scholarly journals Information encoding in the inferior temporal visual cortex: contributions of the firing rates and the correlations between the firing of neurons

2010 ◽  
Vol 2 (7) ◽  
pp. 425-425
Author(s):  
N. C. Aggelopoulos ◽  
E. T. Rolls ◽  
L. Franco
Keyword(s):  
Visual Cortex ◽  
Information Encoding ◽  
Firing Rates ◽  
Inferior Temporal Visual Cortex

scholarly journals Sparse coding in striate and extrastriate visual cortex

2011 ◽  
Vol 105 (6) ◽  
pp. 2907-2919 ◽  
Author(s):  
Ben D. B. Willmore ◽  
James A. Mazer ◽  
Jack L. Gallant
Keyword(s):  
Visual Cortex ◽  
Action Potentials ◽  
Experimental Studies ◽  
Natural Images ◽  
Theoretical Studies ◽  
Exponential Distributions ◽  
Neural Codes ◽  
Firing Rates ◽  
Visual Hierarchy ◽  
Primate Visual Cortex

Theoretical studies of mammalian cortex argue that efficient neural codes should be sparse. However, theoretical and experimental studies have used different definitions of the term “sparse” leading to three assumptions about the nature of sparse codes. First, codes that have high lifetime sparseness require few action potentials. Second, lifetime-sparse codes are also population-sparse. Third, neural codes are optimized to maximize lifetime sparseness. Here, we examine these assumptions in detail and test their validity in primate visual cortex. We show that lifetime and population sparseness are not necessarily correlated and that a code may have high lifetime sparseness regardless of how many action potentials it uses. We measure lifetime sparseness during presentation of natural images in three areas of macaque visual cortex, V1, V2, and V4. We find that lifetime sparseness does not increase across the visual hierarchy. This suggests that the neural code is not simply optimized to maximize lifetime sparseness. We also find that firing rates during a challenging visual task are higher than theoretical values based on metabolic limits and that responses in V1, V2, and V4 are well-described by exponential distributions. These findings are consistent with the hypothesis that neurons are optimized to maximize information transmission subject to metabolic constraints on mean firing rate.

scholarly journals Information in the first spike, the order of spikes, and the number of spikes provided by neurons in the inferior temporal visual cortex

2006 ◽  
Vol 46 (25) ◽  
pp. 4193-4205 ◽  
Author(s):  
Edmund T. Rolls ◽  
Leonardo Franco ◽  
Nikolaos C. Aggelopoulos ◽  
Jose M. Jerez
Keyword(s):  
Visual Cortex ◽  
Inferior Temporal Visual Cortex

Corticogeniculate neurons, corticotectal neurons, and suspected interneurons in visual cortex of awake rabbits: receptive-field properties, axonal properties, and effects of EEG arousal

1987 ◽  
Vol 57 (4) ◽  
pp. 977-1001 ◽  
Author(s):  
H. A. Swadlow ◽  
T. G. Weyand
Keyword(s):  
Electrical Stimulation ◽  
Visual Cortex ◽  
Receptive Field ◽  
Receptive Fields ◽  
Spontaneous Firing ◽  
Visual Responses ◽  
Firing Rates ◽  
Axonal Conduction ◽  
Conduction Velocities ◽  
Stimulation Of

The intrinsic stability of the rabbit eye was exploited to enable receptive-field analysis of antidromically identified corticotectal (CT) neurons (n = 101) and corticogeniculate (CG) neurons (n = 124) in visual area I of awake rabbits. Eye position was monitored to within 1/5 degrees. We also studied the receptive-field properties of neurons synaptically activated via electrical stimulation of the dorsal lateral geniculate nucleus (LGNd). Whereas most CT neurons had either complex (59%) or motion/uniform (15%) receptive fields, we also found CT neurons with simple (9%) and concentric (4%) receptive fields. Most complex CT cells were broadly tuned to both stimulus orientation and velocity, but only 41% of these cells were directionally selective. We could elicit no visual responses from 6% of CT cells, and these cells had significantly lower conduction velocities than visually responsive CT cells. The median spontaneous firing rates for all classes of CT neurons were 4-8 spikes/s. CG neurons had primarily simple (60%) and concentric (9%) receptive fields, and none of these cells had complex receptive fields. CG simple cells were more narrowly tuned to both stimulus orientation and velocity than were complex CT cells, and most (85%) were directionally selective. Axonal conduction velocities of CG neurons (mean = 1.2 m/s) were much lower than those of CT neurons (mean = 6.4 m/s), and CG neurons that were visually unresponsive (23%) had lower axonal conduction velocities than did visually responsive CG neurons. Some visually unresponsive CG neurons (14%) responded with saccadic eye movements. The median spontaneous firing rates for all classes of CG neurons were less than 1 spike/s. All neurons synaptically activated via LGNd stimulation at latencies of less than 2.0 ms had receptive fields that were not orientation selective (89% motion/uniform, 11% concentric), whereas most cells with orientation-selective receptive fields had considerably longer synaptic latencies. Most short-latency motion/uniform neurons responded to electrical stimulation of the LGNd (and visual area II) with a high-frequency burst (500-900 Hz) of three or more spikes. Action potentials of these neurons were of short duration, thresholds of synaptic activation were low, and spontaneous firing rates were the highest seen in rabbit visual cortex. These properties are similar to those reported for interneurons in several regions in mammalian central nervous system. Nonvisual sensory stimuli that resulted in electroencephalographic arousal (hippocampal theta activity) had a profound effect on the visual responses of many visual cortical neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Multiple shared mechanisms for homeostatic plasticity in rodent somatosensory and visual cortex

