1727 Roles of horizontal connection in superficial layer of the kitten primary visual cortex studied in in vivo and in vitro preparation

AbstractPrimary sensory areas of the mammalian neocortex have a remarkable degree of plasticity, allowing neural circuits to adapt to dynamic environments. However, little is known about the effects of traumatic brain injury on visual circuit function. Here we used anatomy and in vivo electrophysiological recordings in adult mice to quantify neuron responses to visual stimuli two weeks and three months after mild controlled cortical impact injury to primary visual cortex (V1). We found that, although V1 remained largely intact in brain-injured mice, there was ~35% reduction in the number of neurons that affected inhibitory cells more broadly than excitatory neurons. V1 neurons showed dramatically reduced activity, impaired responses to visual stimuli and weaker size selectivity and orientation tuning in vivo. Our results show a single, mild contusion injury produces profound and long-lasting impairments in the way V1 neurons encode visual input. These findings provide initial insight into cortical circuit dysfunction following central visual system neurotrauma.

Download Full-text

Motion/direction-sensitive thalamic neurons project extensively to the middle layers of primary visual cortex

10.1101/2021.07.07.451534 ◽

2021 ◽

Author(s):

Jun Zhuang ◽

Yun Wang ◽

Naveen D Ouellette ◽

Emily Turschak ◽

Rylan Larsen ◽

...

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Population Level ◽

Middle Layer ◽

Current View ◽

Motion Direction ◽

Thalamic Neurons ◽

Novel Approach ◽

Single Axon

The motion/direction-sensitive and location-sensitive neurons are two major functional types in mouse visual thalamus that project to the primary visual cortex (V1). It has been proposed that the motion/direction-sensitive neurons mainly target the superficial layers in V1, in contrast to the location-sensitive neurons which mainly target the middle layers. Here, by imaging calcium activities of motion/direction-sensitive and location-sensitive axons in V1, we find no evidence for these cell-type specific laminar biases at population level. Furthermore, using a novel approach to reconstruct single-axon structures with identified in vivo response types, we show that, at single-axon level, the motion/direction-sensitive axons have middle layer preferences and project more densely to the middle layers than the location-sensitive axons. Overall, our results demonstrate that Motion/direction-sensitive thalamic neurons project extensively to the middle layers of V1, challenging the current view of the thalamocortical organizations in the mouse visual system.

Download Full-text

Temporo-nasally biased moving grating selectivity in mouse primary visual cortex

10.1101/708644 ◽

2019 ◽

Author(s):

Marie Tolkiehn ◽

Simon R. Schultz

Keyword(s):

Visual Cortex ◽

Spatial Frequency ◽

Primary Visual Cortex ◽

Moving Objects ◽

Direction Selectivity ◽

Orientation Tuning ◽

High Signal ◽

Forward Movement ◽

Upward Moving

AbstractOrientation tuning in mouse primary visual cortex (V1) has long been reported to have a random or “salt-and-pepper” organisation, lacking the structure found in cats and primates. Laminar in-vivo multi-electrode array recordings here reveal previously elusive structure in the representation of visual patterns in the mouse visual cortex, with temporo-nasally drifting gratings eliciting consistently highest neuronal responses across cortical layers and columns, whilst upward moving gratings reliably evoked the lowest activities. We suggest this bias in direction selectivity to be behaviourally relevant as objects moving into the visual field from the side or behind may pose a predatory threat to the mouse whereas upward moving objects do not. We found furthermore that direction preference and selectivity was affected by stimulus spatial frequency, and that spatial and directional tuning curves showed high signal correlations decreasing with distance between recording sites. In addition, we show that despite this bias in direction selectivity, it is possible to decode stimulus identity and that spatiotemporal features achieve higher accuracy in the decoding task whereas spike count or population counts are sufficient to decode spatial frequencies implying different encoding strategies.Significance statementWe show that temporo-nasally drifting gratings (i.e. opposite the normal visual flow during forward movement) reliably elicit the highest neural activity in mouse primary visual cortex, whereas upward moving gratings reliably evoke the lowest responses. This encoding may be highly behaviourally relevant, as objects approaching from the periphery may pose a threat (e.g. predators), whereas upward moving objects do not. This is a result at odds with the belief that mouse primary visual cortex is randomly organised. Further to this biased representation, we show that direction tuning depends on the underlying spatial frequency and that tuning preference is spatially correlated both across layers and columns and decreases with cortical distance, providing evidence for structural organisation in mouse primary visual cortex.

