Posterior Horn of the Spinal Cord

Searching Google for "posterior horn spinal cord" located 383,000 references:   

Posterior grey column - Wikipedia      
    "The posterior grey column (posterior cornu, dorsal horn, spinal dorsal horn posterior horn) of the spinal cord is one of the three grey columns of the spinal cord. It receives several types of sensory information from the body, including fine touch, proprioception, and vibration. This information is sent from receptors of the skin, bones, and joints through sensory neurons whose cell bodies lie in the dorsal root ganglion."    


Medulla spinalis - Section - English.svg
Cross section of the spinal cord. The posterior horn is the upper protrusion of grey matter, labeled with "2"

Posterior horn | definition of posterior horn by Medical dictionary       
    "the horn-shaped projection of gray matter in the posterior region of the spinal cord. It relays information related to touch and pressure from muscles and regulates precise movement and unconscious proprioception. Also called dorsal column, dorsal horn, posterior column.
Mosby's Medical Dictionary, 9th edition. © 2009, Elsevier.

Searching PubMed for "posterior horn spinal cord " revealed 2908 references:     

1982 841<1214
The dorsal horn of the spinal cord.   
Recent advances in techniques, especially the intraneuronal injection of the enzyme horseradish peroxidase, have led to a new era in our understanding of spinal cord structure and function.  
    Input to the cord is precisely organized:  
    the primary afferent fibres from different types of receptors distribute their anatomically specific collaterals to particular parts of the dorsal horn,  
    afferent fibres from the skin lay down a precise somatotopic map,  
    input to the dorsal horn from descending systems is also distributed in a localized way.  
    The neurones of the dorsal horn are varied in both structure and function, even so some quite specific cell types can be identified and the dendritic trees may respect laminar boundaries as determined cytoarchitectonically (although the majority of neurones have dendrites that cut across these boundaries).  
    The output pathways from the dorsal horn are many and various, but again they arise from cells in definite parts of the dorsal horn. The dorsal horn must be considered as a well-organized, and complex, part of the central nervous system. It cannot be considered as a structural or functional unit but is made up of many interacting parts that process input from the primary afferent fibres, from other levels of the spinal cord and from many descending pathways from the brain. "

   Free Article   
20 page PDF available online for free. 
    My comment
Very informative, with diagrams.  Well worth reading.   I wasn't able to photocopy.   
It turns out that the dorsal horn is much more complex than I had anticipated. 

1983     68<70
Spinocerebellar projections in the turtle. Observations on their origin and terminal organization.
Spinocerebellar projections were studied in the turtle, Pseudemys scripta elegans, by both anterograde (injections of 35S-methionine into various spinal segments) and retrograde (injections of horseradish peroxidase into the cerebellar cortex) tracing techniques.  
    After unilateral HRP injections, labeled neurons were found on both sides of the spinal cord. The total number of retrogradely labeled spinocerebellar tract neurons was relatively small and neuronal aggregations were not observed. Most spinocerebellar tract neurons were found in the ventral horn, dorsal to the motoneuronal cell group. Some cells lay in the spinal intermediate zone and in the dorsal horn.  
    The fibers mainly ascended in the lateral funiculus, some in the ventral and possibly some in the dorsal funiculi. Spinal projections terminated within the cerebellar granular layer. The spinocerebellar target area extended along the whole medio-lateral extent and covered about the rostral four fifths of the cerebellar plate. Individual target areas, separated from each other, as are the anterior and posterior spinocerebellar target areas of higher vertebrates, could not be identified. Similar to mammals, however, the terminal field in the turtle was not a homogenous one but consisted of zones of mossy fiber terminations of varying sizes and intensities."  
    My comment
It's beginning to look like I need to look at the  Cerebellum  and its efferent connections. 

1991 59<70
The spinotrigeminal pathway and its spatial relationship to the origin of trigeminospinal projections in the rat.  

