THE JOURNAL OF COMPARATIVE NEUROLOGY 495:691–708 (2006) Ipsilateral Cortical Connections of Dorsal and Ventral Premotor Areas in New World Owl Monkeys IWONA STEPNIEWSKA,1 TODD M. PREUSS,2,3 AND JON H. KAAS1* 1Department of Psychology, Vanderbilt University, Nashville, Tennessee 37203 2Division of Neuroscience and Center for Behavioral Neuroscience, Emory University, Atlanta, Georgia 30329 3Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia 30322 ABSTRACT In order to compare connections of premotor cortical areas of New World monkeys with those of Old World macaque monkeys and prosimian galagos, we placed injections of fluo- rescent tracers and wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in dorsal (PMD) and ventral (PMV) premotor areas of owl monkeys. Motor areas and injection sites were defined by patterns of movements electrically evoked from the cortex with microelec- trodes. Labeled neurons and axon terminals were located in brain sections cut either in the coronal plane or parallel to the surface of flattened cortex, and they related to architectoni- cally and electrophysiologically defined cortical areas. Both the PMV and PMD had connec- tions with the primary motor cortex (M1), the supplementary motor area (SMA), cingulate motor areas, somatosensory areas S2 and PV, and the posterior parietal cortex. Only the PMV had connections with somatosensory areas 3a, 1, 2, PR, and PV. The PMD received inputs from more caudal portions of the cortex of the lateral sulcus and more medial portions of the posterior parietal cortex than the PMV. The PMD and PMV were only weakly interconnected. New World owl monkeys, Old World macaque monkeys, and galagos share a number of PMV and PMD connections, suggesting preservation of a common sensorimotor network from early primates. Comparisons of PMD and PMV connectivity with the cortex of the lateral sulcus and posterior parietal cortex of owl monkeys, galagos, and macaques help identify areas that could be homologous. J. Comp. Neurol. 495:691–708, 2006. © 2006 Wiley-Liss, Inc. Indexing terms: motor cortex; posterior parietal cortex; motor system; primates; primate evolution The cortical motor system appears to be exceptionally 1991a–c; Wu et al., 2000; Fang et al., 2006), and humans well developed in primates. In addition to the primary (e.g., Fink et al., 1997; Geyer et al., 2000). Thus, the motor cortex (M1), which is common to all eutherian mam- cortical motor system has a number of matching subdivi- mals (Beck et al., 1996), primates have well-differentiated sions in prosimian (strepsirhine) primates, platyrhine an- dorsal (PMD) and ventral (PMV) premotor areas, a sup- thropoids (New World monkeys), and catarhine anthro- plementary motor area (SMA), a frontal eye field (FEF), and two or more cingulate motor fields (Kaas, 2004a). The organization and connections of these areas have been particularly well studied in macaque monkeys (Godschalk Grant sponsor: National Institutes of Health; Grant number: NS 16446. et al., 1995; Picard and Strick, 1996; Rizzolatti et al., 1998; *Correspondence to: Jon H. Kaas, Department of Psychology, Vanderbilt for review, see Wise et al., 1997; Luppino and Rizzolatti, University, 301 David K Wilson Hall, 111 21st Ave. South, Nashville, TN 2000; Picard and Strick, 2001; Dum and Strick, 2002), but 37203. E-mail: [email protected]. Received 18 July 2005; Revised 11 October 2005; Accepted 10 November there is good evidence for these areas in New World mon- 2005 keys (Stepniewska et al., 1993; Preuss et al., 1996, 1997) DOI 10.1002/cne.20906 and in prosimian galagos (Preuss and Goldman-Rakic, Published online in Wiley InterScience (www.interscience.wiley.com). © 2006 WILEY-LISS, INC. 692 I. STEPNIEWSKA ET AL. TABLE 1. The Cases, Areas, and Tracers Injected Case PMD injection PMV injection M1 Plane of Cut Survival (in days) 90-55L Caudal: DY crystal FL: 3%FB (0.25 ␮l) Coronal 4 Face. 2% WGA-HRP (0.03 ␮l) 91-72L Rostral: 10% FR (0.25 ␮l) FL: 2%WGA-HRP (0.05 ␮l) Coronal 5 92-42L Caudal: 10% FR (0.2 ␮l) Flattened 7 92-83L Caudal: DY pellet FL: FR pellet FL: FB pellet Flattened 9 93-4L FL rep.: DY pellet Coronal 6 94-26L Caudal: 10% FR (0.1 ␮l) FL: 2% WGA-HRP (0.03 ␮l) Flattened 7 Rostral: 2% DY (0.2 ␮l) Face: 3% FB 0.15 ␮l DY,-diamidino yellow; FB, fast blue; FL, forelimb; FR, Fluoro Ruby; WGA-HRP, wheat germ agglutinin. poids (Old World monkeys, apes, and humans). Such a movement representations of the PMD and in the forelimb distribution indicates that a constellation of motor areas and face representations of the PMV, as determined by emerged early in primate evolution, in the period from 65 microstimulation mapping (Preuss et al., 1996). In two to 85 million years ago (Martin, 2004) and has been re- cases tracers were also placed in the forelimb representa- tained in the major branches. tion of the primary motor cortex (M1). Experimental pro- Whereas the connections of motor and premotor areas cedures were approved by the Vanderbilt Animal Care have been extensively studied in macaque monkeys, and and Use