Dynamic Encoding of Natural Luminance Sequences by LGN Bursts
Figure 3
Detection of the Onset of Excitatory Luminance Sequences
(A) LGN responses to a noisy stimulus in which an excitatory sequence randomly appeared were simulated with and without bursts using the IFB and IF models (see Materials and Methods). The stimulus was classified as S0 (black) or S1 (red), depending on whether or not each interval contained the excitatory transient of the sequence. A typical realization of the stimulus with SNR = 1/2 is shown (intensity averaged over all pixels in RF center). The black line indicates the actual stimulus and the gray line indicates the underlying sequence.
(B) Voltage traces of the IFB and IF responses to the stimulus shown in (A) at two different resting potentials, VR = −67 mV (top) and VR = −50 mV (bottom), with VT = −60 mV. The interval in the response that corresponds to condition S1 is shaded. (The response was shifted for presentation to remove latency between stimulus and response). The spike threshold ( VΘ, green), burst de-inactivation potential and threshold ( VT, red), and resting potential ( VR, blue) are shown.
(C) The probability distributions of the firing rate of the IFB and IF models during the S0 (black) and S1 (red) stimulus conditions at VR = −67 mV (top) and VR = −50 mV (bottom) with stimulus SNR = 1/2. Distributions were calculated using the response to a stimulus segment that contained 100 sequences.
(D) ROC curves for the IFB and IF models at VR = −67 mV (top) and VR = −50 mV (bottom) calculated from the distributions in (C) using likelihood ratios as described in Materials and Methods. The area under the ROC curve is indicated.