In the escape system of the cockroach, Periplaneta americana, a population of uniquely identifiable thoracic interneurons (type A or TIAs) receive information about wind via chemical synapses from a population of ventral giant interneurons (vGIs). The TIAs are involved in the integration of sensory information necessary for orienting the animal during escape. It is likely that there are times in an animal's life when it is advantageous to modify the effectiveness of synaptic transmission between the vGIs and the TIAs. Given the central position of the TIAs in the escape system, this would greatly alter associated motor outputs. We tested the ability of octopamine, serotonin, and dopamine to modulate synaptic transmission between vGIs and TIAs. Both octopamine and dopamine significantly increased the amplitude of vGI-evoked excitatory postsynaptic potentials (EPSPs) in TIAs at 10(-4)-10(-2) M, and 10(-3) M, respectively. On the other hand, serotonin significantly decreased the vGI-evoked EPSPs in TIAs at 10(-4)-10(-3) M. These results indicate that octopamine, serotonin, and dopamine are capable of modulating the efficacy of transmission of important neural connections within this circuit.
We determined how the Mauthner cell and other large, fast-conducting reticulospinal neurons of the goldfish responded to acoustic stimuli likely to be important in coordinating body movements underlying escape. The goal was to learn about the neurophysiological responses to these stimuli and the underlying processes of sensorimotor integration. We compared the intracellularly recorded postsynaptic responses (PSPs) of 9 Mauthner cells and a population of 12 other reticulospinal neurons to acoustic pressure and acceleration stimuli. All recorded cells received both pressure and acceleration inputs and responded to stimuli regardless of initial polarity. Thus these cells receive acoustic components necessary to determine source direction. We observed that the Mauthner cell was broadly tuned to acoustic pressure from 100 to 2,000 Hz, with a Q(10dB) of 0.5-1.1 over the best frequency range, 400-800 Hz. This broad tuning is probably due to input from S1 afferents and is similar to tuning of the behavioral audiogram. Our data suggest that cells have relatively more sustained responses to acceleration than to pressure stimuli, to which they rapidly adapted. For a given cell, PSP latencies and amplitudes varied inversely with stimulus intensity. For the entire population of cells studied, minimum onset latencies (i.e., those at the highest intensities) ranged from 0.7 to 7.6 ms for acoustic pressure and 0.7 to 9.8 ms for acceleration. This distribution in minimum onset latencies is consistent with earlier EMG and kinematic findings and supports our previous hypothesis that escape trajectory angle is controlled, in part, by varying the activation time of neurons in the escape network. While the Mauthner cell latency did not differ to both onset polarities of pressure and acceleration, this was not true of all cells. Also, the Mauthner cell responses to pressure were approximately 0.6 ms faster than to acceleration; for the other cells, this difference was 1.1 ms with some cells having differences =3 ms. To both pressure and acceleration, the average, minimum Mauthner cell latency was approximately 1 ms faster than the average of the 12 other cells. These data are consistent with the hypothesis that the Mauthner cell fires first, followed by other reticulospinal neurons, which more finely regulate escape trajectory. Finally, analysis of our results suggests that while pressure is more important in depolarizing the cell near threshold, high levels of acceleration, perhaps from fluid flow, may be very important in activating the system in a directional manner.
Here we describe a 4-yr course reform and its outcomes. The upper-division neurophysiology course gradually transformed from a traditional lecture in 2004 to a more student-centered course in 2008, through the addition of evidence-based active learning practices, such as deliberate problem-solving practice on homework and peer learning structures, both inside and outside of class. Due to the incremental nature of the reforms and absence of pre-reform learning assessments, we needed a way to retrospectively assess the effectiveness of our efforts. To do this, we first looked at performance on 12 conserved exam questions. Students performed significantly higher post-reform on questions requiring lower-level cognitive skills and those requiring higher-level cognitive skills. Furthermore, student performance on conserved questions was higher post-reform in both the top and bottom quartiles of students, although lower-quartile student performance did not improve until after the first exam. To examine student learning more broadly, we also used Bloom's taxonomy to quantify a significant increase in the Bloom's level of exams, with students performing equally well post-reform on exams that had over twice as many questions at higher cognitive skill levels. Finally, we believe that four factors provided critical contributions to the success of the course reform, including: transformation efforts across multiple course components, alignment between formative and evaluative course materials, student buy-in to course instruction, and instructional support. This reform demonstrates both the effectiveness of incorporating student-centered, active learning into our course, and the utility of using Bloom's level as a metric to assess course reform.
ONE OF THE MORE WIDELY USED TOOLS to both inform course design and measure expert-like skills is Bloom's taxonomy of educational objectives for the cognitive domain (2,13,22). This tool divides assessment of cognitive skills into six different levels: knowledge/remember, comprehension/understand, application/apply, analysis/analyze, synthesis/create, and evaluation/evaluate (2, 6). The first two levels are generally considered to represent lower levels of mastery (lower-order cognitive skills) and the last three represent higher-order levels of mastery involving critical thinking (higher-order cognitive skills) with apply-level questions often bridging the gap between the two (e.g., Refs. 5,8,10,11,23,and 24). While Bloom's taxonomy is widely used by science educators, learning and mastering the concepts of the cognitive domain to categorize educational materials into the six levels identified in Bloom's taxonomy are not trivial tasks.
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