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Motion Perception (motion + perception)
Selected AbstractsMeasuring kinaesthetic sensitivity in typically developing childrenDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 9 2009KRISTEN PICKETT MS This study presents a method to quantify a child's sensitivity to passive limb motion, which is an important aspect of kinaesthesia not easily examined clinically. Psychophysical detection thresholds to passive forearm motion were determined in a group of 20 typically developing pre-adolescent children (mean age 12y 6mo, SD 10mo, range 11,13y) and a group of 10 healthy adults (mean age 29y 10mo, SD 10y 7mo, range 18,50y). A newly designed passive motion apparatus was used to measure the time to detection of forearm motion and the errors in determining movement direction. Results showed that limb motion sensitivity became increasingly variable below 0.3°/s in children and adults. In comparison with adults, movement detection times in the pediatric group were increased by between 4% and 108% for the range of tested velocities (0.075,1.35°/s). At 0.075°/s, 5% of the children, but 50% of the adults, made no directional error, indicating that motion perception became unreliable at such low velocity in both groups. The findings demonstrate that sensitivity to passive forearm motion in children should be tested at a range between 0.075 and 0.3°/s. They further suggest that passive motion sensitivity may not be fully developed in pre-adolescent children. [source] Directional responses of visual wulst neurones to grating and plaid patterns in the awake owlEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2007Jerome Baron Abstract The avian retinothalamofugal pathway reaches the telencephalon in an area known as visual wulst. A close functional analogy between this area and the early visual cortex of mammals has been established in owls. The goal of the present study was to assess quantitatively the directional selectivity and motion integration capability of visual wulst neurones, aspects that have not been previously investigated. We recorded extracellularly from a total of 101 cells in awake burrowing owls. From this sample, 88% of the units exhibited modulated directional responses to sinusoidal gratings, with a mean direction index of 0.74 ± 0.03 and tuning bandwidth of 28 ± 1.16°. A direction index higher than 0.5 was observed in 66% of the cells, thereby qualifying them as direction selective. Motion integration was tested with moving plaids, made by adding two sinusoidal gratings of different orientations. We found that 80% of direction-selective cells responded optimally to the motion direction of the component gratings, whereas none responded to the global motion of plaids, whose direction was intermediate to that of the gratings. The remaining 20% were unclassifiable. The strength of component motion selectivity rapidly increased over a 200 ms period following stimulus onset, maintaining a relatively sustained profile thereafter. Overall, our data suggest that, as in the mammalian primary visual cortex, the visual wulst neurones of owls signal the local orientated features of a moving object. How and where these potentially ambiguous signals are integrated in the owl brain might be important for understanding the mechanisms underlying global motion perception. [source] A double dissociation between striate and extrastriate visual cortex for pattern motion perception revealed using rTMSHUMAN BRAIN MAPPING, Issue 10 2009Benjamin Thompson Abstract The neural mechanisms underlying the integration and segregation of motion signals are often studied using plaid stimuli. These stimuli consist of two spatially coincident dynamic gratings of differing orientations, which are either perceived to move in two unique directions or are integrated by the visual system to elicit the percept of a checkerboard moving in a single direction. Computations pertaining to the motion of the individual component gratings are thought to take place in striate cortex (V1) whereas motion integration is thought to involve neurons in dorsal stream extrastriate visual areas, particularly V5/MT. By combining a psychophysical task that employed plaid stimuli with 1 Hz offline repetitive transcranial magnetic stimulation (rTMS), we demonstrated a double dissociation between striate and extrastriate visual cortex in terms of their contributions to motion integration. rTMS over striate cortex increased coherent motion percepts whereas rTMS over extrastriate cortex had the opposite effect. These effects were robust directly after the stimulation administration and gradually returned to baseline within 15 minutes. This double dissociation is consistent with previous patient data and the recent hypothesis that both coherent and transparent motion percepts are supported by the visual system simultaneously and compete for perceptual dominance. Hum Brain Mapp 2009. © 2009 Wiley-Liss, Inc. [source] Imaging brain activity during natural vision using CASL perfusion fMRIHUMAN BRAIN MAPPING, Issue 7 2007Hengyi Rao Abstract Functional MRI (fMRI) has begun to be used to explore human brain activity during ecological and natural conditions. Arterial spin labeling (ASL) perfusion fMRI provides an appealing approach for imaging sustained brain activity during natural conditions because of its long-term temporal stability and ability to noninvasively quantify absolute cerebral blood flow (CBF). The present study used ASL perfusion fMRI to measure brain activation patterns associated with