Ming-Chou Ho

Effects of instantaneous object input and past experience on object-based attention

Evidence for object-based attention typically comes from studies using displays with unchanged objects, and no consensus has yet been reached as to whether the object effect would be altered by changing object displays or having seen this change across-trials. We examined this by using modifications of the double-rectangle cuing paradigm of Egly et al. [Egly, R., Driver, J., & Rafal, R. D. (1994). Shifting visual attention between objects and locations: Evidence from normal and parietal lesion subjects. Journal of Experimental Psychology: General, 123, 161-177], and our results, when the objects remained unchanging, replicated the original object effect. However, no object effect was found when the rectangles disappeared from view in the last (target) frame. This was true regardless of the likelihood of the rectangles disappearing, indicating the importance of instantaneous object inputs for object-based attention. The across-trial experience of seeing a different object (boomerang), however, was found to influence the object effect when the cued rectangles persisted throughout the trial. Unlike previous studies, which emphasize one or the other, we demonstrate clearly that instantaneous object inputs and past experience interact to determine the way attention selects objects.

Perceptual load modulates object-based attention.

Two experimental series are reported using both reaction time (RT) and a data-limited perceptual report to examine the effects of perceptual load on object-based attention. Perceptual load was manipulated across 3 levels by increasing the complexity of perceptual judgments. Data from the RT-based experiments showed object-based effects when the target was near the cued location. Results from the data-limited procedure showed that, with low perceptual load, attention spread along the cued object, supporting an object-based attention account. As load increased, attention was constrained to object locations near the cue, but attention still favored the cued object, inconsistent with a scanning prioritization account of object-based attention effects. Furthermore, findings showed that perceptual load modulates object selection in a manner similar to spatial attention, suggesting that there might be a common process underlying object-based and spatial attention.

Object-based attention: Sensory enhancement or scanning prioritization

The three experiments reported here test whether object-modulated attentional spreading can be obtained when the target location is 100% certain. Experiment 1 uses the reaction time (RT)-based flanker task similar to Shomstein and Yantis (2002), and replicates the null result of the object-modulated attentional spreading. RT and accuracy (ACC) have been shown to reflect different processes: postperceptual decision vs. perceptual process (Santee & Egeth, 1982). Experiment 2 adopts the data-limited ACC-based measure and reports that attention could spread within the attended object. To avoid ceiling effects, Experiment 3 adjusts the presentation time based on the trials where the target and flankers were compatible and on the same objects, and provides the convergent evidence supporting the object-modulated attentional spreading. These results suggest that because the RT-based measure is less sensitive in reflecting the quality of perceptual representations, it is not sufficiently a strong evidence to distinguish between sensory enhancement and scanning prioritization accounts.

Attentional biases for betel nut cues in heavy and light chewers.

The betel nut (Areca catecu) is regarded by the World Health Organization as the fourth most prevalent human carcinogen. Our study aims to investigate whether habitual chewers show bias in their attention toward betel nut usage. In the current study, heavy and light betel nut chewers were instructed to respond to a probe presented immediately after either one of a pair of areca-related picture and non-areca-matched picture. The presentation durations of these pictures were manipulated to investigate attentional biases under awareness threshold (17 ms), in initial orienting (200 ms), and maintenance of attention (2,000 ms). Faster response to the probe replacing the areca-related picture, in comparison with a matched picture, indicated attentional bias. The results showed that neither group showed subliminal attentional biases. Further, heavy chewers, but not light chewers, exhibited supraliminal biases toward betel nut cues in initial orienting of attention and maintained attention. Moreover, attentional bias scores at 2,000 ms were also shown to be positively associated with betel nut craving and dependence. Implications of the current findings are thoroughly discussed in the article.

Evaluation of structural connectivity changes in betel-quid chewers using generalized q-sampling MRI

RationaleBetel quid (BQ) is a common addictive substance in many Asian countries. However, few studies have focused on the influences of BQ on the brain. It remains unclear how BQ can affect structural brain abnormalities in BQ chewers.ObjectivesWe aimed to use generalized q-sampling imaging (GQI) to evaluate the impact of the neurological structure of white matter caused by BQ.MethodsThe study population comprised 16 BQ chewers, 15 tobacco and alcohol controls, and 17 healthy controls. We used GQI with voxel-based statistical analysis (VBA) to evaluate structural brain and connectivity abnormalities in the BQ chewers compared to the tobacco and alcohol controls and the healthy controls. Graph theoretical analysis (GTA) and network-based statistical (NBS) analysis were also performed to identify the structural network differences among the three groups.ResultsUsing GQI, we found increases in diffusion anisotropy in the right anterior cingulate cortex (ACC), the midbrain, the bilateral angular gyrus, the right superior temporal gyrus (rSTG), the bilateral superior occipital gyrus, the left middle occipital gyrus, the bilateral superior and inferior parietal lobule, and the bilateral postcentral and precentral gyrus in the BQ chewers when compared to the tobacco and alcohol controls and the healthy controls. In GTA and NBS analyses, we found more connections in connectivity among the BQ chewers, particularly in the bilateral anterior cingulum.ConclusionsOur results provided further evidence indicating that BQ chewing may lead to brain structure and connectivity changes in BQ chewers.

