Browsing by Subject "Bisection discrimination task"

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Open Access
Functional changes in the human cortex over the course of visual perceptual learning
(2020-03) Akkoyunlu, Beyza
In this study we assessed functional changes through visual perceptual learning with bisection discrimination task. Before learning, after third session of learning and after learning ended, behavioral threshold and fMRI data has been collected. Our results showed that while participants showed threshold decrease in the midlearning session, the post-learning thresholds are turned to pre-learning levels. These results might be due to fatigue which caused by our experiment. Besides to training condition, we also tested location and task speciﬁcity. The results showed that only 150◦polar angle location showed signiﬁcant change between sessions. Along with the behavioral data, we collected task-based fMRI data while participants performing training and control conditions in the scanner. The analysis showed task-based BOLD response changed with session. However, post-hoc tests did not reveal signiﬁcant results. The resting-state functional connectivity analysis showed that the functional connectivity between V1 and V2 regions is signiﬁcantly increased. The Post Hoc analysis showed signiﬁcant change in the 210◦and 150◦polar angle conditions. The changes in the behavioral and functional connectivity measurements at 150◦polar angle conditions, these results might indicate the eﬀect of the inter-hemispheric connections. Moreover, our analysis on resting state data also revealed that, while there is no change between pre-learning and mid-learning sessions, connectivity changes signiﬁcantly in the post-learning session compared to other sessions. This ﬁnding supports the idea that functional connectivity changes related to perceptual learning might be occurring at the late phases of the learning. Overall, to rule out the confounds in the behavioral measurements and to link the behavioral data with the neural data, additional measurements should be taken in the future.
Open Access
Investigating the effects of perceptual learning on the function and microstructure of the visual cortex
(2020-12) Erişen, Dilara
Perceptual learning is the long-term improvement of the ability to process sensory stimuli through experience. Although an extensively studied field, the mechanism and locus of plasticity underlying visual perceptual learning is subject of debate. Here, we investigated the experience-dependent plasticity in the visual cortex across the time course of perceptual learning of bisection discrimination task. Population receptive field (pRF) analysis was used to examine functional architecture of the visual cortex. Microstructural properties of the visual cortex were characterized with neurite orientation dispersion and density imaging (NODDI). We compared pre-, mid-, and post-training values of pRF size, neurite density, and orientation dispersion in the trained location as well as in two control locations where no training has been received. The values in the trained location did not change with time and did not differ from control locations. In addition, we assessed the microstructural properties in the white matter tract between the training location and the mirror-symmetric control location and did not observe any change with training. In conclusion, we found no training-related changes in the early visual cortex (V1-V3). Our results are limited by the lack of performance improvement with training and the small sample size. Moreover, we were not able to identify visual areas beyond V1-V3 leaving high-level visual areas unexplored. Suggestions for further research include redesigning the behavioral training paradigm, optimization of pRF protocol to identify high-level visual areas, and repeating the study with a larger sample size.