Download Full-text

Oxytocin shapes spontaneous activity patterns in the developing visual cortex by activating somatostatin interneurons

10.1101/866251 ◽

2019 ◽

Cited By ~ 1

Author(s):

Paloma P Maldonado ◽

Alvaro Nuno-Perez ◽

Jan Kirchner ◽

Elizabeth Hammock ◽

Julijana Gjorgjieva ◽

...

Keyword(s):

Visual Cortex ◽

Spontaneous Activity ◽

Sensory Processing ◽

Activity Patterns ◽

Network Activity ◽

Synaptic Connections ◽

Pairwise Correlations ◽

Early Brain Development

SummarySpontaneous network activity shapes emerging neuronal circuits during early brain development, however how neuromodulation influences this activity is not fully understood. Here, we report that the neuromodulator oxytocin powerfully shapes spontaneous activity patterns. In vivo, oxytocin strongly decreased the frequency and pairwise correlations of spontaneous activity events in visual cortex (V1), but not in somatosensory cortex (S1). This differential effect was a consequence of oxytocin only increasing inhibition in V1 and increasing both inhibition and excitation in S1. The increase in inhibition was mediated by the depolarization and increase in excitability of somatostatin+ (SST) interneurons specifically. Accordingly, silencing SST+ neurons pharmacogenetically fully blocked oxytocin’s effect on inhibition in vitro as well its effect on spontaneous activity patterns in vivo. Thus, oxytocin decreases the excitatory/inhibitory ratio and modulates specific features of V1 spontaneous activity patterns that are crucial for refining developing synaptic connections and sensory processing later in life.

Download Full-text

Effects of norepinephrine upon superficial layer neurons in the superior colliculus of the hamster: In vitro studies

Visual Neuroscience ◽

10.1017/s0952523899163156 ◽

1999 ◽

Vol 16 (3) ◽

pp. 557-570 ◽

Cited By ~ 9

Author(s):

HONGJING TAN ◽

RICHARD D. MOONEY ◽

ROBERT W. RHOADES

Keyword(s):

Superior Colliculus ◽

Optic Tract ◽

Reversal Potential ◽

Outward Current ◽

Input Resistance ◽

Superficial Layer ◽

Membrane Properties ◽

Induced Response

Intracellular recording techniques were used to evaluate the effects of norepinephrine (NE) on the membrane properties of superficial layer (stratum griseum superficiale and stratum opticum) superior colliculus (SC) cells. Of the 207 cells tested, 44.4% (N = 92) were hyperpolarized by ≥3 mV and 8.7% (N = 18) were depolarized by ≥3 mV by application of NE. Hyperpolarization induced by NE was dose dependent (EC50 = 8.1 μM) and was associated with decreased input resistance and outward current which had a reversal potential of −94.0 mV. Depolarization was associated with a very slight rise in input resistance and had a reversal potential of −93.1 mV for the single cell tested. Pharmacologic experiments demonstrated that isoproterenol, dobutamine, and p-aminoclonidine all hyperpolarized SC cells. These results are consistent with the conclusion that NE-induced hyperpolarization of SC cells is mediated by both α2 and β1 adrenoceptors. The α1 adrenoceptor agonists, methoxamine and phenylephrine, depolarized 35% (6 of 17) of the SC cells tested by ≥3 mV. Most of the SC cells tested exhibited responses indicative of expression of more than one adrenoceptor. Application of p-aminoclonidine or dobutamine inhibited transsynaptic responses in SC cells evoked by electrical stimulation of optic tract axons. Inhibition of evoked responses by these agents was usually, but not invariably, associated with a hyperpolarization of the cell membrane and a reduction in depolarizing potentials evoked by application of glutamate. The present in vitro results are consistent with those of the companion in vivo study which suggested that NE-induced response suppression in superficial layer SC neurons was primarily postsynaptic and chiefly mediated by both α2 and β1 adrenoceptors.

