Seeing what is not there shows the costs of perceptual learning

Abstract

Perceptual learning is an improvement in one's sensory abilities after training and is thought to help us to better adapt to the sensory environment. Here, we show that perceptual learning also can lead to misperceptions, such that subjects actually perceive stimuli when none are physically presented. After learning, subjects not only showed enhanced performance when tested with the motion direction of the trained stimulus but also often reported seeing dots moving in the trained direction when no stimulus was displayed. We further show that these misperceptions are not attributable to a response bias. These results show that there are costs as well as benefits to perceptual learning and that performance enhancements for a specific feature also can be accompanied by misperceptions of the visual environment.motion ͉ plasticity vision ͉ learning ͉ psychophysics A central issue in neuroscience is how the adult brain selectively adapts to important environmental changes. Although the brain needs to adapt to new environments, its architecture must protect itself from modification from the continual bombardment of undesirable information. How the brain solves this so-called stability-plasticity dilemma (1, 2) in its sensory areas is largely unresolved.Plasticity in the early sensory systems has traditionally been thought to occur only during early development and then to be hard-wired in adults (3). This view has been substantiated by studies of critical period development in which gross plasticity of early sensory areas only occurs for a brief period after birth (4, 5). These data were used to support the hypothesis that as opposed to higher-level perceptual stages, the low-level sensory stages need to consistently process primitive sensory features, such as in vision orientation, spatial frequency, and local motion. The stabilization of sensory systems after birth is important because plasticity in sensory areas would alter the input to higher-level processing areas and fundamentally affect our perceptions as well as the comparison between new perceptions and learned templates.Recently, the view that once sensory systems are stabilized they never change has been challenged by studies of perceptual learning (6-11), which show that even in adults, perceptual abilities can be sharpened with repeated exposure or training. For example, experts such as radiologists develop with training refined abilities to distinguish subtle patterns of tumors in images that show no pattern to the untrained eye (12). Psychophysical studies of visual plasticity have demonstrated that detection or discrimination thresholds can be reduced and usually show a high degree of specificity with respect to the orientation (9, 13, 14), direction (15, 16), retinotopic location (9, 13, 17), and ocularity (13) of the trained visual stimuli. The specificity of perceptual learning has been regarded as a manifestation of plasticity in sensory cortical processes including very low-level stages of processing (18-21), although this does not exclude the invo...

Perceptual Learning via Modification of Cortical Top-Down Signals

“…Because these synaptic modifications would affect any input stream through V1, however, perceptual learning would inevitably deteriorate the information processing in other situations. Although negative transfer of learning to other tasks is known to appear (see, e.g., [12]), perceptual learning is typically task-specific and does not deteriorate perception in other tasks; see, e.g., the reviews [13,14]. While improving in brightness discrimination between a context-modulated test bar and a displaced reference bar, for instance, the edge detection capability is expected to not suffer.…”

Perceptual learning in contrast detection: presence and cost of shifts in response criteria

“…Had false alarm rates decreased-that is, had observers been unbiased, as is typically assumed (Dosher & Lu, 1999;Fine & Jacobs, 2002;Gold et al, 1999)-the increases in hit rates would have produced increases in d roughly 50%-60% greater than the increases observed in the last session. Thus, the failure to improve performance on target-absent trials has the predictable cost of diminishing perceptual sensitivity (see also Seitz et al, 2005).…”

“…To the extent that decisional factors play a role in perceptual learning (either in addition to or instead of changes in perceptual sensitivity), it is necessary to consider influences, mechanisms, and cortical circuits beyond those considered in most models of perceptual learning (e.g., Dosher & Lu, 1999;Gold, Bennett, & Sekuler, 1999;Petrov et al, 2005), which typically assume that decisional criteria are not influenced by practice. The work reported here documents the need to consider these possibilities and provides estimates of the extent to which shifts in decisional criteria actually produce levels of perceptual performance that are systematically lower than they otherwise would be (see also Seitz, Nanez, Holloway, Koyama, & Watanabe, 2005).…”

Higher brain functions served by the lowly rodent primary visual cortex

“…Third, human V1 responses are modulated by prior reward history (Serences 2008;Stanisor et al 2013) and code expected reward value (Thomas et al 2013). Fourth, predicted motion modulates the response of V1 neurons (Guo et al 2007;Alink et al 2010) and can result in perceptual illusions (Muckli et al 2005;Seitz et al 2005).…”