Journal of Neuroscience, Vol 6, 3564-3575, Copyright © 1986 by Society for Neuroscience
Synaptic organization of claustral and geniculate afferents to the visual cortex of the cat
S LeVay
Claustral and geniculate afferents to area 17 were labeled by anterograde
axonal transport of peroxidase-conjugated wheatgerm agglutinin, and
examined in the electron microscope. A peroxidase reaction protocol that
led to labeling in the form of minute holes in the EM sections was used.
Both types of afferents formed type 1 (presumed excitatory) synapses
exclusively. In agreement with previous reports the great majority of
geniculate afferents to layers 4 and 6 contacted dendritic spines. The
claustral afferents to layers 1 and 6 also predominantly contacted spines.
In layer 4, however, claustral afferents contacted spines and dendritic
shafts about equally. The results suggest a substantial claustral input to
smooth-dendrite cells in layer 4, which are thought to be inhibitory in
function. This may be the circuit by which the claustrum helps to generate
end-stopped cortical receptive fields (Sherk and LeVay, 1983).