Temporal Dynamics of Shape Analysis in Macaque Visual Area V2

2004 ◽  
Vol 92 (5) ◽  
pp. 3030-3042 ◽  
Author(s):  
Jay Hegdé ◽  
David C. Van Essen
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Temporal Dynamics ◽  
Visual Stimulation ◽  
Signal To Noise Ratio ◽  
Stimulus Onset ◽  
Visual Area ◽  
Response Modulation ◽  
Population Response ◽  
Area V2

The firing rate of visual cortical neurons typically changes substantially during a sustained visual stimulus. To assess whether, and to what extent, the information about shape conveyed by neurons in visual area V2 changes over the course of the response, we recorded the responses of V2 neurons in awake, fixating monkeys while presenting a diverse set of static shape stimuli within the classical receptive field. We analyzed the time course of various measures of responsiveness and stimulus-related response modulation at the level of individual cells and of the population. For a majority of V2 cells, the response modulation was maximal during the initial transient response (40–80 ms after stimulus onset). During the same period, the population response was relatively correlated, in that V2 cells tended to respond similarly to specific subsets of stimuli. Over the ensuing 80–100 ms, the signal-to-noise ratio of individual cells generally declined, but to a lesser degree than the evoked-response rate during the corresponding time bins, and the response profiles became decorrelated for many individual cells. Concomitantly, the population response became substantially decorrelated. Our results indicate that the information about stimulus shape evolves dynamically and relatively rapidly in V2 during static visual stimulation in ways that may contribute to form discrimination.

Mechanisms of Feature- and Space-Based Attention: Response Modulation and Baseline Increases

2007 ◽  
Vol 98 (4) ◽  
pp. 2110-2121 ◽  
Author(s):  
Stephanie A. McMains ◽  
Hilda M. Fehd ◽  
Tatiana-Aloi Emmanouil ◽  
Sabine Kastner
Keyword(s):  
Target Location ◽  
Stimulus Onset ◽  
Visual Area ◽  
Response Modulation ◽  
Neural Responses ◽  
Attentional Modulation ◽  
Stimulus Preference ◽  
Baseline Activity ◽  
Object Based ◽  
Evoked Activity

Selective attention modulates neural activity in the visual system both in the presence and in the absence of visual stimuli. When subjects direct attention to a particular location in a visual scene in anticipation of the stimulus onset, there is an increase in baseline activity. How do such baseline increases relate to the attentional modulation of stimulus-driven activity? Using functional magnetic resonance imaging, we demonstrate that baseline increases related to the expectation of motion or color stimuli at a peripheral target location do not predict the modulation of neural responses evoked by these stimuli when attended. In areas such as MT and TEO that were more effectively activated by one stimulus type than the other, attentional modulation of visually evoked activity depended on the stimulus preference of a visual area and was stronger for the effective than for the noneffective stimulus. In contrast, baseline increases did not reflect the stimulus preference of a visual area. Rather, these signals were shown to be spatially specific and appeared to be dominated by the location information and not by the feature information of the cue with the experimental paradigms under study. These findings provide evidence that baseline increases in visual cortex during cue periods do not reflect the activation of a memory template that includes particular stimulus properties of the expected target, but rather carry information about the location of an expected target stimulus. In addition, when the stimulus contained both color and motion, an object-based attention effect was observed, with significant attentional modulation in the area that responded preferentially to the unattended feature.

Short-latency ocular following responses of monkey. II. Dependence on a prior saccadic eye movement

1986 ◽  
Vol 56 (5) ◽  
pp. 1355-1380 ◽  
Author(s):  
K. Kawano ◽  
F. A. Miles
Keyword(s):  
Time Course ◽  
Visual Stimulation ◽  
Interocular Transfer ◽  
Sine Wave ◽  
Stimulus Onset ◽  
Short Latency ◽  
Visual Scene ◽  
Retinal Stimulation ◽  
Ocular Following ◽  
Eye Velocity

