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Showing papers on "Receptive field published in 2014"


Journal ArticleDOI
15 May 2014-Nature
TL;DR: A mathematical model shows how such ‘space–time wiring specificity’ could endow SAC dendrites with receptive fields that are oriented in space–time and therefore respond selectively to stimuli that move in the outward direction from the soma.
Abstract: How does the mammalian retina detect motion? This classic problem in visual neuroscience has remained unsolved for 50 years. In search of clues, here we reconstruct Off-type starburst amacrine cells (SACs) and bipolar cells (BCs) in serial electron microscopic images with help from EyeWire, an online community of ‘citizen neuroscientists’. On the basis of quantitative analyses of contact area and branch depth in the retina, we find evidence that one BC type prefers to wire with a SAC dendrite near the SAC soma, whereas another BC type prefers to wire far from the soma. The near type is known to lag the far type in time of visual response. A mathematical model shows how such ‘space–time wiring specificity’ could endow SAC dendrites with receptive fields that are oriented in space–time and therefore respond selectively to stimuli that move in the outward direction from the soma. Motion detection by the retina is thought to rely largely on the biophysics of starburst amacrine cell dendrites; here machine learning is used with gamified crowdsourcing to draw the wiring diagram involving amacrine and bipolar cells to identify a plausible circuit mechanism for direction selectivity; the model suggests similarities between mammalian and insect vision. Motion detection by the mammalian retina has been thought to rely largely on the intrinsic biophysics of the dendrites of starburst amacrine cells (SACs). Now Sebastian Seung and colleagues have combined new machine-learning techniques with crowd sourcing via the EyeWire brain-mapping game to redraw the wiring diagram for amacrine cells and bipolar cells. Their results show that direction selectivity is established at the presynaptic level — in the spatiotemporal inputs to the amacrine cells — identifying neural circuits rather than intrinsic properties of SACs as the key to direction selectivity. This new model brings the mouse retina closer in certain respects to the Reichardt motion detector characteristic of insect vision.

455 citations


Journal ArticleDOI
27 Mar 2014-Nature
TL;DR: During saccade preparation, rather than remap, RFs of neurons in a prefrontal gaze control area massively converge towards the saccadic target, resulting in a threefold increase in the proportion of RFs responding to stimuli near the target region.
Abstract: Saccadic eye movements cause substantial shifts in the retinal image as we take in visual scenes, but our perception is stable and continuous; here, visual receptive fields are shown to shift dramatically towards the saccadic goal, running counter to the long-standing hypothesis of receptive field remapping as the basis of perceived stability. As we take in a visual scene we make rapid eye movements — called saccades — that bring different parts of the scene to the fovea, the region of the retina with highest acuity. These eye movements cause substantial shifts in the retinal image, but our perception of the visual world is stable and continuous. Tirin Moore and colleagues find a possible mechanism for this stability in prefrontal neurons. They show that during preparation for eye movement, neurons shift their visual receptive fields (those regions of space that neurons are most responsive to) in order to massively over-represent behaviourally relevant areas, consistent with human visual perception. These findings run counter to a long-standing hypothesis — that receptive fields predictively remap, shifting the representation of visual space by neurons in the brain in anticipation of the outcome of each eye movement. We experience the visual world through a series of saccadic eye movements, each one shifting our gaze to bring objects of interest to the fovea for further processing. Although such movements lead to frequent and substantial displacements of the retinal image, these displacements go unnoticed. It is widely assumed that a primary mechanism underlying this apparent stability is an anticipatory shifting of visual receptive fields (RFs) from their presaccadic to their postsaccadic locations before movement onset1. Evidence of this predictive ‘remapping’ of RFs has been particularly apparent within brain structures involved in gaze control2,3,4. However, critically absent among that evidence are detailed measurements of visual RFs before movement onset. Here we show that during saccade preparation, rather than remap, RFs of neurons in a prefrontal gaze control area massively converge towards the saccadic target. We mapped the visual RFs of prefrontal neurons during stable fixation and immediately before the onset of eye movements, using multi-electrode recordings in monkeys. Following movements from an initial fixation point to a target, RFs remained stationary in retinocentric space. However, in the period immediately before movement onset, RFs shifted by as much as 18 degrees of visual angle, and converged towards the target location. This convergence resulted in a threefold increase in the proportion of RFs responding to stimuli near the target region. In addition, like in human observers5,6, the population of prefrontal neurons grossly mislocalized presaccadic stimuli as being closer to the target. Our results show that RF shifts do not predict the retinal displacements due to saccades, but instead reflect the overriding perception of target space during eye movements.

