On Feb 3, 2010, the Journal of Neuroscience published a research article from ION entitled "Synaptic Mechanisms of Direction Selectivity in Primary Auditory Cortex". This work was carried out by Ph.D. student Chang-quan Ye under the supervision of Drs. Xiao-hui Zhang and Mu-ming Poo.

Frequency modulation (FM) is a prominent feature in animal vocalization and human speech. The synaptic mechanisms underlying FM direction selectivity in primary auditory cortex (AI) are not well understood. In this study, by performing in vivo whole-cell recording, the authors separated the evoked excitatory and inhibitory inputs of AI neurons and demonstrated that both the differential delay of the excitatory input and the spectral offset between excitation and inhibition are positively correlated with direction selectivity of the neuron, providing the experimental evidence for the different role of excitation and inhibition in shaping FM direction selectivity. Furthermore, direction selectivity measured from the spiking output is significantly stronger than that based on the sub-threshold membrane potentials, indicating that the selectivity is further sharpened by the spike generation mechanism. These findings provided direct experimental evidence in support of the long existing theoretical model for general synaptic mechanisms of the feature detection of cortical sensory neurons, and shed lights on the circuit mechanism of the sensory information processing of the brain.

Paper link: Ye C. Q., Poo M.M., Dan Y., and Zhang  X.H. (2010) Synaptic mechanisms of direction selectivity in primary auditory cortex. J Neurosci. 30: 1861-1868.