Directional asymmetry of neurons in cortical areas MT and MST projecting to the NOT-DTN in macaques.
K.-P.Hoffmann, F. Bremmer, A. Thiele & C. Distler
Journal of Neurophysiology, 87: 2113-2123,2002
The cortical projection to the subcortical pathway underlying the optokinetic reflex was studied using antidromic
electrical stimulation in the midbrain structures nucleus of the optic tract and dorsal terminal nucleus of the
accessory optic system (NOT-DTN) while simultaneously recording from cortical neurons in the superior temporal
sulcus (STS) of macaque monkeys. Projection neurons were found in all subregions of the middle temporal area (MT)
as well as in the medial superior temporal area (MST). Antidromic latencies ranged from 0.9 to 6 ms with a median
of 1.8 ms. There was a strong bias in the population of cortical neurons projecting to the NOT-DTN for ipsiversive
stimulus movement (towards the recording side), whereas in the population of cortical neurons not projecting to
the NOT-DTN a more or less equal distribution of stimulus directions was evident. Our data indicate that there
is no special area in the posterior STS coding for ipsiversive horizontal stimulus movement. Instead, a specific
selection of cortical neurons from areas MT and MST forms the projection to the NOT-DTN and as a subpopulation
has the same directional bias as their subcortical target neurons. These findings are discussed in relation to
the functional grouping of cortical output as an organizational principle for specific motor responses.
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