DSpace collection: 期刊論文

Trial type probability modulates the cost of antisaccades

title: Trial type probability modulates the cost of antisaccades abstract: Chiau HY, Tseng P, Su JH, Tzeng OJ, Hung DL, Muggleton NG, Juan CH. Trial type probability modulates the cost of antisaccades. J Neurophysiol 106: 515-526, 2011. First published May 4, 2011; doi:10.1152/jn.00399.2010.-The antisaccade task, where eye movements are made away from a target, has been used to investigate the flexibility of cognitive control of behavior. Antisaccades usually have longer saccade latencies than prosaccades, the so-called antisaccade cost. Recent studies have shown that this antisaccade cost can be modulated by event probability. This may mean that the antisaccade cost can be reduced, or even reversed, if the probability of surrounding events favors the execution of antisaccades. The probabilities of prosaccades and antisaccades were systematically manipulated by changing the proportion of a certain type of trial in an interleaved pro/antisaccades task. We aimed to disentangle the intertwined relationship between trial type probabilities and the antisaccade cost with the ultimate goal of elucidating how probabilities of trial types modulate human flexible behaviors, as well as the characteristics of such modulation effects. To this end, we examined whether implicit trial type probability can influence saccade latencies and also manipulated the difficulty of cue discriminability to see how effects of trial type probability would change when the demand on visual perceptual analysis was high or low. A mixed-effects model was applied to the analysis to dissect the factors contributing to the modulation effects of trial type probabilities. Our results suggest that the trial type probability is one robust determinant of antisaccade cost. These findings highlight the importance of implicit probability in the flexibility of cognitive control of behavior.

The Location Probability Effects of Saccade Reaction Times Are Modulated in the Frontal Eye Fields but Not in the Supplementary Eye Field

title: The Location Probability Effects of Saccade Reaction Times Are Modulated in the Frontal Eye Fields but Not in the Supplementary Eye Field abstract: The visual system constantly utilizes regularities that are embedded in the environment and by doing so reduces the computational burden of processing visual information. Recent findings have demonstrated that probabilistic information can override attentional effects, such as the cost of making an eye movement away from a visual target (antisaccade cost). The neural substrates of such probability effects have been associated with activity in the superior colliculus (SC). Given the immense reciprocal connections to SC, it is plausible that this modulation originates from higher oculomotor regions, such as the frontal eye field (FEF) and the supplementary eye field (SEF). To test this possibility, the present study employed theta burst transcranial magnetic stimulation (TMS) to selectively interfere with FEF and SEF activity. We found that TMS disrupted the effect of location probability when TMS was applied over FEF. This was not observed in the SEF TMS condition. Together, these 2 experiments suggest that the FEF plays a critical role not only in initiating saccades but also in modulating the effects of location probability on saccade production.

The Benefit of Object Interactions Arises in the Lateral Occipital Cortex Independent of Attentional Modulation from the Intraparietal Sulcus: A Transcranial Magnetic Stimulation Study

title: The Benefit of Object Interactions Arises in the Lateral Occipital Cortex Independent of Attentional Modulation from the Intraparietal Sulcus: A Transcranial Magnetic Stimulation Study abstract: Our visual experience is generally not of isolated objects, but of scenes, where multiple objects are interacting. Such interactions (e.g., a watering can positioned to pour water toward a plant) have been shown to facilitate object identification compared with when the objects are depicted as not interacting (e.g., a watering can positioned away from the plant) (Green and Hummel, 2004, 2006). What is the neural basis for this advantage? Recent fMRI studies have identified the lateral occipital cortex (LO) as a potential neural origin of this behavioral benefit, as LO showed greater responses to object pairs depicted as interacting compared with when they are not (Kim and Biederman, 2010; Roberts and Humphreys, 2010). However, it is possible that LO was modulated by an attention-sensitive region, the intraparietal sulcus (IPS), which sometimes showed a similar pattern of responses as that of LO in the Kim and Biederman (2010) investigation. To test this hypothesis, we delivered transcranial magnetic stimulation (TMS) to human subjects' LO and IPS while they detected a target object that was or was not interacting with another object to form a scene. TMS delivered to LO but not IPS abolished the facilitation in identifying interacting objects compared with noninteracting depictions observed in the absence of TMS, suggesting that it is LO and not IPS that is critical for the coding of object interactions.

Sublexical ambiguity effect in reading Chinese disyllabic compounds

title: Sublexical ambiguity effect in reading Chinese disyllabic compounds abstract: For Chinese compounds, neighbors can share either both orthographic forms and meanings, or orthographic forms only. In this study, central presentation and visual half-field (VF) presentation methods were used in conjunction with ERP measures to investigate how readers solve the sublexical semantic ambiguity of the first constituent character in reading a disyllabic compound. The sublexical ambiguity of the first character was manipulated while the orthographic neighborhood sizes of the first and second character (NS1, NS2) were controlled. Subjective rating of number of meanings corresponding to a character was used as an index of sublexical ambiguity. Results showed that low sublexical ambiguity words elicited a more negative N400 than high sublexical ambiguity words when words were centrally presented. Similar patterns were found when words were presented to the left VF. Interestingly, different patterns were observed for pseudowords. With left VF presentation, high sublexical ambiguity psudowords showed a more negative N400 than low sublexical ambiguity pseudowords. In contrast, with right VF presentation, low sublexical ambiguity pseudowords showed a more negative N400 than high sublexical ambiguity pseudowords. These findings indicate that a level of morphological representation between form and meaning needs to be established and refined in Chinese. In addition, hemispheric asymmetries in the use of word information in ambiguity resolution should be taken into account, even at sublexical level. (C) 2011 Elsevier Inc. All rights reserved.