Journal of neurophysiology
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In the auditory cortex of barbiturate-anesthetized cats, the posterior auditory field (field P) was identified by its tonotopic organization, and single neurons in that field were studied quantitatively for their sensitivity to the frequency and intensity of tonal stimuli presented via calibrated, sealed stimulating systems. Field P neurons had narrow, V-shaped, threshold frequency tuning curves. At suprathreshold levels, spike counts were generally greatest at frequencies at or close to the neuron's threshold best frequency (BF). ⋯ For other neurons, the optimal sound pressure level tended to be constant across frequency despite threshold variations of up to 20 dB. The minimum response latencies of posterior-field neurons were generally in the range of 20-50 ms, while cells in the primary auditory cortex (AI) in the same animals generally had minimum latent periods of less than 20 ms. Comparison of these data with those previously presented for neurons in two other cortical auditory fields suggests that the cat's auditory cortex might show an interfield segregation of neurons according to their coding properties.
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Several identified neurons of the Aplysia buccal ganglia respond to choline. Iontophoretic applications of either choline or acetylcholine (ACh) to voltage-clamped inhibitory follower neurons produce similar currents. Peak amplitudes of choline responses were 10-100% of ACh responses on the same cell. ⋯ Both the time integral of synaptic conductance and the ratio of synaptic charge transfer to peak synaptic current of the early inward component of the cell 7 response are reduced by depolarization. Voltage-dependent duration thus combines with reduced driving force in diminishing the excitatory effect of this component at depolarized levels, allowing the inhibitory component to predominate. In this diphasic synapse, voltage dependence of the time course of one component thus serves an easily identified function.