Biology 347 General Physiology Lab

Auditory and Visual Reflexes

 

Objectives

 

 

Introduction

During our day-to-day lives we detect changes in the environment and react appropriately. An external stimulus is detected by one or more neurons, which sends the sensory information to the central nervous system, where it is processed. If a motor response is initiated, it usually involves a series of action potentials which produce a muscle contraction and a movement of one or more parts of the body. A simple reflex is perhaps the easiest of this type of stimulus-response reaction. A loud sound or something flying at your eye makes you blink, while a tap on the tendon under the knee cap produces the knee-jerk (or myotactic) reflex.

 

A simple reflex like the myotactic reflex is produced via single synapses between sensory axons and motor neurons. The required circuitry for this reflex is confined to the spinal cord. Sensory information also ascends to higher centers, but the brain is not necessary or required to perform the reflex. More complex reflexes usually involve additional (inter-) neurons and more than one population of motor neurons. Thus, more neurons and synapses are involved, which usually results in a longer delay between stimulus and response and often a more complex response. One example of such a complex response is the flexion withdrawal reflex, where a noxious stimulus to one leg causes withdrawal of the stimulated leg and extension of the other.

In this lab you will study the time taken between a stimulus and the response. These reaction time measurements will be made from an individual subjected to harmless visual and sound stimuli. In addition, the effect of priming and prediction will be examined.

 

Procedure: Equipment Set-up  

1.      Start the Labscribe software on your computer.

2.      Pull down the Settings menu. First select Human Nerve then select the Auditory-VisualReflexes-LS2 settings file.

3.       After a short time, LabScribe will appear on the computerscreen as configured by the Auditory-VisualReflexes-LS2 settings.

4.      Plug the event marker into Channel 3 on the iWorx unit.

 

Procedure: Reaction Time and Visual Cues

1.      Instruct the subject to:

€ Sit in a chair and face the computer screen.

€ Position a hand on the keyboard in a manner that enables the subject to push the Enter key as quickly as possible.

€ Watch the right side of the computer screen and quickly press the Enter key on the keyboard when the signal generated by the event marker first appears.

2.      Out of sight of the subject, another student should prepare to quietly press and release the button of the event marker. In this exercise, the subject will perform ten trials.

3.      Type <Subject¹s Name> Visual Cues in the Mark box that is to the right of the Mark button.

4.      Click on the Record button. Instruct the subject to press the Enter key on the keyboard to mark the recording as soon as he or she sees the visual cue on the right side of the computer screen.

5.      Instruct the subject that the exercise has begun and that a visual cue could appear on the screen at any time

6.      Use the event marker to deliver ten visual cues to the subject. The cues should not be less than five seconds nor more than ten seconds apart.

7.       After the tenth cue, click Stop to halt recording. Save your recording.

Procedure: Data Analysis

1.      Scroll to the beginning of the data recorded for Reaction Time a Visual Cues to display the first trial on the Main window.

2.      Use the Display Time icons to adjust the Display Time of the Main window to show both the visual cue made with the event marker and the mark made by the subject¹s response on the Main window.

3.      Click on the Analysis window icon in the toolbar or select Analysis from the Windows menu to transfer the data displayed in the Main window to the Analysis window.

4.      Look at the Function Table that is above the display of the Reaction Time channel displayed in the Analysis window. The mathematical function, T2-T1, should appear in this table. The value for T2-T1 is seen in the table across the top margin of the Reaction Time channel.

5.      Use the mouse to click on and drag a cursor to the onset of the signal used as the visual cue. Drag the other cursor over the mark made by the subject responding to the visual cue.

6.      Once the cursors are placed in the correct positions for determining the reaction time, record the value for T2-T1 in Table 1. Repeat this analysis for the remaining nine trails.

 

Procedure: Reaction Time and Auditory Cues

1.      Cover the computer screen with an opaque piece of construction paper to prevent the subject from seeing any signal on the screen as a visual cue.

2.      Instruct the subject to:

€ Sit in a chair in front of the computer keyboard.

