amplitude and phase of the Fourier component at one or more frequencies of interest. We introduce a new statistic for the evaluation of these Fourier components. This statistic, denoted T2circ, is based on the same physiologic assumptions concerning the sources of variability of a Fourier component that are made in the use of the Rayleigh phase-coherence statistic as well as the standard T2 statistic (Hotelling 1931) for multivariate data. However, the T2circ statistic also exploits the relationship between the real and imaginary components of Fourier estimates, which is not exploited by T2, and utilizes amplitude information, which is ignored by the Rayleigh criterion. For these reasons, the T2circ statistic is more efficient than previously used criteria for detection and quantitation of steady-state responses, both in principle and in practice.

Fluctuations of steady-state VEPs: interaction of driven evoked potentials and the EEG

We performed a detailed analysis of the variability of a steady-state human evoked potential (EP) and the spectral properties of the simultaneously recorded electroencephalogram (EEG). This allowed us to determine whether the background EEG was influenced by the evoked potential stimulus, and to what extent variability of evoked potential estimates is simply due to the addition of the background EEG. Steady-state visual evoked potentials (VEPs) were elicited by a checkerboard undergoing contrast-reversal modulation at 1 of 3 fundamental frequencies f: 5.0 Hz, 7.5 Hz, and 10.0 Hz. To a first approximation, the evoked potential (at frequency 2 f) and the undriven components of the EEG combined linearly. However, two kinds of interactions were present: (i) patterned visual stimulation decreased the power in the undriven EEG in the 5-17 Hz range by as much as a factor of 2; (ii) superimposed on this overall effect of pattern stimulation, there were changes in the EEG power at specific harmonics of the input frequency. Power increased by as much as 6-fold at the stimulus reversal rate (2 f) and its second harmonic (4 f). These findings imply a complex non-linear interaction between the visual input and the EEG.

New horizons for robot-assisted therapy in pediatrics.

The field of rehabilitation robotics has grown substantially during the past 15 yrs. Studies of upper limb robot-assisted therapy for adults with moderate to severe hemiparesis after stroke have shown significant gains compared with usual care in isolated control, coordination, and strength in the paretic arm (J Rehabil Res Dev 2006;43:171-84; Top Stroke Rehabil 2007;14:22-44; Neurorehabil Neural Repair 2008;22:111-21). While attempts to increase the understanding of the key active ingredients of these interventions continue, researchers have recently extended their focus to children with neurologically based movement disorders arising from cerebral palsy and acquired brain injury or stroke. This studys aim was to provide a narrative review that highlights recent pediatric studies of robot-assisted therapies for the upper and lower limbs. Potential benefits will be discussed, as well as challenges and needs for future development.

Robot-assisted task-specific training in cerebral palsy

Our goal was to examine the feasibility of applying therapeutic robotics to children and adults with severe to moderate impairment due to cerebral palsy (CP). Pilot results demonstrated significant gains for both groups. These results suggest that robot‐mediated therapy may be an effective tool to ameliorate the debilitating effects of CP and provide new opportunities for reducing impairment and improving coordination.

Comparison of Measures of Visual Acuity in Infants: Teller Acuity Cards and Sweep Visual Evoked Potentials

Purpose: This study compares the development of acuity in the same infants during one testing session using Teller acuity cards (TAC) and sweep visual evoked potentials (sVEP). We asked whether different testing methods in two centers would produce different developmental time courses. Methods: Forty-eight infants were tested in two centers. The standard procedure for TAC was used. For sVEP acuity, the amplitude response curve derived from time-locked cortical activity was used to extrapolate to zero response, giving an acuity estimate for each infant. Results: sVJEP acuity was generally higher than TAC acuity. The rate of development was steeper for TAC than sVEP acuity with TAC starting at a much lower level. The ratio of sVEP to TAC acuity decreased exponentially with age reaching an asymptote of about 1.44 at 6 months. Conclusions: Results were indistinguishable between centers suggesting that comparison of acuity measures obtained using variations of these methods across centers is possible.

Felbamate for Refractory Infantile Spasms

etiology of the vasculopathy and an early diagnosis can be achieved with appropriate therapy initiated. The incidence of HIV associated varicella zoster vasculopathy may be greater than recognized. Our patient had a radiologic infarct before the eruption of a rash. Skin manifestations of varicella zoster infection may be absent or occur after the onset of central nervous system disease.2 At present, interventions for varicella zoster central nervous system vasculopathy have limited impact. With an ability to determine the etiologic agent of vasculopathy in pediatric AIDS earlier, more aggressive and novel therapeutic interventions including foscarnet sodium may be explored.

The effect of random or sequential presentation of targets during robot-assisted therapy on children

BACKGROUND Robot assisted upper extremity therapy has been shown to be effective in adult stroke patients and in children with cerebral palsy (CP) and other acquired brain injuries (ABI). The patients active involvement is a factor in its efficacy. However, this demands focused attention during training sessions, which can be a challenge for children. OBJECTIVE To compare results of training requiring two different levels of focused attention. Differences in short term performance and retention of gains as a function of training protocol as measured by the Fugl-Meyer (FM) were predicted. METHODS Thirty-one children with CP or ABI were randomly divided into two groups. All received 16 one hour sessions of robot-assisted therapy (twice a week for 8 weeks) where they moved a robot handle to direct a cursor on the screen toward designated targets. One group had targets presented sequentially in clockwise fashion, the other presented in random order. Thus, one group could anticipate the position of each target, the other could not. RESULTS Both groups showed significant functional improvement after therapy, but no significant difference between groups was observed. CONCLUSIONS Assist-as-needed robotic training is effective in children with CP or ABI with small non-significant differences attributed to attentional demand.

Pediatric Anklebot: Pilot clinical trial

We are currently examining the therapeutic efficacy of the pediAnklebot, an impedance-controlled low-friction, back-drivable robotic device that trains the ankle of neurologically impaired children of ages 6-10 years old. In this paper, we present the first clinical results from a small feasibility study involving 4 children with Cerebral Palsy. The children used the pediAnklebot in seated position to train their ankle twice per week for a total of 6 weeks (12 sessions). The initial results indicate an improvement of the ankles functions including its pointing abilities and gait speed. The observed clinical outcome reinforces our confidence that the pediAnklebot, driven by our adaptive, assist-as-needed, robotic therapy can harness plasticity to guide habilitation during childhood.