Browsing by Subject "Associative learning"

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Open Access
EEG correlates of audiovisual associations in motion perception
(2018-12) Benlialper, Gaye
The process of associative learning has been considered to be one of the promising research areas in neuroscience to understand human perception, sensory plasticity, and multisensory integration that affects the way of perceiving external environment. Evidence suggests that associative learning causes unexpected lowlevel sensory plasticity in brain. Yet, how this effect occurs in low-level visual motion areas remains unclear. In order to examine the effect of audiovisual associations on visual motion perception, we conducted an experiment in which subjects are exposed to pre association test, associative learning and post association test phases. Moreover, EEG was recorded simultaneously to investigate neural mechanisms behind this effect. In associative learning task, a particular sound (low-frequency or high-frequency) was accompanied with a specific direction of random dot motion (leftward or rightward), and participants were asked to attend both sound and direction. Pre- and post-association tasks in which auditory-only, visual-only, audiovisual trials were presented are identical. During these trials, participants were asked to decide the direction of moving dots with a keypress except in auditory-only trials. We hypothesized that there will be significant differences in responses between pre- and post-association phases in accord with associative pairings that were given in associative learning phase. T-test results validated our hypothesis with a significance level at 0.01 (p-value = 0.008). In terms of neural mechanisms behind this effect, we also hypothesized that this effect originates from feedback mechanisms. ERP results indicated that associative learning in uences early temporal processes (100-150 ms) to auditory only condition, and interaction effect occurs late in time after stimulus onset (around 500 ms). In this context, ERP results supports the hypothesis by revealing that modulation in early temporal areas transmits information to high level association areas that project information to low level visual areas, thus high latency is observed after stimulus onset.
Open Access
Examining the effects of audiovisual associations on motion perception through task-based fMRI
(Yerkure Tanitim ve Yayincilik Hizmetleri A.S., 2018) Kafalıgönül, Hulusi
Examining the effects of audiovisual associations on motion perception through task-based fMRI Objective: Previous studies showed that associative learning can lead to drastic changes in perceptual experience and unexpected levels of sensory plasticity in the adult brain. However, how associative learning is involved in shaping perception and the underlying neural mechanisms are quite poorly understood. In the current study, by taking advantage of well-studied visual motion-processing hierarchy, the roles of different brain areas in audiovisual association-induced changes in motion perception are investigated. Method: Using a previously developed audiovisual associative paradigm, behavioral and Blood Oxygen Level Dependent (BOLD) data were collected from adult human participants (n=13) before and after the association phase. Behavioral data were collected through reports on visual motion direction. Functional magnetic resonance imaging (fMRI) was based on block design and the functional data were analyzed according to a general linear model. Results: Audiovisual associations, acquired within a short time and without any feedback, significantly affected the perception of motion direction. This effect was much more salient when the physical direction of visual motion was ambiguous. Moreover, fMRI findings pointed out that the BOLD activities across different cortical regions changed after the associative phase. Conclusion: Taken together, these findings indicate that low-level sensory, multisensory and high-level cognitive areas play a role in the effects of audiovisual associations on motion perception. In general, this suggests that our prior experiences acquired through associations may affect perceptual processing at different hierarchical levels and over different cortical areas.
Open Access
Odour intensity learning in fruit flies
(2009) Yarali, A.; Ehser, S.; Hapil F.Z.; Huang J.; Gerber, B.
Animals' behaviour towards odours depends on both odour quality and odour intensity. While neuronal coding of odour quality is fairly well studied, how odour intensity is treated by olfactory systems is less clear. Here we study odour intensity processing at the behavioural level, using the fruit fly Drosophila melanogaster. We trained flies by pairing a MEDIUM intensity of an odour with electric shock, and then, at a following test phase, measured flies' conditioned avoidance of either this previously trained MEDIUM intensity or a LOWer or a HIGHer intensity. With respect to 3-octanol, n-amylacetate and 4-methylcyclohexanol, we found that conditioned avoidance is strongest when training and test intensities match, speaking for intensity-specific memories. With respect to a fourth odour, benzaldehyde, on the other hand, we found no such intensity specificity. These results form the basis for further studies of odour intensity processing at the behavioural, neuronal and molecular level. © 2009 The Royal Society.