Soc. Neurosci. Abstr.
HORIZONTAL INTERACTIONS IN THE MONKEY INFERIOR TEMPORAL CORTEX.
I. Fujita1,2*, H.
Tanigawa1, H. Ojima3 and M. Kato1.
1Dept. Cognitive Neuroscience, Osaka Univ. Medical School;
2PRESTO, JRDC, Osaka 565; 3Dept. Anatomy, Toho Univ.,
Tokyo 143, Japan.
In area TE of the monkey
inferior temporal cortex, horizontal axons run parallel to the pial
surface and mediate interaction between distant sites. Distribution
and type of horizontally projecting neurons determine the nature of
the interaction. In this study, fluorescent retrograde tracers, fast
blue (FB) or diamidino yellow (DY), were injected into the TE of
Japanese macaques. The distribution of retrogradely labeled cells was
analyzed in fixed slices. Lucifer Yellow was then intracellularly
injected into DY-labeled cells, and their dendritic morphology was
examined by confocal laser scanning microscopy. Single injections of
FB or DY, which covered all layers and were 0.2-0.4 mm wide, labeled
more than 20 columnar clusters of cells as well as cells diffusely
scattered between the clusters. In the clusters, labeled cells were
found in layers 2 to 6 with a few labeled cells in layer 4. The
clustering of labeled cells in layers 5 and 6 tended to be looser
than that in layers 2 and 3. In layers 2 and 3, all the cells so far
injected with Lucifer Yellow were symmetrical pyramidal cells
(120/120). A few cells labeled in layer 4 were also pyramidal cells
(4/4). In layers 5 and 6, asymmetrical pyramidal cells and fusiform
cells (36/88) and nonpyramidal interneurons (9/88) were labeled in
addition to symmetrical pyramidal cells (43/88). No difference was
detected in the laminar distribution and type of labeled cells
between the clusters and interclusters. The results suggest that
horizontal interactions in the TE are predominantly mediated by
standard pyramidal cells, and contribution of other types of cells
may differ between the supragranular and infragranular layers.