2000 49<70
Propriospinal afferent and efferent connections of the lateral and medial areas of the dorsal horn (laminae I-IV) in the rat lumbar spinal cord.
The different subdivisions along the mediolateral extent of the superficial dorsal horn of the spinal cord are generally regarded as identical structures that execute the function of sensory information processing without any significant communication with other regions of the spinal gray matter. In contrast to this standing, here we endeavor to show that neural assemblies along the mediolateral extent of laminae I-IV cannot be regarded as identical structures.  
    After injecting Phaseolus vulgaris leucoagglutinin and biotinylated dextran amine into various areas of the superficial dorsal horn (laminae I-IV) at the level of the lumbar spinal cord in rats, we have demonstrated that the medial and lateral areas of the superficial dorsal horn show the following distinct features in their propriospinal afferent and efferent connections:  
    1) A 300- to 400-microm-long section of the medial aspects of laminae I-IV projects to and receives afferent fibers from a three segment long compartment of the spinal dorsal gray matter, whereas the same length of the lateral aspects of laminae I-IV projects to and receives afferent fibers from the entire rostrocaudal extent of the lumbar spinal cord.  
    2) The medial aspects of laminae I-IV project extensively to the lateral areas of the superficial dorsal horn. In contrast to this, the lateral areas of laminae I-IV, with the exception of a few fibers at the segmental level, do not project back to the medial territories.  
    3) There is a substantial direct commissural connection between the lateral aspects of laminae I-IV on the two sides of the lumbar spinal cord. The medial part of laminae I-IV, however, does not establish any direct connection with the gray matter on the opposite side.  
    4) The lateral aspects of laminae I-IV appear to be the primary source of fibers projecting to the ipsi- and contralateral ventral horns and supraspinal brain centers. Projecting fibers arise from the medial subdivision of laminae I-IV in a substantially lower number. The findings indicate that the medial and lateral areas of the superficial spinal dorsal horn of rats may play different roles in sensory information processing."  
    My comment
Note:  "... supraspinal brain centers ..."   These are the connections I'm looking for. 

2000  46<70
Stimulation of the mesencephalic locomotor region inhibits the discharge of neurons in the superficial laminae of the dorsal horn of cats.   

2008  17<70  
Vesicular glutamate transporters define two sets of glutamatergic afferents to the somatosensory thalamus and two thalamocortical projections in the mouse.
The ventral posterior nucleus of the thalamus (VP) receives two major sets of excitatory inputs, one from the ascending somatosensory pathways originating in the dorsal horn, dorsal column nuclei, and trigeminal nuclei, and the other originating from the cerebral cortex.  
    Both systems use glutamate as neurotransmitter, as do the thalamocortical axons relaying somatosensory information from the VP to the primary somatosensory cortex (SI). 
    The synapses formed by these projection systems differ anatomically, physiologically, and in their capacity for short-term synaptic plasticity. Glutamate uptake into synaptic vesicles and its release at central synapses depend on two isoforms of vesicular glutamate transporters, VGluT1 and VGluT2. Despite ample evidence of their complementary distribution, some instances exist of co-localization in the same brain areas or at the same synapses. In the thalamus, the two transcripts coexist in cells of the VP and other nuclei but not in the posterior or intralaminar nuclei. We show that the two isoforms are completely segregated at VP synapses, despite their widespread expression throughout the dorsal and ventral thalamus.  
    We present immunocytochemical, ultrastructural, gene expression, and connectional evidence that VGluT1 in the VP is only found at corticothalamic synapses, whereas VGluT2 is only found at terminals made by axons originating in the spinal cord and brainstem. 
     By contrast, the two VGluT isoforms are co-localized in thalamocortical axon terminals targeting layer IV, but not in those targeting layer I, suggesting the presence of two distinct projection systems related to the core/matrix pattern of organization of thalamocortical connectivity described in other mammals."  
    My comment
Note:  "axons originating in the spinal cord and brainstem"   These are the connections I'm looking for. 

