Low-level sensory plasticity during task-irrelevant perceptual learning: Evidence from conventional and double training procedures

Abstract

Studies of perceptual learning have focused on aspects of learning that are related to early stages of sensory processing. However, conclusions that perceptual learning results in low-level sensory plasticity are controversial, since such learning may also be attributed to plasticity in later stages of sensory processing or in readout from sensory to decision stages, or to changes in high-level central processing. To address this controversy, we developed a novel random dot motion (RDM) stimulus to target motion cells selective to contrast polarity by ensuring the motion direction information arises only from signal dot onsets and not their offsets, and used these stimuli in the paradigm of task-irrelevant perceptual learning (TIPL). In TIPL, learning is achieved in response to a stimulus by subliminally pairing that stimulus with the targets of an unrelated training task. In this manner, we are able to probe learning for an aspect of motion processing thought to be a function of directional V1 simple cells with a learning procedure that dissociates the learned stimulus from the decision processes relevant to the training task. Our results show direction-selective learning for the designated contrast polarity that does not transfer to the opposite contrast polarity. This polarity specificity was replicated in a double training procedure in which subjects were additionally exposed to the opposite polarity. Taken together, these results suggest that TIPL for motion stimuli may occur at the stage of directional V1 simple cells. Finally, a theoretical explanation is provided to understand the data.

The contribution of area MT to visual motion perception depends on training

“…Our results are consistent with previous psychophysical studies indicating the spatial specificity of training effects Hochstein, 1996, 1997;Karni and Sagi, 1991) (Figure 7). Less psychophysical work has been devoted to the question of generalization across stimulus cues, and the results have been somewhat contradictory (Ivanchenko and Jacobs, 2007;Pilly et al, 2010;Rivest et al, 1997). Our results suggest that the neural readout of a single stimulus quantity (motion direction) depends strongly on the subject's experience with the particular cue that defines the quantity.…”

Two‐stage model in perceptual learning: toward a unified theory

“…Since the initial discovery of TI-VPL, 81 a number of studies have been conducted on TI-VPL. 82,83,88,[98][99][100][101][102][103][104][105][106][107][108][109][110] However, the mechanism of TI-VPL has yet to be well clarified. Some studies have developed models that focus on accounting for TR-VPL, but not for TI-VPL.…”

Perceptual learning: Functions, mechanisms, and applications

“…Pilly, Grossberg and Seitz (2010) addressed the question of where perceptual learning occurs in visual processing. Participants were exposed to task-irrelevant random dot motion stimuli to target motion cells selective to contrast polarity by ensuring that the motion direction information arises only from onsets but not offsets of signal dots.…”