JOSHUA C. BRUMBERG
Society for Neuroscience
New York Academy of the Sciences
Faculty for Undergraduate Neuroscience
Chair Barrels Organizing Committee (since 2004) – International meeting focused on the rodent sensorimotor system
The function of an electronic device such as a transistor radio can be explained based on its identifiable circuit elements; resistors, capacitors and transistors. Similarly, understanding the individual elements of a cortical circuit and how they interact brings us a step closer to understanding the function of the circuit as a whole and ultimately its behavior in response to environmental stimuli. While the analogy applies to the neocortex, deciphering the cortical microcircuit is much more difficult due to the diversity of components and the numbers of interconnections between the different elements. The focus of the Brumberg’s lab research is to characterize the neurons of the mouse barrel cortex with an emphasis on the interactions between the sensory and motor systems that govern the animals whisking behavior.
Using the Golgi-Cox silver impregnation technique, we have characterized the normal morphological development and have defined the morphological classes of neurons in layer VI of barrel cortex. We have demonstrated that sensory deprivation (via whisker clipping) leads to increase in soma size and dendritic length and we are currently investigating how altering glutamatergic inputs (via transgenic mice and pharmacological approaches) can possibly provide a mechanism for the observed morphological changes. Using tract tracing methods we have characterized the reciprocal connections between the primary motor cortex (M1) and the primary somatosensory cortex (S1). This pathway is thought to be important for conveying information necessary to allow the motor system to update its motor plans in order to adapt to changes in the sensory periphery.
We utilize both sharp intracellular and whole cell patch clamp recordings to characterize the intrinsic properties of neurons as well as studying the nature of their inputs. In many instances we use retrograde tracers in conjunction with our recording studies to correlate a neurons’ intrinsic properties with its axonal target.
We have developed a novel in vitro slice preparation that contains the whisker representations of both the primary motor cortex (M1) and S1 (barrel cortex) and maintains their synaptic connectivity. Initial field potential recordings have shown that M1 inputs to S1 display paired pulse facilitation whereas S1 inputs to M1 do not. Intracellular recording studies are ongoing to study the synaptic basis of these differences. Recent whole cell patch clamp studies in the lab have focused on the morphology and physiology of identified callosal neurons. It appears that callosal neurons in layers 2/3 and layer V have very homogeneous physiological properties but the laminar targets of their callosally projecting axons target different lamina.
Through this integrated approach we are attempting to define the neuronal building blocks and their synaptic partners within mouse barrel cortex to understand the structure and functions of the cortical micro-circuit which is thought to underlie cortical computations and cognitive functions.
Cao, R., Higashikubo B.T., Cardin, J., Knoblich, U., Ramos, R.L., Nelson, M.T., Moore, C.I., Brumberg, J.C. Pinacidil induces vascular dilation and hyperemia in vivo and does not impact biophysical properties of neurons and astrocytes in vitro. Clev Clinic J Med, 76(2009):S80-S85.
Chen, C-C, Abrams, S. Pinhas, A., Brumberg J.C. Morphological Heterogeneity of Layer VI Neurons in Mouse Barrel Cortex. Journal of Comparative Neurology, 512(2009):726-746.
Ramos, R.L., Smith, P.T., DeCola, C., Tam, D., Corzo, O., Brumberg, J.C. Cytoarchitecture and transcriptional profiles of neocortical malformation in inbred mice. Cerebral Cortex, 18(2008):2614-2628.
Ramos, R.L., Tam, D., Brumberg, J.C., Physiology and morphology of callosal projection neurons in mouse, Neuroscience. 153(2008):654-63.
Gutkin, B.S., Brumberg, J.C., Cortical neurons as non-linear oscillators: Experiment and theory. Brain Research. 1171(2007):122-37.
Brumberg, J.C., Nowak, L.G., McCormick, D.A. Ionic mechanisms underlying repetitive high frequency burst firing in cortical neurons. J. Neurosci., 20(2000):4829-4843.
Brumberg, J.C., Pinto, D.J, Simons, D.J. Spatial gradients and inhibitory summation in the rat whisker barrel system. J. Neurophysiol., 76(1996):130-140.