Brain Research, 146 (1978) 159-164 '.~ Elsevier/North-Holland Biomedical Press
159
Sensitivity of the human perioral reflex to parameters of mechanical stretch
CHARLES R. LARSON, JOHN W. FOLK1NS, MICHAEL D. McCLEAN and ERIC M. MULLER Department of Speech and Hearing Sciences, University of Washington Seattle, Wash., Department of Speech Pathology and Audiology, University of Iowa, Iowa City, Iowa and Department of Communicative Disorders, University of Wisconshl, Madison, Wisc. (U.S.A.)
(Accepted November 10th, 1977)
The perioral reflex may be important for motor control of the lips, but little is known regarding the mechanisms of this reflex. Since the lips are involved in a variety of motor activities, e.g. deglutition, mastication, speech and facial expression, a more thorough understanding of the perioral reflex in motor control is necessary. The recent findings that the perioral reflex amplitude is modulated during speech 1445 shows the utility of this reflex for the study of neural processes involved in motor control. Previous studies of perioral reflexes in humans have used mechanical 'taps' or electrical shock as the stimulus~,4, v. Although these methods have proven beneficial for describing many reflex properties, they have not quantified the adequate stimuli for the perioral reflex. Therefore, the purpose of the present study was to analyze the perioral reflex as a function of the physical properties of the mechanical stimulus. Four normal adult males, aged 28-32, served as subjects. The lips were stimulated mechanically with a position servo controlled electromagnet (Fig. I A). This instrument had a yield per applied unit force of less than 0.1 mm per Newton (N). A lip force transducer was developed from a stainless steel beam (7 c m x 0.8 cm x 0.2 cm) instrumented with strain gauges. One end of the beam was placed in the right corner of the mouth and the other end was fastened at a right angle to the end of the electromagnet. In this way, stimuli were applied to the corner of the mouth by movement of the electromagnet. Two stainless steel beams (2 c m x 12 cm × 0.2 cm) instrumented with strain gauges were placed between the upper and lower incisors to transduce jaw closing force. Electromyographic (EMG) reflexes were recorded from bipolar hooked-wire electrodes inserted into the orbicularis oris inferior muscle (OO1) on the right side. Subjects were seated with the head supported by a chin rest. The lip force transducer was positioned to extend the corner of the mouth approximately 3 mm from the resting position. The stimulus was applied in a lateral direction in the horizontal plane. Reflexes were elicited during two conditions of lip and jaw activation: (1) the subject applied no force on the transducers, i.e., both lips and jaw were passive and (2) the subject maintained a force of approximately 3 N with the jaw and 0.5 N with the lips. The electromagnet was programmed to either stretch or release stretch of the corner
160
lectromagnet
I~~"
/1// /lt t
o e /Transducer ansaucer Lip Force
* Jaw
Force
Transducer
mm
STRETCH
~e
.
,0"~,%% 4,
. L,'/: .~
, r~.'
.. "i "
,
-
. -
RELEASE 3
mm
STRET CH
q
RELEASE
,~ .~ 'c ~
I0
msec
Fig. 1. A: mechanical stimulator and force transducers. B: reflexes elicited by stretch and release stimuli of 1.0 and 3.0 mm amplitude while the subject was contracting the lip and jaw muscles isometrically. Shown with each stimulus is rectified OOI EMG averaged for 20 reflexes. When the stimulator was programmed for high velocity ramps, minor ringing followed movement of the stimulator rod and coil to the prescribed position.
161
A
• •
Isometric Passive
O
3,0 mm
o~ v 100.
t
75.
159
Sensitivity of the human perioral reflex to parameters of mechanical stretch
CHARLES R. LARSON, JOHN W. FOLK1NS, MICHAEL D. McCLEAN and ERIC M. MULLER Department of Speech and Hearing Sciences, University of Washington Seattle, Wash., Department of Speech Pathology and Audiology, University of Iowa, Iowa City, Iowa and Department of Communicative Disorders, University of Wisconshl, Madison, Wisc. (U.S.A.)
(Accepted November 10th, 1977)
The perioral reflex may be important for motor control of the lips, but little is known regarding the mechanisms of this reflex. Since the lips are involved in a variety of motor activities, e.g. deglutition, mastication, speech and facial expression, a more thorough understanding of the perioral reflex in motor control is necessary. The recent findings that the perioral reflex amplitude is modulated during speech 1445 shows the utility of this reflex for the study of neural processes involved in motor control. Previous studies of perioral reflexes in humans have used mechanical 'taps' or electrical shock as the stimulus~,4, v. Although these methods have proven beneficial for describing many reflex properties, they have not quantified the adequate stimuli for the perioral reflex. Therefore, the purpose of the present study was to analyze the perioral reflex as a function of the physical properties of the mechanical stimulus. Four normal adult males, aged 28-32, served as subjects. The lips were stimulated mechanically with a position servo controlled electromagnet (Fig. I A). This instrument had a yield per applied unit force of less than 0.1 mm per Newton (N). A lip force transducer was developed from a stainless steel beam (7 c m x 0.8 cm x 0.2 cm) instrumented with strain gauges. One end of the beam was placed in the right corner of the mouth and the other end was fastened at a right angle to the end of the electromagnet. In this way, stimuli were applied to the corner of the mouth by movement of the electromagnet. Two stainless steel beams (2 c m x 12 cm × 0.2 cm) instrumented with strain gauges were placed between the upper and lower incisors to transduce jaw closing force. Electromyographic (EMG) reflexes were recorded from bipolar hooked-wire electrodes inserted into the orbicularis oris inferior muscle (OO1) on the right side. Subjects were seated with the head supported by a chin rest. The lip force transducer was positioned to extend the corner of the mouth approximately 3 mm from the resting position. The stimulus was applied in a lateral direction in the horizontal plane. Reflexes were elicited during two conditions of lip and jaw activation: (1) the subject applied no force on the transducers, i.e., both lips and jaw were passive and (2) the subject maintained a force of approximately 3 N with the jaw and 0.5 N with the lips. The electromagnet was programmed to either stretch or release stretch of the corner
160
lectromagnet
I~~"
/1// /lt t
o e /Transducer ansaucer Lip Force
* Jaw
Force
Transducer
mm
STRETCH
~e
.
,0"~,%% 4,
. L,'/: .~
, r~.'
.. "i "
,
-
. -
RELEASE 3
mm
STRET CH
q
RELEASE
,~ .~ 'c ~
I0
msec
Fig. 1. A: mechanical stimulator and force transducers. B: reflexes elicited by stretch and release stimuli of 1.0 and 3.0 mm amplitude while the subject was contracting the lip and jaw muscles isometrically. Shown with each stimulus is rectified OOI EMG averaged for 20 reflexes. When the stimulator was programmed for high velocity ramps, minor ringing followed movement of the stimulator rod and coil to the prescribed position.
161
A
• •
Isometric Passive
O
3,0 mm
o~ v 100.
t
75.
