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.

Anatomical Studies:

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.

Physiological Studies:

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.

Publications:

• Brumberg, J.C. & Gutkin, B.S. Cortical pyramidal cells function as non-linear oscillators: Experiment and spike-generation theory. Brain Res, 1171(2007): 122-137.
• McRae, P.A., Rocco, M.M., Kelly, G., Brumberg, J.C. & Matthews, R.T. Sensory deprivation alters aggrecan and perineuronal net expression in the mouse barrel cortex. J. Neurosci, 27(2007): 5405-5413.
• Ramos, R.L., Moiseff, A., and Brumberg, J.C. Utility and versatility of extracellular recordings from the cockroach for neurophysiological instruction and demonstration. Journal of Undergraduate Neuroscience Education, 5, (2007) A28-A34.
• Rocco, M.M. & Brumberg J.C. The sensorimotor slice. J. Neurosci Methods., 165(2007): 139-147.
• 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.
• Brumberg, J.C., Pinto, D.J, Simons, D.J. Cortical columnar processing in the rat whisker-to-barrel system. J. Neurophysiol., 82(1999):1808-1817.
• 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.
• Pinto, D.J, Brumberg, J.C., Simons, D.J. Circuit dynamics and coding strategies in rodent somatosensory cortex. J. Neurophysiol., 83(2000):1158-1166.
• Brumberg, J.C., Hamzei-Sichani, F., Yuste, R. Morphological and physiological characterization of layer 6 cortico-fugal neurons from mouse primary visual cortex. J. Neurophysiol., 89(2003):2854-2867.
• Pinto, D.J, Hartings, J.A., Brumberg, J.C., Simons, D.J. Cortical damping: An alternative role for recurrent excitation in thalamocortical circuits. Cerebral Cortex, 13(2003):33-44.
• Descalzo, V.F., Nowak, L.G., Brumberg, J.C., McCormick, D.A., Sanchez-Vives, M.V. Slow Adaptation in Fast-Spiking Neurons of Visual Cortex. J. Neurophysiol., 93(2005):1111-1118