Neural Basis of Visual Perception

Shih-Kuo Chen (Life Science, National Taiwan University, Taiwan)

Title: Neuronal connection of intrinsically photosensitive retinal ganglion cells: how light influence physiological functions

Abstract: Retinal ganglion cells (RGCs) in the retina receive input from classical photoreceptor rod and cone through bipolar cells and many lateral processing from amacrine cell. For image forming function, classic photoreceptor rods and cones are primary photon detector located at the outer retina. However, recent studies showed that a small population of melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) located at the inner retina is essential for many non-image forming visual functions. There are many subtypes of ipRGCs which provide environmental luminance signal for circadian photoentrainmnet, pupillary light reflex. Furthermore, ipRGCs could also influence the physiological functions of upstream order of retinal neuron such as dopaminergic amacrine cell and even the retinal development through intra-retinal axon collaterals. Therefore, ipRGC could conveying luminance signal from the inner retina to outer retina to control light adaptation and simultaneously to the hypothalamus for other non-image forming function such as circadian clock modulation. We also construct the innervation pattern of ipRGC to the SCN, the brain nucleus controls circadian clock. Unlike regular sensory neurons which usually innervate opposite side of the brain, a single ipRGC can project bi-lateral innervation to both left and right side of the brain. This innervation pattern could provide information input to SCN for potential better synchronization of the biological clock. Together, our studies showed that the atypical photoreceptor in the retina can modulate many of our physiological function from vision to clock.



Andrea Benucci (Riken Brain Science Institute, Japan)

Title: Plasticity for stimulus selectivity in the visual cortex of adult mice induced by patterned optogenetic stimulation

Abstract: Functional plasticity in cortical networks plays an important role in a variety of learning and adaptive behaviors. However, little is known about its functional properties in-vivo and in adult animals. In this study we first established an in-vivo preparation for simultaneous imaging and spatially-patterned optogenetic stimulation based on a digital-micromirror-device (DMD). In awake, adult mice expressing GCaMP8 and Chrimson in the primary visual cortex (V1), we paired DMD stimulation of a single neuron (the “driver”) to a delayed stimulation (Dt = 10 ms) of several tens of surrounding neurons aiming to induce driver-surround spike-timing dependent plasticity (STDP). We found that the preferred orientation of neurons in the surround changed depending on the preferred orientation of the driver, with a significant increase in the fraction of neurons tuned to the orientation orthogonal to that of the driver. Despite these plastic changes, the network as a whole could still reliably encode stimulus orientations thanks to a subgroup of non-plastic cells. Such neurons were vigorously responding to the visual stimulation, while weakly responsive cells exhibited larger degrees of plasticity. In an effort to explain the orthogonal effect, we used a standard ring model combined with a STDP rule. Under the assumption that the driver’s optogenetic stimulation elicited network’s activations more broadly tuned in the orientation domain than visual stimulation, the model could qualitatively explain the orthogonal effect. In conclusion this study reveals a previously unreported functional specificity of in-vivo cortical plasticity, where the activity of just one cell can induce network-level, orientation-specific changes. Furthermore, the discovery of an inverse relationship between plasticity and visual responsiveness suggests a general mechanistic principle for the implementation of an “exploration vs exploitation” learning rule in adult cortical networks.



Manabu Tanifuji (Riken Brain Science Institute, Japan)

Title: 3D topology of orientation columns in visual cortex revealed by functional optical coherence tomography

Abstract: Optical intrinsic signal imaging (OISI) enabled us to visualize spatial arrangement of the orientation columns across the cortical surface and led us to discovery of the orientation singularity (pinwheel). Because of integrated information along the cortical depth axis in OISI, on the other hand, the detailed structure along depth axis has not been more than speculated. Here, we visualized the functional structure along depth axis of orientation columns in cat visual cortex with µm-scale spatial resolution and mm-scale measurement range by means of functional optical coherence tomography (fOCT). fOCT resolves changes in light scattering at different depth of the tissue that reflect strength of neural activation. As expected, in iso-orientation domains, the preferred orientation did not change along depth axis and orientation preference of the vertically elongated regions shifted gradually along the axis parallel to cortical surface. To our surprise, however, the orientation singularity was not always elongated vertically. It was often twisted, went parallel to the cortical surface or joined with other singularity. Thus, the orientation singularity is not a point in space that is replicated in multiple layers as we expected previously. It is rather like string running in various trajectories across layers.



