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Clawhand

Impaired hand function is one of the most frequently persisting consequences of stroke. Advanced rehabilitation techniques, may improve hand function in stroke survivors, however, many of these techniques, including robot therapy, require some residual movement of the impaired arm or hand and therefore are not applicable to severely disabled stroke survivors.
Electrical stimulation at discrete skin locations on the foot sole of stroke patients with a Babinski sign has shown to inhibit the plantar grasp reflex and to modulate topographically discrete cutaneous reflexes, with gait-related mechanical properties.

Since spinal reflexes during rhythmic upper limb movements present similar phase-dependent modulations, we postulate that an analog, state-dependent condition, with topographically discrete cutaneous reflexes, exists for the clawing hand, during quadrupedal walking. We, therefore, hypothesize that quadrupedal walking emerges as an adaptation to the instability of the trunk and can be considered as a temporary status of human devolution based on neurological damage. Using a stimulus of rectangular pulses (1 ms duration, 200 Hz frequency) through a constant current stimulator, we could facilitate hand lift and placing reactions, mimicking crawling, in 3 stroke patients with a nonfunctional, spastic, claw hand. On this basis we propose a completely new robot design for upper limb rehabilitation, supporting different types of quadrupedal walking and initiated through palmar hand skin stimulation with the aim of developing gross motor control of a severely spastic hand.

Itching and its relation to spasticity

From the thalamus, the pruritic nerve impulse is transmitted to different regions of the brain. Functional neuroimaging studies have identified many different subcortical and cortical areas involved in itch. These areas relate to the sensory perception of itch, evaluation of the sensation, motivation, attention, emotion, and motor functions, such as motor planning. In addition, the precuneus, involved in memory, visual-spatial awareness and consciousness, is activated after acute itch stimulation. In contrast, no activation of the precuneus was identified, after the application of an acute pain stimulus. Once scratching begins, imaging shows activation of the reward system due to the feeling of pleasure. During this short sensation stroke patients experience a sudden, extreme sensation of spasticity reduction.

Freezing in Parkinson from a Bellman equation point of view.

Dynamic Programming is a class of algorithms, which seek to simplify complex problems by breaking them up into sub-problems and solving the sub-problems recursively (by a function that calls itself). We try to look at freezing in Parkinson's disease from a Bellman equation point of view to understand the interplay of neurotransmission. At this point, we introduce the notion of active agents that sense a subset of states and can change others. We want to quantify this exchange with the environment with sensory, and action or control signals. We will describe sensory sampling as a probabilistic mapping, in the presence of sensory noise. Control can be represented by treating 'action' as a state, which we will call hidden states because they are not sensed directly. From the point of view of reinforcement learning and optimum control theory, action depends on sensory signals, where this dependency constitutes a policy.

EEG coherence training after stroke

Neurofeedback training of motor cortex activations with brain-computer interface systems has the potential to enhance recovery in stroke patients.

We tried in one of our patients to train resting-state functional connectivity associated with motor performance.

“EEG Connectivity” is a property of the “excitable medium” of axons, synaptic rise and fall times and burst durations of neurons and is defined by the magnitude of coupling between neurons. Magnitude is typically defined by the strength, duration and time delays as measured by electrical recording of the electrical fields of the brain produced by the excitable medium. Connectivity does not occur at the speed of light and is best measured when there are time delays, in fact, volume conduction of electricity is not a property of the excitable medium and it occurs at zero time delay. This important property of the excitable medium sources of the EEG versus the electrical properties means that time delays determine whether or not and to the extent that an excitable medium is responsible for the electrical potentials measured at the scalp surface. Volume conduction defined at zero phase lag is the electrical personality and lagged correlations and is the excitable medium personality of EEG.

The concerned stroke patient trained alpha-band coherence between his hand motor area and the rest of the brain using neurofeedback with source functional connectivity analysis and visual feedback. The patient with chronic stroke learned to enhance alpha-band coherence of his affected primary motor cortex in 7 neurofeedback sessions applied over one month. Coherence increased specifically in the targeted motor cortex and in alpha frequencies. This increase was associated with clinically meaningful and lasting improvement of motor function. These results provide proof of concept that neurofeedback training of alpha-band coherence is feasible and behaviorally useful

Start of the treatment: the patient has difficulties to keep the ball in the center

End of the treatment: the patient can keep the ball more in the center