Committee and followed the guidelines of the more recently in galagos, much less is known about such National Institutes of Health. connections in New World monkeys. Major connections of Surgical procedures were described in detail by the M1 have been described in owl monkeys (Stepniewska Stepniewska et al. (1993). All procedures were carried out et al., 1993) and Cebus monkeys (Dum and Strick, 2005), under aseptic conditions. Anesthesia was induced with and the connections of the FEF have been reported for intramuscular injections of ketamine hydrochloride (30 squirrel and owl monkeys (Huerta et al., 1987), but the mg/kg) and xylazine (1 mg/kg), and supplemental injec- connections of PMV and PMD are known only for the tions were given as needed to maintain a surgical level of frontal lobe in Cebus monkeys (Dum and Strick, 2005), anesthesia. Bone covering part of the frontal lobe was and only in part from studies of the connections of the M1 removed and the dura reflected to expose the cortex from in owl monkeys (Stepniewska et al., 1993) and the frontal the central sulcus (CS) to the dimple of the inferior arcu- eye field in owl monkeys and squirrel monkeys (Huerta et ate sulcus (IAS). The cortex was covered with silicone oil al., 1987). In the present study, we directly determined to prevent desiccation and to limit brain pulsation. The the connections of the PMV and PMD of owl monkeys. locations of electrode penetrations and tracer injections Injection sites were defined by intracortical microstimula- were marked on a photograph of the exposed frontal lobe. tion, and motor areas were delineated electrophysiologi- After a short microstimulation session to identify areas for cally and architectonically in the same monkeys (Preuss et placing injections (see below), fluorescent tracers (DY, FB, al., 1996). FR) and WGA-HRP were placed in the forelimb and eye- Our study had two main goals. First, we wanted to movement representations of the PMD and in the forelimb compare the cortical connection patterns in owl monkeys and face representations of the PMV (Table 1). In two with those in galagos and macaques. Similarities across cases, an additional tracer was injected into the M1. Trac- these primates would suggest connectional networks that ers were either injected with 1–2-␮l Hamilton syringes have been retained since early in primate evolution, with a glass micropipette attached to the tip of the syringe whereas differences would suggest specializations within needle (0.03–0.05 ␮l of WGA-HRP and 0.1–0.25 ␮lof the different lines of primate evolution. Second, the con- fluorescent tracers) or deposited in the cortex in the form nections of well-defined cortical areas with cortical regions of a crystal or pellet. that are not well understood can help reveal the organi- Following the injections, the cortex was covered with zation of the latter regions. Although the subdivisions of gelatin film, the skull opening was closed with a dental motor and premotor cortex are now reasonably well char- acrylic cap, and the skin was sutured. After a survival acterized in owl monkeys (Gould et al., 1986; Stepniewska period of 4–9 days to allow tracers to be transported, the et al.,1993; Preuss et al., 1996), the organization of the skull was opened again, and additional locations in the posterior parietal cortex in these and other New World same hemisphere were stimulated with a microelectrode monkeys is not well known. Because the PMD and PMV in order to determine the organization of the motor and have dense interconnections with the posterior parietal premotor cortex more extensively. At the end of the stim- cortex in macaques and galagos, such connections in owl ulation session, electrolytic lesions were placed to mark monkeys would indicate the likely locations of areas in the the M1 and PM boundaries and the borders between dif- posterior parietal cortex that have been defined in other ferent body representations within these two cortical re- primates. gions. Lesions to mark cortical locations were made by passing 10 ␮A of direct current for 10 seconds via the microelectrodes. These lesions and other landmarks sub- MATERIAL AND METHODS sequently allowed the electrophysiological results to be Experiments were performed on six adult owl monkeys related to the architecture. Results of the physiological (Aotus trivirgatus). Fluorescent dyes (diamidino yellow and histological investigations are described elsewhere [DY], fast blue [FB], and Fluoro Ruby [FR]) and wheat (Preuss et al., 1996). At the end of the experiment, each germ agglutinin conjugated to horseradish peroxidase owl monkey was given a lethal dose of barbiturate and (WGA-HRP) were placed in the forelimb and eye- perfused through the heart with buffered physiological PREMOTOR CORTEX CONNECTIONS 693 saline, followed by 2% paraformaldehyde in phosphate flattened cortex, boundaries and labeled neurons were buffer, and then by 2% paraformaldehyde in phosphate superimposed in representative sections, providing a flat- buffer with 10% sucrose.