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Aphasia: (also called dysphasia) defect in the expression and comprehension of language caused by damage to the temporal and the frontal lobes of the brain. Aphasia can be caused by a head injury, a tumour, a stroke, or an infection. Symptoms vary with the location and extent of the brain tissues involved.

Damage to the frontal lobe may result in Broca aphasia. Individuals with this form of aphasia are able to comprehend speech but have great difficulty expressing their thoughts. People with Broca aphasia speak in short phrases that include only nouns and verbs (telegraphic speech). Individuals with Wernicke aphasia, which may result from damage to the temporal lobe, speak in long, garbled sentences (word salad) and have poor speech comprehension. Global aphasia may result from extensive brain damage. Individuals with global aphasia exhibit symptoms of both Broca and Wernicke aphasia.

Speech therapy may be useful to treat aphasia. In some instances, improvement may be due to assumption of some language functions by other areas of the brain; recovery is usually incomplete, however. (From Encyclopaedia Britannica Deluxe Edition 2004)

Apraxia the inability to carry out useful or skilled acts while motor power and mental capacity remain intact. Apraxia is usually caused by damage to specific areas of the cerebrum. Kinetic, or motor, apraxia affects the upper extremities so that the individual cannot carry out fine motor acts, such as turning a key in a lock, even though there is no muscle weakness.

Ideational apraxia is characterized by the inability to formulate a plan of action. A plan is never fully organized, and the part that is organized cannot be remembered long enough to be performed. Portions of an act may be completed in an improper sequence. The individual may strike a match, for example, to light a campfire but then will hold the match until it burns his fingers. This type of apraxia is usually caused by a lesion of the cerebral cortex.

Ideokinetic apraxia is caused by an interruption of impulses in the association tracts of the nervous system, so that there is no coordination between ideation and motor activity. An affected individual will complain, for example, that he cannot use his hand, but then he will slap a mosquito with it. People with ideokinetic apraxia are unable to perform certain acts (e.g., whistling or making a fist) upon command but are able to do so automatically. Ideokinetic apraxia is usually caused by a lesion in the supramarginal gyrus of the cerebral cortex.

Constructional apraxia, typically caused by a lesion in the right cerebral hemisphere, is the inability to construct elements in the correct fashion to form a meaningful whole—e.g., being unable to build a structure with blocks or to copy a design. (From Encyclopaedia Britannica Deluxe Edition 2004)

Athetosis: Slow, purposeless, and involuntary movements of the hands, feet, face, tongue, and neck (as well as other muscle groups). The fingers are separately flexed and extended in an entirely irregular way. The hands as a whole are also moved, and the arms, toes, and feet may be affected. The condition is usually caused by malfunctioning of the basal ganglia of the cerebrum. The movements may or may not continue during sleep. They cannot be arrested for more than a moment by willpower and are aggravated by voluntary movements. (From Encyclopaedia Britannica Deluxe Edition 2004)

Nerve signals are the electrical currents we use to control our muscles. Nerve signals cause contractions within the muscle and those contractions create electromyographic (EMG) signals which can be measured in microvolts (μV). The sensors which are placed on the skin to detect these signals are called EMG sensors.

When the spinal cord, or any other part of the neuromuscular system is impaired by accident or condition (such as multiple sclerosis, ALS or cerebral palsy) or by events and influences such as surgery and anaesthesia, those electrical currents are impaired - but frequently are not completely shut down. Even in paralyzed areas (such as an arm or leg), usable EMG signals can often be detected within specific muscles.

In these cases, NeuroSwitch aims to utilize these signals to enable the person to control Assistive Technology and designated computer programs.

In the diagram, nerve-induced signals captured from the skin on the forearm by the three white EMG sensors are collected and filtered by the black box, a TAI NeuroEDUCATOR EMG monitor, and fed into the computer, where NeuroSwitch further filters and analyses the signals, and turns them into commands to control programs and attached electronic and robotic devices. 

The key to the success of the NeuroSwitch system is in its patented algorithms which enable the system to respond in real-time to any change in a person's neuromuscular state.

As you will know, people with disabilities experience frequent and often substantial neuromuscular fatigue, change in response, and neuromuscular states including Spasticity and athetosis

Spasticity - a state of increased muscular tone in which abnormal stretch reflexes intensify muscle resistance to passive movements. (Definition from the National Institutes of Neurological Disorders and Stroke).