title: Pathways of attention: synaptic relationships of frontal eye field to V4, lateral intraparietal cortex, and area 46 in macaque monkey.
abstract: The frontal eye field (FEF) of the primate neocortex occupies a pivotal position in the matrix of inter-areal projections. In addition to its role in directing saccadic eye movements, it is the source of an attentional signal that modulates the activity of neurons in extrastriate and parietal cortex. Here, we tested the prediction that FEF preferentially excites inhibitory neurons in target areas during attentional modulation. Using the anterograde tracer biotinylated dextran amine, we found that the projections from FEF terminate in all cortical layers of area 46, lateral intraparietal area (LIP), and visual area V4. Axons in layer 1 spread extensively, those in layer 2/3 were most numerous, individual axons in layer 4 formed sprays of collaterals, and those of the deep layers were the finest caliber and irregular. All labeled synapses were the typical asymmetric morphology of excitatory synapses of pyramidal neurons. Dendritic spines were the most frequent synaptic target in all areas (95% in area 46, 89% in V4, 84% in LIP, 78% intrinsic local FEF). The remaining targets were one soma and dendritic shafts, most of which showed characteristics of inhibitory neurons with smooth dendrites (5% of all targets in area 46, 2% in V4, 9% in LIP, and 13% in FEF).
authors.affiliation: Institute for Neuroinformatics, University of Zürich and ETH Zürich, 8057 Zürich, Switzerland. jca@ini.phys.ethz.ch
authors.forename: John C
authors.initials: JC
authors.lastname: Anderson
authors.forename: Henry
authors.initials: H
authors.lastname: Kennedy
authors.forename: Kevan A C
authors.initials: KA
authors.lastname: Martin
mesh_terms: D000818:Animals; D001288:Attention / Q000502:physiology*; D001522:Behavior, Animal; D001710:Biotin / Q000031:analogs & derivatives / Q000378:metabolism; D001931:Brain Mapping; D003712:Dendrites / Q000378:metabolism / Q000648:ultrastructure; D003911:Dextrans / Q000378:metabolism; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D008252:Macaca fascicularis; D008253:Macaca mulatta; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D010296:Parietal Lobe / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D017729:Presynaptic Terminals / Q000502:physiology / Q000648:ultrastructure; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D003911:Dextrans; C076397:biotinylated dextran amine; D005680:gamma-Aminobutyric Acid; D001710:Biotin