184 citations


Journal ArticleDOI
TL;DR: It is submitted that peripheral neurons in the touch-processing pathway, as with peripheral neuron in the visual- processing pathway, perform feature extraction computations that are typically attributed to neurons inThe cerebral cortex.
Abstract: A fundamental feature of first-order neurons in the tactile system is that their distal axon branches in the skin and forms many transduction sites, yielding complex receptive fields with many highly sensitive zones. We found that this arrangement constitutes a peripheral neural mechanism that allows individual neurons to signal geometric features of touched objects. Specifically, we observed that two types of first-order tactile neurons that densely innervate the glabrous skin of the human fingertips signaled edge orientation via both the intensity and the temporal structure of their responses. Moreover, we found that the spatial layout of a neuron's highly sensitive zones predicted its sensitivity to particular edge orientations. We submit that peripheral neurons in the touch-processing pathway, as with peripheral neurons in the visual-processing pathway, perform feature extraction computations that are typically attributed to neurons in the cerebral cortex.

175 citations


Journal ArticleDOI
TL;DR: It is found that M2–M5 cells could detect spatial differences in light intensity, implicating an ability to analyse the form of visual stimuli.
Abstract: Intrinsically photosensitive retinal ganglion cells (ipRGCs) mediate non-image-forming visual responses, including pupillary constriction, circadian photoentrainment and suppression of pineal melatonin secretion. Five morphological types of ipRGCs, M1-M5, have been identified in mice. In order to understand their functions better, we studied the photoresponses of all five cell types, by whole-cell recording from fluorescently labelled ipRGCs visualized using multiphoton microscopy. All ipRGC types generated melanopsin-based ('intrinsic') as well as synaptically driven ('extrinsic') light responses. The intrinsic photoresponses of M1 cells were lower threshold, higher amplitude and faster than those of M2-M5. The peak amplitudes of extrinsic light responses differed among the ipRGC types; however, the responses of all cell types had comparable thresholds, kinetics and waveforms, and all cells received rod input. While all five types exhibited inhibitory amacrine-cell and excitatory bipolar-cell inputs from the 'on' channel, M1 and M3 received additional 'off'-channel inhibition, possibly through their 'off'-sublamina dendrites. The M2-M5 ipRGCs had centre-surround-organized receptive fields, implicating a capacity to detect spatial contrast. In contrast, the receptive fields of M1 cells lacked surround antagonism, which might be caused by the surround of the inhibitory input nullifying the surround of the excitatory input. All ipRGCs responded robustly to a wide range of motion speeds, and M1-M4 cells appeared tuned to different speeds, suggesting that they might analyse the speed of motion. Retrograde labelling revealed that M1-M4 cells project to the superior colliculus, suggesting that the contrast and motion information signalled by these cells could be used by this sensorimotor area to detect novel objects and motion in the visual field.