natural vision by concurrently recording CBF and blood oxygen level-dependent (BOLD) contrasts while subjects were freely viewing a cartoon movie. Reliable quantitative whole-brain CBF values (,60 mL/100g/min) as well as regional CBF values (45,80 mL/100g/min) were measured during movie viewing and resting states. The perfusion contrast revealed CBF increases in multiple visual pathway areas and frontal areas, and CBF decreases in ventromedial frontal cortex and superior temporal cortex during movie viewing compared to resting states. Concurrent BOLD contrast revealed similar but weaker activation and deactivation patterns. Regression analyses of both CBF data and BOLD data showed significant associations between activation in the middle temporal (MT) region and subjects' perception of motion. Region of interest analysis based on a priori literature-defined MT demonstrated significant monotonic stepwise associations between the intensity of motion perception and the CBF and BOLD signal changes. These results demonstrate the feasibility of using ASL perfusion fMRI for imaging both sustained and dynamic effects in neural activation during natural and ecologically valid situations, and support the notion of maintained functional segregation and specialization during natural vision. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source] Rollvection versus linearvection: Comparison of brain activations in PETHUMAN BRAIN MAPPING, Issue 3 2004Angela Deutschländer Abstract We conducted a PET study to directly compare the differential effects of visual motion stimulation that induced either rollvection about the line of sight or forward linearvection along this axis in the same subjects. The main question was, whether the areas that respond to vection are identical or separate and distinct for rollvection and linearvection. Eleven healthy volunteers were exposed to large-field (100° × 60°) visual motion stimulation consisting of (1) dots accelerating from a focus of expansion to the edge of the screen (forward linearvection) and (2) dots rotating counterclockwise in the frontal plane (clockwise rollvection). These two stimuli, which induced apparent self-motion in all subjects, were compared to each other and to a stationary visual pattern. Linearvection and rollvection led to bilateral activations of visual areas including medial parieto-occipital (PO), occipito-temporal (MT/V5), and ventral occipital (fusiform gyri) cortical areas, as well as superior parietal sites. Activations in the polar visual cortex around the calcarine sulcus (BA 17, BA 18) were larger and more significant during linearvection. Temporo-parietal sites displayed higher activity levels during rollvection. Differential activation of PO or MT/V5 was not found. Both stimuli led to simultaneous deactivations of retroinsular regions (more pronounced during linearvection); this is compatible with an inhibitory interaction between the visual and the vestibular systems for motion perception. Hum. Brain Mapp. 21:143,153, 2004. © 2004 Wiley-Liss, Inc. [source] Biological Motion Displays Elicit Social Behavior in 12-Month-OldsCHILD DEVELOPMENT, Issue 4 2009Jennifer M. D. Yoon To test the hypothesis that biological motion perception is developmentally integrated with important social cognitive abilities, 12-month-olds (N = 36) were shown a display of a human point-light figure turning to observe a target. Infants spontaneously and reliably followed the figure's "gaze" despite the absence of familiar and socially informative features such as a face or eyes. This suggests that biological motion displays are sufficient to convey rich psychological information such as attentional orientation and is the first evidence to show that biological motion perception and social cognitive abilities are functionally integrated early in the course of typical development. The question of whether common neural substrates for biological motion perception and analysis of gaze direction underlies the functional integration seen behaviorally is discussed. [source] The predicting brain: Unconscious repetition, conscious reflection and therapeutic changeTHE INTERNATIONAL JOURNAL OF PSYCHOANALYSIS, Issue 4 2007Regina Pally Neuroscience indicates that ,repetition' is fundamental to brain function. The brain non-consciously predicts what is most likely to happen and sets in motion perceptions, emotions, behaviors and interpersonal responses best adapted to what is expected-before events occur. Predictions enable individuals to be ready ,ahead of time' so reactions occur rapidly and smoothly when events occur. The brain uses past learning as the guide for what to expect in the future. Because of prediction, present experience and responses are shaped by the past. Predictions from early life can be deeply encoded and enduring. Predictions based on the past allow for more efficient brain function in the present, but can lead to mistakes. When what is predicted does not occur, consciousness can be engaged to monitor and correct the situation. But if a perception or emotion seems reasonable for the situation, a person might not notice an error, and a maladaptive ,repetition' may remain unchanged. The author discusses how predictions contribute to psychological defenses and transference repetition, and how conscious self-reflection facilitates therapeutic change. The neuroscience of prediction indicates why, in certain cases, active engagement by the analyst may be necessary. The author makes the argument for use of a ,neuroscience interpretation'. [source] | |||||||||||||