Attentional attraction of receptive fields can explain spatial and temporal effects of attention

A multitude of attentional effects were found at both the neural and behavioural levels of perception; however, the nature of the attentional mechanism is an unsettled issue. It is typically assumed that the fundamental impact of attention is enhancement of neuronal responses, but some attentional effects are difficult to explain by such gain modulations. Here we offer a different view: We suggest that the most fundamental impact of attention is the attraction (shift) of receptive fields towards the attended location. We further show, both conceptually and by model simulations, that this attraction of receptive fields can explain a diverse range of attentional effects, spatial as well as temporal, linking physiological measurements at the unit level with psychophysical observations (e.g., enhanced contrast sensitivity, enhanced spatial resolution, the Mexican-hat profile of attention, prolonged perceived duration, prior entry, degraded temporal resolution).     

Seeing changes: How familiarity alters our perception of change

The impact of object familiarity on change blindness was examined. Familiarity was operationalized by manipulating the orientation (upright vs. inverted) of letters: Upright letters formed familiar stimuli whereas inverted letters produced unfamiliar stimuli. Across four experiments, orientation was shown to affect the ability to detect change. In Experiment 1, the orientation effect was independent of the number of distractors (set size), suggesting that orientation and set size affect separate processes. In Experiment 1b, it was shown that the orientation effect did not depend on the alternation of a particular letter pair. In Experiment 2 an interaction between set size and stimulus quality suggests that set size has its effects early in processing, whereas additivity between stimulus quality and orientation suggests that orientation has an effect on later processing. Experiment 3 replicates and extends the findings from Experiments 1 and 2. A stage model of change blindness is proposed and extended by drawing on constructs from Rensink (2000b, 2002, 2005).     

The effect of spatial and nonspatial contextual information on visual object memory

Recent research has found visual object memory can be stored as part of a larger scene representation rather than independently of scene context. The present study examined how spatial and nonspatial contextual information modulate visual object memory. Two experiments tested participants’ visual memory by using a change detection task in which a target object's orientation was either the same as it appeared during initial viewing or changed. In addition, we examined the effect of spatial and nonspatial contextual manipulations on change detection performance. The results revealed that visual object representations can be maintained reliably after viewing arrays of objects. Moreover, change detection performance was significantly higher when either spatial or nonspatial contextual information remained the same in the test image. We concluded that while processing complex visual stimuli such as object arrays, visual object memory can be stored as part of a comprehensive scene representation, and both spatial and nonspatial contextual changes modulate visual memory retrieval and comparison.     

Incidental memory for parts of scenes from eye movements

Incidental memory for parts of scenes was examined in two search experiments and one memory control experiment. Eye movements were recorded during the search experiments and used to select gaze-contingent sections from search scenes for a surprise memory recognition task. Results from the recognition task showed incidental memory was better for sections viewed longer and with multiple fixations. Sections not fixated during search were still recognized above chance as well. Differences in sections did not affect memory performance in a control experiment when viewing time was held constant. These results show that memory for parts of scenes can occur incidentally during search and encoding of tested sections is better with longer viewing time and with multiple fixations.     

The bandwidth of consolidation into visual short-term memory depends on the visual feature

We investigated the nature of the bandwidth limit in the consolidation of visual information into visual short-term memory. In the first two experiments, we examined whether previous results showing differential consolidation bandwidth for colour and orientation resulted from methodological differences by testing the consolidation of colour information with methods used in prior orientation experiments. We briefly presented two colour patches with masks, either sequentially or simultaneously, followed by a location cue indicating the target. Participants identified the target colour via buttonpress (Experiment 1) or by clicking a location on a colour wheel (Experiment 2). Although these methods have previously demonstrated that two orientations are consolidated in a strictly serial fashion, here we found equivalent performance in the sequential and simultaneous conditions, suggesting that two colours can be consolidated in parallel. To investigate whether this difference resulted from different consolidation mechanisms or a common mechanism with different features consuming different amounts of bandwidth, Experiment 3 presented a colour patch and an oriented grating either sequentially or simultaneously. We found a lower performance in the simultaneous than the sequential condition, with orientation showing a larger impairment than colour. These results suggest that consolidation of both features share common mechanisms. However, it seems that colour requires less information to be encoded than orientation. As a result, two colours can be consolidated in parallel without exceeding the bandwidth limit, whereas two orientations or an orientation and a colour exceed the bandwidth and appear to be consolidated serially.     

Dissociations in Visual Attention Deficits among Persons with Mild Cognitive Impairment

ABSTRACT

Impairments in visual attention and visual information processing have been identified as part of the neuropsychological features of Alzheimer's disease (AD), even in its earliest stages. There is increasing recognition that these deficits may be selective rather than global, with some attentional subtypes being more vulnerable than others. The few studies that have investigated attentional deficits in mild cognitive impairment (MCI), a putatively prodromal phase of AD, have not satisfactorily addressed the possible selectivity in attentional deficits in MCI. This study examined potential dissociations in visual attention deficits in MCI using a measure that assesses simple, divided, and selective attention. The results indicated a hierarchy of attentional impairments, with divided attention being the most affected and simple attention the least. Among participants with MCI, 53% showed evidence of impairment in divided attention compared to 19% of controls (OR = 4.81, p < .001). Poorer visual attention was also associated with poorer overall cognitive status. The implications of these findings for early identification of MCI, prevention of functional decline in MCI, and delay/reversal of cognitive degradation in MCI are discussed.     

