Abstract
College students in two sections of a general psychology course participated in a demonstration of a simple neural circuit. The activity was based on a neural circuit that Jeffress proposed for localizing sounds. Students in one section responded to a questionnaire prior to participating in the activity, while students in the other section responded to the questionnaire after participating in the activity. Students who had participated in the activity reported greater understanding of the concept of a neural circuit and of how the brain can produce complex behavior. The activity may be a useful addition to previously published class simulations on neural functioning. Instructors may wish to use the activity in classes such as general psychology, sensation and perception, and physiological psychology.
The biological basis of behavior is a core aspect of both psychological science and of most introductory courses in psychology. It is important that students gain an understanding of how the nervous system relates to behavior, and to that end instructors may use class activities. Participation in activities may help students to learn and remember important concepts. When VanderStoep, Fagerlin, and Feenstra (2000) asked students to report the top 10 things they remembered from an introductory psychology course, they found that students tended to remember events such as watching videos or taking part in activities. In one of VanderStoep et al.’s two studies, a “demonstration of neuron firing” was the eighth most commonly reported event that students recalled from the class at the end of the semester.
The literature contains descriptions of several activities for helping students learn about neural structure and function. For example, Reardon, Durso, and Wilson (2000) asked students to represent excitatory and inhibitory input by holding up cards, while another student representing the neuron used a card to indicate whether the neuron reached threshold and fired or not. The activity demonstrated the concepts of temporal and spatial summation of input. Reardon et al. also described a demonstration of synaptic transmission that illustrated processes such as neurotransmitter release, receptor site stimulation, and reuptake of neurotransmitter substances.
A common theme in demonstrations of neural function is that students play the roles of neurons or parts of neurons. In a demonstration designed for a large introductory class, Hamilton and Knox (1985) involved 30 students in simulating the knee-jerk reflex. Students played the roles of different parts of the circuit (e.g., soma of the afferent neuron, muscle). Students used props or costumes to represent their roles. For example, students representing the afferent axon wore trash bags to represent myelin. Nearly 100% of the students indicated that they believed the demonstration would help them remember the material. In Felsten’s (2000) simulation of action potential propagation, students represented myelinated segments of axons. Students perceived the exercise as more helpful and engaging than the textbook in helping them to understand action potentials.
The previously reported activities provide useful ways to demonstrate concepts about neural function. In the present article, I describe an activity for illustrating the concept of a neural circuit. The goal is to provide students with a vivid illustration of how neurons work together to process information. The activity described in the present article is a unique addition to previously published activities because it simulates a neural circuit for a perceptual task.
Jeffress (1948) proposed a neural circuit that could code differences in time of arrival between the two ears and thereby localize sound sources. The proposed circuit involved a delay line originating from each ear. A delay line is a set of connected neurons, with additional delay added as each neuron transmits the signal to the next neuron in the line. Neurons in the delay line from each ear send input to a series of interneurons that serve to compare information coming from the left and right ears. The interneurons require stimulation from both the left and right delay lines simultaneously to reach threshold and send an action potential. The most important aspect of the circuit is that the particular interneuron that reaches threshold depends on the time of arrival difference between ears. If a particular sound reaches the left ear before the right ear, then the activated interneuron is closer to the right ear end of the circuit than to the left ear end. Jeffress suggested that the circuit might exist in an area of the midbrain.
Early investigators viewed the Jeffress (1948) model as an elegant solution for how relatively slow processing in neurons could resolve time differences as short as 10–20 microseconds (Schnupp, 2001). Although there is good evidence for the Jeffress model in birds (Grothe, Pecka, & McAlpine, 2010), research on other animals such as the guinea pig has indicated that the neural circuitry for representing time differences between ears may vary across species (Schnupp, 2001).
In this article, I describe how I demonstrate the Jeffress (1948) model in an introductory psychology class. The demonstration may provide a useful example of how a neural circuit can process perceptual information and thus help students gain a greater appreciation of brain function. I report data on how the activity may enhance students’ understanding of the importance of neural circuits.
Method
Participants
A total of 92 students at a midwestern public university volunteered to participate. Students had enrolled in one of the two sections of my general psychology course.
Materials and Procedure
All students completed a questionnaire that included ratings of their understanding of the following: Why it is important to know how neurons work, the concept of a neural circuit, and how the brain can produce complex behavior. The rating scale ranged from 1 for no understanding to 10 for complete understanding. In addition, the questionnaire included five true or false statements about neural circuits (e.g., a small number of neurons could produce a complex mental process).
I randomly selected one section of the course to complete the questionnaire before participating in the neural circuit activity (before section). Students in the other section completed the questionnaire after participating in the activity (after section). I explained to students in both sections that participation in the activity was a normal part of the course, but that they could choose whether or not to complete the questionnaire and allow me to use their responses for research purposes. I distributed an informed consent statement. Students indicated their consent by depositing their completed questionnaires in a box outside the classroom. A total of 44 students in the before section (85% of enrolled students) and 48 students in the after section (81% of enrolled students) returned the questionnaires.
I asked students to arrange themselves into three rows in the hallway outside the classroom. The two outside rows represented input from the left and right ears, while the middle row represented interneurons. Each left ear neuron and each right ear neuron sent input to a designated interneuron in the middle row. I played the role of the sound source by stimulating the first neuron in the rows for the right and left ears. See Figure 1 for a diagram of the neural circuit. I asked students to make sure that they lined up evenly so that it was clear which person in the middle row matched up with the person in the outside rows. I also made sure that the students spaced themselves evenly so that they could touch the next person in line on the shoulder.
