INTRODUCTION

The population of individuals with profound and multiple disabilities (PMD) consists of people with severe to profound intellectual disability and significant motor impairment. Individuals with PMD often have limited verbal communication abilities, and instead rely on gestures and vocalizations. Additional challenges can be present in learning, mobility and attention [1].

Enabling individuals with PMD to exert a greater degree of control over their environment can enhance their self-determination and form the basis for physical, occupational and communication therapies. One form of self-determined response is controlling access to a preferred source of stimulation, such as music [1]. To meet this need, we are developing a switch-activated MP3 player that can be used to teach cause and effect or provide motivating feedback to individuals with PMD. When a user presses the switch, music will be played for a set amount of time (between 2 and 60 seconds) through attached headphones or a speaker. Each time the switch is activated, the music will play from the point in the song where it previously stopped. When one song ends, the next song will automatically start playing.

RELATED RESEARCH

There is limited prior research in this area. A total of 12 participants (ranging in age from 4 to 18 years old) received intervention in seven studies conducted by Lancioni and colleagues [2–8]. In each study, the therapeutic aim was to enable participants to control access to preferred stimulation (e.g., music, songs, vibration, and/or lights) through switch activation. All these studies used a single-subject design with baseline and intervention phases. Switch activations that occurred during baseline phases did not produce any stimulation, whereas switch activations that occurred during the intervention phase produced 4 – 10 seconds of stimulation (e.g., music, vibration, lights). In each study, the dependent variable was the number of switch activations per session. Across all studies, switch activations were roughly three times higher during intervention sessions than during baseline sessions [1].

There is one relevant product on the market, the Cause/Effect Boombox from RJ Cooper and Associates , shown in Figure 1. The Boombox contains an MP3 player with a built-in timer, a 3" button, and a switch jack for an external switch. In "timed mode", the music plays for a desired number of seconds, then pauses. Songs are stored on a removable mini-SD card. The switch-activated MP3 player we are developing differs in the following ways:

• The Boombox does not have an audio jack for use with headphones, which makes it less useful in classroom settings.
• The Boombox is too large for use in mobile/wearable applications.
• The Boombox does not record any usage data for documenting clinical progress.

METHODS

The switch-activated MP3 player is shown in Figure 2. The device consists of a battery, a speaker, a microprocessor and a switch interface. Any switch with a 3.5mm plug can be plugged into the device. When the switch is activated, music is played for a set amount of time (between 2 and 60 seconds). Each time the switch is activated, the music plays from the point in the song where it last stopped. When one song ends, the next song automatically starts playing. A flowchart of the system's operation is shown in Figure 3.

Songs are loaded onto an SD card in MP3 format. Up to 10 songs can be loaded onto the card. The clinician can set the music volume and the duration that music is played. A video showing the current prototype is available on YouTube .

RESULTS

"Jane" is a 4-year-old student at the Western Pennsylvania School for Blind Children (WPSBC) . Her diagnoses and conditions include moderate ASD, cortical visual impairment, multiple congenital anomalies, trach dependency, and hypotonia. She currently accesses a variety of switches depending on her positioning and activity. Jane can use a jellybean, grasp and light-up gel switch. Her switch activations have been used for environmental control, switch toys, single/sequential message speech-generating devices, trials with powered mobility and some tape-recorded music. Her response time for switch activation can be as long as 60 seconds and sometimes requires hand-over-hand assistance.

Jane has been using the switch-activated MP3 player since September 2018. Music has been and continues to be a motivator for her and she especially enjoys listening to music from the Bubble Guppies TV show as well as current "pop" songs. When accessing a switch paired with personally-selected music through the MP3 player, she has been able to independently activate the switch within 10 seconds. Jane's level of alertness appears increased, as she rarely becomes sleepy during the activity and she often rocks/moves her body in response to the music. The music was also able to generate incidental/increased peer interaction, as the ambulatory students approach her when the music is playing.

DISCUSSION

The switch-activated MP3 player gives clinicians a simple mechanism for providing customized musical feedback when teaching switch activation skills. There is one device on the market that provides similar functionality, but its size precludes mobile use. The switch-activated MP3 player remains a work in progress. Planned modifications to the device include:

• "Next Track" and "Previous Track" buttons that allow the clinician to move between songs. This would allow songs for multiple users to be stored on the same SD card.
• An enclosure that allows for access to SD card reader and other controls while protecting the microprocessor and other components. The current prototype has no "box" for the microprocessor, leaving the electronics completely exposed. In order to protect the electronics, the SLP positions a switch and a speaker (both connected to the prototype with long cords) next to the child and leaves the remainder of the prototype out of the child's reach.
• Data recording to SD card. The current prototype does not record any data during use, but information about when each switch press occurs would be useful both clinically and for research purposes. Documenting the number of switch presses during each session would allow the SLP to track the child's progress over time. Similarly, an objective record of switch activations would reduce a potential source of bias in any empirical evaluation of the system.
• Additional operating modes. The current prototype has a single operating mode, in which the music plays for a predetermined amount of time after each switch activation. A "momentary" operating mode will play music as long as the switch is activated. A "latched" operating mode will toggle between playing and pausing the music with each switch activation.