Fig. 12.

Possible microcircuit for the assembly of presaccadic remapping. The schematic depicts progression from partial to full remapping across layers of the FEF and over time [after Douglas and Martin (2004)]. Corticortical visual input and thalamocortical corollary discharge lead to partial remapping at the RF or FF in layer IV recipient neurons. The recipient neurons show only increasing modulations, because inputs from distant cortex and thalamus are glutamatergic. The thalamic-recipient excitatory layer IV neurons convey a RF increase signal directly to layer II/III. The thalamic-recipient ambiguous [presumed low-threshold spiking (LTS)] interneurons project locally to inhibit excitatory neurons, which in turn, project to layer II/III, conveying a FF decrease signal. These RF and FF components are inverted in a layer II/III network and sent, as components or assembled, down to layer V (and possibly to other cortical areas). Single neurons in layer V distribute fully assembled, bimodal remapping signals subcortically, e.g., to the SC. Note, layer IV thalamic-recipient putative inhibitory (fast-spiking) neurons are not illustrated. As addressed in discussion, they may provide a dendritic shunting influence (Quaia et al. 1998) that coordinates the incoming corticocortical and thalamic signals to achieve the RF and FF modulations found, respectively, in layer IV excitatory and presumed LTS inhibitory neurons. LIP, lateral intraparietal cortex.