Diagram of Jeffress neural circuit demonstration. Each circle represents a neuron simulated by a student. Arrows indicate excitatory connections. Transmission of a message is indicated by tapping a student on the shoulder.
I then provided instructions to students representing the lines of neurons coming from the left and right ears. I asked students in these two lines to face in opposite directions. I explained that I would represent the sound reaching the left ear and the right ear by tapping the shoulder of the first student in each line. I instructed all students in the left and right ear rows that they would reach threshold and send their outgoing messages after receiving a shoulder tap from the person behind them in line. Each student was to send outgoing messages (via shoulder taps) simultaneously to the next person in line and the corresponding person in the middle row. To represent this pattern of stimulation, I demonstrated how the students were to use the left hand to tap the shoulder of the next student in line while simultaneously using the right hand to tap the shoulder of the person standing in the middle row.
I instructed students in the middle row that they needed to have simultaneous input (shoulder taps) from both of their corresponding neurons in the left and right ear rows in order to reach threshold. I told students in the middle row to simulate reaching threshold by raising both hands over their heads (i.e., making a “touchdown” signal).
I asked students in the outside rows to proceed at an even, slow pace, leaving their hands on the shoulder of the next person in line and the person in the middle row for about 2 sec. I reminded students in the middle row to indicate reaching threshold if they had hands on both shoulders at the same time, even if it was only for a short time. I conducted a practice run for each of the outside rows.
I explained to students that although sound travels quickly, it has a finite speed. Therefore, if the sound comes from the left side of the body, it reaches the left ear before it reaches the right ear. I simulated the sound by tapping the shoulder of the first person in the left ear row. I then ran to the other end of the formation to tap the shoulder of the first person in the right ear row. The students observed that when the sound arrived at the left ear first, the middle row neuron that reached threshold (and made the touchdown signal) was closer to the right ear end of the circuit than to the left ear end.
After simulating the sound arriving at the left ear first, I then started the sound at the right ear first, resulting in a middle row neuron close to the left ear end reaching threshold. After this second demonstration, I asked students what would happen if the sound stimulated both ears at the same time, as would happen if the sound source came from directly in front or directly behind the person. Students responded correctly that a middle row neuron close to the middle of the line would reach threshold. I ended the activity by pointing out that if a simple neural circuit with a small number of neurons could determine the direction of a sound, then more complex circuits with larger numbers of neurons could perform more complex functions. The entire activity required approximately 20–30 min of class time.
Results
The before and after sections both scored highly on the true–false items, with means above 4 out of 5 for both groups. As the true–false questions were apparently simple enough for students to answer based on previous knowledge, their performance on these items did not constitute a useful measure of learning from the demonstration.
I conducted independent samples t tests to compare the two sections on the three ratings of level of understanding of neural function. I used the Bonferroni method to adjust the α level to .0125 to correct for the four comparisons (the three ratings and the intended comparison of performance on the true–false items).
Although students in the after section (M = 8.44, SD = 1.88) provided a higher mean rating than students in the before section (M = 7.30, SD = 2.66) on understanding “why it is important to know how neurons work,” the difference was not significant with the Bonferroni correction, t(76.73) = 2.36, p = .02, d = .50 (degrees of freedom and significance level reflect adjustments for unequal variance). Students in the after section (M = 8.21, SD = 1.86) provided significantly higher ratings than students in the before section (M = 4.84, SD = 2.54) on understanding “the concept of a neural circuit,” t(90) = 7.30, p < .001, d = 1.51. Similarly, the mean rating was significantly higher in the after section (M = 7.58, SD = 2.43) than in the before section (M = 5.55, SD = 2.28) on understanding “how the brain can produce complex behavior,” t(90) = 4.14, p < .001, d = .86. The latter two differences were large effect sizes as indicated by Cohen’s d.
Discussion
Students who participated in the activity reported having greater understanding of the concept of a neural circuit and of how the brain can produce complex behavior compared to students who had not yet participated in the activity. Results did not provide support for increased knowledge after participating in the activity, although a ceiling effect on the true–false items may have occurred. It may have been possible to correctly answer the majority of the true–false items based on having read the textbook prior to attending class on the day of the demonstration. The content knowledge covered in the demonstration was not very extensive, as the main purpose was to help students understand how circuits of neurons could produce complex behavior.
The significant differences between class sections on ratings of understanding may reflect students’ perception of learning rather than actual understanding. Actual knowledge of neural circuitry could be assessed by asking students to diagram the neural circuit, but the purpose of the activity was to help students understand the concept of a neural circuit rather than to teach them the specifics of the Jeffress (1948) model or any other particular circuit.
The activity complements previously published simulations of neural functioning by demonstrating a relatively simple neural circuit that performs a perceptual function. I developed the activity because I was concerned that students did not appreciate the importance of neural circuits even if they had a basic understanding of how neurons function. I chose the Jeffress (1948) neural circuit because it actually works in the brains of some animals (Grothe et al., 2010) and yet is simple enough to demonstrate in an introductory class.
I normally use the activity in a class of 50–60 students. A class could complete the demonstration with as few as 15 students. There is no upper limit on the number of students who could participate, although it may be more time consuming with more than about 90 students participating. In larger classes, a subset of the students could participate in the neural circuit while other students observe.
Students appear to enjoy the physical nature of the activity and the entertainment value of seeing their instructor sprint from one end of the formation to the other. Although I did not measure students’ memory for the activity at the end of the course, VanderStoep et al.’s (2000) findings suggest that participation in vivid activities may lead to lasting memories.
Footnotes
Acknowledgments
I thank the students in my classes for their enthusiastic participation. I am also grateful for numerous helpful suggestions from the reviewers of this manuscript.
The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
The author received no financial support for the research, authorship, and/or publication of this article.