2017 ◽  
Vol 372 (1715) ◽  
pp. 20160157 ◽  
Author(s):  
Melanie A. Gainey ◽  
Daniel E. Feldman
Keyword(s):  
Visual Cortex ◽  
Sensory Deprivation ◽  
Homeostatic Plasticity ◽  
Intrinsic Excitability ◽  
Synaptic Scaling ◽  
Cellular Mechanisms ◽  
Firing Rates ◽  
Parvalbumin Interneuron ◽  
Activity Dependent ◽  
V1 Cortex

We compare the circuit and cellular mechanisms for homeostatic plasticity that have been discovered in rodent somatosensory (S1) and visual (V1) cortex. Both areas use similar mechanisms to restore mean firing rate after sensory deprivation. Two time scales of homeostasis are evident, with distinct mechanisms. Slow homeostasis occurs over several days, and is mediated by homeostatic synaptic scaling in excitatory networks and, in some cases, homeostatic adjustment of pyramidal cell intrinsic excitability. Fast homeostasis occurs within less than 1 day, and is mediated by rapid disinhibition, implemented by activity-dependent plasticity in parvalbumin interneuron circuits. These processes interact with Hebbian synaptic plasticity to maintain cortical firing rates during learned adjustments in sensory representations. This article is part of the themed issue ‘Integrating Hebbian and homeostatic plasticity’.

scholarly journals Locomotion enhances neural encoding of visual stimuli in mouse V1

2017 ◽  
Author(s):  
Maria C. Dadarlat ◽  
Michael P. Stryker
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Visual Stimuli ◽  
Major Effect ◽  
Neural Population ◽  
Neural Encoding ◽  
Firing Rates ◽  
Fold Reduction ◽  
Layer V ◽  
The Relationship

AbstractNeurons in mouse primary visual cortex (V1) are selective for particular properties of visual stimuli. Locomotion causes a change in cortical state that leaves their selectivity unchanged but strengthens their responses. Both locomotion and the change in cortical state are initiated by projections from the mesencephalic locomotor region (MLR), the latter through a disinhibitory circuit in V1. The function served by this change in cortical state is unknown. By recording simultaneously from a large number of single neurons in alert mice viewing moving gratings, we investigated the relationship between locomotion and the information contained within the neural population. We found that locomotion improved encoding of visual stimuli in V1 by two mechanisms. First, locomotion-induced increases in firing rates enhanced the mutual information between visual stimuli and single neuron responses over a fixed window of time. Second, stimulus discriminability was improved, even for fixed population firing rates, because of a decrease in noise correlations across the population during locomotion. These two mechanisms contributed differently to improvements in discriminability across cortical layers, with changes in firing rates most important in the upper layers and changes in noise correlations most important in layer V. Together, these changes resulted in a three- to five-fold reduction in the time needed to precisely encode grating direction and orientation. These results support the hypothesis that cortical state shifts during locomotion to accommodate an increased load on the visual system when mice are moving.Significance StatementThis paper contains three novel findings about the representation of information in neurons within the primary visual cortex of the mouse. First, we show that locomotion reduces by at least a factor of three the time needed for information to accumulate in the visual cortex that allows the distinction of different visual stimuli. Second, we show that the effect of locomotion is to increase information in cells of all layers of the visual cortex. Third we show that the means by which information is enhanced by locomotion differs between the upper layers, where the major effect is the increasing of firing rates, and in layer V, where the major effect is the reduction in noise correlations.

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