Figure 3.
Low-calcium technique to separate direct versus synaptic inputs. A, Total inward current map in a layer 6 corticocollicular neuron. B, Same neuron, but here the map is shown using inward currents obtained using low-calcium aCSF. C, Subtraction map, obtained by subtracting the individual traces used to obtain the map shown in B from the current traces used to create the map shown in A. D, Traces taken from the laser stimulation site denoted with an asterisk, demonstrating that this site contains a short-latency, multipeaked response, with the latter portion of the response being eliminated using a low-calcium aCSF solution, suggesting that this latter portion is synaptic in nature. E, Direct inward current map of a layer 5 neuron obtained using low-calcium aCSF. Below the map is a series of current traces taken from the boxed area of the map. F, Direct inward current map of a layer 5 neuron obtained using TTX. Below the map is a series of current traces taken from the boxed area of the map. G, Correlation of the amplitude of responses of the direct inward current obtained using low-calcium aCSF (abscissa) and TTX (ordinate), measured at each stimulation site eliciting a response. Correlation coefficient (0.957) obtained using Spearman's correlation. Triangular outlined image corresponds to a diagram of the recording pipette, the tip of which points to the location of the recorded cell. Colorbars indicate F statistic.