Ph.D., Johns Hopkins University School of Medicine
Assistant Professor
Department of Neuroscience
464 Sidney Frank Hall of Life Sciences
Tel: (401) 863-6015
Email: Carlos_Aizenman@brown.edu
Go to lab web page

The long term goal of my research is to understand the role of experience in the development of neural circuits. To address this question it is necessary to first understand what mechanisms regulate and maintain the normal morphology, synaptic connectivity, excitability, and output properties of the neurons which constitute these circuits, and then observe how these mechanisms are affected by experience. Over the last few decades, research has shown that neural activity plays a critical role during the development of the visual system. However, less is known about how the visual system adapts to neural activity over a shorter time scale during development. This is important, since neurons must be able to function within a useful dynamic range when faced with changing environmental and developmental conditions. In order to do this, neurons have been shown to homeostatically adapt their synaptic and intrinsic electrophysiologically relevant conditions. By understanding how the developing nervous system responds and adjusts to periods of enhanced activity we can begin to comprehend how this activity can be maximally utilized to guide long-term developmental changes.

In my research I address these issues by taking advantage of the Xenopus laevis tadpole visual system. The optictectal neurons in the tadpole receive direct monosynaptic inputs from the contralateral retina, and form a developmental gradient where it is possible to study neurons at different stages of their development in the same preparation. The synaptic and dendritic maturation of tectal neurons is well characterized and provides a starting point from which to study the roles that visual experience and a variety of signaling mechanisms play in these processes. Moreover tectal neurons are easily accessible, allowing us to take advantage of several established techniques for altering gene expression in individual neurons and then observe the effects of these genes of interest in the electrophysiological and morphological properties of these cells.

My research has used a novel appraoch where freely swimming tadpoles are presented with a moving visual stimulus for a few hours. This allowed us to directly test the effects of visual experience over a relatively short timescale in a highly plastic, developing nervous system. A variety of mechanisms have emerged where tectal neurons respond to persistent visual stimulation by altering both their intrinsic excitability and their synaptic properties. We are now in a position to study these mechanisms in depth using diverse electrophysiological, imaging and molecular techniques.

Pratt KG and Aizenman CD. Spike-timing dependent plasticity of recurrent excitation in the developing visual system Submitted- Oct. 2007

Pratt KG and Aizenman CD. Homeostatic regulation of intrinsic excitability and synaptic transmission in a developing visual circuit. J Neuroscience 2007 - 27 (31):8268

Aizenman CD and Cline HT. Enhanced visual activity in vivo forms nascent synapses in the developing retinotectal projection. J Neurophysiol. 2007 Apr;97(4):2949-57.

C. D. Aizenman, C. J. Akerman, K.R. Jensen and H. T. Cline. "Visually driven regulation of intrinsic neuronal excitability improves stimulus detection in vivo." Neuron, 39(5):831-42 (2003)

C.D. Aizenman, E.J. Huang, D.J. Linden. "Morphological Correlates of Intrinsic Electrical Excitability in Neurons of the Deep Cerebellar Nuclei" J. Neurophysiolgy, 89 (4):1738-1747 (2003)

Li Z, Aizenman CD, Cline HT. Regulation of rho GTPases by crosstalk and neuronal activity in vivo. Neuron. 2002 Feb 28;33(5):741-50.

C. D. Aizenman, G. Munoz-Elias and H.T. Cline. "Visually driven modulation of glutamatergic synaptic transmission is mediated by the regulation of intracellular polyamines." Neuron, 34(4):623-634 (2002)

C. D. Aizenman and D. J. Linden. "Rapid, synaptically-driven increases in the intrinsic excitability of cerebellar deep nuclear neurons." Nature Neuroscience, 3:109-111 (2000)

C.D. Aizenman, E.J. Huang, P.B. Manis, D.J. Linden. "Use-Dependent Changes in Synaptic Strength at the Purkinje Cell to Deep Nuclear Synapse." in Cerebelar Modules, N. Gerrits (Ed.), Progress in Brain Research 124:257-273, Elsevier (2000).