The typical analysis that goes along with these stimuli is shown in Fig. 4 where a spike-triggered average (STA) is created by taking selleck kinase inhibitor the mean of the instantaneous frames present at each observed spike. When the stimuli are spectrally white, and the STA is generalized to taking the average for multiple frame delays prior to each spike, the computation becomes equivalent to determining the average preferred stimulus of a given neuron, or the first order Weiner kernel (Marmarelis and Marmarelis, 1978 and Victor and Knight, 1979) and thus is a description of the linear part

of the neuron’s transfer function. The requirement for spectral whiteness is met by the use of carefully-constructed stimuli such as M-sequences that have been used to map RFs in the primate retina (Benardete and Kaplan, 1997a and Benardete and Kaplan, 1997b), LGN (Reid and Shapley, 2002 and Usrey and Reid, 2000), V1 (Cottaris and De Valois, 1998), and higher order visual areas (Bair

et al., 2002). In the Nutlin-3a manufacturer primate LGN in particular, Reid and Shapley (2002) used M-sequences to investigate functional differences between cell types in the different LGN laminae, including examining the specific retinal cone contribution to thalamic responses by shifting the black-and-white luminance axis in their checkerboards to cone-isolating colors. They found that M cell responses were transient, red-green P cell responses were relatively sustained, and blue K cell responses were the most sustained (Reid and Shapley, 2002). Although

in cats rather than monkeys, Reid et al. (1997) also performed a similar experiment to examine the linear receptive field properties of Y cells with Rolziracetam high temporal resolution. Most M and P cells in the primate LGN have linear firing properties that can be explained by linearly weighting the stimulus light pattern by a CRF map (see Fig. 2), however, as described in Section 4, nonlinear properties such as EC suppression of M cells have been found. These nonlinear RF properties can be examined using spike-triggered covariance (STC) analysis. Solomon et al. (2010) used flickering uniform fields to stimulate primate LGN neurons, and STAs and STCs to derive estimates of the linear and second-order nonlinear receptive fields. The authors arrived at the interesting conclusion that there is a class of nonlinear cells in the LGN that encode contrast energy. Thus future investigations will benefit from taking into account nonlinearities in experimental design and analysis. Chichilnisky presents an analysis of the advantages and disadvantages of random white noise stimuli (Chichilnisky, 2001). The benefits include minimizing the effects of adaptation, the ability to compute model-free linear responses easily, and model-free nonlinear ones with sufficient data, or, by the inclusion of a simple model, the ability to compute standard nonlinear responses quickly.