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Evolution of mammalian sensorimotor cortex: thalamic projections to parietal cortical areas in Monodelphis domestica.

Dooley JC, Franca JG, Seelke AM, Cooke DF, Krubitzer LA - Front Neuroanat (2015)

Bottom Line: Our results provide further evidence to support the hypothesized basic mammalian plan of thalamic projections to S1, with the lateral and medial ventral posterior thalamic nuclei (VPl and VPm) projecting to S1 body and S1 face, respectively.Notably, MM is distinguished from SC by relatively dense projections from the dorsal division of the lateral geniculate nucleus and pulvinar.Further we provide additional support for a primitive posterior parietal cortex which receives input from multiple modalities.

View Article: PubMed Central - PubMed

Affiliation: Center for Neuroscience, University of California, Davis Davis, CA, USA.

ABSTRACT
The current experiments build upon previous studies designed to reveal the network of parietal cortical areas present in the common mammalian ancestor. Understanding this ancestral network is essential for highlighting the basic somatosensory circuitry present in all mammals, and how this basic plan was modified to generate species specific behaviors. Our animal model, the short-tailed opossum (Monodelphis domestica), is a South American marsupial that has been proposed to have a similar ecological niche and morphology to the earliest common mammalian ancestor. In this investigation, we injected retrograde neuroanatomical tracers into the face and body representations of primary somatosensory cortex (S1), the rostral and caudal somatosensory fields (SR and SC), as well as a multimodal region (MM). Projections from different architectonically defined thalamic nuclei were then quantified. Our results provide further evidence to support the hypothesized basic mammalian plan of thalamic projections to S1, with the lateral and medial ventral posterior thalamic nuclei (VPl and VPm) projecting to S1 body and S1 face, respectively. Additional strong projections are from the medial division of posterior nucleus (Pom). SR receives projections from several midline nuclei, including the medial dorsal, ventral medial nucleus, and Pom. SC and MM show similar patterns of connectivity, with projections from the ventral anterior and ventral lateral nuclei, VPm and VPl, and the entire posterior nucleus (medial and lateral). Notably, MM is distinguished from SC by relatively dense projections from the dorsal division of the lateral geniculate nucleus and pulvinar. We discuss the finding that S1 of the short-tailed opossum has a similar pattern of projections as other marsupials and mammals, but also some distinct projections not present in other mammals. Further we provide additional support for a primitive posterior parietal cortex which receives input from multiple modalities.

No MeSH data available.


Related in: MedlinePlus

Thalamic projections to multimodal region (MM) in case 08-80. (A) Injection site of FE in MM. (B) Fluorescent image of the FE injection site and surrounding halo. (C–G) Labeled neurons can be seen projecting to MM from large portions of VL/VA as well as from VPl and VPm. Additionally, densely packed label neurons are observed in Pol; moderate numbers of labeled neurons in LGNd and Pul. (H) Percent of labeled thalamic neurons projecting from various thalamic nuclei to MM. Conventions as in previous figures.
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Figure 12: Thalamic projections to multimodal region (MM) in case 08-80. (A) Injection site of FE in MM. (B) Fluorescent image of the FE injection site and surrounding halo. (C–G) Labeled neurons can be seen projecting to MM from large portions of VL/VA as well as from VPl and VPm. Additionally, densely packed label neurons are observed in Pol; moderate numbers of labeled neurons in LGNd and Pul. (H) Percent of labeled thalamic neurons projecting from various thalamic nuclei to MM. Conventions as in previous figures.

Mentions: One injection was entirely restricted to MM (Figure 12A). In this case, MM received strong projections from VP and Pol (26.8 and 27.7% respectively, see Figures 10F,G). Additionally, MM also received significant projections from VL/VA (12.7%) and moderate projections from both LGNd and the pulvinar (6.6% for both nuclei). Thus, MM is distinguished from SC by its relatively dense projections from LGNd and the pulvinar, giving MM a more multimodal connectional profile compared to the primarily somatosensory SC, Additionally, we had one injection entirely restricted to SR (Figure 13). Unlike other cortical parietal areas described thus far, SR received substantially more projections from both VM (20.6%) and Pom (20.1%) than from VP (10.3%, see Figures 13D–H). SR also received very dense projections from several midline structures that do not consistently project to S1, SC, or MM. For example, SR received strong projections from MD (16.1%), while VA/VL (8.9%), VMb (8.4%), and PF (5.5%) all have moderate projections to SR. Weak projections were also observed from CL and CeM (1.1 and 1.2%, respectively).


