Simultaneous Visual Stimulation Research Articles

Effects of optogenetic and visual stimulation on gamma activity in the visual cortex

Studying brain functions and activity during gamma oscillations can be a challenge because it requires careful planning to create the necessary conditions for a controlled experiment. Such an experiment consists of placing the brain into a gamma state and investigating cognitive processing with a careful design. Cortical oscillations in the gamma frequency range (30–80 Hz) play an essential role in a variety of cognitive processes, including visual processing and cognition. The present study aims to investigate the effects of a visual stimulus on the primary visual cortex under gamma oscillations. Specifically, we sought to explore the behavior of gamma oscillations triggered by optogenetic stimulation in the II and IV layers of the visual cortex, both with and without concurrent visual stimulation. Our results show that optogenetic stimulation increases the power of gamma oscillation in both layers of the visual cortex. However, the combined stimuli resulted in a reduction of gamma power in layer II and an increase and reinforcement in gamma power in layer IV. Modelling the results with the Wilson-Cowan model suggests changes in the input of the excitatory population due to the combined stimuli. In addition, our analysis of the data using the Lempel-Ziv complexity method supports our interpretations from the modeling. Thus, our results suggest that optogenetic stimulation enhances low gamma power in both layers of the visual cortex, while simultaneous visual stimulation has differing effects on the two layers, reducing gamma power in layer II and increasing it in layer IV.

Lighting up sound preferences: cross-modal influences on the precedence effect in treefrogs

Perception is frequently cross-modal, involving interactions among stimuli in multiple sensory modalities. Cross-modal integration of sensory stimuli is well established in humans and laboratory mammals, but the understanding of its mechanisms and evolution is limited by a lack of data from a broader taxonomic range in an ecological framework. Our aim in this study was to test whether the precedence effect, the bias in sound localization towards earlier arriving sounds, which is modulated by simultaneous visual stimulation in humans, is also susceptible to cross-modal effects of visual stimulation in two treefrog species, Hyla versicolor and Hyla cinerea. We used two-choice playback experiments to test whether female preferences for leading male advertisement call stimuli were enhanced or suppressed, respectively, by visual stimuli co-localized with leading or lagging call elements. In contrast to humans, strong female leader preferences were generally robust to cross-modal visual stimulation. We propose that divergence in both sensory systems and ecology has led to variation in the relative reliability of visual and acoustic cues of direction, which may explain the differences between humans and frogs. We argue that studies of cross-modal effects on sensory processing are an important tool for understanding the evolution of perceptual mechanisms.

Visuo-tactile interactions in the congenitally deaf: a behavioral and event-related potential study.

Auditory deprivation is known to be accompanied by alterations in visual processing. Yet not much is known about tactile processing and the interplay of the intact sensory modalities in the deaf. We presented visual, tactile, and visuo-tactile stimuli to congenitally deaf and hearing individuals in a speeded detection task. Analyses of multisensory responses showed a redundant signals effect that was attributable to a coactivation mechanism in both groups, although the redundancy gain was less in the deaf. In line with these behavioral results, on a neural level, there were multisensory interactions in both groups that were again weaker in the deaf. In hearing but not deaf participants, somatosensory event-related potential N200 latencies were modulated by simultaneous visual stimulation. A comparison of unisensory responses between groups revealed larger N200 amplitudes for visual and shorter N200 latencies for tactile stimuli in the deaf. Furthermore, P300 amplitudes were also larger in the deaf. This group difference was significant for tactile and approached significance for visual targets. The differences in visual and tactile processing between deaf and hearing participants, however, were not reflected in behavior. Both the behavioral and electroencephalography (EEG) results suggest more pronounced multisensory interaction in hearing than in deaf individuals. Visuo-tactile enhancements could not be explained by perceptual deficiency, but could be partly attributable to inverse effectiveness.