The ocular following responses elicited by brief unexpected movements of the visual scene were studied in eight rhesus monkeys. Test patterns were random dots except in one experiment when sine-wave gratings were used. Test stimuli were velocity steps of 100-ms duration applied after spontaneous saccades. Two response measures were used: the initial peak in the eye velocity profile (ei), and the average final eye velocity over the period of 110-140 ms measured from stimulus onset (ef). Responses were best when the test ramps began soon after saccades and attenuated progressively as the postsaccadic delay interval was increased: postsaccadic enhancement of ocular following. The decline in ei was roughly exponential: average time constant, 60 ms; average asymptote, 22%. Later measures (ef) were generally less affected. We suggest that this transient enhancement aids the visual suppression of postsaccadic ocular drifts (glissades) and the tracking of moving images newly acquired with a saccade. The magnitude of the postsaccadic enhancement was dependent on the amount of retinal stimulation during the antecedent saccade; when this stimulation was compromised, as when a vertical saccade was made while viewing a grating pattern with vertically oriented stripes, subsequent enhancement of ocular following was much reduced. Further, saccade-like conditioning movements of the visual scene resulted in an enhancement of the ocular following, elicited by subsequent test ramps, that was similar in magnitude and time course to that in the wake of real saccades. We conclude that the postsaccadic enhancement of ocular following is largely due to the visual stimulation produced by the saccade sweeping the scene across the retina. Data obtained with the visual field partitioned into central and peripheral regions (center 20-60 degrees diam) and with gaze centered suggested that the short-latency ocular following system and the enhancement mechanism that modulates it both receive their major inputs from the central 40 degrees of the retina. Further, when this central region was partitioned, enhancement was obtained only when the conditioning and test stimuli were presented to the same region of retina. Visual enhancement showed only weak interocular transfer: the conditioning and test stimuli had to be seen by the same eye to produce appreciable enhancement. These data suggest that the enhancement involves local spatial interactions at an "early" point in the visual pathway before the inputs from the two eyes have converged. When the conditioning and test stimuli impinged on different regions of the retina, brief powerful suppression of ocular following was obtained.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Monitoring the haemodynamic response to visual stimulation in glaucoma patients

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Re ◽  
D. Messenio ◽  
G. Marano ◽  
L. Spinelli ◽  
I. Pirovano ◽  
...  
Keyword(s):  
Time Course ◽  
Near Infrared ◽  
Visual Stimulation ◽  
Open Angle Glaucoma ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Ease Of Use ◽  
Haemodynamic Response ◽  
Functional Near Infrared Spectroscopy ◽  
Domain Functional

AbstractIn this paper, we used time-domain functional near infrared spectroscopy (TD-fNIRS) to evaluate the haemodynamic response function (HRF) in the occipital cortex following visual stimulation in glaucomatous eyes as compared to healthy eyes. A total of 98 subjects were enrolled in the study and clinically classified as healthy subjects, glaucoma patients (primary open-angle glaucoma) and mixed subjects (i.e. with a different classification for the two eyes). After quality check data were used from HRF of 73 healthy and 62 glaucomatous eyes. The amplitudes of the oxygenated and deoxygenated haemoglobin concentrations, together with their latencies with respect to the stimulus onset, were estimated by fitting their time course with a canonical HRF. Statistical analysis showed that the amplitudes of both haemodynamic parameters show a significant association with the pathology and a significant discriminating ability, while no significant result was found for latencies. Overall, our findings together with the ease of use and noninvasiveness of TD-NIRS, make this technique a promising candidate as a supporting tool for a better evaluation of the glaucoma pathology.

scholarly journals The same ultra-rapid parallel brain dynamics underpin the production and perception of speech

2021 ◽  
Author(s):  
Amie Fairs ◽  
Amandine Michelas ◽  
Sophie Dufour ◽  
Kristof Strijkers
Keyword(s):  
Language Processing ◽  
Time Course ◽  
Linear Models ◽  
Temporal Dynamics ◽  
Building Blocks ◽  
Naming Task ◽  
Stimulus Onset ◽  
Language Models ◽  
Mixed Linear Models ◽  
Listening Task

AbstractThe temporal dynamics by which linguistic information becomes available is one of the key properties to understand how language is organised in the brain. An unresolved debate between different brain language models is whether words, the building blocks of language, are activated in a sequential or parallel manner. In this study we approached this issue from a novel perspective by directly comparing the time course of word component activation in speech production versus perception. In an overt object naming task and a passive listening task we analysed with mixed linear models at the single-trial level the event-related brain potentials elicited by the same lexico-semantic and phonological word knowledge in the two language modalities. Results revealed that both word components manifested simultaneously as early as 75 ms after stimulus onset in production and perception; differences between the language modalities only became apparent after 300 ms of processing. The data provide evidence for ultra-rapid parallel dynamics of language processing and are interpreted within a neural assembly framework where words recruit the same integrated cell assemblies across production and perception. These word assemblies ignite early on in parallel and only later on reverberate in a behaviour-specific manner.

