Volume 17, Number 23,
Issue of December 1, 1997
pp. 9233-9247
Subcortical Input to the Smooth and Saccadic Eye Movement
Subregions of the Frontal Eye Field in Cebus Monkey
Received Jan. 2, 1997; revised Sept. 11, 1997; accepted Sept. 15, 1997.
Jun-ru Tian1 and
James
C. Lynch1, 2, 3
Departments of 1 Anatomy, 2 Ophthalmology,
and 3 Neurology, University of Mississippi Medical Center,
Jackson, Mississippi 39216-4505
We have recently identified two functional subregions in the
frontal eye field (FEF) of the Cebus monkey, a smooth
eye movement subregion (FEFsem) and a saccadic subregion (FEFsac). The
thalamic input to these two subregions was studied and quantified to
gain more information about the influence of the cerebellum and basal ganglia on the oculomotor control mechanisms of the cerebral cortex. A
recent study using transneuronal transport of virus demonstrated that
there are neurons in the basal ganglia and cerebellum that project to
the FEFsac with only a single intervening synapse ().
In the present study, we concentrated on the thalamic input to the
FEFsem to define possible basal ganglia-thalamus-cortex and
cerebellum-thalamus-cortex channels of information flow to the
FEFsem. We localized the functional subregions using low threshold microstimulation, and retrogradely transported fluorescent tracers were
then placed into the FEFsem and FEFsac.
The neurons that project to the FEFsem are distributed in (1) the
rostral portion of the ventral lateral nucleus, pars caudalis, (2) the
caudal portion of the ventral lateral nucleus, pars caudalis, (3) the
mediodorsal nucleus, (4) the ventral anterior nucleus, pars
parvocellularis, and (5) the ventral anterior nucleus, pars magnocellularis. In contrast, the large majority of neurons that project to the FEFsac are located in the paralaminar region of the
mediodorsal nucleus. The FEFsac and FEFsem thus each receive neural
input from both basal ganglia-receiving and
cerebellar-receiving cell groups in the thalamus, but each receives
input from a unique combination of thalamic nuclei.
Key words:
pursuit eye movements;
saccades;
basal ganglia;
substantia nigra;
cerebellum;
frontal eye field;
supplementary eye
field;
thalamus;
Cebus monkeys