1,721,433 research outputs found
Tactile cognition in rodents
Full text linkSince the discovery 50 years ago of the precisely ordered representation of the whiskers in somatosensory cortex, the rodent tactile sensory system has been a fertile ground for the study of sensory processing. With the growing sophistication of touch-based behavioral paradigms, together with advances in neurophysiological methodology, a new approach is emerging. By posing increasingly complex perceptual and memory problems, in many cases analogous to human psychophysical tasks, investigators now explore the operations underlying rodent problem solving. We define the neural basis of tactile cognition as the transformation from a stage in which neuronal activity encodes elemental features, local in space and in time, to a stage in which neuronal activity is an explicit representation of the behavioral operations underlying the current task. Selecting a set of whisker-based behavioral tasks, we show that rodents achieve high level performance through the workings of neuronal cir-cuits that are accessible, decodable, and manipulatable. As a means towards exploring tactile cognition, this review presents leading psychophysical paradigms and, where known, their neural correlates
Rats Generate Vibrissal Sensory Evidence until Boundary Crossing Triggers a Decision
No full textBehaviors in which primates collect externally generated streams of sensory evidence, such as judgment of random dot motion direction, are explained by a bounded integration decision model. Does this model extend to rodents, and does it account for behavior in which the motor system generates evidence through interactions with the environment? In this study, rats palpated surfaces to identify the texture before them, showing marked trial-to-trial variability in the number of touches prior to expressing their choice. By high-speed video, we tracked whisker kinematic features and characterized how they encoded the contacted texture. Next, we quantified the evidence for each candidate texture transmitted on each touch by the specified whisker kinematic features. The instant of choice was well fit by modeling the brain as an integrator that gives the greatest weight to vibrissal evidence on first touch and exponentially less weight to evidence on successive touches; according to this model, the rat makes a decision when the accumulated quantity of evidence for one texture reaches a boundary. In summary, evidence appears to be accumulated within the brain until sufficient to support a well-grounded choice. These findings extend the framework of bounded sensory integration from primates to rodents and from passively received evidence to evidence that is actively generated by the sensorimotor system. Faced with uncertain sensory inputs, primates integrate evidence over time to a decision boundary. Zuo and Diamond ask whether rats’ employ bounded integration as they generate tactile evidence to identify texture. On each trial, rats accumulate vibrissal signals across touches; they make a decision when the integrated quantity reaches a boundary
Texture Identification by Bounded Integration of Sensory Cortical Signals
No full textRecent work demonstrated that when a rat palpates a surface to identify its texture, signals generated by whisker kinematics are integrated by the brain, one touch at a time, until the accumulated evidence supports a well-grounded choice. The framework of decision making through bounded integration, previously attributed to primates, thus extends to rodents. In the present study, we ask whether vibrissal somatosensory cortex (vS1 and vS2) functions as the integrator of incoming evidence or, alternatively, as a relay of evidence to a downstream integrator. Rats carried out 1–6 touches per trial to discriminate among candidate textures. We calculated the evidence for each texture, per touch, carried by the firing rates of sets of neurons in vS1 and vS2. The quantity of information within vS1 and vS2 did not grow progressively; instead, the decision was accounted for by modeling a downstream integrator that accumulated packets of vS1 and vS2 texture information until the total quantity of evidence for one texture reached a boundary. In this behavioral task, vibrissal somatosensory cortex appears to act as a sensory relay. Bounded integration is likely to take place in regions targeted by somatosensory cortex. When a rat palpates a surface to identify texture, vibrissal kinematic evidence is integrated by the brain one touch at a time. In this study, Zuo and Diamond find that vibrissal somatosensory cortex (vS1 and vS2) acts as a touch-by-touch distributor of evidence to a downstream integrator, where accumulation to a boundary triggers the decision
Perceptual Uncertainty
Full text linkThe number of the distinct tactile percepts exceeds the number of receptor types in the skin, signifying that perception cannot be explained by a one-to-one mapping from a single receptor channel to a corresponding percept. The abundance of touch experiences results from multiplexing (the coexistence of multiple codes within a single channel, increasing the available information content of that channel) and from the mixture of receptor channels by divergence and convergence. When a neuronal representation emerges through the combination of receptor channels, perceptual uncertainty can occur—a perceptual judgment is affected by a stimulus feature that would be, ideally, excluded from the task. Though uncertainty seems at first glance to reflect nonoptimality in sensory processing, it is actually a consequence of efficient coding mechanisms that exploit prior knowledge about objects that are touched. Studies that analyze how perceptual judgments are “fooled” by variations in sensory input can reveal the neuronal mechanisms underlying the tactile experience
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
C. T. McLaughlin Diamond-M Ranch horse show
No full textC. T. McLaughlin Diamond-M Ranch horse show, horse and rider unidentified, 06/1939https://mavmatrix.uta.edu/specialcollections_startelegram1930s/6935/thumbnail.jp
C. T. McLaughlin Diamond-M Ranch horse show
No full textC. T. McLaughlin Diamond-M Ranch horse show, lunch time, people not identified, 06/1939https://mavmatrix.uta.edu/specialcollections_startelegram1930s/6937/thumbnail.jp
C. T. McLaughlin Diamond-M Ranch horse show
No full textC. T. McLaughlin Diamond-M Ranch horse show, horses and riders unidentified, 06/1939https://mavmatrix.uta.edu/specialcollections_startelegram1930s/6934/thumbnail.jp
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