Frontal eye field in prosimian galagos: Intracortical microstimulation and tracing studies

Abstract

The frontal eye field (FEF) in prosimian primates was identified as a small cortical region, above and anterior to the anterior frontal sulcus, from which saccadic eye movements were evoked with electrical stimulation. Tracer injections revealed FEF connections with cortical and subcortical structures participating in higher order visual processing. Ipsilateral cortical connections were the densest with adjoining parts of the dorsal premotor and prefrontal cortex (PFC). Label in a region corresponding to supplementary eye field (SEF) of other primates, suggests the existence of SEF in galagos. Other connections were with ventral premotor cortex (PMV), the caudal half of posterior parietal cortex, cingulate cortex, visual areas within the superior temporal sulcus, and inferotemporal cortex. Callosal connections were mostly with the region of the FEF of another hemisphere, SEF, PFC, and PMV. Most subcortical connections were ipsilateral, but some were bilateral. Dense bilateral connections were to caudate nuclei. Densest reciprocal ipsilateral connections were with the paralamellar portion of mediodorsal nucleus, intralaminar nuclei and magnocellular portion of ventral anterior nucleus. Other FEF connections were with the claustrum, reticular nucleus, zona incerta, lateral posterior and medial pulvinar nuclei, nucleus limitans, pretectal area, nucleus of Darkschewitsch, mesencephalic and pontine reticular formation and pontine nuclei. Surprisingly, the superior colliculus (SC) contained only sparse anterograde label. Although most FEF connections in galagos are similar to those in monkeys, the FEF-SC connections appear to be much less. This suggests that a major contribution of the FEF to visuomotor functions of SC emerged with the evolution of anthropoid primates.

Internal Subdivisions of the Marmoset Claustrum Complex: Identification by Myeloarchitectural Features and High Field Strength Imaging

“…The molecular basis of claustrum function is starting to become clear (Kivell et al, 2014; Tantra et al, 2018), and both structural and functional connectomic studies have highlighted the importance of the claustrum complex for understanding connectivity in both normal and pathological brain states (Fernández-Miranda et al, 2008; Reser et al, 2014, 2017; Bruni et al, 2018; Fillinger et al, 2018; Rabellino et al, 2018; Randerath et al, 2018; Ribas et al, 2018; Stepniewska et al, 2018). However, there have only been a few coarse attempts to describe the extrinsic connectivity of the claustrum in terms of its internal structure (LeVay and Sherk, 1981; Pearson et al, 1982; Macchi et al, 1983; Tanné-Gariépy et al, 2002; Gattass et al, 2014; Reser et al, 2014), and the phylogenetic relationships of various components of the claustrum complex have only recently been described (Smith et al, 2019).…”

Interactions within and between parallel parietal-frontal networks involved in complex motor behaviors in prosimian galagos and a squirrel monkey

“…With two stimulating electrodes, the center of greatest activation may move to between the electrode sites. Both the eye movement domains in PPC and the frontal eye field (FEF) of galagos (Fang et al 2005;Stepniewska et al 2018;Wu et al 2000) and other primates (Schall 2015; I. Stepniewska, R. M. Friedman, A. W. Roe, and J. H. Kaas, unpublished observations) contain maps of eye movements extents and directions, so the center of activation within the map determines the movement (e.g., Mirpour et al 2010).…”

The comparative anatomy of frontal eye fields in primates

“…Corticocortical connections have been observed with the inferior parietal lobule (Rozzi et al, 2006) but lot of less attention has been paid on that oculomotor-associated premotor area. Some changes in connections of FEF and visuomotor functions have emerged since the time prosimian and anthropoid primate lines of evolution diverged (Stepniewska et al, 2018) and needs for additional marker especially fibers colocalizations between structures to study their evolution and function. Some of these debates are resurfacing about homologous neuroanatomy not only for FEF location, but also for the identification of homologous white matter bundles at the level of the external/extreme capsule in both monkeys and humans (Mars et al, 2016;Petit et al, 2018).…”