2015   3<70
Identifying local and descending inputs for primary sensory neurons.   

    "Primary pain and touch sensory neurons not only detect internal and external sensory stimuli, but also receive inputs from other neurons. However, the neuronal derived inputs for primary neurons have not been systematically identified.   
    Using a monosynaptic rabies viruses-based transneuronal tracing method combined with sensory-specific Cre-drivers, we found that sensory neurons receive intraganglion, intraspinal, and supraspinal inputs, the latter of which are mainly derived from the rostroventral medulla (RVM). The viral-traced central neurons were largely inhibitory but also consisted of some glutamatergic neurons in the spinal cord and serotonergic neurons in the RVM. The majority of RVM-derived descending inputs were dual GABAergic and enkephalinergic (opioidergic). These inputs projected through the dorsolateral funiculus and primarily innervated layers I, II, and V of the dorsal horn, where pain-sensory afferents terminate. Silencing or activation of the dual GABA/enkephalinergic RVM neurons in adult animals substantially increased or decreased behavioral sensitivity, respectively, to heat and mechanical stimuli. These results are consistent with the fact that both GABA and enkephalin can exert presynaptic inhibition of the sensory afferents. Taken together, this work provides a systematic view of and a set of tools for examining peri- and extrasynaptic regulations of pain-afferent transmission."  
    My comment
Note:  " sensory neurons receive  ...  supraspinal inputs"    These are the connections I'm looking for.  
    Free PMC Article

2015   2<70
The Periaqueductal Gray Orchestrates Sensory and Motor Circuits at Multiple Levels of the Neuraxis.   

    "The periaqueductal gray (PAG) coordinates behaviors essential to survival, including striking changes in movement and posture (e.g., escape behaviors in response to noxious stimuli vs freezing in response to fear-evoking stimuli). However, the neural circuits underlying the expression of these behaviors remain poorly understood.  
    We demonstrate in vivo in rats that activation of the ventrolateral PAG (vlPAG) affects motor systems at multiple levels of the neuraxis through the following:  
    (1) differential control of spinal neurons that forward sensory information to the cerebellum via spino-olivo-cerebellar pathways (nociceptive signals are reduced while proprioceptive signals are enhanced);  
    (2) alterations in cerebellar nuclear output as revealed by changes in expression of Fos-like immunoreactivity; and  
    (3) regulation of spinal reflex circuits, as shown by an increase in α-motoneuron excitability.  
    The capacity to coordinate sensory and motor functions is demonstrated in awake, behaving rats, in which natural activation of the vlPAG in fear-conditioned animals reduced transmission in spino-olivo-cerebellar pathways during periods of freezing that were associated with increased muscle tone and thus motor outflow. The increase in spinal motor reflex excitability and reduction in transmission of ascending sensory signals via spino-olivo-cerebellar pathways occurred simultaneously. We suggest that the interactions revealed in the present study between the vlPAG and sensorimotor circuits could form the neural substrate for survival behaviors associated with vlPAG activation.

Neural circuits that coordinate survival behaviors remain poorly understood. We demonstrate in rats that the periaqueductal gray (PAG) affects motor systems at the following multiple levels of the neuraxis:  
    (1) through altering transmission in spino-olivary pathways that forward sensory signals to the cerebellum, reducing and enhancing transmission of nociceptive and proprioceptive information, respectively;  
    (2) by alterations in cerebellar output; and  
    (3) through enhancement of spinal motor reflex pathways.  
    The sensory and motor effects occurred at the same time and were present in both anesthetized animals and behavioral experiments in which fear conditioning naturally activated the PAG. The results provide insights into the neural circuits that enable an animal to be ready and able to react to danger, thus assisting in survival 
    My comment
Note:  "spino-olivo-cerebellar pathways"         These are the connections I'm looking for. 
    Free PMC Article  

    My overall conclusion
It seems clear that I need to look at the efferent  Cerebellar  pathways.