Shifting Attention in Feature Space: Fast Facilitation of the To-Be-Attended Feature Is Followed by Slow Inhibition of the To-Be-Ignored Feature

2020 ◽  
pp. 1-10
Author(s):  
Paula Vieweg ◽  
Matthias M. Müller
Keyword(s):  
Visual Cortex ◽  
Time Course ◽  
Temporal Dynamics ◽  
Signal To Noise Ratio ◽  
Feature Space ◽  
Statistical Testing ◽  
Limiting Factors ◽  
Early Visual Cortex ◽  
Vertical Bars ◽  
Time Invariant

In an explorative study, we investigated the time course of attentional selection shifts in feature-based attention in early visual cortex by means of steady-state visual evoked potentials (SSVEPs). To this end, we presented four flickering random dot kinematograms with red/blue, horizontal/vertical bars, respectively. Given the oscillatory nature of SSVEPs, we were able to investigate neural temporal dynamics of facilitation and inhibition/suppression when participants shifted attention either within (i.e., color to color) or between feature dimensions (i.e., color to orientation). Extending a previous study of our laboratory [Müller, M. M., Trautmann, M., & Keitel, C. Early visual cortex dynamics during top–down modulated shifts of feature-selective attention. Journal of Cognitive Neuroscience, 28, 643–655, 2016] to a full factorial design, we replicated a critical finding of our previous study: Facilitation of color was quickest, regardless of the origin of the shift (from color or orientation). Furthermore, facilitation of the newly to-be-attended and inhibition/suppression of the then to-be-ignored feature is not a time-invariant process that occurs instantaneously, but a biphasic one with longer time delays between the two processes. Interestingly, inhibition/suppression of the to-be-ignored feature after the shifting cue had a much longer latency with between- compared to within-dimensional shifts (by about 130–150 msec). The exploratory nature of our study is reasoned by two limiting factors: (a) Identical to our precursor study, we found no attentional SSVEP amplitude time course modulation for orientation, and (b) the signal-to-noise ratio for single trials was too poor to allow for reliable statistical testing of the latencies that were obtained with running t tests of averaged data.

GABA inactivation of visual area MT modifies the responsiveness and direction selectivity of V2 neurons in Cebus monkeys

2011 ◽  
Vol 28 (6) ◽  
pp. 513-527 ◽  
Author(s):  
ANA KARLA JANSEN-AMORIM ◽  
BRUSS LIMA ◽  
MARIO FIORANI ◽  
RICARDO GATTASS
Keyword(s):  
Receptive Field ◽  
Signal To Noise Ratio ◽  
Neuronal Response ◽  
Direction Selectivity ◽  
Visual Area ◽  
Area Mt ◽  
Receptive Field Properties ◽  
Area V2 ◽  
Before And After ◽  
Direction Tuning

AbstractWe investigated the contribution of the projections from area MT to the receptive field properties of cells in visual area V2 in anesthetized and paralyzed Cebus apella monkeys. We recorded extracellular single-unit activity using tungsten microelectrodes in three monkeys before and after pressure injection of a 0.25-mol/l GABA solution. The visual stimulus consisted of a single bar moving in one of eight directions. In total, 72 V2 neurons were studied in 18 sessions of GABA injection into area MT. A group of 22 neurons was investigated over a shorter period of time ranging from 15 to 60 min, during which the activity did not return to baseline levels. The remaining 50 neurons were studied over a period of at least 2 h, and no statistical difference was observed in the neuronal response before and long after GABA inactivation. The effects on these 50 neurons consisted of an early (1–20 min) significant general decrease in excitability with changes in either orientation or direction selectivity. The differential decrease in excitability resulted in an intermediate improvement (20–40 min) of the signal-to-noise ratio for the stimulus-driven activity. The inactivation depended on the quantity of GABA injected into area MT and persisted for a period of 2 h. The GABA inactivation in area MT produced inhibition of most cells (72%) and a significant change of direction tuning in the majority (56%) of V2 neurons. Both increases and also decreases in the direction tuning of V2 neurons were observed. These feedback projections are capable of modulating not only the levels of spontaneous and driven activity of V2 neurons but also the V2 receptive field properties, such as direction selectivity.

