White Noise Stimuli Research Articles

Reported maternal childhood maltreatment experiences, amygdala activation and functional connectivity to infant cry.

Maternal childhood maltreatment experiences (CMEs) may influence responses to infants and affect child outcomes. We examined associations between CME and mothers’ neural responses and functional connectivity to infant distress. We hypothesized that mothers with greater CME would exhibit higher amygdala reactivity and amygdala–supplementary motor area (SMA) functional connectivity to own infant’s cries. Postpartum mothers (N = 57) assessed for CME completed an functional magnetic resonance imaging task with cry and white-noise stimuli. Amygdala region-of-interest and psychophysiological interaction analyses were performed. Our models tested associations of CME with activation and connectivity during task conditions (own/other and cry/noise). Exploratory analyses with parenting behaviors were performed. Mothers with higher CME exhibited higher amygdala activation to own baby’s cries vs other stimuli (F1,392 = 6.9, P < 0.01, N = 57) and higher differential connectivity to cry vs noise between amygdala and SMA (F1,165 = 22.3, P < 0.001). Exploratory analyses revealed positive associations between both amygdala activation and connectivity and maternal non-intrusiveness (Ps < 0.05). Increased amygdala activation to own infant’s cry and higher amygdala–SMA functional connectivity suggest motor responses to baby’s distress. These findings were associated with less intrusive maternal behaviors. Follow-up studies might replicate these findings, add more granular parenting assessments and explore how cue processing leads to a motivated maternal approach in clinical populations.

The Accuracy of Smartphone Sound Level Meter Applications (SLMAs) in Measuring Sound Levels in Clinical Rooms.

The accuracy of smartphone sound level meter applications (SLMAs) has been investigated with varied results, based on differences in platform, device, app, available features, test stimuli, and methodology. This article determines the accuracy of smartphone SLMAs with and without calibration of external and internal microphones for measuring sound levels in clinical rooms. Quasi-experimental research design comparing the accuracy of two smartphone SLMAs with and without calibration of external and internal microphones. Two iOS-based smartphone SLMAs (NIOSH SLM and SPL Meter) on an iPhone 6S were used with and without calibrated external and internal microphones. Measures included: (1) white noise (WN) stimuli from 20 to 100 dB sound pressure level in a sound-treated test booth and (2) sound levels in quiet in four nonsound-treated clinical rooms and in simulated background sound conditions using music at 45, 55, and 80 dBA. Chi-square analysis was used to determine a significant difference (p ≤ 0.05) in sound measures between the SLMAs and a Type 1 SLM. Measures of WN signals and room sound level measures in quiet and simulated background sound conditions were significantly more accurate at levels ≥ 40 dBA using the SLMAs with calibrated external and internal microphones. However, SLMA measures with and without calibration of external and internal microphones overestimated sound levels < 40 dBA. The SLMAs studied with calibrated external or internal microphones are able to verify the room environment for audiologic screening at 1,000, 2,000, and 4,000 Hz at 20 dB hearing level (American Academy of Audiology and American Speech-Language-Hearing Association) using supra-aural earphones (American National Standards Institute S3.1-1999 [R2018]). However, the tested SLMAs overestimated low-level sound < 40 dBA, even when the external or internal microphones were calibrated. Clinicians are advised to calibrate the microphones prior to using measurement systems involving smartphones and SLMAs to measure room sound levels and to monitor background noise levels throughout the provision of clinical services.

Economic threat heightens conflict detection: sLORETA evidence.

Economic threat has far-reaching emotional and social consequences, yet the impact of economic threat on neurocognitive processes has received little empirical scrutiny. Here, we examined the causal relationship between economic threat and conflict detection, a critical process in cognitive control associated with the anterior cingulate cortex (ACC). Participants (N = 103) were first randomly assigned to read about a gloomy economic forecast (Economic Threat condition) or a stable economic forecast (No-Threat Control condition). Notably, these forecasts were based on real, publicly available economic predictions. Participants then completed a passive auditory oddball task composed of frequent standard tones and infrequent, aversive white-noise bursts, a task that elicits the N2, an event-related potential component linked to conflict detection. Results revealed that participants in the Economic Threat condition evidenced increased activation source localized to the ACC during the N2 to white-noise stimuli. Further, ACC activation to conflict mediated an effect of Economic Threat on increased justification for personal wealth. Economic threat thus has implications for basic neurocognitive function. Discussion centers on how effects on conflict detection could shed light on the broader emotional and social consequences of economic threat.

