Axonal distribution and functional topography of layer 6 pyramidal cells in the primary visual cortex of the cat (Area 18).

In the cerebral cortex, the interaction of excitatory and inhibitory synaptic inputs shapes the responses of neurons to sensory stimuli, stabilizes network dynamics1 and improves the efficiency and robustness of the neural code2–4. Excitatory neurons receive inhibitory inputs that track excitation5–8. However, how this co-tuning of excitation and inhibition is achieved by cortical circuits is unclear, since inhibitory interneurons are thought to pool the inputs of nearby excitatory cells and provide them with non-specific inhibition proportional to the activity of the local network9–13. Here we show that although parvalbumin-expressing (PV) inhibitory cells in mouse primary visual cortex make connections with the majority of nearby pyramidal cells, the strength of their synaptic connections is structured according to the similarity of the cells’ responses. Individual PV cells strongly inhibit those pyramidal cells that provide them with strong excitation and share their visual selectivity. This fine-tuning of synaptic weights supports co-tuning of inhibitory and excitatory inputs onto individual pyramidal cells despite dense connectivity between inhibitory and excitatory neurons. Our results indicate that individual PV cells are preferentially integrated into subnetworks of inter-connected, co-tuned pyramidal cells, stabilising their recurrent dynamics. Conversely, weak but dense inhibitory connectivity between subnetworks is sufficient to support competition between them, de-correlating their output. We suggest that the history and structure of correlated firing adjusts the weights of both inhibitory and excitatory connections, supporting stable amplification and selective recruitment of cortical subnetworks.

Download Full-text

Cortical reorganization of the visual system in post-stroke hemianopia studied with fMRI

Stroke ◽

10.1161/str.32.suppl_1.334 ◽

2001 ◽

Vol 32 (suppl_1) ◽

pp. 334-334

Author(s):

Gereon Nelles ◽

Guido Widmann ◽

Joachim Esser ◽

Anette Meistrowitz ◽

Johannes Weber ◽

...

Keyword(s):

Visual Cortex ◽

Visual Field ◽

Visual System ◽

Primary Visual Cortex ◽

Visual Stimuli ◽

Checkerboard Pattern ◽

Partial Recovery ◽

Area 18 ◽

Area 19 ◽

Stimulation Of

102 Introduction: Restitution of unilateral visual field defects following occipital cortex lesions occurs rarely. Partial recovery, however, can be observed in patients with incomplete lesion of the visual cortex. Our objective was to study the neuroplastic changes in the visual system that underlie such recovery. Methods and Results: Six patients with a left PCA-territory cortical stroke and 6 healthy control subjects were studied during rest and during visual stimulation using a 1.5 T fMRI with a 40 mT gradient. Visual stimuli were projected with a laptop computer onto a 154 x 115 cm screen, placed 90 cm in front of the gantry. Subjects were asked to fixate a red point in the center of the screen during both conditions. During stimulation, a black-and-white checkerboard pattern reversal was presented in each hemifield. For each side, 120 volumes of 48 contiguous axial fMRI images were obtained during rest and during hemifield stimulation in alternating order (60 volumes for each condition). Significant differences of rCBF between stimulation and rest were assessed as group analyses using statistical parametric mapping (SPM 99; p<0.01, corrected for multiple comparison). In controls, strong increases of rCBF (Z=7.6) occurred in the contralateral primary visual cortex V1 (area 17) and in V3a (area 18) and V5 (area 19). No differences were found between the right and left side in controls. During stimulation of the unaffected (left) visual field in hemianopic patients, activation occurred in contralateral V1, but the strongest increases of rCBF (Z>10) were seen in contralateral V3a (area 18) and V5 (area 19). During stimulation of the hemianopic (right) visual field, no activation was found in the primary visual cortex of either hemisphere. The most significant activation (Z=9.2) was seen in the ipsilateral V3a and V5 areas, and contralateral (left) V3a. Conclusions: Partial recovery from hemianopia is associated with strong ipsilateral activation of the visual system. Processing of visual stimuli in the hemianopic side spares the primary visual cortex and may involve recruitment of neurons in ipsilateral (contralesional) areas V3a and V5.

Download Full-text

A biological blueprint for the axons of superficial layer pyramidal cells in cat primary visual cortex

Brain Structure and Function ◽

10.1007/s00429-017-1410-6 ◽

2017 ◽

Vol 222 (8) ◽

pp. 3407-3430 ◽

Cited By ~ 3

Author(s):

Kevan A. C. Martin ◽

Stephan Roth ◽

Elisha S. Rusch

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Pyramidal Cells ◽

Superficial Layer

Download Full-text

Expression of GABAAReceptor Subunit mRNAs by Layer V Pyramidal Cells of the Rat Primary Visual Cortex

European Journal of Neuroscience ◽

10.1111/j.1460-9568.1997.tb01435.x ◽

1997 ◽

Vol 9 (4) ◽

pp. 857-862 ◽

Cited By ~ 19

Author(s):

Diego Ruano ◽

David Perrais ◽

Jean Rosier ◽

Nicole Ropert

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Pyramidal Cells ◽

Layer V

Download Full-text

Opposing forms of adaptation in mouse visual cortex are controlled by distinct inhibitory microcircuits and gated by locomotion

10.1101/2020.01.16.909788 ◽

2020 ◽

Cited By ~ 1

Author(s):

Tristan G. Heintz ◽

Antonio J. Hinojosa ◽

Leon Lagnado

Keyword(s):

Visual Cortex ◽

Primary Visual Cortex ◽

Internal State ◽

Pyramidal Cells ◽

External World ◽

Neural Circuitry ◽

Cortical Processing ◽

Locomotor Behaviour ◽

Different Types ◽

Mouse Visual Cortex

SummaryCortical processing of sensory signals adjusts to changes in both the external world and the internal state of the animal. We investigated the neural circuitry by which these processes interact in the primary visual cortex of mice. An increase in contrast caused as many pyramidal cells (PCs) to sensitize as depress, reflecting the dynamics of adaptation in different types of interneuron (PV, SST and VIP). Optogenetic manipulations demonstrate that the net effect within PCs reflects the balance of PV inputs, driving depression, and a subset of SST interneurons, driving sensitization. Locomotor behaviour increased the gain of PC responses by disinhibition through both the VIP->SST and SST->PV pathways, thereby maintaining the balance between opposing forms of plasticity. These experiments reveal how inhibitory microcircuits interact to purpose different subsets of PCs for the signalling of increases or decreases in contrast while also allowing for behavioural control of gain across the population.

Download Full-text