Topographic Organization of Excitatory and Inhibitory Commissural Connections in the Superior Colliculi and Their Functional Roles in Saccade Generation

Our electrophysiological study showed that there are topographic connections between excitatory and inhibitory commissural neurons (CNs) in one superior colliculus (SC) and tectoreticular neurons (TRNs) in the opposite SC. To obtain morphological evidence for these topographic commissural connections between the SCs, tracers were injected into various parts of the SC, the inhibitory burst neuron (IBN) area and Forel's field H (FFH), in the cat. Retrogradely labeled CNs were classified into three types according to their somatic areas and identified as GABA-positive or -negative immunohistochemically. Caudal SC injections labeled small GABA-positive CNs (<200 μm2) in the deep layers of the opposite rostral SC. Rostral SC injections mainly labeled medium-sized GABA-negative CNs (200–700 μm2) in the upper intermediate layer of the opposite rostral SC and small GABA-positive CNs in its deeper layers. Lateral SC injections labeled small GABA-positive CNs in the opposite medial SC and mainly medium-sized GABA-negative CNs in its lateral part. Medial SC injections labeled small GABA-positive CNs in the lateral SC and medium-sized GABA-negative CNs in the medial SC. In comparison, TRNs projecting to the FFH or IBN region were large (>700 μm2) and medium-sized. Many of the medium-sized GABA-negative CNs were TRNs projecting to the FFH. These results indicate that mirror-symmetric excitatory pathways link medial to medial (upper field) and lateral to lateral (lower field) parts of the SCs, whereas upper and lower field representations are linked by reciprocal inhibitory pathways in the tectal commissure. These connections presumably play important roles in conjugate upward and downward vertical saccades.

Download Full-text

Commissural Excitation and Inhibition by the Superior Colliculus in Tectoreticular Neurons Projecting to Omnipause Neuron and Inhibitory Burst Neuron Regions

Journal of Neurophysiology ◽

10.1152/jn.00347.2005 ◽

2005 ◽

Vol 94 (3) ◽

pp. 1707-1726 ◽

Cited By ~ 38

Author(s):

M. Takahashi ◽

Y. Sugiuchi ◽

Y. Izawa ◽

Y. Shinoda

Keyword(s):

Superior Colliculus ◽

Inhibitory Neurons ◽

Functional Roles ◽

Commissural Neurons ◽

Burst Neuron ◽

Electrophysiological Studies ◽

Disynaptic Inhibition ◽

Forel's Field H ◽

Commissural Connections ◽

Stimulation Of

Previous electrophysiological studies have shown that the commissural connections between the two superior colliculi are mainly inhibitory with fewer excitatory connections. However, the functional roles of the commissural connections are not well understood, so we sought to clarify the physiology of tectal commissural excitation and inhibition of tectoreticular neurons (TRNs) in the “fixation ” and “saccade ” zones of the superior colliculus (SC). By recording intracellular potentials, we identified TRNs by their antidromic responses to stimulation of the omnipause neuron (OPN) and inhibitory burst neuron (IBN) regions and analyzed the effects of stimulation of the contralateral SC on these TRNs in anesthetized cats. TRNs in the caudal SC (saccade neurons) projected to the IBN region, and received mono- or disynaptic inhibition from the entire rostrocaudal extent of the contralateral SC. In contrast, TRNs in the rostral SC projected to the OPN or IBN region and received monosynaptic excitation from the most rostral level of the contralateral SC, and mono- or disynaptic inhibition from its entire rostrocaudal extent. Among the rostral TRNs with commissural excitation, IBN-projecting TRNs also projected to Forel's field H (vertical gaze center), suggesting that they were most likely saccade neurons related to vertical saccades. In contrast, TRNs projecting only to the OPN region were most likely fixation neurons. Most putative inhibitory neurons in the rostral SC had multiple axon branches throughout the rostrocaudal extent of the contralateral SC, whereas excitatory commissural neurons, most of which were rostral TRNs, distributed terminals to a discrete region in the rostral SC.