Effects of white noise auditory stimulus on stability and balance in sit-to-stand and standing motion of chronic stroke patients

Purpose The purpose of this study was to investigate the effect of auditory stimulus using white noise on stability and balance during sit-to-stand and standing tasks of chronic stroke patients. Methods Eighteen chronic stroke patients participated in this study. They asked to perform the tasks of sit-to-stand, standing with eyes open and standing with eyes closed before and after listening to white noise. Eight infrared cameras and one force plate were used to evaluate the stability and balance before and after the white noise stimulus during each task. Results There was no significant difference between before and after white noise stimulus in all tasks. On the other hand, the anteroposterior range of CoP was significantly decreased after white noise stimulus in standing with eyes-closed (p&lt;.05), and the sagittal angle of CoP-CoM was significantly decreased after white noise stimulus in standing with eyes-open and eyes-closed (p&lt;.05). Conclusion Auditory stimulus using white noise improves the balance of chronic stroke patients. Therefore it is thought to be helpful for the independent daily life of chronic stroke patients.

Optogenetic activation of corticogeniculate feedback stabilizes response gain and increases information coding in LGN neurons.

In spite of their anatomical robustness, it has been difficult to establish the functional role of corticogeniculate circuits connecting primary visual cortex with the lateral geniculate nucleus of the thalamus (LGN) in the feedback direction. Growing evidence suggests that corticogeniculate feedback does not directly shape the spatial receptive field properties of LGN neurons, but rather regulates the timing and precision of LGN responses and the information coding capacity of LGN neurons. We propose that corticogeniculate feedback specifically stabilizes the response gain of LGN neurons, thereby increasing their information coding capacity. Inspired by early work by McClurkin et al. (1994), we manipulated the activity of corticogeniculate neurons to test this hypothesis. We used optogenetic methods to selectively and reversibly enhance the activity of corticogeniculate neurons in anesthetized ferrets while recording responses of LGN neurons to drifting gratings and white noise stimuli. We found that optogenetic activation of corticogeniculate feedback systematically reduced LGN gain variability and increased information coding capacity among LGN neurons. Optogenetic activation of corticogeniculate neurons generated similar increases in information encoded in LGN responses to drifting gratings and white noise stimuli. Together, these findings suggest that the influence of corticogeniculate feedback on LGN response precision and information coding capacity could be mediated through reductions in gain variability.

Sound Generator: Analysis of the Effectiveness of Noise in the Habituation of Tinnitus.

Introduction Tinnitus is a disorder that affects 10 to 15% of de world's population. Sound therapy performed through hearing aids (HAs) with integrated sound generator (SG) is one of the forms of tinnitus treatment. Objective To analyze the effectiveness of four masking noises in relieving tinnitus in individuals with mild and moderate bilateral sensorineural hearing loss and their influence in speech perception. Methods The participants were 35 individuals with tinnitus and mild and moderate bilateral sensorineural hearing loss, divided into four groups. All groups underwent HA and SG adaptation, being regulated in the combined mode (HA and SG). In group 1 (G1), the white noise stimulus was applied, in group 2 (G2), pink noise was applied, in group 3 (G3), speech noise, and in group 4 (G4), the high tone was applied. All patients were subjected to the following procedures: audiological diagnosis, acuphenometry, tinnitus handicap inventory (THI), visual analogue scale (VAS), and hearing in noise test (HINT). The procedures were performed prior to and after hearing intervention, and after 3 months of use of HA and SG. Results All groups presented a statistically significant difference for the THI, VAS, and HINT pre and postintervention. In the case of the HINT, only pink noise presented a significant difference. However, in the comparation among groups there was no significant difference. Conclusion The present study made it possible to conclude that the four noises were equally effective in relieving tinnitus, with no statistically significant differences between the analyzed groups.