Auditory MEG mismatch responses modified by visual stimulation accompanying auditory stimulation

We investigated the effects of visual stimulation on auditory mismatch responses using a magnetoencephalography (MEG) system. Mismatch magnetic fields (MMNms, equivalents of EEG mismatch negativity, MMN) were recorded in 10 healthy subjects under three audio-visual conditions, which consisted of auditory stimulation with a static visual stimulation (A-0), auditory + synchronous visual stimulation (AV-S), and auditory + asynchronous visual stimulation (AV-R). Clear MMNms were obtained from eight subjects. The amplitude of the root mean square (r.m.s.) value, as well as the global field power, under AV-S conditions were greater compared to those recorded under other conditions in the right hemisphere (P = 0.0087, ANOVA). The latency difference of the N1ms, equivalents of the N1 ERP component recorded in the right hemisphere 100 msec after stimulation and elicited by standard and deviant stimuli, was significantly smaller under AV-S conditions than under other conditions (P = 0.016). There was no difference in the dipole localization for MMNm among the conditions. The results indicate that simultaneous visual stimulation enhances auditory MMNm. The mismatch response can be determined not only by the physical amount of deviated stimulation but also by a deviated feature produced due to accompanying stimulation of a different modality.

A Computational Study of How Orientation Bias in the Lateral Geniculate Nucleus Can Give Rise to Orientation Selectivity in Primary Visual Cortex

Controversy remains about how orientation selectivity emerges in simple cells of the mammalian primary visual cortex. In this paper, we present a computational model of how the orientation-biased responses of cells in lateral geniculate nucleus (LGN) can contribute to the orientation selectivity in simple cells in cats. We propose that simple cells are excited by lateral geniculate fields with an orientation-bias and disynaptically inhibited by unoriented lateral geniculate fields (or biased fields pooled across orientations), both at approximately the same retinotopic co-ordinates. This interaction, combined with recurrent cortical excitation and inhibition, helps to create the sharp orientation tuning seen in simple cell responses. Along with describing orientation selectivity, the model also accounts for the spatial frequency and length–response functions in simple cells, in normal conditions as well as under the influence of the GABAA antagonist, bicuculline. In addition, the model captures the response properties of LGN and simple cells to simultaneous visual stimulation and electrical stimulation of the LGN. We show that the sharp selectivity for stimulus orientation seen in primary visual cortical cells can be achieved without the excitatory convergence of the LGN input cells with receptive fields along a line in visual space, which has been a core assumption in classical models of visual cortex. We have also simulated how the full range of orientations seen in the cortex can emerge from the activity among broadly tuned channels tuned to a limited number of optimum orientations, just as in the classical case of coding for color in trichromatic primates.

Visual stimulation enhances auditory processing in 3‐month‐old infants and adults

Behavioral work demonstrates human infants are sensitive to a host of intersensory properties and this sensitivity promotes early learning and memory. However, little is known regarding the neural basis of this ability in infants. Using event-related potentials (ERPs) with infants and adults, we show that during passive viewing auditory evoked brain responses are increased with the presence of simultaneous visual stimulation. Results converge with previous adult neuroimaging studies, single-cell recordings in nonhuman animals, and behavioral studies with human infants to provide evidence for an elevated status of multisensory stimulation in infancy. Furthermore, these results may provide a neural marker of multisensory audio-visual processing in infants that can be used to test developmental theories of how information is integrated across the senses to form a unitary perception of the world.

Spatio-temporal brain activation profiles associated with line bisection judgments and double simultaneous visual stimulation

We used magnetic source imaging (MSI) to investigate the spatio-temporal patterns of brain activity associated with line bisection judgments and double simultaneous visual stimulation in 14 healthy adults. Consistent with lesion and hemodynamic neuroimaging studies, we found the greatest number of activity sources in right inferior parietal cortex. These sources were most prominent, on average, between 200 and 300 ms after the onset of single (left, right, or center) target stimuli. A greater number of significant activity sources were found in right inferior parietal, occipital, and prefrontal cortices during bilateral compared with unilateral stimulus presentation. Based on these observations, we suggest that a more parsimonious physiological explanation of visual extinction than the hemispheric rivalry account may be the additional neuronal excitation required in right occipital and parietal cortices for accurate bilateral visual perception.

