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spatial constraints on probability learning in visual working memory

VISUAL COGNITION 2017年第1-3期25卷 34-50页

作者： Won, Bo-Yeong Leber, Andrew B. Univ Calif Davis Ctr Mind & Brain 267 Cousteau Pl Davis CA 95618 USA Ohio State Univ Dept Psychol Columbus OH USA

Visual working memory is limited in capacity so it is essential to use it efficiently. Previous work has shown that statistical learning can help boost working memory efficiency by prioritizing the encoding and/or maintenance of objects most likely to be tested. In this study, we considered that the potential benefits of statistical learning could be limited by spatial constraints. Across three experiments, we found that statistical learning prioritizes working memory allocation to items based on their likelihood of being tested, but this prioritization is greatly modulated by spatial constraints. In particular, when two locations each had a high probability of being tested, we primarily observed performance benefits over low probable locations when these two locations were horizontally adjacent to one another. Vertically adjacent and diagonally arranged high probable locations produced no accuracy benefit over low probable locations and a modest response time benefit. These findings contrast with previously observed hemifield-independent effects (i.e., a "bilateral field advantage") and reveal surprising limitations on the potential benefits of statistical learning.

关键词： Statistical learning working memory spatial coding hemifield independence bilateral field advantage

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Visual-Motor Transformations Within Frontal Eye Fields During Head-Unrestrained Gaze Shifts in the Monkey

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CEREBRAL CORTEX 2015年第10期25卷 3932-3952页

作者： Sajad, Amirsaman Sadeh, Morteza Keith, Gerald P. Yan, Xiaogang Wang, Hongying Crawford, John Douglas York Univ Ctr Vis Res Toronto ON M3J 1P3 Canada York Univ Canadian Act & Percept Network CAPnet Toronto ON M3J 1P3 Canada York Univ Neurosci Grad Diploma Program Toronto ON M3J 1P3 Canada York Univ Dept Biol Toronto ON M3J 1P3 Canada York Univ Sch Kinesiol & Hlth Sci Toronto ON M3J 1P3 Canada York Univ Dept Psychol Toronto ON M3J 1P3 Canada

A fundamental question in sensorimotor control concerns the transformation of spatial signals from the retina into eye and head motor commands required for accurate gaze shifts. Here, we investigated these transformations by identifying the spatial codes embedded in visually evoked and movement-related responses in the frontal eye fields (FEFs) during head-unrestrained gaze shifts. Monkeys made delayed gaze shifts to the remembered location of briefly presented visual stimuli, with delay serving to dissociate visual and movement responses. A statistical analysis of nonparametric model fits to response field data from 57 neurons (38 with visual and 49 with movement activities) eliminated most effector-specific, head-fixed, and space-fixed models, but confirmed the dominance of eye-centered codes observed in head-restrained studies. More importantly, the visual response encoded target location, whereas the movement response mainly encoded the final position of the imminent gaze shift (including gaze errors). This spatiotemporal distinction between target and gaze coding was present not only at the population level, but even at the single-cell level. We propose that an imperfect visual-motor transformation occurs during the brief memory interval between perception and action, and further transformations from the FEF's eye-centered gaze motor code to effector-specific codes in motor frames occur downstream in the subcortical areas.

关键词： eye-head coordination frontal eye field gaze control sensorimotor transformation spatial coding

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spatial interactions between consecutive manual responses

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EXPERIMENTAL BRAIN RESEARCH 2015年第11期233卷 3283-3290页

作者： Avery, Brittany Cowper-Smith, Christopher D. Westwood, David A. Dalhousie Univ Div Kinesiol Halifax NS B3H 4R2 Canada Dalhousie Univ Dept Psychol & Neurosci Halifax NS Canada

We have shown that the latency to initiate a reaching movement is increased if its direction is the same as a previous movement compared to movements that differ by 90A degrees or 180A degrees (Cowper-Smith and Westwood in Atten Percept Psychophys 75:1914-1922, 2013). An influential study (Taylor and Klein in J Exp Psychol Hum Percept Perform 26:1639-1656, 2000), however, reported the opposite spatial pattern for manual keypress responses: repeated responses on the same side had reduced reaction time compared to responses on opposite sides. In order to determine whether there are fundamental differences in the patterns of spatial interactions between button-pressing responses and reaching movements, we compared both types of manual responses using common methods. Reaching movements and manual keypress responses were performed in separate blocks of trials using consecutive central arrow stimuli that directed participants to respond to left or right targets. Reaction times were greater for manual responses made to the same target as a previous response (M = 390 ms) as compared to the opposite target (M = 365 ms;similarity main effect: p < 0.001) regardless of whether the response was a reaching movement or a keypress response. This finding is broadly consistent with an inhibitory mechanism operating at the level of motor output that discourages movements that achieve the same spatial goal as a recent action.