Glycinergic and GABAergic interneurons shift the location and differentially alter the size of ganglion cell receptive field centers in the mammalian retina

By using the multi-electrode array (MEA) recording technique in conjunction with white-noise checkerboard stimuli and reverse correlation methods, we studied modulatory actions of glycinergic and GABAergic interneurons on spatiotemporal profiles of ganglion cells (GCs) in dark-adapted mouse retinas. We found that application of 2 µM strychnine decreased receptive field center radii of GCs by a mean value of 11%, and shifted the GC receptive field (RF) centers by a mean distance of 28.3 µm. On the other hand, 200 µM picrotoxin + 100 µM bicuculline + 50 µM TPMPA increased GC receptive field center radii by a mean value of 19%, and shifted the GC RF centers by a mean distance of 53.7 µm. Glycinergic neurons in the mouse retina are narrow-field amacrine cells that have been shown to mediate ON-OFF crossover inhibitory synapses within the RGs’ RF center, therefore they may increase the size and shift the location of GC RF center by synergistic addition to bipolar cell inputs to GCs. GABAergic neurons are wide-field amacrine cells and horizontal cells that are known to mediate antagonistic surround responses of GCs, and thus they decrease the GCs’ RF center size. Our results suggest that a major global function of glycinergic and GABAergic interneurons in the mammalian retina is to provide the flexibility for adjusting the size and location of GCs’ RF centers. The apparent shifts of GC RF centers suggest that the synergistic addition by GlyACs and the surround inhibition by GABAergic interneurons are not spatially symmetrical within GC RFs.

Acoustic\u2013phonetic and auditory mechanisms of adaptation in the perception of sibilant fricatives

Listeners are highly proficient at adapting to contextual variation when perceiving speech. In the present study, we examined the effects of brief speech and nonspeech contexts on the perception of sibilant fricatives. We explored three theoretically motivated accounts of contextual adaptation, based on phonetic cue calibration, phonetic covariation, and auditory contrast. Under the cue calibration account, listeners adapt by estimating a talker-specific average for each phonetic cue or dimension; under the cue covariation account, listeners adapt by exploiting consistencies in how the realization of speech sounds varies across talkers; under the auditory contrast account, adaptation results from (partial) masking of spectral components that are shared by adjacent stimuli. The spectral center of gravity, a phonetic cue to fricative identity, was manipulated for several types of context sound: /z/-initial syllables, /v/-initial syllables, and white noise matched in long-term average spectrum (LTAS) to the /z/-initial stimuli. Listeners’ perception of the /s/–/ʃ/ contrast was significantly influenced by /z/-initial syllables and LTAS-matched white noise stimuli, but not by /v/-initial syllables. No significant difference in adaptation was observed between exposure to /z/-initial syllables and matched white noise stimuli, and speech did not have a considerable advantage over noise when the two were presented consecutively within a context. The pattern of findings is most consistent with the auditory contrast account of short-term perceptual adaptation. The cue covariation account makes accurate predictions for speech contexts, but not for nonspeech contexts or for the absence of a speech-versus-nonspeech difference.

The statistics of how natural images drive the responses of neurons.

To model the responses of neurons in the early visual system, at least three basic components are required: a receptive field, a normalization term, and a specification of encoding noise. Here, we examine how the receptive field, the normalization factor, and the encoding noise affect the drive to model-neuron responses when stimulated with natural images. We show that when these components are modeled appropriately, the response drives elicited by natural stimuli are Gaussian-distributed and scale invariant, and very nearly maximize the sensitivity (d′) for natural-image discrimination. We discuss the statistical models of natural stimuli that can account for these response statistics, and we show how some commonly used modeling practices may distort these results. Finally, we show that normalization can equalize important properties of neural response across different stimulus types. Specifically, narrowband (stimulus- and feature-specific) normalization causes model neurons to yield Gaussian response-drive statistics when stimulated with natural stimuli, 1/f noise stimuli, and white-noise stimuli. The current work makes recommendations for best practices and lays a foundation, grounded in the response statistics to natural stimuli, upon which to build principled models of more complex visual tasks.