Download Full-text

Commissural Mirror-Symmetric Excitation and Reciprocal Inhibition Between the Two Superior Colliculi and Their Roles in Vertical and Horizontal Eye Movements

Journal of Neurophysiology ◽

10.1152/jn.00696.2007 ◽

2007 ◽

Vol 98 (5) ◽

pp. 2664-2682 ◽

Cited By ~ 29

Author(s):

M. Takahashi ◽

Y. Sugiuchi ◽

Y. Shinoda

Keyword(s):

Reciprocal Inhibition ◽

Lateral Part ◽

Medial Part ◽

Superior Colliculi ◽

Functional Roles ◽

Topographical Distribution ◽

Premotor Neurons ◽

Forel's Field H ◽

Commissural Connections ◽

Monosynaptic Excitation

The functional roles of commissural excitation and inhibition between the two superior colliculi (SCs) are not yet well understood. We previously showed the existence of strong excitatory commissural connections between the rostral SCs, although commissural connections had been considered to be mainly inhibitory. In this study, by recording intracellular potentials, we examined the topographical distribution of commissural monosynaptic excitation and inhibition from the contralateral medial and lateral SC to tectoreticular neurons (TRNs) in the medial or lateral SC of anesthetized cats. About 85% of TRNs examined projected to both the ipsilateral Forel's field H and the contralateral inhibitory burst neuron region where the respective premotor neurons for vertical and horizontal saccades reside. Medial TRNs received strong commissural excitation from the medial part of the opposite SC, whereas lateral TRNs received excitation mainly from its lateral part. Injection of wheat germ agglutinin–horseradish peroxidase into the lateral or medial SC retrogradely labeled many larger neurons in the lateral or medial part of the contralateral SC, respectively. These results indicated that excitatory commissural connections exist between the medial and medial parts and between the lateral and lateral parts of the rostral SCs. These may play an important role in reinforcing the conjugacy of upward and downward saccades, respectively. In contrast, medial SC projections to lateral SC TRNs and lateral SC projections to medial TRNs mainly produce strong inhibition. This shows that regions representing upward saccades inhibit contralateral regions representing downward saccades and vice versa.

Download Full-text

Trophic ecology, habitat, and migratory behaviour of the viperfish Chauliodus sloani reveal a key mesopelagic player

Scientific Reports ◽

10.1038/s41598-020-77222-8 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Leandro Nolé Eduardo ◽

Flávia Lucena-Frédou ◽

Michael Maia Mincarone ◽

Andrey Soares ◽

François Le Loc’h ◽

...

Keyword(s):

Trophic Ecology ◽

Anthropogenic Activities ◽

Biological Knowledge ◽

Full Time ◽

Migratory Behaviour ◽

Tropical Regions ◽

Functional Roles ◽

Physicochemical Features ◽

Deep Layers

AbstractMesopelagic fishes are numerically the most important vertebrate group of all world’s oceans. While these species are increasingly threatened by anthropogenic activities, basic biological knowledge is still lacking. For instance, major uncertainties remain on the behaviour, ecology, and thus functional roles of mesopelagic micronektivores, particularly regarding their interactions with physicochemical features. Here, we examine the trophic ecology, habitat, and migratory behaviour of the viperfish (Chauliodus sloani)—a poorly known and abundant deep-sea species—to further understand the ecology and thus functional role of mesopelagic micronektivores. Moreover, we explore how physical drivers may affect these features and how these relationships are likely to change over large oceanic areas. The viperfish heavily preys on epipelagic migrant species, especially myctophids, and presents spatial and trophic ontogenetic shifts. Temperature restricts its vertical distribution. Therefore, its trophodynamics, migratory behaviour, and functional roles are expected to be modulated by the latitudinal change in temperature. For instance, in most tropical regions the viperfish stay full-time feeding, excreting, and serving as prey (e.g. for bathypelagic predators) at deep layers. On the contrary, in temperate regions, the viperfish ascend to superficial waters where they trophically interact with epipelagic predators and may release carbon where its remineralization is the greatest.

