Learning to ignore: psychophysics and computational modeling of fast learning of direction in noisy motion stimuli

Eye-transfer tests, external noise manipulations, and observer models were used to systematically characterize learning mechanisms in judging motion direction of moving objects in visual periphery (Experiment 1) and fovea (Experiment 2) and to investigate the degree of transfer of the learning mechanisms from trained to untrained eyes. Perceptual learning in one eye was measured over 10 practice sessions. Subsequent learning in the untrained eye was assessed in five transfer sessions. We characterized the magnitude of transfer of each learning mechanism to the untrained eye by separately analyzing the magnitude of subsequent learning in low and high external noise conditions. In both experiments, we found that learning in the trained eye reduced contrast thresholds uniformly across all of the external noise levels: 47 ؎ 10% and 62 ؎ 8% in experiments 1 and 2, respectively. Two mechanisms, stimulus enhancement and template retuning, accounted for the observed performance improvements. The degree of transfer to the untrained eye depended on the amount of external noise added to the signal stimuli: In high external noise conditions, learning transferred completely to the untrained eye in both experiments. In low external noise conditions, there was only partial transfer of learning: 63% in experiment 1 and 54% in experiment 2. The results suggest that template retuning, which is effective in high external noise conditions, is mostly binocular, whereas stimulus enhancement, which is effective in low external noise displays, is largely monocular. The two independent mechanisms underlie perceptual learning of motion direction identification in monocular and binocular motion systems. interocular transfer ͉ stimulus enhancement ͉ external noise exclusion ͉ mechanisms of perceptual learning

Section: Summary and Discussionsupporting

confidence: 81%

Independent perceptual learning in monocular and binocular motion systems

Lü

Chu

Dosher

et al. 2005

“…Most quantitative models of perceptual learning are based on reweighting or some other form of selection from stable early representations (13,14,26,29,(47)(48)(49)(50). As learning continues, only the most relevant neural representations survive in decision.…”

Section: Discussionmentioning

confidence: 99%

An integrated reweighting theory of perceptual learning

Dosher

Jeter²,

Liu³

et al. 2013

134

190

Improvements in performance on visual tasks due to practice are often specific to a retinal position or stimulus feature. Many researchers suggest that specific perceptual learning alters selective retinotopic representations in early visual analysis. However, transfer is almost always practically advantageous, and it does occur. If perceptual learning alters location-specific representations, how does it transfer to new locations? An integrated reweighting theory explains transfer over retinal locations by incorporating higher level location-independent representations into a multilevel learning system. Location transfer is mediated through locationindependent representations, whereas stimulus feature transfer is determined by stimulus similarity at both location-specific and location-independent levels. Transfer to new locations/positions differs fundamentally from transfer to new stimuli. After substantial initial training on an orientation discrimination task, switches to a new location or position are compared with switches to new orientations in the same position, or switches of both. Position switches led to the highest degree of transfer, whereas orientation switches led to the highest levels of specificity. A computational model of integrated reweighting is developed and tested that incorporates the details of the stimuli and the experiment. Transfer to an identical orientation task in a new position is mediated via more broadly tuned location-invariant representations, whereas changing orientation in the same position invokes interference or independent learning of the new orientations at both levels, reflecting stimulus dissimilarity. Consistent with single-cell recording studies, perceptual learning alters the weighting of both early and midlevel representations of the visual system. reweighting models | Hebbian models A lmost all perceptual tasks exhibit perceptual learning, improving people's ability to detect, discriminate, or identify visual stimuli. These improvements due to practice are the basis of visual expertise. Practice improves the ability to perceive orientation, spatial frequency, patterns and texture, motion direction, and other stimulus features (1-4). Learned perceptual improvements generally show some specificity to the feature and to the retinal location of training. Specificity of trained improvements to retinal location and feature in behavioral studies of texture orientation (5, 6) or simple pattern orientation judgments (7,8) inspired early researchers to posit that practice altered the responses of early visual representations (V1/V2) with small receptive fields, retinotopic structure, and relatively narrow orientation and spatial frequency tuning (6).However, the generalization of learned perceptual skills over retinal locations is almost always practically advantageous, and is sometimes observed (9). Whether perceptual learning reflects changes in retinotopic representations in early visual cortical areas (6) or alternatively-as we have suggested elsewhere-is primarily acco...