The melanopsin-directed white noise electroretinogram (wnERG)

The white noise electroretinogram (wnERG) provides a measure of the impulse response function under conditions of retinal equilibrium; it is yet to be determined how the electrical response generated by melanopsin ganglion cell photoreception is expressed in the impulse response. To this end, we recorded the human wnERG to continuous temporal white noise (TWN) stimuli that were melanopsin-directed (rod and cone silent) or cone-directed (rod and melanopsin silent). The impulse response of the electroretinogram was derived by cross-correlating the TWN stimulus with the wnERG response. We observed that the LMS-cone directed wnERG contained the expected N1 wave (24.1 ± 2.4 ms; mean ± SEM) and P1 wave (49.7 ± 1.8 ms). Melanopsin-directed stimuli produced a unique wnERG with a slower negative deflection (Nm) at 62.9 ± 3.3 ms followed by a positive deflection (Pm) at 126.3 ± 5.1 ms. Additional experiments indicated this melanopsin-directed wnERG response was not due to cone intrusion. The Nm and NmPm amplitudes increased with illuminance (32,000–80,000 Td; no rod intrusion) and melanopsin contrast (10–36% Michelson contrast). As there are known pathways connecting melanopsin cells to the outer retina, we then measured the wnERG to combined melanopsin and cone-directed stimuli to quantify melanopsin interactions with cone signalling. With the combined stimuli, the N1P1 amplitudes were suppressed by ~59%, which may be a result of a destructive interference between the positive (P1) and negative (Nm) waves generated by the cone and melanopsin pathways. We conclude that the human wnERG to melanopsin-directed stimuli may reflect the combined response of intra-retinal melanopsin pathways, independent of rod and cone photoreception.

The Accuracy of Smartphone Sound Level Meter Applications With and Without Calibration

The purpose of this study is to determine the accuracy of smartphone sound level meter applications (SLMAs) with calibration features across stimulus levels and for ambient room noise measures in the clinical setting. The accuracy of 3 iOS-based smartphone SLMAs (SLMA1: Analyzer [Version 2.7.2, DSP Mobile], SLMA2: Sound Level Meter Pro [Version 2.2, Mint Muse LLC], and SLMA3: SPL Meter [Version 9.3, Andrew Smith, Studio Six Digital]), using a single smartphone device (iPhone 6S Model A1688, iOS 9.3.4, Apple), was evaluated with and without calibration using a 1000-Hz narrowband noise (NBN) and white noise (WN) stimuli over a range of sound levels (20-100 dB) and in ambient noise measures of 8 speech and hearing room environments. A simultaneous and corresponding SLMA and Type 1 sound level meter (SLM) measure per condition were documented with a photo image; each condition was replicated 5 times. Mean SLMA and SLM measures were compared. SLMA measures were considered accurate if within ± 2 dB of the SLM. Measures of NBN and WN signals using these SLMAs were accurate at levels above 40-50 dB when calibrated. NBN and WN signals using some SLMAs were significantly (p < .05) more accurate with calibration at levels > 40 to 50 dB. SLMA measures with or without calibration adjustment were inaccurate and overestimated room ambient noise levels < 50 dB. These findings suggest that some SLMAs are accurate for measuring NBN and WN stimuli within the range of 50-100 dB in sound-treated environments when calibrated. However, outcomes indicated that some SLMAs, even with calibration, overestimated low ambient noise levels and may not accurately verify quiet room environments < 50 dB for clinical services. These results should not be generalized for all smartphone types, and continued research on SLMAs using next-generation smartphone devices is warranted.

Computational modelling of salamander retinal ganglion cells using machine learning approaches

Artificial vision using computational models that can mimic biological vision is an area of ongoing research. One of the main themes within this research is the study of the retina and in particular, retinal ganglion cells which are responsible for encoding the visual stimuli. A common approach to modelling the internal processes of retinal ganglion cells is the use of a linear – non-linear cascade model, which models the cell’s response using a linear filter followed by a static non-linearity. However, the resulting model is generally restrictive as it is often a poor estimator of the neuron’s response. In this paper we present an alternative to the linear – non-linear model by modelling retinal ganglion cells using a number of machine learning techniques which have a proven track record for learning complex non-linearities in many different domains. A comparison of the model predicted spike rate shows that the machine learning models perform better than the standard linear – non-linear approach in the case of temporal white noise stimuli.

On the role of transient depolarization-activated K+ current in microvillar photoreceptors.

