Projections from the amygdala to basoventral and mediodorsal prefrontal regions in the rhesus monkey

Abstract

The sources of ipsilateral projections from the amygdala to basoventral and mediodorsal prefrontal cortices were studied with retrograde tracers (horseradish peroxidase or fluorescent dyes) in 13 rhesus monkeys. The basoventral regions injected with tracers included the orbital periallocortex and proisocortex, orbital areas 13, 11, and 12, lateral area 12, and ventral area 46. The mediodorsal regions included portions of medial areas 25, 32, 14, and dorsal area 8. The above sites represent areas within two architectonic series of cortices referred to as basoventral or mediodorsal on the basis of their anatomic location. Each series consists of areas that show a gradual increase in the number of layers and their delineation in a direction from the caudal orbital and medial limbic cortices, which have an incipient laminar organization, towards the eulaminated periarcuate cortices (Barbas and Pandya, J. Comp. Neurol. 286: 353-375, '89). Labeled neurons projecting to the prefrontal cortex were found in the basolateral, basomedial (also known as accessory basal), lateral, and ventral cortical nuclei, and in the anterior amygdaloid and amygdalopiriform areas. The distribution of labeled neurons differed both quantitatively and qualitatively depending on whether the injection sites were in basoventral or mediodorsal prefrontal cortices. Cases with caudal orbital injections had the most labeled neurons in the amygdala, followed by cases with injections in cortices situated medioventrally. The latter received a high proportion of their amygdaloid projections from the basomedial nucleus. The lateral amygdaloid nucleus sent a robust projection to the least architectonically differentiated orbital periallocortex, and a weaker projection to the adjoining orbital proisocortical regions, but did not appear to project to either medial proisocortical sites or to the more differentiated ventrolateral or dorsolateral prefrontal cortices. In addition, there were topographical differences in the origin of projections from one amygdaloid nucleus directed to various prefrontal cortices. These differences were correlated either with the destination of the axons of afferent amygdaloid neurons to basoventral or to mediodorsal prefrontal cortices and/or with their projection to areas with varying degrees of laminar organization within the basoventral or mediodorsal sector. The clearest topography was observed for projections originating in the basolateral nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Pathways for emotion: interactions of prefrontal and anterior temporal pathways in the amygdala of the rhesus monkey

“…Our results con¢rm and extend previous studies which had primarily focused on the ascending projections (e.g. Porrino et al, 1981;Barbas and De Olmos, 1990;Morecraft et al, 1992).…”

“…1C) did not result in signi¢cant anterograde label in the amygdala (Table 2). However retrogradely labeled neurons were present in the BLmc, as reported previously (Barbas and De Olmos, 1990). …”

“…Patterns designating injection sites refer to the type of tracer used: black, £uorescent dyes; stripes, BDA ; black outline, [ 3 H] amino acids; gray, HRP-WGA. , 1995bDermon and Barbas, 1994;Barbas and Blatt, 1995;Rempel-Clower and Barbas, 1998), including a study restricted to description of projection neurons directed from the amygdala to the prefrontal cortex (Barbas and De Olmos, 1990). Injections of tracers included all layers of the injected cortices.…”

“…For example, in contrast to the wealth of information on the projections from the amygdala to prefrontal cortices (e.g. Nauta, 1961;Jacobson and Trojanowski, 1975;Porrino et al, 1981;Barbas and De Olmos, 1990;Morecraft et al, 1992;Carmichael and Price, 1995a), little is known about pathways in the reverse direction in primates (Pandya et al, 1973;Aggleton et al, 1980;Van Hoesen, 1981;Carmichael and Price, 1995a;Chiba et al, 2001), which likely in£uence the activity of the amygdala in behavior. Here we addressed the extent to which components of these pathways intersect in the amygdala by investigating: (1) the organization of descending projections from prefrontal cortices, and their relationship to output from the amygdala to prefrontal cortices; (2) whether prefrontal and anterior temporal cortices have common sites of connections in the amygdala, that may form the structural basis to evaluate the emotional signi¢cance of the environment; (3) whether orbitofrontal and medial prefrontal cortices share zones of in£uence with hypothalamic autonomic structures in the amygdala.…”

Mechanisms of Action Underlying the Effect of Repetitive Transcranial Magnetic Stimulation on Mood: Behavioral and Brain Imaging Studies

“…The anatomical corticocortical connectivity between the ACC and both the prefrontal and motor cortices provides pathways for communication between the cognitive and motor systems (Barbas and Pandya, 1989;Dum and Strick, 1991;Van Hoesen, 1992, 1993;Bates and Goldman-Rakic, 1993;Picard and Strick, 1996). Emotional and motivational states can further influence and/or involve the ACC via regulatory input from brainstem monoaminergic nuclei as well as via input from the amygdala, thalamus, and ventral striatum (Barbas and De Olmos, 1990;Barbas et al, 1991;Kunishio and Haber, 1994;Ongur and Price, 2000). In light of the proposed role of the ACC in paralinguistic aspects of speech during changes in emotion and motivation, it is important to note that the regions of ACC surrounding the genu of the corpus callosum have numerous connections with cortical and subcortical regions involved in vocalization, including those in the periaqueductal gray (Jurgens, 1976a(Jurgens, , b, 1983Muller-Preuss and Jurgens, 1976;Morecraft and Van Hoesen, 1993;An et al, 1998).…”