Pharmacological inactivation of pretectal nuclei reveals different modulatory effects on retino-geniculate transmission by X and Y cells in the cat.

The modulatory influence of pretectal neurons on retino-geniculate transmission in the cat was studied by cross-correlation analysis of single-unit activity simultaneously recorded from the dorsal lateral geniculate nucleus (dLGN) and the pretectum (PT) and with reversible inactivation of the PT by GABA microiontophoresis during simultaneous visual stimulation of PT and dLGN neurons. Visually induced population activity in PT nuclei was achieved by a moving (or counterphasing) grating which was presented in the background of the light spot used to stimulate the dLGN neuron. As a control, the light spot was presented on a stationary grating to avoid stimulation of PT neurons but to yield the same illumination of the background. Extracellularly recorded dLGN relay cells of the X- and Y-type were found to be differentially affected by the PT-dLGN projection. During visual stimulation of PT cells, X cells were strongly inhibited and this effect was significantly reduced during PT inactivation. By contrast, the visual responses of most Y cells were affected neither by PT stimulation nor by PT inactivation. In addition, the temporal structure of spike patterns during the light response was examined with autocorrelograms and spike-interval distributions. X-on cells often exhibited a multimodal interval distribution and oscillatory type of activity. During stimulation of the PT interval distributions changed in a characteristic manner and oscillations disappeared. Both effects could be almost totally cancelled by PT inactivation. By contrast, the temporal structure of Y-cell responses was not affected. Our results demonstrate for the first time a pretectal modulation of retino-geniculate transmission in cat dLGN which is clearly different for X and Y cells. This influence seems to be mediated via (inhibitory) interneurons, since we found no indication for a direct coupling between PT and dLGN units. This projection might contribute to the well-known phenomenon of saccadic suppression.

Pineal lesion produces bilateral visual and auditory inattention in the rat

Unilateral lesions in such brain regions as medial frontal cortex and superior colliculus produce polysensory neglect contralateral to the lesion. Since the pineal gland is an unpaired brain structure, both electrophysiologically and hormonally responsive to visual and auditory stimulation, it may modulate bilateral sensory attention mechanisms. Long-Evans male rats were given pineal or sham lesions and were tested behaviourally. Sensory assessment revealed that in comparison to sham animals rats with pineal lesion exhibited unilateral visual and auditory neglect to stimuli presented on either side of the body. Animals with pineal lesions were more likely than sham-lesioned animals to demonstrate visual allesthesis and, compared to sham-lesioned rats, showed extinction on the left side to bilateral simultaneous visual stimulation. This is the first report that midline neuroendocrine damage can produce bilateral sensory inattention.

Stability of auditory evoked potentials during simultaneous visual stimulation

During sensory interaction, an accessory stimulus in a second modality can have a facilitating or inhibiting effect upon some measurable response to a stimulus applied to a primary modality. This study examined whether increased intensity of an accessory light stimulus facilitates or inhibits auditory evoked potentials to click stimuli. Click-evoked potentials were recorded from the round window (cochlear microphonic and auditory nerve), cochlear nucleus, and auditory cortex of unanesthetized cats, and measured before, during, and after simultaneous accessory light stimulation of different intensities. At all electrode sites, the mean peak-to-peak amplitudes of click-evoked potentials were not significantly different during simultaneous visual and auditory stimulation when compared with the pretest and posttest control periods of auditory stimulation. In addition, at all sites, the amplitude of the click-evoked potentials remained constant as accessory light stimulation was increased in intensity. The results suggest that sensory interaction effects do not occur when both the auditory and visual stimuli are irrelevant. If such effects do occur, they are so weak as to be undemonstrable for a wide range of visual stimulus intensities.

Effect of brightness of simultaneous visual stimulation on absolute auditory sensitivity.

Effect of brightness of simultaneous visual stimulation on absolute auditory sensitivity.

The effect of simultaneous visual stimulation on absolute auditory sensitivity.

The effect of simultaneous visual stimulation on absolute auditory sensitivity.