Download Full-text

Functional Organisation of the Mouse Superior Colliculus

10.31234/osf.io/2yaj7 ◽

2021 ◽

Author(s):

Thomas Wheatcroft ◽

Aman B Saleem ◽

Samuel G Solomon

Keyword(s):

Superior Colliculus ◽

Recent Work ◽

Brain Areas ◽

Functional Roles ◽

Functional Organisation ◽

Deep Layers ◽

Convergence And Divergence ◽

Small Change ◽

And Control ◽

Inputs And Outputs

The superior colliculus (SC) is a highly conserved area of the mammalian midbrain that is widely implicated in the organisation and control of behaviour. SC receives input from a large number of brain areas, and provides outputs to a large number of areas. The convergence and divergence of anatomical connections with different areas and systems provides challenges for understanding how SC contributes to behaviours. Recent work in mouse has provided large anatomical datasets, and a wealth of new data from experiments that identify and manipulate different cells within SC, and its inputs and outputs. These data offer an opportunity to better understand the functional roles of SC. However, some of the observations appear, at first sight, to be contradictory. Here we review this recent work and suggest a simple framework which can capture the observations, and that requires only a small change to previous models. Specifically, the functional organisation of SC can be explained by supposing that three largely distinct circuits support three largely distinct classes of behaviour - arrest, turning towards, and the triggering of escape or pursuit. These behavioural classes are supported by the optic, intermediate and deep layers respectively.

Download Full-text

Topographic organization of commissural connections between the two superior colliculi and their functional roles for generating horizontal and vertical Saccades

Neuroscience Research ◽

10.1016/j.neures.2010.07.227 ◽

2010 ◽

Vol 68 ◽

pp. e105

Author(s):

Mayu Takahashi ◽

Yuriko Sugiuchi ◽

Yoshikazu Shinoda

Keyword(s):

Superior Colliculi ◽

Functional Roles ◽

Topographic Organization ◽

Vertical Saccades ◽

Commissural Connections

Download Full-text

Cell junctions in the excitable epithelium of bioluminescent scales on a polynoid worm: a freeze-fracture and electrophysiological study

Journal of Cell Science ◽

10.1242/jcs.41.1.341 ◽

1980 ◽

Vol 41 (1) ◽

pp. 341-368

Author(s):

A. Bilbaut

Keyword(s):

Epithelial Cells ◽

Gap Junctions ◽

Action Potentials ◽

Electrophysiological Study ◽

Freeze Fracture ◽

Intercellular Junctions ◽

Cell Junctions ◽

Functional Roles ◽

Electrophysiological Properties ◽

Current Passage

The bioluminescent scales of the polynoid worm Acholoe are covered by a dorsal and ventral monolayer of epithelium. The luminous activity is intracellular and arises from the ventral epithelial cells, which are modified as photocytes. Photogenic and non-photogenic epithelial cells have been examined with regard to intercellular junctions and electrophysiological properties. Desmosomes, septate and gap junctions are described between all the epithelial cells. Lanthanum impregnation and freeze-fracture reveal that the septate junctions belong to the pleated-type found in molluscs, arthropods and other annelid tissues. Freeze-fractured gap junctions show polygonal arrays of membrane particles on the P face and complementary pits on the E face. Gap junctions are of the P type as reported in vertebrate, mollusc and some annelid tissues. Intracellular current passage also induces propagated non-overshooting action potentials in all the epithelial cells; in photocytes, an increase of injected current elicits another response which is a propagated 2-component overshooting action potential correlated with luminous activity. This study shows the coexistence of septate and gap junctions in a conducting and excitable invertebrate epithelium. The results are discussed in relation to the functional roles of intercellular junctions in invertebrate epithelia. It is concluded that the gap junctions found in this excitable epithelium represent the structural sites of the cell-to-cell propagation of action potentials.