147 citations


Journal ArticleDOI
TL;DR: A fundamental difference in visual processing between ON and OFF channels is demonstrated and reveal a competitive advantage for OFF neurons over ON neurons at low spatial frequencies, which could be important during cortical development when retinal images are blurred by immature optics in infant eyes.
Abstract: Astronomers and physicists noticed centuries ago that visual spatial resolution is higher for dark than light stimuli, but the neuronal mechanisms for this perceptual asymmetry remain unknown. Here we demonstrate that the asymmetry is caused by a neuronal nonlinearity in the early visual pathway. We show that neurons driven by darks (OFF neurons) increase their responses roughly linearly with luminance decrements, independent of the background luminance. However, neurons driven by lights (ON neurons) saturate their responses with small increases in luminance and need bright backgrounds to approach the linearity of OFF neurons. We show that, as a consequence of this difference in linearity, receptive fields are larger in ON than OFF thalamic neurons, and cortical neurons are more strongly driven by darks than lights at low spatial frequencies. This ON/OFF asymmetry in linearity could be demonstrated in the visual cortex of cats, monkeys, and humans and in the cat visual thalamus. Furthermore, in the cat visual thalamus, we show that the neuronal nonlinearity is present at the ON receptive field center of ON-center neurons and ON receptive field surround of OFF-center neurons, suggesting an origin at the level of the photoreceptor. These results demonstrate a fundamental difference in visual processing between ON and OFF channels and reveal a competitive advantage for OFF neurons over ON neurons at low spatial frequencies, which could be important during cortical development when retinal images are blurred by immature optics in infant eyes.

119 citations


Journal ArticleDOI
TL;DR: Functional MRI and population receptive field analysis suggests that visual cortical function in ASDs may be characterized by extrastriate cortical hyperexcitability or differential attentional deployment, and that visual cortex in ASD is not characterized by sharper spatial selectivity.
Abstract: Previous behavioral research suggests enhanced local visual processing in individuals with autism spectrum disorders (ASDs). Here we used functional MRI and population receptive field (pRF) analysis to test whether the response selectivity of human visual cortex is atypical in individuals with high-functioning ASDs compared with neurotypical, demographically matched controls. For each voxel, we fitted a pRF model to fMRI signals measured while participants viewed flickering bar stimuli traversing the visual field. In most extrastriate regions, perifoveal pRFs were larger in the ASD group than in controls. We observed no differences in V1 or V3A. Differences in the hemodynamic response function, eye movements, or increased measurement noise could not account for these results; individuals with ASDs showed stronger, more reliable responses to visual stimulation. Interestingly, pRF sizes also correlated with individual differences in autistic traits but there were no correlations with behavioral measures of visual processing. Our findings thus suggest that visual cortex in ASDs is not characterized by sharper spatial selectivity. Instead, we speculate that visual cortical function in ASDs may be characterized by extrastriate cortical hyperexcitability or differential attentional deployment.

114 citations


Journal ArticleDOI
17 Sep 2014-Neuron
TL;DR: Surprisingly, despite having similar receptive fields and response properties, each cuneate neuron responded to a unique combination of these inputs, suggesting distinct haptic input features are encoded already at subcortical processing stages.

109 citations


Journal ArticleDOI
TL;DR: It is proposed that the feedforward circuit-mediated inhibition from PV neurons, which has an analogous function to lateral inhibition, enables upper L2/3 excitatory neurons to rapidly refine auditory representation.
Abstract: Sensory information undergoes ordered and coordinated processing across cortical layers. Whereas cortical layer (L) 4 faithfully acquires thalamic information, the superficial layers appear well staged for more refined processing of L4-relayed signals to generate corticocortical outputs. However, the specific role of superficial layer processing and how it is specified by local synaptic circuits remains not well understood. Here, in the mouse primary auditory cortex, we showed that upper L2/3 circuits play a crucial role in refining functional selectivity of excitatory neurons by sharpening auditory tonal receptive fields and enhancing contrast of frequency representation. This refinement is mediated by synaptic inhibition being more broadly recruited than excitation, with the inhibition predominantly originating from interneurons in the same cortical layer. By comparing the onsets of synaptic inputs as well as of spiking responses of different types of neuron, we found that the broadly tuned, fast responding inhibition observed in excitatory cells can be primarily attributed to feedforward inhibition originating from parvalbumin (PV)-positive neurons, whereas somatostatin (SOM)-positive interneurons respond much later compared with the onset of inhibitory inputs to excitatory neurons. We propose that the feedforward circuit-mediated inhibition from PV neurons, which has an analogous function to lateral inhibition, enables upper L2/3 excitatory neurons to rapidly refine auditory representation.