€ Position a hand on the keyboard in a manner that enables the subject to push the Enter key as quickly as possible.

€ Listen for the click (sound) of the event marker as the other student presses the button and then press the Enter key as quickly as possible.

3.      Out of sight of the subject, another student should prepare to sharply tap the button of the event marker to create a auditory cue that is also recorded as a signal on the Reaction Time channel. In this exercise, the subject will perform ten trials.

4.      Type Auditory Cues in the Mark box that is to the right of the Mark button.

5.      Click on the Record button. Instruct the subject to press the Enter key on the keyboard to mark the recording.

6.      Instruct the subject that the exercise has begun and that an auditory cue could be heard at any time

7.      Use the event marker to deliver ten auditory cues to the subject. The cues should not be less than five seconds nor more than ten seconds apart.

8.      After the tenth cue, click Stop to halt recording. Save the recording.

9.      Record the reaction time, using the same procedure above in Data Analysis, in Table 2.

 

Procedure: Reaction Time and Prompted Auditory Cues

1.      Repeat the procedure for Reaction Time and Auditory Cues, with an additional step. Before each auditory cue is delivered, tell the subject to get ready to respond to the cue. It is best to use a one word cue before immediately clicking the event marker button.

2.      Record the reaction times in Table 3.

 

Procedure: Reaction Time and Predictable Auditory Cues

1.      Repeat the procedure for Reaction Time and Auditory Cues, with a predictable interval of five seconds between each auditory cue.

2.      Record the reaction times in Table 4.

 

 

 

Table 1: Reaction Time and Visual Cues

 

 

Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Trial 7

Trial 8

Trial 9

Trial 10

Reaction Time (ms)

 

 

 

 

 

 

 

 

 

 

 

Mean Reaction Time of Subject to Visual Cues: _______________________

 

 

 

 

Table 2: Reaction Time and Auditory Cues

 

 

Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Trial 7

Trial 8

Trial 9

Trial 10

Reaction Time (ms)

 

 

 

 

 

 

 

 

 

 

 

 

Mean Reaction Time of Subject to Auditory Cues: _______________________

 

 

 

Table 3: Reaction Time and Prompted Auditory Cues

 

 

Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Trial 7

Trial 8

Trial 9

Trial 10

Reaction Time (ms)

 

 

 

 

 

 

 

 

 

 

 

 

Mean Reaction Time of Subject to Prompted Auditory Cues: _______________________

 

 

 

Table 4: Reaction Time and Predictable Auditory Cues

 

 

Trial 1

Trial 2

Trial 3

Trial 4

Trial 5

Trial 6

Trial 7

Trial 8

Trial 9

Trial 10

Reaction Time (ms)

 

 

 

 

 

 

 

 

 

 

 

 

Mean Reaction Time of Subject to Predictable Auditory Cues: _______________________

 

 

 

 

Table 5: Class Data on Mean Reaction Times

 

 

Mean Reaction Time (ms)

Cue

Group 1

Group 2

Group 3

Group 4

Group 5

Group 6

Visual

 

 

 

 

 

 

Auditory

 

 

 

 

 

 

Prompted Auditory

 

 

 

 

 

 

Predictable Auditory

 

 

 

 

 

 

 

 

 

Questions and Conclusions

 

1.      How does the subject¹s mean reaction time to visual cues compare to his or her mean reaction time to auditory cues?

 

 

 

 

 

 

2.      What would cause a longer reaction time to one type of cue as compared to another?

 

 

 

 

 

 

 

3.      How do your subject¹s mean reaction times compare to those of other subjects?

 

 

 

 

 

 

 

 

4.      Do all subjects respond more quickly to the same cue?

 

 

 

 

 

 

 

5.      To which auditory cue did your subject respond most quickly?

 

 

 

 

 

 

6.      To which auditory cue did your subject respond to most slowly? For what reasons?

 

 

 

 

 

 

 

7.      Did your subject respond more quickly or more slowly to same auditory cue as the other members of the class?