OFF response transformations in the whisker/barrel system

1994 ◽  
Vol 72 (1) ◽  
pp. 392-401 ◽  
Author(s):  
H. T. Kyriazi ◽  
G. E. Carvell ◽  
D. J. Simons
Keyword(s):  
Trigeminal Ganglion ◽  
Stimulus Duration ◽  
Cortical Neurons ◽  
Time Course ◽  
Ganglion Cells ◽  
Stimulus Onset ◽  
Cortical Layer ◽  
Activity Levels ◽  
Central Inhibition ◽  
Short Stimulus

1. Previous studies have demonstrated marked differences in the relative sizes of ON and OFF responses of neurons in the whisker/barrel system. In particular, OFF responses are unexpectedly large in thalamic neurons. Extracellular unit recordings were used to examine whether varying the time between stimulus onset and offset differently affects OFF responses of neurons in the trigeminal ganglion, ventrobasal thalamus, and somatosensory cortical layer IV. Controlled whisker stimuli were used to deflect individual vibrissal hairs in different directions. We hypothesized that, in part because of the gradual waning of central inhibition evoked by stimulus onset, OFF responses of thalamic and cortical neurons but not trigeminal ganglion cells would increase in size with longer duration stimuli, with relative changes being greatest in the cortex. 2. OFF response magnitudes for thalamic and cortical neuronal populations increased as the stimulus duration was increased from 200 to 1,400 ms. Increases were greater at nonoptimal deflection angles. Similarly, individual cells having smaller OFF responses for the duration-short stimulus tended to display proportionately greater increases when the stimulus was lengthened. OFF responses of trigeminal ganglion cells were largely unaffected by stimulus duration. 3. Barrel neurons were subclassified as regular-spike units (RSUs) or fast-spike units (FSUs) on the basis of the time course of their action potentials. ON and OFF responses were smaller in the former and, when the stimulus was lengthened, percentage increases in their OFF responses were greater than those in FSUs. Results illustrate nonlinear transformations of the thalamic input signal by RSUs, which are presumed to be excitatory barrel neurons, and extend previous findings of response similarities between thalamocortical units (TCUs) and FSUs, the latter of which are thought to be inhibitory. 4. The time course of OFF response suppression in cortical neurons suggests that stimulus onset evokes central inhibition having two components, a potent one lasting several tens of milliseconds and a weaker one lasting many hundreds of milliseconds. Background activity levels in cortex and thalamus were diminished for> or = 1,800 ms after whisker movement. 5. For TCUs, 200-ms stimuli were less likely than 1,400-ms stimuli to elicit an OFF response, but when responses occurred they consisted of a greater number of spikes timed closer together. By contrast, the 200-ms stimulus OFF responses of the RSUs and FSUs displayed longer interspike intervals than did their 1400-ms responses, with no change in the number of spikes per response.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Changing the responses of cortical neurons from sub- to suprathreshold using single spikes in vivo

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Verena Pawlak ◽  
David S Greenberg ◽  
Henning Sprekeler ◽  
Wulfram Gerstner ◽  
Jason ND Kerr
Keyword(s):  
Cortical Neurons ◽  
Time Course ◽  
Visual Stimulation ◽  
Spike Timing ◽  
Sensory Cortex ◽  
Sensory Coding ◽  
Computational Simulations ◽  
Subthreshold Voltage ◽  
Stimulus Features

Action Potential (APs) patterns of sensory cortex neurons encode a variety of stimulus features, but how can a neuron change the feature to which it responds? Here, we show that in vivo a spike-timing-dependent plasticity (STDP) protocol—consisting of pairing a postsynaptic AP with visually driven presynaptic inputs—modifies a neurons' AP-response in a bidirectional way that depends on the relative AP-timing during pairing. Whereas postsynaptic APs repeatedly following presynaptic activation can convert subthreshold into suprathreshold responses, APs repeatedly preceding presynaptic activation reduce AP responses to visual stimulation. These changes were paralleled by restructuring of the neurons response to surround stimulus locations and membrane-potential time-course. Computational simulations could reproduce the observed subthreshold voltage changes only when presynaptic temporal jitter was included. Together this shows that STDP rules can modify output patterns of sensory neurons and the timing of single-APs plays a crucial role in sensory coding and plasticity.

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