103 citations


Journal ArticleDOI
19 Nov 2014-Neuron
TL;DR: A functional glutamatergic circuit that mediates noncanonical excitatory interactions in the retina and probably plays a role in generating ON-OFF responses, crossover excitation, and lateral excitation is revealed.

98 citations


Journal ArticleDOI
TL;DR: It is shown that light elicits a change in synaptic proton concentration with the correct magnitude, kinetics and spatial dependence to account for lateral inhibition, and the possibility that protons are unrecognized retrograde messengers elsewhere in the nervous system is raised.
Abstract: The reciprocal synapse between photoreceptors and horizontal cells underlies lateral inhibition and establishes the antagonistic center-surround receptive fields of retinal neurons to enhance visual contrast. Despite decades of study, the signal mediating the negative feedback from horizontal cells to cones has remained under debate because the small, invaginated synaptic cleft has precluded measurement. Using zebrafish retinas, we show that light elicits a change in synaptic proton concentration with the correct magnitude, kinetics and spatial dependence to account for lateral inhibition. Light, which hyperpolarizes horizontal cells, causes synaptic alkalinization, whereas activating an exogenously expressed ligand-gated Na(+) channel, which depolarizes horizontal cells, causes synaptic acidification. Whereas acidification was prevented by blocking a proton pump, re-alkalinization was prevented by blocking proton-permeant ion channels, suggesting that distinct mechanisms underlie proton efflux and influx. These findings reveal that protons mediate lateral inhibition in the retina, raising the possibility that protons are unrecognized retrograde messengers elsewhere in the nervous system.

85 citations


Journal ArticleDOI
TL;DR: An important goal for further investigation will be to explore the hypothesis that distinct bistratified S-ON versus midget S-OFF retinal circuits are the substrates for human psychophysical detection mechanisms attributed to S- on versus S-off perceptual channels.
Abstract: Anatomical and physiological approaches are beginning to reveal the synaptic origins of parallel ON- and OFF-pathway retinal circuits for the transmission of short (S-) wavelength sensitive cone signals in the primate retina. Anatomical data suggest that synaptic output from S-cones is largely segregated; central elements of synaptic triads arise almost exclusively from the “blue-cone” bipolar cell, a presumed ON bipolar, whereas triad-associated contacts derive primarily from the “flat” midget bipolar cell, a hyperpolarizing, OFF bipolar. Similarly, horizontal cell connectivity is also segregated, with only the H2 cell-type receiving numerous contacts from S-cones. Negative feedback from long (L-) and middle (M-) wavelength sensitive cones via the H2 horizontal cells elicits an antagonistic surround in S-cones demonstrating that S versus L + M or “blue-yellow” opponency is first established in the S-cone. However, the S-cone output utilizes distinct synaptic mechanisms to create color opponency at the ganglion cell level. The blue-cone bipolar cell is presynaptic to the small bistratified, “blue-ON” ganglion cell. S versus L + M cone opponency arises postsynaptically by converging S-ON and LM-OFF excitatory bipolar inputs to the ganglion cell’s bistratified dendritic tree. The common L + M cone surrounds of the parallel S-ON and LM-OFF cone bipolar inputs appear to cancel resulting in “blue-yellow” antagonism without center-surround spatial opponency. By contrast, in midget ganglion cells, opponency arises by the differential weighting of cone inputs to the receptive field center versus surround. In the macula, the “private-line” connection from a midget ganglion cell to a single cone predicts that S versus L + M opponency is transmitted from the S-cone to the S-OFF midget bipolar and ganglion cell. Beyond the macula, OFF-midget ganglion cell dendritic trees enlarge and collect additional input from multiple L and M cones. Thus S-OFF opponency via the midget pathway would be expected to become more complex in the near retinal periphery as L and/or M and S cone inputs sum to the receptive field center. An important goal for further investigation will be to explore the hypothesis that distinct bistratified S-ON versus midget S-OFF retinal circuits are the substrates for human psychophysical detection mechanisms attributed to S-ON versus S-OFF perceptual channels.

