The organization of projections from the mediodorsal nucleus of the thalamus to orbital and medial prefrontal cortex in macaque monkeys

Abstract

The organization of interconnections between the mediodorsal nucleus of the thalamus (MD) and the orbital and medial prefrontal cortex and the agranular insular cortex in the monkey was studied by retrograde and anterograde tracing techniques. In addition to the magnocellular and parvicellular divisions of MD, three other subdivisions can be recognized on the basis of myeloarchitecture, cytoarchitecture, and connections. The first two of these represent a parcellation of the magnocellular division into a lateral, fiber-rich MD pars fibrosa and a medial, poorly myelinated MD pars paramediana adjacent to the midline. The third is a small, poorly myelinated area located at the caudomedial and dorsal edges of MD; it is referred to as MD pars caudodorsalis. MD pars fibrosa is reciprocally interconnected primarily with areas 11, 12 and 13 in the central and lateral part of the orbital cortex. There is a general organization within this projection, with the rostrocaudal axis of the cortex represented from dorsal to ventral in the pars fibrosa, and the mediolateral cortical axis represented from medial to lateral. Cells that project to area 12 also extend laterally into the adjacent pars parvicellularis. MD pars paramediana is more heavily interconnected with the caudal and medial portions of the orbital region, particularly the agranular insular areas and the caudal parts of areas 13 and 14. Cells that project to two caudal areas, 13a and Iad, do not fit with the general organization, in that they are located in the dorsomedial parts of the pars fibrosa and pars paramediana, where they overlap with cells that project to area 14. The pars fibrosa and pars paramediana receive inputs from areas of the ventral forebrain such as the amygdala, piriform (olfactory) cortex, and entorhinal cortex, which project directly to the orbital and agranular insular cortex, as well as from the ventral pallidum. MD pars caudodorsalis is reciprocally interconnected with areas 14, 24, and 32 on the medial surface of the prefrontal cortex. In this part of the nucleus the dorsoventral axis of the medial prefrontal cortex is represented from caudal to rostral in the thalamus. The amygdala and other ventral forebrain structures do not send fibers into the pars caudodorsalis, even though some of these structures project directly to the medial prefrontal cortex. Ventral to MD, and separated from it by the internal medullary lamina, a small region was recognized that appears to be comparable to the anteroventral part of the submedial nucleus previously defined in the rat and cat.(ABSTRACT TRUNCATED AT 400 WORDS)

Experimental Petit Mal-Like Seizure Induced by Microinjection of Kainic Acid Into the Unilateral Mediodorsal Nucleus of the Thalamus

“…Ipsilateral side dominant limbic structures were involved in the epileptic excitation in the present model, probably based on the neuronal connections between limbic structures, mainly in the basolateral nucleus of the amygdala, and the magnocellular division of the MD. 21) In the present study, SWDs were continuously observed at about 2.5 Hz for 5-7 hours after kainic acid injection to the unilateral MD in rats, and epileptiform activity propagated to the cortex and thalamic nucleus, and to the limbic system. These discharges were synchronized in the bilateral MDs.…”

Unraveling the contributions of the diencephalon to recognition memory: A review

“…1; Ray and Price 1993). This arrangement is notable, as removal of the medial and orbital prefrontal cortices induces severe DNMS deficits in monkeys (Fig.…”

Low dopamine striatal D2 receptors are associated with prefrontal metabolism in obese subjects: Possible contributing factors

“…The ventral CG (BA 25) is implicated in mediating the emotional responses to salient stimuli (rewarding as well as aversive) (Elliott et al, 2000) and imaging studies have shown that BA 25 is activated by natural and drug rewards (Breiter et al, 1997, Francis et al, 1999Berns et al, 2001). Thus the negative association between D2 receptors and the tendency to eat when exposed to negative emotions we previously reported in healthy controls (Volkow et al, 2003) could be mediated by modulation of BA 25.The association between metabolic activity in prefrontal regions and D2 receptors could reflect projections to the prefrontal cortex from ventral and dorsal striatum (Ray and Price, 1993), which are regions implicated in the reinforcing and motivational effects of food (Koob and Bloom, 1988) and/or from the ventral tegmental area (VTA) and substantia nigra (SN), which are the main DA projections to striatum (Oades and Halliday, 1987). However, the prefrontal cortex also sends projections to the striatum so the association could reflect the prefrontal regulation of DA striatal activity (Murase et al, 1993).…”

“…The association between metabolic activity in prefrontal regions and D2 receptors could reflect projections to the prefrontal cortex from ventral and dorsal striatum (Ray and Price, 1993), which are regions implicated in the reinforcing and motivational effects of food (Koob and Bloom, 1988) and/or from the ventral tegmental area (VTA) and substantia nigra (SN), which are the main DA projections to striatum (Oades and Halliday, 1987). However, the prefrontal cortex also sends projections to the striatum so the association could reflect the prefrontal regulation of DA striatal activity (Murase et al, 1993).…”