Longitudinal changes in visual memory processes and representations with training

Non-human primate electrophysiology studies provide fundamental knowledge about working memory. However, monkey studies typically employ distinct methods from human studies and accordingly examine neural function at a different level of analysis. Likewise, these studies often reach divergent conclusions about the neural substrates for working memory stimulus representation and maintenance processes. Moreover, unlike humans, monkeys typically undergo many months of task training, comprising thousands of trials of repeated stimulus exposure, to participate in these studies.

In this collaboration with Arielle Tambini and Jacob Miller, we are attempting to bridge this training divide. We scanned ourselves repeatedly with fMRI, over 3+ months of task and stimulus training. During training, we learned a set of complex fractal stimuli that were embedded within a series of associative and working memory tasks. We are now examining how fMRI measures associated with task processes, as well as stimulus representations, evolve with training and behavioral indices of learning.

Causal fronto-parietal substrates of working memory capacity

See the OHBM poster and check out the project on OSF

Although WM is widely considered to be essential to many facets of cognition, the psychological and neural mechanisms that determine its capacity are vigorously debated. A vast body of research has attributed critical roles to frontal and parietal cortex, but the findings have been inconsistent as to exactly what these regions do to support WM, and whether their roles are dissociable from one another. Along with colleague Jason Scimeca, we are using fMRI to localize functional regions that are considered critical WM nodes: dorsolateral PFC, superior intraparietal sulcus (IPS), and inferior IPS. We are then perturbing these regions with focal TMS and using quantitative modeling of behavior to characterize their roles in canonical visual WM tasks. This registered report has been peer-reviewed and will produce a large publicly available dataset of MRI, TMS, and cognitive battery outcomes.

A core function of working memory (WM) is to maintain information in the face of disruptions and more immediate attention-demanding tasks. Sometimes WM is surprisingly robust to these demands, and other times it becomes badly impaired. This project manipulates perceptual and attentional dual-task demands during WM maintenance to address the perplexing inconsistencies in whether WM content is susceptible to distraction. We use network analyses of fMRI data to gauge a) how distinct dual-task demands impact WM maintenance and b) how they can be managed for successful performance.  This study is testing the hypothesis that task-based functional network reconfiguration can protect WM content from disruption. 

Competition and control during working memory processing

Modulating cortico-striatal circuits for turning internal representations into actions

An output gating mechanism may be involved in selecting actively maintained information from within working memory (WM) to guide behavior. But, we often maintain WM content that is relevant for a future goal while we are engaged in more immediate actions. As a consequence, WM representations may unintentionally influence ongoing (but unrelated) motor behavior. Imagine, for instance, accidentally typing out or saying the wrong word aloud in conversation because it was going through your mind. Through this collaboration with Rich Ivry, we are examining the impact of WM maintenance on action execution. We're using both excitatory and inhibitory transcranial magnetic stimulation (TMS) to a lateral PFC site—targeted based on connectivity with the striatum—to test the proposed role of cortico-striatal circuitry in adaptively modulating WM output gating. 

Adaptive biases in perception and memory

Serial dependence in visual perception describes when stimuli appear more similar to recent stimuli than they truly are (Kiyonaga, Scimeca, Bliss, & Whitney, 2017). By smoothing perception over the ever-changing image on the retina, this bias may stabilize our visual experience from one moment to the next. But while there is a compelling rationale for the adaptive role of serial dependence, the argument is mostly theoretical. Although this perceptual continuity is generally helpful, it fundamentally reflects a misapprehension of the current stimulus, and could therefore impair processing when the previous information is no longer relevant to current goals (i.e., proactive interference). Through this collaboration with David Whitney, we are exploring whether and how serial dependence flexibly adapts to current goals.