Shaky hands can tame the mouse

Updated: Mar 28 2005, 05:30am hrs
Precisely moving a cursor with a mouse is difficult with a hand that shakes because of motor impairment. Now an IBM researcher has invented an inexpensive adapter that minimises the effect of such tremors.

Tens of millions of people worldwide experience involuntary hand movements because of conditions like Parkinsons disease and essential tremor.

The adapter, which is the size of a hand-held calculator, plugs in between the mouse and the computer. A microprocessor within the device takes the motion data that normally goes to the computer and applies an algorithm that filters out all the high-frequency motion caused by the tremor.

It leaves the steady part of the motion alone, said James L Levine, the research staff member at IBM who invented the device. The adapter can be switched off so that others can use the mouse in the standard way.

The mouse filter is being offered on the Web for about $100 by a small British electronics firm, Montrose Secam (montrosesecam.com). I was trying to find a solution for my own tremor, which I inherited from my father, said James Cosgrave, a director of the company. When I switch on this adapter, I can use the mouse as well as the average person.

The mouse adapter has several controls, including one that rejects the extra mouse clicks of twitchy fingers. Another control makes it easier to double-click, a motion that can be difficult for many people with motor-control problems.

Levine became interested in the problem of using a mouse about three years ago at a workshop on information technology for older people. I remembered an incident with an uncle of mine who tried to use our computer, and he couldnt do it because he had so much tremor, he said.

Levine is an experimental physicist with a specialty in instrumentation. Thats exactly what this problem required measuring something when there is the noise of hand tremor so it was natural to think of applying a digital filter, he said.

To test the device, Levine called on Cathy Bodine, who directs a program at the University of Colorado School of Medicine in Denver that works with people with disabilities. Bodine contacted a local tremor group as well as a national support group to recruit people who could identify crucial properties they wanted in the prototype, and then test these properties.

The participants had to click on buttons on the screen, she said, opening and closing programs, as well as drawing the letter X with the device, both with the filter on and off. There was a huge difference between using the filter and not using it.

Meanwhile, in England, Cosgrave was trying to find a solution to his own difficulties with a computer mouse. Cosgrave, a retired airline pilot who continues to fly a small airplane, said his tremor had not interfered with his abilities in the cockpit. But it causes the cursor on my computer to dance around the screen with a mind of its own, he said.

Clicking on small boxes is particularly difficult. The little points you have to click on, I cant find those, he said, but when I switch on the adapter, its a different matter altogether.

Anne Eisenberg / NY TIMES