Sasaki, Y. | Search bioRxiv

bioRxiv2018

Causal evidence for LTP-based interference in visual learning

Training related skills in close succession results in interference but the reasons for this interference are not understood. Here we test the hypothesis that interference occurs due to competition of long-term potentiation (LTP): the LTP induced by one task impedes the LTP induced by the other. Human subjects performed two consecutive training sessions on different Gabor orientations. Immediately after the offset of the first training, we applied continuous theta burst stimulation (cTBS) to interfere with the LTP processes produced by the first training. We found that cTBS to a control site (vertex) resulted in substantial anterograde interference for the second training. Critically, cTBS to the visual cortex not only disrupted learning on the immediately preceding training, but also released the second training from the anterograde interference. These results provide strong support for the LTP-based theory of interference and suggest the possibility of directly manipulating the competition between different learning periods.

neuroscience↗

bioRxiv2018

Trained-feature specific offline learning in an orientation detection task

It has been suggested that sleep provides additional enhancement of visual perceptual learning (VPL) acquired before sleep, termed offline performance gains. A majority of the studies that found offline performance gains of VPL used discrimination tasks including the texture discrimination task (TDT). This makes it questionable whether offline performance gains on VPL are generalized to other visual tasks. The present study examined whether a Gabor orientation detection task, which is a standard task in VPL, shows offline performance gains. In Experiment 1, we investigated whether sleep leads to offline performance gains on the task. Subjects were trained with the Gabor orientation detection task, and re-tested it after a 12-hr interval that included either nightly sleep or only wakefulness. We found that performance on the task improved to a significantly greater degree after the interval that included sleep and wakefulness than the interval including wakefulness alone. In addition, offline performance gains were specific to the trained orientation. In Experiment 2, we tested whether offline performance gains occur by a nap. Also, we tested whether spontaneous sigma activity in early visual areas during non-rapid eye movement (NREM) sleep, previously implicated in offline performance gains of TDT, was associated with offline performance gains of the task. A different group of subjects had a nap with polysomnography. The subjects were trained with the task before the nap and re-tested after the nap. The performance of the task improved significantly after the nap only on the trained orientation. Sigma activity in the trained region of early visual areas during NREM sleep was significantly larger than in the untrained region, in correlation with offline performance gains. These aspects were also found with VPL of TDT. The results of the present study demonstrate that offline performance gains are not specific to a discrimination task such as TDT, and can be generalized to other forms of VPL tasks, along with trained-feature specificity. Moreover, the present results also suggest that sigma activity in the trained region of early visual areas plays an important role in offline performance gains of VPL of detection as well as discrimination tasks.

neuroscience↗

bioRxiv2017

Feature-specific awake reactivation in human V1 after visual training

Converging human studies have demonstrated that brain activity patterns observed during task performance reemerge in the following restful awake state. Such \"awake reactivation\" has been demonstrated across higher-order cortex for complex images or associations. However, it remains unclear what specific training components are reactivated in these studies. Here we sought to provide evidence for the reactivation of a particular visual feature - Gabor orientation. Following extensive training on a visual task, we found robust reactivation in human V1 that lasted at least eight minutes. This effect was not present in higher retinotopic areas such as V2, V3, V3A, or V4v, demonstrating that the effects in V1 are not due to top-down processes such as conscious rehearsal. Furthermore, the amount of awake reactivation predicted the amount of performance improvement on the visual task. These results demonstrate that functionally-relevant awake reactivation of specific visual features occurs in early sensory cortex.

neuroscience↗