“…Our results demonstrated rapid learning. Only a few minutes of a single session sufficed for human subjects to improve their performance from scoring close to chance to scoring almost perfect (1). Furthermore, when presented with a previously untrained direction discrimination (e.g., up or down), or when the same stimulus was displayed in a different location in the visual field, subjects' scores immediately returned to chance levels.…”

mentioning

confidence: 92%

“…In previous psychophysical studies of perceptual learning of a direction-of-motion discrimination task we found that the subjects' performance improves with practice over less than 300 trials in a single testing session, is retained over time, and is specific for the particular stimulus attributes (1). Given the time course of minutes over which this learning takes place, the neural substrates of the perceptual learning can be studied by using functional MRI (fMRI) as described here.…”

mentioning

confidence: 99%

“…The remarkable but still poorly understood phenomenon of rapid perceptual learning has been investigated psychophysically in several laboratories, including ours (1,3,(13)(14)(15)(16). In trying to characterize the rapid learning of direction discrimination in global-motion stimuli we investigated psychophysically the specificity of perceptual learning with respect to the stimulus attributes, visual field position, and the eye tested.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Neural systems underlying learning and representation of global motion

Vaina

Belliveau

Roziers

et al. 1998

Self Cite

106

A BSTR ACTWe demonstrate performance-related changes in cortical and cerebellar activity. The largest learning-dependent changes were observed in the anterior lateral cerebellum, where the extent and intensity of activation correlated inversely with psychophysical performance. After learning had occurred (a few minutes), the cerebellar activation almost disappeared; however, it was restored when the subjects were presented with a novel, untrained direction of motion for which psychophysical performance also reverted to chance level. Similar reductions in the extent and intensity of brain activations in relation to learning occurred in the superior colliculus, anterior cingulate, and parts of the extrastriate cortex. The motion direction-sensitive middle temporal visual complex was a notable exception, where there was an expansion of the cortical territory activated by the trained stimulus. Together, these results indicate that the learning and representation of visual motion discrimination are mediated by different, but probably interacting, neuronal subsystems.In previous psychophysical studies of perceptual learning of a direction-of-motion discrimination task we found that the subjects' performance improves with practice over less than 300 trials in a single testing session, is retained over time, and is specific for the particular stimulus attributes (1). Given the time course of minutes over which this learning takes place, the neural substrates of the perceptual learning can be studied by using functional MRI (fMRI) as described here.Until recently, the predominant view of plasticity of cortical maps and of functional properties of neurons in the early levels of cortical sensory processing was that they are specific to early development and are fixed in adulthood. Research over the past 15 years has amply demonstrated that this is not the case. It is now clearly established that cortical maps in the early stages of sensory processing in the adult animal are not fixed, but dynamic throughout life. Lesion studies in different adult mammalian species, including humans, have demonstrated significant neuronal plasticity. When a specific cortical area is deprived of its normal afferent inputs, it reorganizes so that it becomes responsive to inputs that were initially represented only by the surrounding cortex (for a review, see ref.2). Another important form of neural plasticity, known as perceptual learning, relies on changes resulting from practicing stimulus discrimination. These two forms of cortical plasticity are complementary. In the former, there is a peripheral or central reduction of the input, whereas in the latter there is an enrichment of the input (3).Currently, considerable research is aimed toward understanding the relationship between neuronal activity and performance on a task, particularly within the framework of perceptual learning. One proposal is that learning largely implies an increased representation of the trained stimulus, and thus the effects of learning may be manifested as recruitme...