Photoreceptors in the compound eyes of most insect species express two functional types of depolarization-activated potassium currents: a transient A-type current (IA) and a sustained delayed rectifier current (IDR). The role of Shaker-dependent IA in Drosophila melanogaster photoreceptors was previously investigated by comparing intracellular recordings from Shaker and wild-type photoreceptors. Shaker channels were proposed to be involved in low-frequency signal amplification in dim light and reduction of the metabolic cost of information transfer. Here, I study the function of IA in photoreceptors of the cockroach Panchlora nivea using the patch-clamp method. Responses to Gaussian white-noise stimuli reveal that blockade of IA with 4-aminopyridine has no discernible effect on voltage responses or information processing. However, because open-channel blockers are often ineffective at low membrane potentials, no conclusion on the role of IA could be made on the basis of negative results of pharmacological tests. Using a relatively large set of control data, a physiological variability analysis was performed to discern the role of IA. Amplitudes of the IA window current and half-activation potentials correlate strongly with membrane corner frequencies, especially in dim light, indicating that IA facilitates transmission of higher frequencies. Consistent with voltage-dependent inactivation of IA, these correlations decrease with depolarization in brighter backgrounds. In contrast, correlations involving IDR are comparatively weak. Upon reexamining photoreceptor conductance in wild-type and Shaker strains of D. melanogaster, I find a biphasic voltage dependence near the resting potential in a minority of photoreceptors from both strains, indicating that Shaker channels are not crucial for early amplification of voltage signals in D. melanogaster photoreceptors. Leak current in Shaker photoreceptors at the level of the soma is not elevated. These results suggest a novel role for IA in facilitating transmission of high-frequency signals in microvillar photoreceptors.

Functional characterization of the retinal output upon optogenetic stimulation

Functional characterization of the retinal output upon optogenetic stimulation

Temporal filters of electrically stimulated retinal ganglion cells

Event Abstract Back to Event Temporal filters of electrically stimulated retinal ganglion cells Larissa Hoefling1*, Philipp Berens2, 3, 4 and Günther Zeck1 1 Natural and Medical Sciences Institute, Germany 2 Institut für Ophthalmologische Forschung, Universität Tübingen, Germany 3 Werner Reichardt Centrum für Integrative Neurowissenschaften (CIN), Universität Tübingen, Germany 4 Bernstein Center for Computational Neuroscience, Germany Motivation Degenerative diseases like Retinitis Pigmentosa lead to blindness due to the degeneration of photoreceptors, while leaving the network of bipolar, horizontal, amacrine and ganglion cells largely intact. This remaining network can be stimulated electrically to evoke visual percepts, an approach that is already used in retinal implants. We stimulate rd10 mouse retinal ganglion cells (RGCs) using a smooth electrical stimulus waveform to mimic physiological retinal activity, and simultaneously record their responses to map temporal electrical filters (TEF). The TEFs could guide the development of more efficient stimulation protocols for retinal prostheses. Methods We use a high-density CMOS-based microelectrode array to simultaneously deliver smoothed white Gaussian noise stimuli via 1024 capacitive stimulation electrodes and record on 4225 recording electrodes from adult rd10 mouse retina prepared ex vivo and interfaced with the chip in flat-mount epiretinal configuration. Our approach allows recording of single neuron activity during stimulation without interference from stimulus artefacts. Custom-written data analysis software is used to recover the temporal electrical receptive fields of RGCs. Results Using a physiologically plausible smoothed white Gaussian noise stimulus, we are able to activate retinal ganglion cells at low current densities (≤1.5 mA/cm²). Ganglion cell activity is evoked and modulated in a reliable manner for repetitive stimulus presentations. We found two distinct types of TEFs for ON and OFF cells, respectively, suggesting that ON and OFF cells may be activated selectively. Conclusion We present and discuss smooth electrical stimulation as an alternative to pulsatile stimuli for electrically activating retinal ganglion cells in degenerating mouse retina. Acknowledgements Acknowldegement. This research is supported by a grant of the Baden Württemberg Stiftung (RetNetControl, FKZ: NEU 013) Keywords: Electrical Stimulation, receptive field properties, Temporal filters, retinal processing, linear nonlinear models, Retinal Ganglion Cells, CMOS-MEAs Conference: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays, Reutlingen, Germany, 4 Jul - 6 Jul, 2018. Presentation Type: Poster Presentation Topic: Neural Networks Citation: Hoefling L, Berens P and Zeck G (2019). Temporal filters of electrically stimulated retinal ganglion cells. Conference Abstract: MEA Meeting 2018 | 11th International Meeting on Substrate Integrated Microelectrode Arrays. doi: 10.3389/conf.fncel.2018.38.00082 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Mar 2018; Published Online: 17 Jan 2019. * Correspondence: Ms. Larissa Hoefling, Natural and Medical Sciences Institute, Reutlingen, Germany, larissa.hoefling@student.uni-tuebingen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Larissa Hoefling Philipp Berens Günther Zeck Google Larissa Hoefling Philipp Berens Günther Zeck Google Scholar Larissa Hoefling Philipp Berens Günther Zeck PubMed Larissa Hoefling Philipp Berens Günther Zeck Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Olfactory coding in the turbulent realm.