Download Full-text

Structural Variation and Polysaccharide Profiling of Intervessel Pit Membranes

10.1101/2021.06.07.447397 ◽

2021 ◽

Author(s):

Qiang Sun

Keyword(s):

Structural Integrity ◽

Vascular Diseases ◽

Primary Cell Wall ◽

Accurate Information ◽

Functional Roles ◽

Microscopy Technique ◽

Pit Membrane ◽

Deep Layers ◽

Polysaccharide Composition ◽

Different Depths

Functional roles of intervessel pit membrane (PM) depend on its structure and polysaccharide composition, which are mostly unknown or lack of accurate information. This study uses grapevine as a model plant and an immunogold-scanning electron microscopy technique to simultaneously analyze structures and polysaccharide compositions of intervessel PMs in relation to their functions. Intervessel PMs with different structural integrity were found in functional xylem with about 90 % of them being intact with a smooth or relatively smooth surface and the rest 10 % with progressively degraded structures. The results also elucidated details of the removal process of wall materials from surface toward its depth during the natural intervessel PM degradation. Four groups of pectic and hemicellulosic polysaccharides were present in intervessel PMs but displayed differential spatial distributions and quantities: weakly methyl-esterified homogalacturonans abundant in the surficial layers, heavily methyl-esterified homogalacturonans and xylans mostly in deep layers, and fucosylated xyloglucans relatively uniform in presence at different depths of an intervessel PM. This information is crucial to reveal the polysaccharide profiling of primary cell wall and to understand intervessel PM's roles in the safety and regulation of water transport as well as the plant susceptibility to vascular diseases.

Download Full-text

Spatial Arrangement of Glomerular Molecular-Feature Clusters in the Odorant-Receptor Class Domains of the Mouse Olfactory Bulb

Journal of Neurophysiology ◽

10.1152/jn.00035.2010 ◽

2010 ◽

Vol 103 (6) ◽

pp. 3490-3500 ◽

Cited By ~ 44

Author(s):

Hideyuki Matsumoto ◽

Ko Kobayakawa ◽

Reiko Kobayakawa ◽

Takuya Tashiro ◽

Kenji Mori ◽

...

Keyword(s):

Fatty Acid ◽

Olfactory Bulb ◽

Transgenic Mice ◽

Odorant Receptor ◽

Spatial Arrangement ◽

Lateral Part ◽

Molecular Feature ◽

Functional Roles ◽

Glomerular Layer ◽

Cluster A

The glomerular layer of the mammalian olfactory bulb (OB) forms odorant receptor (OR) maps. Each OR map is structurally and functionally compartmentalized into zones (dorsal and ventral) and domains (DI and DII in the dorsal zone). We previously reported that glomeruli with similar molecular receptive range properties formed molecular feature clusters at stereotypical positions in the rat OB. However, the spatial arrangement of the molecular feature clusters with regard to the OR zones and domains has not been systematically examined. In this study, we optically mapped the molecular feature clusters of glomeruli within the domain and zone framework of the OB using domain-visible class II GFP transgenic mice. In all mice examined, fatty acid-responsive cluster A was located in the lateral part of domain DI, whereas clusters B, C, and D were arranged in an anterior to posterior order within domain DII. We also found a new cluster of glomeruli that respond to fox odor trimethyl-thiazoline and its structural analogs (heterocyclic odorants that contain sulfur and nitrogen atoms within the ring). This cluster (named cluster J) was located posterior to cluster D within the DII domain. These results show that molecular feature clusters correspond to specific subsets of glomeruli in selective domains of the OR map, suggesting that the molecular feature clusters represent specific ORs that have similar molecular receptive range properties and functional roles.

Download Full-text