Journal ArticleDOI
TL;DR: This work combined intracellular recording in rats with a multi-directional, multi-whisker stimulator system to estimate receptive fields by reverse correlation of stimuli to synaptic inputs, and found that spatiotemporal receptive fields were identified orders of magnitude faster than by conventional spike-based approaches.
Abstract: Of all of the sensory areas, barrel cortex is among the best understood in terms of circuitry, yet least understood in terms of sensory function. We combined intracellular recording in rats with a multi-directional, multi-whisker stimulator system to estimate receptive fields by reverse correlation of stimuli to synaptic inputs. Spatiotemporal receptive fields were identified orders of magnitude faster than by conventional spike-based approaches, even for neurons with little spiking activity. Given a suitable stimulus representation, a linear model captured the stimulus-response relationship for all neurons with high accuracy. In contrast with conventional single-whisker stimuli, complex stimuli revealed markedly sharpened receptive fields, largely as a result of adaptation. This phenomenon allowed the surround to facilitate rather than to suppress responses to the principal whisker. Optimized stimuli enhanced firing in layers 4-6, but not in layers 2/3, which remained sparsely active. Surround facilitation through adaptation may be required for discriminating complex shapes and textures during natural sensing.

Journal ArticleDOI
TL;DR: Behavioral and neuroimaging studies on sound localization, and some of the competing models of representation of auditory space in humans are discussed.

Journal ArticleDOI
22 Oct 2014-Neuron
TL;DR: It is shown that normal visual experience after eye opening is required for V1 neurons to develop a sensitivity for the statistical structure of natural stimuli extending beyond the boundaries of their receptive fields, which leads to improvements in coding efficiency for full-field natural scenes.

Journal ArticleDOI
TL;DR: The results demonstrate how the frequency and power of oscillations, and hence spike times, can be modulated by both sensory input and behavioral context, with powerful oscillations signifying a cortical state under inhibitory control in which spikes are sparse and spike timing is precise.
Abstract: Precise spike times carry information and are important for synaptic plasticity. Synchronizing oscillations such as gamma bursts could coordinate spike times, thus regulating information transmission in the cortex. Oscillations are driven by inhibitory neurons and are modulated by sensory stimuli and behavioral states. How their power and frequency are regulated is an open question. Using a model cortical circuit, we propose a regulatory mechanism that depends on the activity balance of monosynaptic and disynaptic pathways to inhibitory neurons: Monosynaptic input causes more powerful oscillations whereas disynaptic input increases the frequency of oscillations. The balance of stimulation to the two pathways modulates the overall distribution of spikes, with stronger disynaptic stimulation (e.g., preferred stimuli inside visual receptive fields) producing high firing rates and weak oscillations; in contrast, stronger monosynaptic stimulation (e.g., suppressive contextual stimulation from outside visual receptive fields) generates low firing rates and strong oscillatory regulation of spike timing, as observed in alert cortex processing complex natural stimuli. By accounting for otherwise paradoxical experimental findings, our results demonstrate how the frequency and power of oscillations, and hence spike times, can be modulated by both sensory input and behavioral context, with powerful oscillations signifying a cortical state under inhibitory control in which spikes are sparse and spike timing is precise.

Journal ArticleDOI
TL;DR: It is demonstrated that associative cortical areas may not represent the external world in a complete and continuous fashion.

Journal ArticleDOI
TL;DR: It is argued that surround modulation in V1 consists of multiple components having different spatio-temporal and tuning properties, generated by different neural circuits and serving different visual functions.

Journal ArticleDOI
19 Feb 2014-Neuron
TL;DR: It is suggested that afferent-derived Activin regulates the dendritic field size of their postsynaptic partners to ensure appropriate synaptic partnership.