Long-distance olfactory search behaviors depend on odor detection dynamics. Due to turbulence, olfactory signals travel as bursts of variable concentration and spacing and are characterized by long-tail distributions of odor/no-odor events, challenging the computing capacities of olfactory systems. How animals encode complex olfactory scenes to track the plume far from the source remains unclear. Here we focus on the coding of the plume temporal dynamics in moths. We compare responses of olfactory receptor neurons (ORNs) and antennal lobe projection neurons (PNs) to sequences of pheromone stimuli either with white-noise patterns or with realistic turbulent temporal structures simulating a large range of distances (8 to 64 m) from the odor source. For the first time, we analyze what information is extracted by the olfactory system at large distances from the source. Neuronal responses are analyzed using linear–nonlinear models fitted with white-noise stimuli and used for predicting responses to turbulent stimuli. We found that neuronal firing rate is less correlated with the dynamic odor time course when distance to the source increases because of improper coding during long odor and no-odor events that characterize large distances. Rapid adaptation during long puffs does not preclude however the detection of puff transitions in PNs. Individual PNs but not individual ORNs encode the onset and offset of odor puffs for any temporal structure of stimuli. A higher spontaneous firing rate coupled to an inhibition phase at the end of PN responses contributes to this coding property. This allows PNs to decode the temporal structure of the odor plume at any distance to the source, an essential piece of information moths can use in their tracking behavior.

Association of different neural processes during different emotional perceptions of white noise and pure tone auditory stimuli.

Sound is a sensory stimulant ubiquitously found throughout our environment. Humans have evolved a system that effectively and automatically converts sound sensory inputs into emotions. Although different emotional responses to sounds with different frequency characteristics are empirically recognized, there is a paucity of studies addressing different emotional responses to these sounds and the underlying neural mechanisms. In this study, we examined effects of pure tone (PT) and white noise (WN) inputs at ordinary loudness levels on emotional responses. We found that WN stimuli produced more aversive responses than PT stimuli. This difference was endorsed by larger late posterior positivity (LPP). In a source localization study, we found increased neural activity in the parietal lobe prior to LPP. These findings show that WN stimuli produce aversive perceptions compared with PT stimuli, at typical loudness levels. In addition, different emotional responses were processed in a similar manner as visual stimulations, as reflected by increased LPP activation. Various emotional effects of WN and PT stimuli, at ordinary loudness levels, could expand our understanding of adverse effects of noise as well as favorable effects associated with music.

Orientation Tuning of Correlated Activity in the Developing Lateral Geniculate Nucleus.

Neural circuits and the cells that comprise them undergo developmental changes in the spatial organization of their connections and in their temporal response properties. Within the lateral geniculate nucleus (LGN) of the dorsal thalamus, these changes have pronounced effects on the spatiotemporal receptive fields (STRFs) of neurons. An open and unresolved question is how STRF maturation affects stimulus-evoked correlated activity between pairs of LGN neurons during development. This is an important question to answer because stimulus-evoked correlated activity likely plays a role in establishing the specificity of thalamocortical connectivity and the receptive fields (RFs) of postsynaptic cortical neurons. Using multielectrode recording methods and white noise stimuli, we recorded neural activity from ensembles of LGN neurons in cats across early development. As expected, there was a progressive maturation of the spatial and temporal properties of visual responses. Using drifting bar stimuli and cross-correlation analysis, we also determined the orientation-tuning bandwidth of correlated activity between pairs of LGN neurons at different stages of development (Sillito and Jones, 2002; Andolina et al., 2007; Stanley et al., 2012; Kelly et al., 2014). Despite the larger RFs and slower responses of immature LGN neurons compared with mature neurons, our results show that correlated activity in the LGN was as tightly tuned for orientation early in development as it was in the adult. Closer examination revealed this age-invariant orientation tuning of correlated activity likely involves cellular mechanisms related to spike fatigue in young animals and a progressive decrease in response latency with development.SIGNIFICANCE STATEMENT Orientation tuning is a fundamental property of neurons in primary visual cortex. An important and unresolved question is how orientation tuning emerges during brain development. This study explores a potential mechanism for the establishment of orientation tuning based on correlated activity patterns among ensembles of maturing neurons in the lateral geniculate nucleus (LGN) of the thalamus. Results show that correlated activity between pairs of LGN neurons is more tightly tuned than predictions based simply on receptive field size, indicating that correlated activity has the properties needed to play an important role in the development of geniculocortical circuits and the emergence of cortical orientation tuning.