Download Full-text

Temporal constraints in associative synaptic plasticity in hippocampus and neocortex

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y95-185 ◽

1995 ◽

Vol 73 (9) ◽

pp. 1295-1311 ◽

Cited By ~ 16

Author(s):

Dominique Debanne ◽

Daniel E. Shulz ◽

Yves Frégnac

Keyword(s):

Visual Cortex ◽

Membrane Potential ◽

Temporal Frequency ◽

Postsynaptic Membrane ◽

Synaptic Potentiation ◽

Test Input ◽

Homosynaptic Depression ◽

Postsynaptic Cell

We present comparative experimental evidence for the induction of synaptic potentiation and depression in organotypic cultures of hippocampus and in visual cortex in vitro and in vivo. The effects of associative pairings on the efficacy of synaptic transmission are analyzed as a function of the temporal delay between presynaptic activity and post-synaptic changes imposed in membrane potential. Synchronous association at a low temporal frequency (<0.5 Hz) between presynaptic input and postsynaptic depolarization resulted in homosynaptic potentiation of functionally identified postsynaptic potentials in the three types of preparation. Synchronous pairing of afferent activity with hyperpolarization of the postsynaptic cell resulted in homosynaptic depression in visual cortex in vivo and in vitro. An associative form of depression was induced in hippocampus when the test input was followed repeatedly with a fixed-delay postsynaptic depolarization imposed either by intracellular current injection or synaptically. The latter process might play a significant role in heterosynaptic plasticity in visual cortex in vivo and in vitro, if it is assumed that associative depression still operates in visual cortex a few seconds after the initial surge of calcium in the postsynaptic cell. We conclude that the precise timing between presynaptic activity and polarization changes in postsynaptic membrane potential up- and down-regulates the efficacy of active pathways.Key words: synaptic potentiation, synaptic depression, asynchrony, covariance, supervised learning.

Download Full-text

Recent findings on oogenesis of Drosophila melanogaster

Development ◽

10.1242/dev.38.1.125 ◽

1977 ◽

Vol 38 (1) ◽

pp. 125-138

Author(s):

F. Giorgi ◽

J. Jacob

Keyword(s):

Drosophila Melanogaster ◽

Fat Body ◽

Radioactive Tracer ◽

Superficial Layer ◽

Ruthenium Red ◽

Time Interval ◽

Intracellular Location ◽

Short Time

Vitellogenic ovaries from Drosophila melanogaster flies have been exposed, either in in vivo or in vitro conditions, to various extracellular tracers in an attempt to determine the possible route of entry of the yolk precursors. Ruthenium red and lanthanum nitrate have been shown to gain access to the oocyte surface by initially passing through the intercellular spaces of the follicle layer. Both these tracers, however, never attain an intracellular location within any of the cells forming the ovarian chamber. Colloidal Thorotrast when injected into adult females has never been detected within any of the ovarian chambers examined, irrespective of their stage. Vitellogenic oocytes exposed to peroxidase in in vivo conditions exhibit the oolemma and all the structural elements present in the cortical ooplasm well labelled within a very short time after the injection. Moreover, with gradually increasing exposure times to peroxidase, the labelled yolk platelets increase progressively in number. At each time interval after the injection, the label over the yolk platelets remains restricted to the superficial layer and never gets into the associated body. The pattern of tritiated lysine incorporation into vitellogenic oocytes has been studied over a period of 20 h. A few hours after injection of the radioactive tracer, the silver grains located over the ooplasm appear distributed at random. A predominant labelling of the yolk platelets as compared to the rest of the ooplasm, becomes evident only with a 6 h delay since the time of injection. When analysed by electrophoresis and isolectrofocusing, the vitellogenic ovary is seen to exhibit a number of protein bands which are common to those of other tissues as, for instance, haemolymph and fat body. The evidence obtained in the present study is discussed in relation to the hypothesis of an extraovarian origin of the yolk precursors and their sequestration into forming yolk platelets.

Download Full-text