Journal ArticleDOI
TL;DR: The results support the view that the deficiency in feature integration and segmentation in peripheral vision is present at the earliest stages of cortical processing.
Abstract: In peripheral vision, objects in clutter are difficult to identify. The exact cause of this “crowding” effect is unclear. To perceive coherent shapes in clutter, the visual system must integrate certain local features across receptive fields while preventing others from being combined. It is believed that this selective feature integration–segmentation process is impaired in peripheral vision, leading to crowding. We used functional magnetic resonance imaging (fMRI) to investigate the neural origin of crowding. We found that crowding was associated with suppressed fMRI signal as early as V1, regardless of whether attention was directed toward or away from a target stimulus. This suppression in early visual cortex was greatest for stimuli that produced the strongest crowding. In contrast, the pattern of activity was mixed in higher level visual areas, such as the lateral occipital cortex. These results support the view that the deficiency in feature integration and segmentation in peripheral vision is present at the earliest stages of cortical processing.

Journal ArticleDOI
TL;DR: These findings suggest neural ‘tunnel vision’ as a form of distractor suppression under high perceptual load in early visual cortex using functional magnetic resonance imaging (fMRI).

Journal ArticleDOI
03 Dec 2014-Neuron
TL;DR: FosGFP expression discriminates between single- and multi-whisker receptive field layer 2 pyramidal neurons, and is targeted by axons from the posteromedial nucleus (POm) associated with broad receptive fields and widespread cortical projections.

Proceedings Article
08 Dec 2014
TL;DR: A statistical model of neural population activity that integrates a nonlinear receptive field model with a latent dynamical model of ongoing cortical activity that captures temporal dynamics and correlations due to shared stimulus drive as well as common noise is introduced.
Abstract: Neural responses in visual cortex are influenced by visual stimuli and by ongoing spiking activity in local circuits. An important challenge in computational neuroscience is to develop models that can account for both of these features in large multi-neuron recordings and to reveal how stimulus representations interact with and depend on cortical dynamics. Here we introduce a statistical model of neural population activity that integrates a nonlinear receptive field model with a latent dynamical model of ongoing cortical activity. This model captures temporal dynamics and correlations due to shared stimulus drive as well as common noise. Moreover, because the nonlinear stimulus inputs are mixed by the ongoing dynamics, the model can account for a multiple idiosyncratic receptive field shapes with a small number of nonlinear inputs to a low-dimensional dynamical model. We introduce a fast estimation method using online expectation maximization with Laplace approximations, for which inference scales linearly in both population size and recording duration. We test this model to multi-channel recordings from primary visual cortex and show that it accounts for neural tuning properties as well as cross-neural correlations.

Journal ArticleDOI
TL;DR: A biologically motivated model is proposed, in which the surround inhibition weights of individual features, including orientation, luminance, and luminance contrast, are combined according to a scale-guided strategy, and the combined weights are used to modulate the final surround inhibition of the neurons.
Abstract: To effectively perform visual tasks like detecting contours, the visual system normally needs to integrate multiple visual features. Sufficient physiological studies have revealed that for a large number of neurons in the primary visual cortex (V1) of monkeys and cats, neuronal responses elicited by the stimuli placed within the classical receptive field (CRF) are substantially modulated, normally inhibited, when difference exists between the CRF and its surround, namely, non-CRF, for various local features. The exquisite sensitivity of V1 neurons to the center-surround stimulus configuration is thought to serve important perceptual functions, including contour detection. In this paper, we propose a biologically motivated model to improve the performance of perceptually salient contour detection. The main contribution is the multifeature-based center-surround framework, in which the surround inhibition weights of individual features, including orientation, luminance, and luminance contrast, are combined according to a scale-guided strategy, and the combined weights are then used to modulate the final surround inhibition of the neurons. The performance was compared with that of single-cue-based models and other existing methods (especially other biologically motivated ones). The results show that combining multiple cues can substantially improve the performance of contour detection compared with the models using single cue. In general, luminance and luminance contrast contribute much more than orientation to the specific task of contour extraction, at least in gray-scale natural images.