Aging and Visual Short-term Memory: Effects of Object Type and Information Load

ABSTRACT

Previous research has observed that the size of age differences in short-term memory (STM) depends on the type of material to be remembered, but has not identified the mechanism underlying this pattern. The current study focused on visual STM and examined the contribution of information load, as estimated by the rate of visual search, to STM for two types of stimuli – meaningful and abstract objects. Results demonstrated higher information load and lower STM for abstract objects. Age differences were greater for abstract than meaningful objects in visual search, but not in STM. Nevertheless, older adults demonstrated a decreased capacity in visual STM for meaningful objects. Furthermore, in support of Salthouse's processing speed theory, controlling for search rates eliminated all differences in STM related to object type and age. The overall pattern of findings suggests that STM for visual objects is dependent upon processing rate, regardless of age or object type.     

Neural Correlates of Age-related Reduction in Visual Motion Priming

ABSTRACT

Previously we reported that priming of visual motion perception is reduced in older adults compared to younger adults (Jiang, Greenwood, & Parasuraman, 1999 Jiang, Y., Greenwood, P. and Parasuraman, R. 1999. Age-related reduction in 3-D motion priming. Psychology and Aging, 14(4): 619–626.  [Google Scholar], Psychology and Aging, 14(4), 619; Jiang, Luo, & Parasuraman, 2002b Jiang, Y., Luo, Y. J. and Parasuraman, R. 2002b. Two-dimensional visual motion priming is reduced in older adults. Neuropsychology, 16(2): 140–145.  [Google Scholar], Neuropsychology, 16(2), 140). To examine the neural mechanisms underlying this age-related effect, event-related brain potentials (ERPs) were recorded during perceptual judgments of motion directions by younger and older adults in two experiments. When judging single-step motion, both younger and older adults evoked significantly larger ERP late positive component (LPC) responses to unambiguous motion compared to LPC responses elicited by ambiguous motion. In contrast, compared to the younger adults, the older adults evoked comparable but delayed ERP responses to single motion steps. In the second experiment the younger and older groups judged the directions of two successive motion-steps (either motion priming or motion reversals). Under short (200–400 ms) stimulus onset asynchrony (SOA), the difference between the ERP responses to priming and reversal conditions was significantly larger for the younger than for the older adults. This study provides the first electrophysiological evidence that brain aging leads to delayed processing of single motion direction and visual motion priming as early as 100 ms in the early visual cortex. Age-related changes in strength and temporal characteristics of neural responses in temporal-parietal regions were particularly pronounced in older adults when successive motion signals are placed closely in time, within 400 ms.     

The Relationship between Contrast Sensitivity,Gait, and Reading Speed in Parkinson's Disease

ABSTRACT

Parkinson's disease (PD) results in reduced walking speed and visual difficulties, including difficulty reading (Davidsdottir, Cronin-Golomb, & Lee, 2005 Davidsdottir, S., Cronin-Golomb, A. and Lee, A. 2005. Visual and spatial symptoms in Parkinson's disease. Vision Research, 45: 1285–1296. [Crossref] , [Google Scholar]). PD is characterized by a reduction in dopamine, which is instrumental in determining a person's contrast sensitivity (CS). This study assessed the relationship between CS, gait (step length and walking speed), and reading speed in 18 non-demented PD volunteers with normal acuity. We found that CS correlated with walking speed (r = .57, p = .01), step length (r = .53, p = .02), and reading speed (r = .54, p = .02). Visual acuity (which has not been tied to dopamine in the same way) correlated with reading speed (r_s = –.65, p = .004), but not with gait measures. We also assessed the contribution of age, education, and cognitive status (Shipley Institute of Living Scale) to these variables. We conclude that CS and age both play an important role in determining gait in PD, while reading speed is related to both acuity and CS, but not age.     

How Much Older Do You Get When a Wrinkle Appears on Your Face? Modifying Age Estimates by Number of Wrinkles

ABSTRACT

The present study investigated the influence of wrinkles on facial age judgments. In Experiment 1, preadolescents, young adults, and middle-aged adults made categorical age judgments for male and female faces. The qualitative (type of wrinkle) and quantitative (density of wrinkles and depth of furrows) contributions of wrinkles were analyzed. Results indicated that the greater the number of wrinkles and the depth of furrows, the older a face was rated. The roles of the gender of the face and the age of the participants were discussed. In Experiment 2, participants performed relative age judgments by comparing pairs of faces. Results revealed that the number of wrinkles had more influence on the perceived facial age than the type of wrinkle. A MDS analysis showed the main dimensions on which participants based their judgments, namely, the number of wrinkles and the depth of furrows. We conclude that the quantitative component is more likely to increase perceived facial age. Nevertheless, other variables, such as the gender of the face and the age of the participants, also seem to be involved in the age estimation process.