关键词： Arm movements Reaching movements Manual responses Target localization spatial coding Inhibition of return Attention

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Reversing the affordance effect: Negative stimulus-response compatibility observed with images of graspable objects

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COGNITIVE PROCESSING 2015年第1期16卷 S72-S72页

作者： Kostov, Kiril Janyan, Armina New Bulgarian Univ Dept Cognit Sci & Psychol Sofia Bulgaria New Bulgarian Univ Res Ctr Cognit Sci Sofia Bulgaria Natl Res Tomsk State Univ Tomsk Russia

Responses are faster when the task-irrelevant orientation of a graspable object’s handle corresponds to the location of the response hand. Over the past decade, research has focused on dissociating between two competing accounts of this effect: One rooted in motoric object affordances and the other resting on attentional mechanisms (i.e., Simon effect). Following this avenue of inquiry, we conducted three experiments, in which subjects had to respond bimanually to grayscale photographs of frying pans and saucepans. In addition to horizontal orientation (control/leftward/rightward handles), Experiments 1 and 2 also manipulated the direction of exogenous attentional shifts (left/right) using laterally placed, colored markers within the objects. Both experiments yielded regular Simon effects based on the location of the colored markers. However, in stark contrast to previous research, a negative stimulus–response compatibility effect was obtained with regard to the orientation of the graspable handles. This reversed affordance effect was also observed using the original, unedited grayscale photographs (Experiment 3), which suggested that its occurrence cannot be attributed to the use of colored markers. These unexpected findings appear to support the idea that Simon effects result from automatic and exogenous attentional orienting mechanisms, whereas affordances arise from controlled and endogenous attentional processes. Such a top-down attentional account of affordance can accommodate the observed reversal of the effect in the context of task characteristics.

关键词： Attention Inverse affordance Negative stimulus–response compatibility Simon effect spatial coding

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Correspondence effects with torches: Grasping affordance or visual feature asymmetry?

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QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY 2014年第4期67卷 665-675页

作者： Song, Xiaolei Chen, Jing Proctor, Robert W. Shaanxi Normal Univ Coll Psychol Xian Peoples R China Purdue Univ Dept Psychol Sci W Lafayette IN 47907 USA

Three experiments were conducted to determine whether an object-based correspondence effect for torch (flashlight) stimuli reported by Pellicano et al. [(2010). Simon-like and functional affordance effects with tools: The effects of object perceptual discrimination and object action state. Quarterly Journal of Experimental Psychology, 63, 2190-2201] is due to a grasping affordance provided by the handle or asymmetry of feature markings on the torch. In Experiment 1 the stimuli were the same as those from Pellicano et al.'s Experiment 2, whereas in Experiments 2 and 3 the stimuli were modified versions with the graspable handle removed. Participants in all experiments performed upright/inverted orientation judgements on the torch stimuli. The results of Experiment 1 replicated those of Pellicano et al.: A small but significant object-based correspondence effect was evident, mainly when the torch was in an active state. With the handle of the torch removed in Experiment 2, making the barrel markings more asymmetric in the display, the correspondence effect was larger. Experiment 3 directly demonstrated an effect of barrel-marking asymmetry on the correspondence effect: When only the half of the markings nearest the light end of the torch was included, the correspondence effect reversed to favour the light end. The results are in agreement with a visual feature-asymmetry account and are difficult to reconcile with a grasping-affordance account.