Journal ArticleDOI
19 Feb 2014-Neuron
TL;DR: A model of the retinothalamic circuit is built that shows how the thalamus might form a resampled map of visual space with the potential to facilitate detection of stimulus position in the presence of sensor noise.

Journal ArticleDOI
TL;DR: The results suggest that normalization signals may be an important mechanism for modulating correlations, and present annular stimuli that encircled—but did not impinge upon—the RFs of the recorded cells, which reduced correlations in the absence of stimulation of the RF.
Abstract: The trial-to-trial response variability of nearby cortical neurons is correlated. These correlations may strongly influence population coding performance. Numerous studies have shown that correlations can be dynamically modified by attention, adaptation, learning, and potent stimulus drive. However, the mechanisms that influence correlation strength remain poorly understood. Here we test whether correlations are influenced by presenting stimuli outside the classical receptive field (RF) of visual neurons, where they recruit a normalization signal termed surround suppression. We recorded simultaneously the activity of dozens of cells using microelectrode arrays implanted in the superficial layers of V1 in anesthetized, paralyzed macaque monkeys. We presented annular stimuli that encircled—but did not impinge upon—the RFs of the recorded cells. We found that these “extra-classical” stimuli reduced correlations in the absence of stimulation of the RF, closely resembling the decorrelating effects of stimulating the RFs directly. Our results suggest that normalization signals may be an important mechanism for modulating correlations.

Journal ArticleDOI
TL;DR: Neurophysiological evidence is provided that remapped responses in area LIP can encode shape information as well as spatial information and is important for understanding what information is retained from each glance.
Abstract: We explore the visual world by making rapid eye movements (saccades) to focus on objects and locations of interest. Despite abrupt retinal image shifts, we see the world as stable. Remapping contributes to visual stability by updating the internal image with every saccade. Neurons in macaque lateral intraparietal cortex (LIP) and other brain areas update information about salient locations around the time of a saccade. The depth of information transfer remains to be thoroughly investigated. Area LIP, as part of the dorsal visual stream, is regarded as a spatially selective area, yet there is evidence that LIP neurons also encode object features. We sought to determine whether LIP remaps shape information. This knowledge is important for understanding what information is retained from each glance. We identified 82 remapping neurons. First, we presented shapes within the receptive field and tested for shape selectivity in a fixation task. Among the remapping neurons, 28 neurons (34%) were selective for shape. Second, we presented the same shapes in the future location of the receptive field around the time of the saccade and tested for shape selectivity during remapping. Thirty-one (38%) neurons were selective for shape. Of 11 neurons that were shape selective in both tasks, 5 showed significant correlation between shape selectivity in the two tasks. Across the population, there was a weak but significant correlation between responses to shape in the two tasks. Our results provide neurophysiological evidence that remapped responses in area LIP can encode shape information as well as spatial information.

Journal ArticleDOI
TL;DR: In this article, the intrinsic signal of neurons was measured using optical imaging to determine the global map of orientation preferences in the cat primary visual system, and axon clusters formed in a variety of different orientation domains, not just the like-orientation domains.
Abstract: The axons of pyramidal neurons in the superficial layers of the neocortex of higher mammals form lateral networks of discrete clusters of synaptic boutons. In primary visual cortex the clusters are reported to link domains that share the same orientation preferences, but how individual neurons contribute to this network is unknown. Here we performed optical imaging to record the intrinsic signal, which is an indirect measure of neuronal firing, and determined the global map of orientation preferences in the cat primary visual system. In the same experiment, single cells were recorded and labelled intracellularly. We found that individual axons arborise within the retinotopic representation of the classical receptive field, but their bouton clusters were not aligned along their preferred axis of orientation along the retinotopic map. Axon clusters formed in a variety of different orientation domains, not just the like-orientation domains. This topography and heterogeneity of single-cell connectivity provides circuits for normalization and context-dependent feature processing of visual scenes.

