Schroeder et al. (1991, 1998) used laminar CSD profiles in response to diffuse light and pattern stimuli to identify the sequential activation pattern corresponding to information processing and transfer via visual regions (i.e., lateral geniculate nucleus, V1, V2 and V4). In each case, the most prominent early cortical response is in and near the thalamorecipient laminae, with a subsequent response in extragranular laminae. Both granular and subsequent supragranular responses reflect neuronal excitation, typically identifiable by the co-localization of extracellular sinks with concurrent MUA increases. The intracortical dynamics of these distinct processes may be differentially biased. Local infusions of the competitive GABA antagonist bicuculline lead to an elaboration of the flash-evoked supragranular sink, which grows to massive proportions in concert with the local MUA (Schroeder et al., 1990). A similar laminar pattern has also been observed for interictal spikes (Ulbert et al., 2004). In a nonpathologic form, the supragranular response may also be overlaid by convergent multisensory (Lakatos et al., 2007) and attentional processes (Lakatos et al., 2008). Feed-forward processing is also evidenced by CSD patterns across regions (Givre et al.,
