The Cognitive and Brain Sciences Program is heavily research oriented. Students work closely with a faculty mentor to gain research skills and experience through laboratory work focused on currently relevant topics, and are encouraged to publish their work. The following is a sample of recent papers authored by graduate students in our program, published in high impact journals:
- Variations in normal color vision: Factors underlying individual differences in hue scaling and their implications for models of color appearance
- Action Properties of Object Images Facilitate Visual Search
- Attentional capture for tool images is driven by the head end of the tool, not the handle
- Decoding information about dynamically occluded objects in visual cortex
- Spatial modulation of motor-sensory recalibration in early deaf individuals
- An fMRI study of visual hemifield integration and cerebral lateralization
- The strategy and motivational influences on the beneficial effect of neurostimulation: A tDCS and fNIRS study
- Intraparietal regions play a material general role in working memory: Evidence supporting an internal attentional role
- Contralateral delay activity tracks the influence of Gestalt grouping principles on active visual working memory representations
Observers with normal color vision vary widely in their judgments of color appearance, such as the specific spectral stimuli they perceive as pure or unique hues. We examined the basis of these individual differences by using factor analysis to examine the variations in hue-scaling functions from both new and previously published data. Observers reported the perceived proportion of red, green, blue or yellow in chromatic stimuli sampling angles at fixed intervals within the LM and S cone-opponent plane. These proportions were converted to hue angles in a perceptual-opponent space defined by red vs. green and blue vs. yellow axes. Factors were then extracted from the correlation matrix using PCA and Varimax rotation.
There is mounting evidence that constraints from action can influence the early stages of object selection, even in the absence of any explicit preparation for action. We examined whether action properties of images can influence visual search, and whether such effects were modulated by hand preference. Observers searched for an oddball target among 3 distractors. The search arrays consisted either of images of graspable “handles” (“action-related” stimuli), or images that were otherwise identical to the handles but in which the semicircular fulcrum element was reoriented so that the stimuli no longer looked like graspable objects (“non-action-related” stimuli). Our results suggest that action properties in images, and constraints for action imposed by preferences for manual interaction with objects, can influence attentional selection in the context of visual search.
Tools afford specialized actions that are tied closely to object identity. Although there is mounting evidence that functional objects, such as tools, capture visuospatial attention relative to non-tool competitors, this leaves open the question of which part of a tool drives attentional capture. We used a modified version of the Posner cueing task to determinewhether attention is oriented towards the head versus the handle of realistic images of common elongated tools. We compared cueing effects for tools with control stimuli that consisted of images of fruit and vegetables of comparable elongation to the tools. Critically, our displays controlled for lower-level influences on attention that can arise from global shape asymmetries in the image cues. Observers were faster to detect low-contrast targets positioned near the head end versus the handle of tools.
During dynamic occlusion, an object passes behind an occluding surface and then later reappears. Even when completely occluded from view, such objects are experienced as continuing to exist or persist behind the occluder even though they are no longer visible. The contents and neural basis of this persistent representation remain poorly understood. We applied functional magnetic resonance imaging in human subjects to examine representations within visual cortex during dynamic occlusion. For gradually occluded, but not for instantly disappearing objects, there was an increase in activity in early visual cortex (V1, V2, and V3).
Audition dominates other senses in temporal processing, and in the absence of auditory cues, temporal perception can be compromised. Moreover, after auditory deprivation, visual attention is selectively enhanced for peripheral visual stimuli. We assessed whether early hearing loss affects motor-sensory recalibration, the ability to adjust the timing of an action and its sensory effect based on the recent experience. Early deaf participants and hearing controls were asked to discriminate the temporal order between a motor action (a keypress) and a visual stimulus (a white circle) before and after adaptation to a delay between the two events. Adaptation to a motor-sensory delay induced distinctive effects in the two groups, with hearing controls showing a recalibration effect for central stimuli only and deaf individuals for peripheral visual stimuli only.
The human brain integrates hemifield-split visual information via interhemispheric transfer. The degree to which neural circuits involved in this process behave differently during word recognition as compared to object recognition is not known. Evidence from neuroimaging (fMRI) suggests that interhemispheric transfer during word viewing converges in the left hemisphere, in two distinct brain areas, an “occipital word form area” (OWFA) and a more anterior occipitotemporal “visual word form area” (VWFA). We used a novel fMRI half-field repetition technique to test whether or not these areas also integrate nonverbal hemifield-split string stimuli of similar visual complexity.
Working memory (WM) capacity falls along a spectrum with some people demonstrating higher and others lower WM capacity. Efforts to improve WM include applying transcranial direct current stimulation (tDCS), in which small amounts of current modulate the activity of underlying neurons and enhance cognitive function. However, not everyone benefits equally from a given tDCS protocol. Recent findings revealed tDCS-related WMbenefits for individualswith higherworkingmemory (WM) capacity.
Determining the role of intraparietal sulcus (IPS) regions in working memory (WM) remains a topic of considerable interest and lack of clarity. Adjudication between competing theoretical perspectives is complicated by divergent findings from different methodologies. For example, fMRI studies typically use full field stimulus presentations and report bilateral IPS activation, whereas EEG studies direct attention to a single hemifield and report a contralateral bias in both hemispheres. We addressed this issue by applying a regions-of-interest fMRI approach to elucidate IPS contributions to WM. We manipulated stimulus type and the cued hemifield to assess the degree to which IPS activations reflect stimulus specific or stimulus general processing consistent with the pure storage or internal attention hypotheses.
Recent studies have demonstrated that factors influencing perception, such as Gestalt grouping cues, can influence the storage of information in visual working memory (VWM). In some cases, stationary cues, such as stimulus similarity, lead to superior VWMperformance. However, the neural correlates underlying these benefits to VWM performance remain unclear. One neural index, the contralateral delay activity (CDA), is an event-related potential that shows increased amplitude according to the number of items held in VWMand asymptotes at an individual’s VWM capacity limit.