ACETYLCHOLINESTERASE HISTOCHEMISTRY IN THE MACAQUE THALAMUS REVEALS TERRITORIES SELECTIVELY CONNECTED TO FRONTAL, PARIETAL AND TEMPORAL ASSOCIATION CORTICES
C. Cavada et al., ACETYLCHOLINESTERASE HISTOCHEMISTRY IN THE MACAQUE THALAMUS REVEALS TERRITORIES SELECTIVELY CONNECTED TO FRONTAL, PARIETAL AND TEMPORAL ASSOCIATION CORTICES, Journal of chemical neuroanatomy, 8(4), 1995, pp. 245-257
The patterns of histochemical staining for acetylcholinesterase (AChE)
activity in the macaque thalamus were analyzed and compared with the
distribution of cells and terminals labeled from injections of axonal
tracers in the dorsolateral and orbital prefrontal cortex, in area 7a
of the posterior parietal cortex and in the polysensory cortex of the
superior temporal sulcus. AChE histochemistry is very useful in deline
ating the thalamic nuclei connected with the association cortex and in
uncovering thalamic subdivisions that are barely evident on cytoarchi
tectonic grounds. Moreover, AChE activity reveals previously unrecogni
zed heterogeneities within several thalamic nuclei, like the ventral a
nterior (VA), where a new ventromedial subdivision (VAvm) is described
, the medial pulvinar (PulM) or the mediodorsal nucleus (MD). In this
nucleus three distinct chemical domains are present: the medial, ventr
al and lateral sectors characterized by low, moderate and high AChE ac
tivities, respectively. The staining pattern of the lateral sector is
markedly heterogeneous with patches of intense AChE activity surrounde
d by a moderately stained matrix. The MD medial sector is connected wi
th the orbitofrontal cortex, whereas the AChE-rich patches in the late
ral sector are selectively connected with the dorsolateral prefrontal,
parietal and temporal association cortices. In the PulM, a dorsomedia
l AChE-rich patch is selectively connected with the orbitofrontal cort
ex, whereas the surrounding territory, which shows moderate AChE activ
ity, is preferentially connected with the parietal and temporal cortic
es. Chemically specific domains in the anterior, ventral anterior, mid
line, and intralaminar thalamic nuclei are also connected with the exa
mined association cortices. These findings indicate that the topograph
ic patterns of the thalamo-cortical connections of primate association
areas conform to the chemical architecture of the thalamus. This impl
ies that because each cortical area is connected to a particular set o
f thalamic regions, the influence of the thalamus on cortical function
is exclusive for each area, highly diverse among the various associat
ion areas, and subject to a wide range of modulation at the thalamic l
evel.