关键词： Grasping Functional affordance Simon effect spatial coding Stimulus-response compatibility

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Visual motion modulates pattern sensitivity ahead, behind, and beside motion

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VISION RESEARCH 2014年 98卷 99-106页

作者： Arnold, Derek H. Marinovic, Welber Whitney, David Univ Queensland Sch Psychol St Lucia Qld 4072 Australia Univ Calif Berkeley Dept Psychol Berkeley CA 94720 USA

Retinal motion can modulate visual sensitivity. For instance, low contrast drifting waveforms (targets) can be easier to detect when abutting the leading edges of movement in adjacent high contrast waveforms (inducers), rather than the trailing edges. This target-inducer interaction is contingent on the adjacent waveforms being consistent with one another - in-phase as opposed to out-of-phase. It has been suggested that this happens because there is a perceptually explicit predictive signal at leading edges of motion that summates with low contrast physical input - a 'predictive summation'. Another possible explanation is a phase sensitive 'spatial summation', a summation of physical inputs spread across the retina (not predictive signals). This should be non-selective in terms of position - it should be evident at leading, adjacent, and at trailing edges of motion. To tease these possibilities apart, we examined target sensitivity at leading, adjacent, and trailing edges of motion. We also examined target sensitivity adjacent to flicker, and for a stimulus that is less susceptible to spatial summation, as it sums to grey across a small retinal expanse. We found evidence for spatial summation in all but the last condition. Finally, we examined sensitivity to an absence of signal at leading and trailing edges of motion, finding greater sensitivity at leading edges. These results are inconsistent with the existence of a perceptually explicit predictive signal in advance of drifting waveforms. Instead, we suggest that phase-contingent target-inducer modulations of sensitivity are explicable in terms of a directionally modulated spatial summation. (C) 2014 Published by Elsevier Ltd.

关键词： Motion spatial coding spatial summation Predictive coding

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The human amygdala encodes value and space during decision making

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NEUROIMAGE 2014年 101卷 712-719页

作者： Ousdal, Olga Therese Specht, Karsten Server, Andres Andreassen, Ole A. Dolan, Ray J. Jensen, Jimmy Univ Oslo Oslo Univ Hosp KG Jebsen Ctr Psychosis Res NORMENTDiv Mental Hlth & Addict Oslo Norway Haukeland Hosp Dept Radiol Bergen Norway UCL Inst Neurol Wellcome Trust Ctr Neuroimaging London England Univ Bergen Dept Biol & Medial Psychol Bergen Norway Oslo Univ Hosp Dept Neuroradiol Oslo Norway Kristianstad Univ Ctr Psychol Kristianstad Sweden Haukeland Hosp Dept Med Engn N-5021 Bergen Norway

Valuable stimuli are invariably localized in space. While our knowledge regarding the neural networks supporting value assignment and comparisons is considerable, we lack a basic understanding of how the human brain integrates motivational and spatial information. The amygdala is a key structure for learning and maintaining the value of sensory stimuli and a recent non-human primate study provided initial evidence that it also acts to integrate value with spatial location, a question we address here in a human setting. We measured haemodynamic responses (fMRI) in amygdala while manipulating the value and spatial configuration of stimuli in a simple stimulus-reward task. Subjects responded significantly faster and showed greater amygdala activation when a reward was dependent on a spatial specific response, compared to when a reward required less spatial specificity. Supplemental analysis supported this spatial specificity by demonstrating that the pattern of amygdala activity varied based on whether subjects responded to a motivational target presented in the ipsilateral or contralateral visual space. Our data show that the human amygdala integrates information about space and value, an integration of likely importance for assigning cognitive resources towards highly valuable stimuli in our environment. (C) 2014 The Authors. Published by Elsevier Inc.

关键词： Amygdala Anterior cingulate cortex Value Emotion spatial coding fMRI

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Creating the bag-of-words with spatial context information for image retrieval

Creating the bag-of-words with spatial context information f...

