Researcher:
Akbıyık, Seda

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Master Student

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Seda

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Akbıyık

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Akbıyık, Seda
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2018 - 201922020 - 20222

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Researcher Of Publications: search.filters.isAuthorOfPublication.48dcb761-1600-4cad-8757-78be58d7bf26

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    Elucidating the common basis for task-dependent differential manifestations of category advantage: a decision theoretic approach
    (Wiley, 2022) N/A; Department of Psychology; Department of Psychology; Akbıyık, Seda; Göksun, Tilbe; Balcı, Fuat; Master Student; Faculty Member; Faculty Member; Department of Psychology; N/A; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; N/A; 47278; 51269
    Cross-category hues are differentiated easier than otherwise equidistant hues that belong to the same linguistic category. This effect is typically manifested through both accuracy and response time gains in tasks with a memory component, whereas only response times are affected when there is no memory component. This raises the question of whether there is a common generative process underlying the differential behavioral manifestations of category advantage in color perception. For instance, within the framework of noisy evidence accumulation models, changes in accuracy can be readily attributed to an increase in the efficacy of perceptual evidence integration (after controlling for threshold setting), whereas changes in response time can also be attributed to shorter nondecisional delays (e.g., due to facilitated signal detection). To address the latent decision processes underlying category advantage across different behavioral demands, we introduce a decision-theoretic perspective (i.e., diffusion decision model) to categorical color perception in three complementary experiments. In Experiment 1, we collected data from a binary color naming task (1) to determine the green-blue boundary in our sample and (2) to trace how parameter estimates of interest in the model output change as a function of color typicality. In Experiments 2 and 3, we used same-different task paradigms (with and without a memory component, respectively) and traced the category advantage in color discrimination in two parameters of the diffusion decision model: nondecision time and drift rate. An increase in drift rate predominantly characterized the category advantage in both tasks. Our results show that improved efficiency in perceptual evidence integration is a common driving force behind different manifestations of category advantage.
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    Cathodal tDCS stimulation of left anterior temporal lobe eliminates cross-category color discrimination response time advantage
    (Elsevier, 2020) N/A; Department of Psychology; Department of Psychology; Akbıyık, Seda; Göksun, Tilbe; Balcı, Fuat; Master Student; Faculty Member; Faculty Member; Department of Psychology; N/A; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); Graduate School of Social Sciences and Humanities; College of Social Sciences and Humanities; College of Social Sciences and Humanities; N/A; 47278; 51269
    The linguistic category-advantage in color perception refers to better discrimination performance for stimuli that belong to different categories (e.g., green vs. blue) than equidistant stimuli from the same category (e.g., blue). Despite the robust nature of category-advantage in color perception, the related cognitive and neural mechanisms are not fully understood. Some views attribute this effect to early alteration of visual processing of color while others attribute it to post-perceptual conceptual processing. The current study investigated the causal role of the left anterior temporal lobe (ATL), as a post-perceptual semantic hub, in categorical color perception. We modulated the activity of the left ATL via cathodal tDCS or sham stimulation (within-subject) while participants were discriminating between successive presentations of color patches. Without stimulation, we found a category-advantage effect in both accuracy and response times. The inhibition of left ATL eliminated the category-advantage effect in terms of RTs but not accuracies. Our results point at the causal role of ATL in categorical color perception and provide indirect support for a post-perceptual processing account of this robust phenomenon.
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    PublicationOpen Access
    The relationship between co-speech gesture production and macrolinguistic discourse abilities in people with focal brain injury
    (Elsevier, 2018) Chatterjee, Anjan; Department of Psychology; Akbıyık, Seda; Karaduman, Ayşenur; Göksun, Tilbe; Master Student; Faculty Member; Department of Psychology; College of Social Sciences and Humanities; N/A; N/A; 47278
    Brain damage is associated with linguistic deficits and might alter co-speech gesture production. Gesture production after focal brain injury has been mainly investigated with respect to intrasentential rather than discourse-level linguistic processing. In this study, we examined 1) spontaneous gesture production patterns of people with left hemisphere damage (LHD) or right hemisphere damage (RHD) in a narrative setting, 2) the neural structures associated with deviations in spontaneous gesture production in these groups, and 3) the relationship between spontaneous gesture production and discourse level linguistic processes (narrative complexity and evaluation competence). Individuals with LHD or RHD (17 people in each group) and neurotypical controls (n = 13) narrated a story from a picture book. Results showed that increase in gesture production for LHD individuals was associated with less complex narratives and lesions of individuals who produced more gestures than neurotypical individuals overlapped in frontal-temporal structures and basal ganglia. Co-speech gesture production of RHD individuals positively correlated with their evaluation competence in narrative. Lesions of RHD individuals who produced more gestures overlapped in the superior temporal gyrus and the inferior parietal lobule. Overall, LHD individuals produced more gestures than neurotypical individuals. The groups did not differ in their use of different gesture forms except that LHD individuals produced more deictic gestures per utterance than RHD individuals and controls. Our findings are consistent with the hypothesis that co-speech gesture production interacts with macro-linguistic levels of discourse and this interaction is affected by the hemispheric lateralization of discourse abilities.
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    PublicationOpen Access
    Differential bilateral primary motor cortex tDCS fails to modulate choice bias and readiness in perceptual decision making
    (Frontiers, 2018) Çakmak, Yusuf O.; Department of Psychology; Türkakın, Esin; Akbıyık, Seda; Akyol, Bihter; Gürdere, Ceren; Balcı, Fuat; Teaching Faculty; PhD Student; Faculty Member; Department of Psychology; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); College of Social Sciences and Humanities; Graduate School of Social Sciences and Humanities; N/A; N/A; N/A; N/A; 51269
    One of the critical factors that guide choice behavior is the prior bias of the decisionmaker with respect to different options, namely, the relative readiness by which the decision-maker opts for a specific choice. Although previous neuroimaging work has shown decision bias related activity in the orbitofrontal cortex, intraparietal sulcus (IPS) and dorsolateral prefrontal cortex, in a recent work by Javadi et al. (2015), primary motor cortex was also implicated. By applying transcranial direct current stimulation (tDCS), they have revealed a causal role of the primary motor cortex excitability in the induction of response time (RT) differences and decision bias in the form of choice probability. The current study aimed to replicate these recent findings with an experimental design that contained a sham group to increase experimental control and an additional testing phase to investigate the possible after-effects of tDCS. The conventional decision outputs such as choice proportion and RT were analyzed along with the theorydriven estimates of choice bias and non-decision related components of RTs (e. g., motor implementation speed of choices made). None of the statistical comparisons favored the alternative hypotheses over the null hypotheses. Consequently, previous findings regarding the effect of primary motor cortex excitability on choice bias and response times could not be replicated with a more controlled experimental design that is recommended for tDCS studies (Horvath et al., 2015). This empirical discrepancy between the two studies adds to the evidence demonstrating inconsistent effects of tDCS in establishing causal relationships between cortical excitability and motor behavior.