Can Betel Nut Chewing Affect the UFOV Size after Sleep Deprivation

Betel nut is a common stimulant in many Asian countries, including Taiwan. However, few behavioral studies focusing on the betel nut chewing effects were reported. The current study examined the effects of betel nut chewing on the useful field of view (UFOV) under sleep deprivation. After one night of deprived sleep, habitual chewers and non-chewers chewed either betel nut or gum before proceeding to the UFOV subtests. In the UFOV subtests, participants needed to identify the central target, divide their attention to the peripheral target, and detect the peripheral target embedded in the distractors while identifying the central target. We report that betel nut chewing could broaden the UFOV size for the habitual chewers, but not for the non-chewers. The implication for people often chewing betel nut for refreshment during long-hour working is discussed.

Spatial short-term memory is impaired in dependent betel quid chewers

RationalBetel quid is regarded as a human carcinogen by the World Health Organization. It remains unknown whether chewing betel quid has a chronic effect on healthy betel quid chewers’ memory.ObjectivesThe present study aims to investigate whether chewing betel quid can affect short-term memory (STM).MethodsThree groups of participants (24 dependent chewers, 24 non-dependent chewers, and 24 non-chewers) were invited to carry out the matrix span task, the object span task, and the digit span task. All span tasks’ results were adopted to assess spatial STM, visual STM, and verbal STM, respectively. Besides, there are three set sizes (small, medium, and large) in each span task.ResultsFor the matrix span task, results showed that the dependent chewers had worse performances than the non-dependent chewers and the non-chewers at medium and large set sizes. For the object span task and digit span task, there were no differences in between groups. In each group, recognition performances were worse with the increasing set size and showing successful manipulation of memory load.ConclusionsThe current study provided the first evidence that dependent betel quid chewing can selectively impair spatial STM rather than visual STM and verbal STM. Theoretical and practical implications of this result are discussed.

Mapping brain functional alterations in betel-quid chewers using resting-state fMRI and network analysis

RationaleThe World Health Organization regards betel quid (BQ) as a human carcinogen, and DSM-IV and ICD-10 dependence symptoms may develop with its heavy use. BQ’s possible effects of an enhanced reward system and disrupted inhibitory control may increase the likelihood of habitual substance use.ObjectivesThe current study aimed to employ resting-state fMRI to examine the hypothesized enhanced reward system (e.g., the basal forebrain system) and disrupted inhibitory control (e.g., the prefrontal system) in BQ chewers.MethodsThe current study recruited three groups of 48 male participants: 16 BQ chewers, 15 tobacco- and alcohol-user controls, and 17 healthy controls. We used functional connectivity (FC), mean fractional amplitude of low-frequency fluctuations (mfALFF), and mean regional homogeneity (mReHo) to evaluate functional alternations in BQ chewers. Graph theoretical analysis (GTA) and network-based statistical (NBS) analysis were also performed to identify the functional network differences among the three groups.ResultsOur hypothesis was partially supported: the enhanced reward system for the BQ chewers (e.g., habitual drug-seeking behavior) was supported; however, their inhibitory control was relatively preserved. In addition, we reported that the BQ chewers may have enhanced visuospatial processing and decreased local segregation.ConclusionsThe current results (showing an enhanced reward system in the chewers) provided the clinicians with important insight for the future development of an effective abstinence treatment.

Early attentional bias for negative words when competition is induced.

Previous research (Zeelenberg, Wagenmakers, & Rotteveel, 2006) revealed that emotionally meaningful words were identified significantly better than neutral words, with no difference between positive and negative words. Since in that study only a single target word was displayed at a time, we hypothesized that the equivalent performances for positive and negative words were due to a lack of competition. To test this, in our Experiment 1, we replicated Zeelenberg and colleagues’ finding, using emotion-laden Chinese words and the identical data-limited method, which measured the accuracy of a briefly shown target. We then introduced competition in Experiment 2 by simultaneously presenting two words during the target frame, and found evidence for an early attentional bias to negative words. In Experiment 3, we confirmed that the bias in Experiment 2 was not due to the inevitable repetition of stimuli. Taken together, these results support our hypothesis that, in the presence of competition, negative words receive attentional priority and consequently have enhanced perceptual representations.

Does the Object-Based Attention Effect Reflect a Benefit or a Cost?

Object-based attention would result if target appearing at an invalid location on the same object is detected more quickly than target on an equidistant location on different object (e.g., Egly, Driver, & Rafal, 1994). Three experiments examined the form of object-based attention typical object-based attention paradigms elicit (object-based benefits from the spread of attention across objects or object-based costs for switching attention between objects). Without a measurement of the time to switch attention from one location to another in the absence of objects, it is not possible to assess the relative costs or benefits of objects on attention. By adding an object-absent condition to typical object-based attention paradigms, the present experiments found that object-based attention is best described in terms of the cost to switch attention between objects.