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International Conference on Mechatronics Engineering and Computing Technology (ICMECT)

作者： Li, Zhenwei Zhang, Jing Liu, Xin Zhuo, Li Beijing Univ Technol Signal & Informat Proc Lab Beijing Peoples R China

ISBN: (纸本)9783038351153

Recently bag-of-words (BoW) model as image feature has been widely used in content-based image retrieval. Most of existing approaches of creating BoW ignore the spatial context information. In order to better describe the image content, the BoW with spatial context information is created in this paper. Firstly, image's regions of interest are detected and the focus of attention shift is produced through visual attention model. The color and SIFT features are extracted from the region of interest and BoW is created through cluster analysis method. Secondly, the spatial context information among objects in an image is generated by using the spatial coding method based on the focus of attention shift. Then the image is represented as the model of BoW with spatial context. Finally, the model of spatial context BoW is applied into image retrieval to evaluate the performance of the proposed method. Experimental results show the proposed method can effectively improve the accuracy of the image retrieval.

关键词： Image retrieval Bag-of-words spatial context spatial coding Focus of attention

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TRANSFORM-DOMAIN DECORRELATION IN DOLBY DIGITAL PLUS

TRANSFORM-DOMAIN DECORRELATION IN DOLBY DIGITAL PLUS

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IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)

作者： Melkote, Vinay Yen, Kuan-Chieh Fellers, Matt Davidson, Grant Kumar, Vivek Dolby Labs Inc San Francisco CA 94103 USA

ISBN: (纸本)9781479928934

The Dolby Digital Plus (DDPlus) multichannel audio codec employs channel coupling for parsimonious transmission of high frequency components of the signal, wherein the transform coefficients of discrete channels beyond a coupling-begin frequency are transmitted as a mono-downmix. The decoder reconstructs individual channels by appropriate panning with frequency-banded gains. While channel coupling is a valuable parametric coding tool for low bit-rate encoding of multichannel audio, the resulting high inter-channel coherence can affect audio post-processors that utilize downmixing, such as headphone virtualizers. To mitigate these effects, a new low-complexity spatial audio coding tool is proposed, whose primary objective is to restore phase diversity in the decoder's output. In this new approach, a decorrelation signal is synthesized directly from the decoded real-valued and critically-sampled transform (MDCT) coefficients, avoiding the expense of computing the imaginary counterpart (MDST) or signal transformation to a different domain (such as QMF). The decorrelation signal is then adaptively mixed with the dry signal and inverse-transformed as in a conventional decoder. The degree of mixing depends on spatial parameters that are either sent in the bitstream or estimated in the decoder from the discrete (not coupled) low-frequency spectral coefficients. Listening tests demonstrate the significant performance benefits obtained in either mode of operation of the proposed tool.

关键词： decorrelation audio coding channel coupling MDCT spatial coding

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Understanding smell-The olfactory stimulus problem

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NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS 2013年第8期37卷 1667-1679页

作者： Auffarth, Benjamin Fdn Res & Technol Inst Mol Biol & Biotechnol Iraklion Greece Free Univ Berlin Dept Neurobiol Berlin Germany BCCN Berlin Germany KTH Royal Inst Technol Sch Comp Sci & Commun Stockholm Sweden

The main problem with sensory processing is the difficulty in relating sensory input to physiological responses and perception. This is especially problematic at higher levels of processing, where complex cues elicit highly specific responses. In olfaction, this relationship is particularly obfuscated by the difficulty of characterizing stimulus statistics and perception. The core questions in olfaction are hence the so-called stimulus problem, which refers to the understanding of the stimulus, and the structure-activity and structure-odor relationships, which refer to the molecular basis of smell. It is widely accepted that the recognition of odorants by receptors is governed by the detection of physico-chemical properties and that the physical space is highly complex. Not surprisingly, ideas differ about how odor stimuli should be classified and about the very nature of information that the brain extracts from odors. Even though there are many measures for smell, there is none that accurately describes all aspects of it. Here, we summarize recent developments in the understanding of olfaction. We argue that an approach to olfactory function where information processing is emphasized could contribute to a high degree to our understanding of smell as a perceptual phenomenon emerging from neural computations. Further, we argue that combined analysis of the stimulus, biology, physiology, and behavior and perception can provide new insights into olfactory function. We hope that the reader can use this review as a competent guide and overview of research activities in olfactory physiology, psychophysics, computation, and psychology. We propose avenues for research, particularly in the systematic characterization of receptive fields and of perception. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Olfactory system Olfactory stimulus-problem Structure-activity relationship Structure-odor relationship Odor perception spatial coding Olfactory receptors Topography Hedonics Basic odors Vertebrate olfaction Insect olfaction

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