Spatiotemporal characteristics of retinal response to network-mediated photovoltaic stimulation.

Subretinal prostheses aim at restoring sight to patients blinded by photoreceptor degeneration using electrical activation of the surviving inner retinal neurons. Today, such implants deliver visual information with low-frequency stimulation, resulting in discontinuous visual percepts. We measured retinal responses to complex visual stimuli delivered at video rate via a photovoltaic subretinal implant and by visible light. Using a multielectrode array to record from retinal ganglion cells (RGCs) in the healthy and degenerated rat retina ex vivo, we estimated their spatiotemporal properties from the spike-triggered average responses to photovoltaic binary white noise stimulus with 70-μm pixel size at 20-Hz frame rate. The average photovoltaic receptive field size was 194 ± 3 μm (mean ± SE), similar to that of visual responses (221 ± 4 μm), but response latency was significantly shorter with photovoltaic stimulation. Both visual and photovoltaic receptive fields had an opposing center-surround structure. In the healthy retina, ON RGCs had photovoltaic OFF responses, and vice versa. This reversal is consistent with depolarization of photoreceptors by electrical pulses, as opposed to their hyperpolarization under increasing light, although alternative mechanisms cannot be excluded. In degenerate retina, both ON and OFF photovoltaic responses were observed, but in the absence of visual responses, it is not clear what functional RGC types they correspond to. Degenerate retina maintained the antagonistic center-surround organization of receptive fields. These fast and spatially localized network-mediated ON and OFF responses to subretinal stimulation via photovoltaic pixels with local return electrodes raise confidence in the possibility of providing more functional prosthetic vision. NEW & NOTEWORTHY Retinal prostheses currently in clinical use have struggled to deliver visual information at naturalistic frequencies, resulting in discontinuous percepts. We demonstrate modulation of the retinal ganglion cells (RGC) activity using complex spatiotemporal stimuli delivered via subretinal photovoltaic implant at 20 Hz in healthy and in degenerate retina. RGCs exhibit fast and localized ON and OFF network-mediated responses, with antagonistic center-surround organization of their receptive fields.

Optogenetic Activation of the Infralimbic Cortex Suppresses the Return of Appetitive Pavlovian-Conditioned Responding Following Extinction.

The infralimbic medial prefrontal cortex (IL) is important for suppressing learned behavior after extinction, but whether this function extends to responses acquired through appetitive Pavlovian conditioning is unclear. We trained male, Long-Evans rats to associate a white-noise conditional stimulus (CS; 10 s; 14 presentations per session) with 10% liquid sucrose (0.2 mL per CS presentation), and recorded entries into the fluid port during the CS. The CS was presented without sucrose in subsequent extinction and test sessions. Increasing IL activity with pretest microinfusions of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA; 0, 0.3 nmol; 0.3 μl/side) reduced the reinstatement of CS-elicited port entries. The same result was obtained when IL neurons that expressed Channelrhodopsin-2 (ChR2) were optically stimulated during CS presentations at test (473 nm, 5 ms pulses at 20 Hz for 10.2 s, unilateral). Optical stimulation of ChR2-expressing IL neurons during CS presentations also reduced spontaneous recovery and context-induced renewal. Furthermore, optical stimulation (1) during intertrial intervals had no impact on renewal, (2) depolarized ChR2-expressing IL pyramidal neurons in vitro, and (3) preferentially increased Fos in ChR2-expressing neurons. These novel converging data highlight a critical role for the IL in suppressing the return of appetitive Pavlovian-conditioned responding following extinction.