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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

Summary of projections across cortical areas investigated in these studies. (A) Illustration of cortical areas, using the same colors as the graphs and diagrams below. Percent of labeled thalamic neurons projecting to (B) SR, (C) S1, (D) SC, and (E) MM. Data are mean ± SEM when applicable. Axes are the same throughout A-D to aid in comparison. Projections to VPm and VPl are summed above VP, with the projections from VPm under the horizontal line and the projections from VPl above the line. (F) Summary of strong projections from the 5 cortical areas discussed throughout the paper. All projections shown make up > 10% of the total thalamic projections to that area.
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Figure 14: Summary of projections across cortical areas investigated in these studies. (A) Illustration of cortical areas, using the same colors as the graphs and diagrams below. Percent of labeled thalamic neurons projecting to (B) SR, (C) S1, (D) SC, and (E) MM. Data are mean ± SEM when applicable. Axes are the same throughout A-D to aid in comparison. Projections to VPm and VPl are summed above VP, with the projections from VPm under the horizontal line and the projections from VPl above the line. (F) Summary of strong projections from the 5 cortical areas discussed throughout the paper. All projections shown make up > 10% of the total thalamic projections to that area.

Mentions: Taken together, these data demonstrate that S1, SC, and MM received the strongest projections from VP; however the strength of those projections decreased from S1 to SC and MM (see Figure 14, Table 3). Conversely, MM had stronger projections from visual structures (LGNd and Pul) while SC has only sparse connections from these nuclei and S1 had no projections from these nuclei. Mimicking the pattern of VP connections, the strength of projections from Pom was weaker as injections moved farther caudal in cortex (e.g., from S1 to SC to MM). Strong projections from Pol were only found in areas caudal to S1 (Figure 14F). Located immediately rostral to S1, SR showed a pattern of projections from thalamic nuclei that was notably different from the other three areas described. Strong projections to SR were seen from midline structures including VM and MD, which only weakly or inconsistently projected to the other cortical areas examined (Figures 14B,F).


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)

Summary of projections across cortical areas investigated in these studies. (A) Illustration of cortical areas, using the same colors as the graphs and diagrams below. Percent of labeled thalamic neurons projecting to (B) SR, (C) S1, (D) SC, and (E) MM. Data are mean ± SEM when applicable. Axes are the same throughout A-D to aid in comparison. Projections to VPm and VPl are summed above VP, with the projections from VPm under the horizontal line and the projections from VPl above the line. (F) Summary of strong projections from the 5 cortical areas discussed throughout the paper. All projections shown make up > 10% of the total thalamic projections to that area.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 14: Summary of projections across cortical areas investigated in these studies. (A) Illustration of cortical areas, using the same colors as the graphs and diagrams below. Percent of labeled thalamic neurons projecting to (B) SR, (C) S1, (D) SC, and (E) MM. Data are mean ± SEM when applicable. Axes are the same throughout A-D to aid in comparison. Projections to VPm and VPl are summed above VP, with the projections from VPm under the horizontal line and the projections from VPl above the line. (F) Summary of strong projections from the 5 cortical areas discussed throughout the paper. All projections shown make up > 10% of the total thalamic projections to that area.
Mentions: Taken together, these data demonstrate that S1, SC, and MM received the strongest projections from VP; however the strength of those projections decreased from S1 to SC and MM (see Figure 14, Table 3). Conversely, MM had stronger projections from visual structures (LGNd and Pul) while SC has only sparse connections from these nuclei and S1 had no projections from these nuclei. Mimicking the pattern of VP connections, the strength of projections from Pom was weaker as injections moved farther caudal in cortex (e.g., from S1 to SC to MM). Strong projections from Pol were only found in areas caudal to S1 (Figure 14F). Located immediately rostral to S1, SR showed a pattern of projections from thalamic nuclei that was notably different from the other three areas described. Strong projections to SR were seen from midline structures including VM and MD, which only weakly or inconsistently projected to the other cortical areas examined (Figures 14B,F).

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