- PROFESSOR Neuroscience
- PROFESSOR Structural and Chemical Biology
Ph.D., Mount Sinai School of Medicine
ResearchMany motor behaviors are mediated by central pattern generators (CPGs) that can generate rhythmic output without afferent input. Physiologically, however, CPGs often receive sensory information so that activity is adjusted to compensate for changes in the environment. When this occurs, changes in motor output are not always solely determined by stimulus properties. Instead peripherally and centrally generated activity is integrated so that stimulus-induced changes in motor output depend on the state of the ongoing motor program. Thus, afferent transmission can be regulated (i.e., gated) during rhythmic activity. Current experiments in our laboratory seek to determine how sensory and motor activity is integrated during feeding behavior in the marine mollusc Aplysia californica. We study the regulation of afferent transmission using both electrophysiological and imaging techniques.
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Evans CG, Kang T, Cropper EC. Selective spike propagation in the central processes of an invertebrate neuron. J Neurophysiol;: in press.
Evans CG, Ludwar BH, Cropper EC. Mechanoafferent neuron with an inexcitabile somatic region: consequences for the regulation of spike propagation and afferent transmission. J Neurophysiol 2007; 97(4): 3126-3130.
Lum CS, Zhurov Y, Cropper EC, Weiss KR, Brezina V. Variability of swallowing performance in intact, freely feeding aplysia. J Neurophysiol 2005 Oct; 94(4): 2427-2446.
Evans CG, Romero A, Cropper EC. Inhibition of afferent transmission in the feeding circuitry of Aplysia: persistence can be as important as size. J Neurophysiol 2005; 93(5): 2940-2949.
Cropper EC, Evans CG, Hurwitz I, Jing J, Proekt A, Romero A, Rosen SC. Feeding neural networks in the mollusc Aplysia. Neurosignals 2004; 13: 70-86.
Shetreat-Klein AN, Cropper EC. Afferent-induced changes in rhythmic motor programs in the feeding circuitry of Aplysia. J Neurophysiol 2004; 92(4): 2312-2322.
Jing J, Cropper EC, Hurwitz I, Weiss KR. The construction of movement with behavior-specific and behavior-independent modules. J Neurosci 2004; 24(28): 6315-6325.
Cropper EC, Evans CG, Jing J, Klein A, Proekt A, Romero A, Rosen SC. Regulation of afferent transmission in the feeding circuitry of Aplysia. Acta Biol. Hung 2004; 55: 211-220.
Evans C, Jing J, Proekt A, Rosen S, Cropper E. Frequency-dependent regulation of afferent transmission in the feeding circuitry of Aplysia. J Neurophsiol. 2003; 90: 3967-3977.Frequency-dependent regulation of afferent transmission in the feeding circuitry of Aplysia. Evans CG, Jing J, Proekt A, Rosen SC, Cropper EC. Physiol./Biophysics, Mt. Sinai Med Schl, New York, New York, USA; Phase Five Communications Inc., New York, New York, USA. During rhythmic behaviors sensori-motor transmission is often regulated so that there are phasic changes in afferent input to follower neurons. We study this type of regulation in the feeding circuit of Aplysia. We characterize effects of the B4/5 interneurons on transmission from the mechanoafferent, B21, to the radula closer motor neuron B8. In quiescent preparations, B4/5 induced PSPs can block spike propagation in the lateral process of B21 and inhibit afferent transmission. B4/5 are, however, active during the retraction phase of motor programs, i.e., when mechanoafferent transmission to B8 presumably occurs. To determine whether mechanoafferent transmission is necessarily inhibited when B4/5 are active, we characterize the B4/5 firing frequency during retraction and show that, for the most part, it is low (below 15 Hz). There is, therefore, a low probability that spike propagation will be inhibited. The relative ineffectiveness of low frequency activity isnot simply a consequence of insufficient PSP magnitude because a single PSP can block spike propagation. Instead, it is related to the fact that PSPs have a short duration. When B4/5 fire at a low frequency, there is, therefore, a low probability that afferent transmission in the lateral process of B21 can be inhibited. In conclusion, we demonstrate that afferent transmission will not always be affected when a neuron that exerts inhibitory effects is active. Although a cell may be ineffective when it fires at a low frequency, ineffectiveness is not necessarily a consequence of spike frequency per se. Instead it may be due to spike timing.
Sasaki K, Brezina V, Weiss KR, Jing J. Distinct inhibitory neurons exert temporally specific control over activity of a motoneuron receiving concurrent excitation and inhibition. J Neurosci. 2009 Sep 23; 29(38): 11732-11744.
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Dr. Cropper did not report having any of the following types of financial relationships with industry during 2012 and/or 2013: consulting, scientific advisory board, industry-sponsored lectures, service on Board of Directors, participation on industry-sponsored committees, equity ownership valued at greater than 5% of a publicly traded company or any value in a privately held company. Please note that this information may differ from information posted on corporate sites due to timing or classification differences.
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