Questions & Answers

7.4) What are the two basic selection methods used with control interfaces?

7.5) What are the scanning formats that can be used to accelerate scanning? Describe them. (See Cook et al, pp. 230-233)

7.25) What are the primary considerations that would lead to the choice of speech recognition as an alternative direct selection method?

7.28) What are the most common alternatives to a computer mouse? List at least one advantage and one disadvantage of each.

7.34) List three types of modifications to keyboards and pointing devices, and give an example of the problems that each solves.

7.35) (Optional question for the engineering students) Describe the three different selection techniques used with scanning and directed scanning. Which one provides the user with more control and why?

7.38) Describe distributed and integrated control. What are their advantages and disadvantages?

5.7) A person’s disabilities and abilities often depend on his/her medical condition. a) A person is known to have spinal cord injury (SCI) at the C5-C6 level. What does this mean in terms of this person's probable motoric and sensory abilities and limitations? b) Repeat part (a) for a person with multiple sclerosis. Include the prognosis of the second individual in contrast to the person with SCI.

solution :

Spinal cord injury (SCI) at the C5-C6 level affects Low-Cervical Nerves. This corresponds to nerves control arms and hands. This person may be able to breathe on its own and speak normally.

Motor and sensory abilities and limitations in person with spinal cord injury (SCI) at the C5-C6 level

Abilities

· This patient can raise his or her arms and bend elbows.

· Should be able to bend wrists back

· Can speak and use the diaphragm, but breathing will be weakened

· May also be able to drive an adapted vehicle

Limitations

· Likely to have some or total paralysis of wrists

· Paralysis in hands, trunk, and legs, typically

· Will need assistance with most activities of daily living, but once in a power wheelchair, can move from one place to another independently

· Little or no voluntary control of bowel or bladder, but may be able to manage on their own with special equipment

Motor and sensory abilities and limitations in person with multiple sclerosis (MS)

Abilities

· The person with MS may be able to accomplish much in the early part of the day but may require assistance with the same tasks in the afternoon

· The person can walk but at a slow pace may require assistance

· Can do math calculation but not at the same speed the person without MS can do

Limitations

· A total lassitude and lack of physical energy

· Difficulty with walking and coordination

· Problems with normal bowel and bladder function leading to constipation or fecal incontinence or frequency and urgency to urinate

· Difficulty focusing on objects, with resultant blurring or even double vision.

· Difficulty with attention and concentration, slow processing of information, impairment in executive functions

· Difficulty in performing activities of daily living due to tremor

· Difficulty moving or controlling the movement of the upper extremities

Prognosis of SCI vs MS

SCI prognosis

After swelling in the spinal cord decreases and any necessary surgery is performed, patients can stabilize and begin the recovery process.

· Recovery will focus on stabilization of the injured area of the spinal cord, but most injuries are permanent.

· Many people who experience a cervical spinal cord injury will require permanent, 24-hour care for the remainder of their lives.

MS prognosis

Multiple sclerosis is rarely fatal and life expectancy is shortened by only a few months. The average life span often stated was 25 - 35 years. It is also reported that as many as 1/3 of all MS patient live life without any persistent disability, and suffer only intermittent, transient episodes of symptoms.

So considering these factors it seems that the prognosis of MS is better than that of SCI.

5.10) A 21-year-old female who has muscular dystrophy requested assistance with computer access, particularly for writing, using spreadsheets, and playing computer games. She lacks movement in all four extremities except for some wrist and finger movements. With her left hand, she is able to reach about 6 in. past her midline. With her right hand, she is able to reach only 2 in. past her midline. Both her hands can reach out about 8 in. from the body. If given wrist support, she has good control of both index fingers. Based on this description, sketch the work area that she appears able to reach with her two hands. Describe the adaptations to a standard or contracted keyboard that she would need to access her home computer. For additional information, consult "The Closing the Gap Product Directory," the "Cooperative Electronic Library on Disability," and the suggested reading materials listed at the end of this chapter.

5.19) (Optional) For persons with good head control and little else, the Head Master (by Prentke Romich Co., Wooster, OH) has been used to emulate the mouse input signals for a computer. The Head Master consists of a headset connected to the computer by a cable. The headset includes a sensor that detects head movements and translates such movements into a signal interpreted as movements of the mouse. A puff and sip pneumatic switch is also attached to headset and substitutes for clicking of the mouse. Based on this brief description of the Head Master, draw a block diagram of how this device might work and what basic components that might be needed in the Head Master. Include in your block diagram the ultrasonic signal source, detectors, timers, and signal processors that would be needed.