Chun-I Yeh (Psychology, National Taiwan University, Taiwan)

Title: Spatial receptive fields of color-responsive neurons in macaque V1

Abstract: Spatial receptive fields have been studied to understand the properties of color- and luminance-responsive neurons in the primary visual cortex V1. In macaque V1, many color-responsive neurons are highly selective for orientation and spatial frequency with drifting gratings (Johnson et al., 2001; Friedman et al., 2003). One might predict that the receptive field structures of color-responsive neurons would consist of multiple elongated on and off sub-regions (like simple cells). However, previous studies had shown mixed results: some found simple-cell-like receptive fields by using dense noise (Horwitz et al., 2007; Johnson et al., 2008), whereas others found receptive fields that were blub-like and less elongated when using sparse noise (Conway and Livingstone, 2006). Here we measured spatial receptive fields of V1 color-responsive neurons with two different stimulus ensembles: Hartley gratings and binary sparse noise, both consisted of equiluminance colors (red and green that represent different cone weights). Receptive fields were calculated by reverse correlation and fitted with the 2-D Gabor function. We studied a total of 206 units in macaque V1 units and found that Hartley maps had significantly higher aspect ratios and greater numbers of subregions than sparse-noise maps. There was a negative correlation between the circular variance measured with drifting gratings and the aspect ratio of the map (significant correlation was found in Hartley but not in sparse noise). Moreover, we found that band-pass color cells had significantly higher aspect ratios that low-pass color cells under all stimulus ensembles. In summary, the receptive field of color-responsive neurons may change accordingly with different stimulus ensembles. For neurons that are well tuned for orientation and spatial frequency, the tuning properties can be well predicted by their properties of receptive fields mapped with Hartley gratings.


Yu-Cheng Pei (Physical and Rehabilitation, Chang Gung Memorial Hospital, Taiwan)

Title: Neuronal processing of cross-finger motion integration in the primary somatosensory cortex

Abstract: Dynamic object manipulation involves tactile motion perceived through multiple fingerpads. Neuronal tuning properties to direction and orientation in the primary somatosensory (S1) cortex have been characterized but the integration of tactile motion across fingers is not yet known. To this end, we used a multi-digit tactile motion stimulator with scanning balls engraved with square-wave gratings to present tactile motion to two nearby fingerpads and recorded the neuronal responses in areas 3b, 1 and 2 of anesthetized monkeys using multi-channel microelectrode arrays. Specifically, either one (one-finger condition) or both (two-finger condition) of the two fingers were presented with the motion stimuli, yielding a variety of combination of stimulus directions presented to the two nearby fingers. We found that a majority of motion-sensitive neurons have two-finger receptive fields. Comparing the activities obtained in one- and two-finger conditions in motion-sensitive neurons, 40% of neurons showed direction/orientation selectivity in the two-finger condition but no selectivity in the one-finger condition. Furthermore, the motion integration observed in the two-finger condition was mainly mediated by a nonlinear suppression of neuronal activities. These results indicate that motion integration across fingers is commonly observed in S1 neurons and can be accounted for by nonlinear suppressions of convergent inputs emanating from two fingers, a novel non-classical receptive field property that is first reported in primate S1.



Huihui Zhou (Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, China)

Title: Visual attention mechanisms in the pulvinar-cortex circuits

Abstract: Visual attention is important in our daily life. For example, we are often facing overwhelming visual inputs at a given moment that easily exceed the processing power of our brain. Attention allows us to focus on a small portion of the inputs, which are important for our behaviors, while ignoring the other less important stimuli. After a long history of studies in animals, it becomes evident that visual attention mechanisms involve a large number of brain areas and complex interactions between them. The pulvinar, the largest nucleus of the primate thalamus, is reciprocally connected with almost all visual areas in cortex. Although numerous studies suggest its important role in visual attention, the mechanisms of attentive stimulus processing in the pulvinar-cortex loop is still unclear. We investigated the interaction between the pulvinar and area V4 in a spatial attention task in non-human primates. Attention enhances gamma oscillatory coupling between the two areas, and the V4 influence on pulvinar by a granger causality analysis. Furthermore, pulvinar deactivation leads to a reduction of attentional effects and sensory-evoked responses in V4. Thus, the cortical interaction with the pulvinar seems necessary for normal attention and sensory processing in visual cortex.


Online Submission Registration Conference Program

 Important Dates

Call for abstracts:
Nov 15,2016

Symposium submission deadline:
Feb 28, 2017

Abstract submission deadline:
Mar 31, 2017 Apr 17, 2017

Early registration deadline:
Mar 31, 2017 Apr 30, 2017

All deadlines are midnight latest time zone on earth.