Evolution of mammalian sensorimotor cortex: thalamic projections to parietal cortical areas in Monodelphis domestica.

Dooley JC, Franca JG, Seelke AM, Cooke DF, Krubitzer LA - Front Neuroanat (2015)

Thalamic projections to multimodal region (MM) in case 08-80. (A) Injection site of FE in MM. (B) Fluorescent image of the FE injection site and surrounding halo. (C–G) Labeled neurons can be seen projecting to MM from large portions of VL/VA as well as from VPl and VPm. Additionally, densely packed label neurons are observed in Pol; moderate numbers of labeled neurons in LGNd and Pul. (H) Percent of labeled thalamic neurons projecting from various thalamic nuclei to MM. Conventions as in previous figures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4286717&req=5

Figure 12: Thalamic projections to multimodal region (MM) in case 08-80. (A) Injection site of FE in MM. (B) Fluorescent image of the FE injection site and surrounding halo. (C–G) Labeled neurons can be seen projecting to MM from large portions of VL/VA as well as from VPl and VPm. Additionally, densely packed label neurons are observed in Pol; moderate numbers of labeled neurons in LGNd and Pul. (H) Percent of labeled thalamic neurons projecting from various thalamic nuclei to MM. Conventions as in previous figures.
Mentions: One injection was entirely restricted to MM (Figure 12A). In this case, MM received strong projections from VP and Pol (26.8 and 27.7% respectively, see Figures 10F,G). Additionally, MM also received significant projections from VL/VA (12.7%) and moderate projections from both LGNd and the pulvinar (6.6% for both nuclei). Thus, MM is distinguished from SC by its relatively dense projections from LGNd and the pulvinar, giving MM a more multimodal connectional profile compared to the primarily somatosensory SC, Additionally, we had one injection entirely restricted to SR (Figure 13). Unlike other cortical parietal areas described thus far, SR received substantially more projections from both VM (20.6%) and Pom (20.1%) than from VP (10.3%, see Figures 13D–H). SR also received very dense projections from several midline structures that do not consistently project to S1, SC, or MM. For example, SR received strong projections from MD (16.1%), while VA/VL (8.9%), VMb (8.4%), and PF (5.5%) all have moderate projections to SR. Weak projections were also observed from CL and CeM (1.1 and 1.2%, respectively).

Bottom Line: Our results provide further evidence to support the hypothesized basic mammalian plan of thalamic projections to S1, with the lateral and medial ventral posterior thalamic nuclei (VPl and VPm) projecting to S1 body and S1 face, respectively.Notably, MM is distinguished from SC by relatively dense projections from the dorsal division of the lateral geniculate nucleus and pulvinar.Further we provide additional support for a primitive posterior parietal cortex which receives input from multiple modalities.

View Article: PubMed Central - PubMed

Affiliation: Center for Neuroscience, University of California, Davis Davis, CA, USA.

ABSTRACT
The current experiments build upon previous studies designed to reveal the network of parietal cortical areas present in the common mammalian ancestor. Understanding this ancestral network is essential for highlighting the basic somatosensory circuitry present in all mammals, and how this basic plan was modified to generate species specific behaviors. Our animal model, the short-tailed opossum (Monodelphis domestica), is a South American marsupial that has been proposed to have a similar ecological niche and morphology to the earliest common mammalian ancestor. In this investigation, we injected retrograde neuroanatomical tracers into the face and body representations of primary somatosensory cortex (S1), the rostral and caudal somatosensory fields (SR and SC), as well as a multimodal region (MM). Projections from different architectonically defined thalamic nuclei were then quantified. Our results provide further evidence to support the hypothesized basic mammalian plan of thalamic projections to S1, with the lateral and medial ventral posterior thalamic nuclei (VPl and VPm) projecting to S1 body and S1 face, respectively. Additional strong projections are from the medial division of posterior nucleus (Pom). SR receives projections from several midline nuclei, including the medial dorsal, ventral medial nucleus, and Pom. SC and MM show similar patterns of connectivity, with projections from the ventral anterior and ventral lateral nuclei, VPm and VPl, and the entire posterior nucleus (medial and lateral). Notably, MM is distinguished from SC by relatively dense projections from the dorsal division of the lateral geniculate nucleus and pulvinar. We discuss the finding that S1 of the short-tailed opossum has a similar pattern of projections as other marsupials and mammals, but also some distinct projections not present in other mammals. Further we provide additional support for a primitive posterior parietal cortex which receives input from multiple modalities.

No MeSH data available.


Related in: MedlinePlus