Neuropeptide Y–expressing spinal inhibitory interneurons are morphologically diverse and include cells innervated by transient receptor potential vanilloid-1–negative C fibres and a subset that targets lamina III projection neurons.

Primary visual cortex (V1) has small receptive fields and processes feedforward information at a fine-18 grained spatial scale, whereas higher visual areas have larger, spatially invariant receptive fields. Therefore, 19 feedback could provide coarse information about the global scene structure or alternatively recover fine-20 grained structure by targeting small receptive fields in V1. We tested if feedback signals generalise across 21 different spatial frequencies of feedforward inputs, or if they are tuned to the spatial scale of the visual 22 scene. Using a partial occlusion paradigm, functional magnetic resonance imaging (fMRI) and multivoxel 23 pattern analysis (MVPA) we investigated whether feedback to V1 contains coarse or fine-grained 24 information by manipulating the spatial frequency of the scene surround outside an occluded image portion. 25We show that feedback transmits both coarse and fine-grained information as it carries information about 26 both low (LSF) and high spatial frequencies (HSF

We investigated the limits of the number of events observers can simultaneously time. For single targets occurring in one of eight positions sensitivity to duration was improved for spatially pre-cued items as compared to post-cued items indicating that exogenous driven attention can improve duration discrimination. Sensitivity to duration for pre-cued items was also marginally better for single items as compared to eight items indicating that even after the allocation of focal attention, distractor items can interfere with the encoding of duration. For an eight item array discrimination was worse for post-cued locations as compared to pre-cued locations indicating both that attention can improve duration discrimination performance and that it was not possible to access a perfect memory trace of the duration of eight elements. The interference from the distractors in the pre-cued eight item array may reflect some mandatory averaging of target and distractor events. To further explore duration averaging we asked subjects to explicitly compare average durations of multiple item arrays against a single item standard duration. Duration discrimination thresholds were significantly lower for single elements as compared to multiple elements, showing that averaging, either automatically or intentionally, impairs duration discrimination. There was no set size effect. Performance was the same for averages of two and eight items, but performance with even an average of two items was worse than for one item. This was also true for sequential presentation indicating poor performance was not due to limits on the division of attention across items. Rather performance appears to be limited by an inability to remember or aggregate duration information from two or more items. Although it is possible to manipulate perceived duration locally, there appears to be no perceptual mechanisms for aggregating local durations across space.

Complete visual information about a scene and the objects within it is often not available to us. For example, objects may be partly occluded by other objects or have sections missing. In the retinal blind spot, there are no photoreceptors and visual input is not detected. However, due to perceptual filling-in by the visual system we often do not perceive these gaps. There is a lack of consensus on how much of the mechanism for perceptual filling-in is similar in the case of a natural scotoma like the blind spot and artificial scotomata such as sections of the stimulus being physically removed. Part of the difficulty in assessing this relationship arises from a lack of direct comparisons between the two cases, with artificial scotomata being tested in different locations in the visual field compared to the blind spot. The peripheral location of the blind spot may explain its enhanced filling-in compared to artificial scotomata, as reported in previous studies. In the present study, we directly compared perceptual filling-in of spatiotemporal information in the blind spot and artificial gaps of the same size and eccentricity. We found stronger perceptual filling-in in the blind spot, suggesting improved filling-in for the blind spot reported in previous studies cannot be simply attributed to its peripheral location.