Journal ArticleDOI
TL;DR: Findings reveal the functional organization and collective visual signaling by a distinctive, high-density amacrine cell population in macaque retina.
Abstract: Amacrine cells are the most diverse and least understood cell class in the retina. Polyaxonal amacrine cells (PACs) are a unique subset identified by multiple long axonal processes. To explore their functional properties, populations of PACs were identified by their distinctive radially propagating spikes in large-scale high-density multielectrode recordings of isolated macaque retina. One group of PACs exhibited stereotyped functional properties and receptive field mosaic organization similar to that of parasol ganglion cells. These PACs had receptive fields coincident with their dendritic fields, but much larger axonal fields, and slow radial spike propagation. They also exhibited ON-OFF light responses, transient response kinetics, sparse and coordinated firing during image transitions, receptive fields with antagonistic surrounds and fine spatial structure, nonlinear spatial summation, and strong homotypic neighbor electrical coupling. These findings reveal the functional organization and collective visual signaling by a distinctive, high-density amacrine cell population.

Journal ArticleDOI
TL;DR: The results reveal the specific roles of experience-dependent and -independent processes in binocular convergence and refinement of On and Off inputs onto single cortical neurons.
Abstract: The convergence of eye-specific thalamic inputs to visual cortical neurons forms the basis of binocular vision. Inputs from the same eye that signal light increment (On) and decrement (Off) are spatially segregated into subregions, giving rise to cortical receptive fields (RFs) that are selective for stimulus orientation. Here we map RFs of binocular neurons in the mouse primary visual cortex using spike-triggered average. We find that subregions of the same sign (On–On and Off–Off) preferentially overlap between the 2 monocular RFs, leading to binocularly matched orientation tuning. We further demonstrate that such subregion correspondence and the consequent matching of RF orientation are disrupted in mice reared in darkness during development. Surprisingly, despite the lack of all postnatal visual experience, a substantial degree of subregion correspondence still remains. In addition, dark-reared mice show normal monocular RF structures and binocular overlap. These results thus reveal the specific roles of experience-dependent and -independent processes in binocular convergence and refinement of On and Off inputs onto single cortical neurons.

Journal ArticleDOI
01 Dec 2014-Pain
TL;DR: Withdrawal thresholds to mechanical stimuli in normal and in hyperalgesic nerve‐injured animals also were increased by transcutaneous light to the affected hindpaw, suggesting that AHTMR neurons play a role not only in threshold‐related withdrawal behavior in the normal animal, but also in sensitized states after nerve injury.
Abstract: Fast-conducting myelinated high-threshold mechanoreceptors (AHTMR) are largely thought to transmit acute nociception from the periphery. However, their roles in normal withdrawal and in nerve injury–induced hyperalgesia are less well accepted. Modulation of this subpopulation of peripheral neurons would help define their roles in withdrawal behaviors. The optically active proton pump, ArchT, was placed in an adeno-associated virus-type 8 viral vector with the CAG promoter and was administered by intrathecal injection resulting in expression in myelinated neurons. Optical inhibition of peripheral neurons at the soma and transcutaneously was possible in the neurons expressing ArchT, but not in neurons from control animals. Receptive field characteristics and electrophysiology determined that inhibition was neuronal subtype–specific with only AHTMR neurons being inhibited. One week after nerve injury the AHTMR are hyperexcitable, but can still be inhibited at the soma and transcutaneously. Withdrawal thresholds to mechanical stimuli in normal and in hyperalgesic nerve-injured animals also were increased by transcutaneous light to the affected hindpaw. This suggests that AHTMR neurons play a role not only in threshold-related withdrawal behavior in the normal animal, but also in sensitized states after nerve injury. This is the first time this subpopulation of neurons has been reversibly modulated to test their contribution to withdrawal-related behaviors before and after nerve injury. This technique may prove useful to define the role of selective neuronal populations in different pain states.