Current Projects
Influence of divided attention on visual object recognition in humans
(w/ John Palmer, Geoffrey Boynton, and Cathleen Moore)
Performing visual tasks with more than one stimulus at a time can be challenging or even impossible (e.g.: we can recognize only one of two simultaneously presented words, see White et al. 2018).
This project has several components:
Effects of divided attention on semantic object categorization. How does dividing attention affect visual object recognition? We use a dual task paradigm to assess performance for recognizing two objects vs one, and compare behavioral findings to theoretical predictions.
Results reported in Popovkina et al., JoV 2021. Data repository: https://osf.io/p3yan/
Hemifield effects on divided attention in visual object recognition. Simple visual judgments appear to be performed in parallel - for example, separately by the left and right primary cortices. Are divided attention effects different for objects presented in separate left and right hemifields, compared to objects overlapping both hemifields?
Results reported in Popovkina et al., JoV 2023. Data repository: https://osf.io/nv9pb/.
Generalization of divided attention effects. Results from Popovkina et al. (2021) appear to be robust across presentation variations (RSVP vs masking). We vary display parameters, categorization level, and semantic content of objects to test whether these results are robust across a variety of object-based tasks. Curiously, judgments of abstract objects with interchangeable parts (like letters in a word) show behavioral deficits similar to word judgments.
Manuscript currently in preparation. Preliminary results presented: VSS, May 2022.
Searching for evidence of serial processing in the brain. Behavioral judgments of two simultaneously presented objects are consistent with the predictions of serial models. Where might we find brain activity that could underlie this limitation in behavior? We leverage insights from work on word recognition (White et al., 2019) and the abstract object set from (3) to probe brain activity in the lateral occipital complex.
Pilot data collection currently underway. Preliminary presented: Optica Fall Vision Meeting, October 2023.
Influence of divided attention on American Sign Language (ASL) recognition
(w/ Jasmine Awad, Dave Young, and Ione Fine)
Does ASL fluency and/or sensory experience modulate performance in a task requiring recognition of multiple ASL letter signs? We are using the dual task paradigm to explore this question in the context of observations about divided attention effects in tasks with word and object judgments.
Data collection currently underway. Preliminary results presented: Optica Fall Vision Meeting, 2023.
Past Projects
Influence of task context on feature-selective responses in primate visual area V4
(w/ Anitha Pasupathy)
Responses of neurons in area V4 are known to be modulated by stimulus-dependent factors (e.g. selectivity for features such as form and color), as well as task-dependent factors (e.g. change in firing rate due to attention).
Are task-dependent modulations independent of neuronal tuning? That is, does stimulus representation in the responses of V4 neurons remain stable with changing task context?
I explored this question using electrophysiological techniques; results reported in Popovkina and Pasupathy, JNeurosci 2022.
Timing of neural signals in primate visual area V4
(w/ Anitha Pasupathy and Polina Zamarashkina)
In the primate visual cortex, both the magnitude of the neuronal response and its timing can carry important information about the visual world, but studies typically focus only on response magnitude. Here, we examine the onset and offset latency of the responses of neurons in area V4 of awake, behaving macaques across several experiments in the context of a variety of stimuli and task paradigms.
We explored this question using a meta-analysis across several studies; results reported in Zamarashkina et al., J Neurophys 2020.
Representation of boundary shape and surface characteristics in primate visual area V4
(w/ Anitha Pasupathy and Wyeth Bair)
Responses of many neurons in area V4 reflect information about object contours, which could subserve boundary-based recognition.
How does the interior fill of objects influence these responses?
I explored this question using a combination of electrophysiological and computational techniques; results reported in Popovkina et al., JNeurophys 2019.