Anthony W. Sali

The role of reward prediction in the control of attention

Previously rewarded stimuli involuntarily capture attention. The learning mechanisms underlying this value-driven attentional capture remain less understood. We tested whether theories of prediction-based associative reward learning explain the conditions under which reward feedback leads to value-based modulations of attentional priority. Across 4 experiments, we manipulated whether stimulus features served as unique predictors of reward outcomes. Participants received monetary rewards for correctly identifying a color-defined target in an initial search task (training phase) and then immediately completed a second, unrewarded visual search task in which color was irrelevant (test phase). In Experiments 1-3, monetary reward followed correct target selection during training, but critically, no target-defining features carried uniquely predictive information about reward outcomes. Under these conditions, we found no evidence of attentional capture by the previous target colors in the subsequent test phase. Conversely, when target colors in the training phase of Experiment 4 carried uniquely predictive information about reward magnitude, we observed significant attentional capture by the previously rewarded color. Our findings show that value-based attentional priority only develops for stimulus features that carry uniquely predictive information about reward, ruling out a purely motivational account and suggesting that mechanisms of reward prediction play an important role in shaping attentional priorities.

Learned states of preparatory attentional control

Individuals regularly experience fluctuations in the ability to perform cognitive operations. Although previous research has focused on predicting cognitive flexibility from persistent individual traits, as well as from spontaneous fluctuations in neural activity, the role of learning in shaping preparatory attentional control remains poorly understood. Across 3 experiments, we manipulated the statistical regularities of an attentional orienting paradigm to examine whether individuals modulated attentional flexibility, the readiness to perform a spatial shift of attention, across learned contexts. We found evidence of learning-based modulations in preparatory attentional control settings when the probability of shifting the focus of attention differed based on temporally or color-defined contexts. Furthermore, in the case of color-defined contexts, these modulations in preparatory control persisted even after a change in the underlying statistical properties. Our results indicate that dynamic adjustments in preparatory attentional control are sensitive to the underlying statistical regularities of an environment. This finding has implications for understanding disordered patterns of attentional control and how these patterns might be modified with training.

Information Processing Biases in the Brain: Implications for Decision-Making and Self-Governance

To make behavioral choices that are in line with our goals and our moral beliefs, we need to gather and consider information about our current situation. Most information present in our environment is not relevant to the choices we need or would want to make and thus could interfere with our ability to behave in ways that reflect our underlying values. Certain sources of information could even lead us to make choices we later regret, and thus it would be beneficial to be able to ignore that information. Our ability to exert successful self-governance depends on our ability to attend to sources of information that we deem important to our decision-making processes. We generally assume that, at any moment, we have the ability to choose what we pay attention to. However, recent research indicates that what we pay attention to is influenced by our prior experiences, including reward history and past successes and failures, even when we are not aware of this history. Even momentary distractions can cause us to miss or discount information that should have a greater influence on our decisions given our values. Such biases in attention thus raise questions about the degree to which the choices that we make may be poorly informed and not truly reflect our ability to otherwise exert self-governance.

Neural Basis of Cognitive Control over Movement Inhibition: Human fMRI and Primate Electrophysiology Evidence

Executive control involves the ability to flexibly inhibit or change an action when it is contextually inappropriate. Using the complimentary techniques of human fMRI and monkey electrophysiology in a context-dependent stop signal task, we found a functional double dissociation between the right ventrolateral prefrontal cortex (rVLPFC) and the bi-lateral frontal eye field (FEF). Different regions of rVLPFC were associated with context-based signal meaning versus intention to inhibit a response, while FEF activity corresponded to success or failure of the response inhibition regardless of the stimulus response mapping or the context. These results were validated by electrophysiological recordings in rVLPFC and FEF from one monkey. Inhibition of a planned behavior is therefore likely not governed by a single brain system as had been previously proposed, but instead depends on two distinct neural processes involving different sub-regions of the rVLPFC and their interactions with other motor-related brain regions.

Reinforcement learning modulates the stability of cognitive control settings for object selection

Cognitive flexibility reflects both a trait that reliably differs between individuals and a state that can fluctuate moment-to-moment. Whether individuals can undergo persistent changes in cognitive flexibility as a result of reward learning is less understood. Here, we investigated whether reinforcing a periodic shift in an object selection strategy can make an individual more prone to switch strategies in a subsequent unrelated task. Participants completed two different choice tasks in which they selected one of four objects in an attempt to obtain a hidden reward on each trial. During a training phase, objects were defined by color. Participants received either consistent reward contingencies in which one color was more often rewarded, or contingencies in which the color that was more often rewarded changed periodically and without warning. Following the training phase, all participants completed a test phase in which reward contingencies were defined by spatial location and the location that was more often rewarded remained constant across the entire task. Those participants who received inconsistent contingencies during training continued to make more variable selections during the test phase in comparison to those who received the consistent training. Furthermore, a difference in the likelihood to switch selections on a trial-by-trial basis emerged between training groups: participants who received consistent contingencies during training were less likely to switch object selections following an unrewarded trial and more likely to repeat a selection following reward. Our findings provide evidence that the extent to which priority shifting is reinforced modulates the stability of cognitive control settings in a persistent manner, such that individuals become generally more or less prone to shifting priorities in the future.

Reinforcement learning modulates preparatory states of cognitive flexibility

Third, our results demonstrate that failures of colour cued spatial memory consist almost entirely of binding failures, not guesses, unlike spatially cued colour memory. This asymmetry suggests that location information may be uniquely maintained after a colour location binding is lost. Overall, these results favour a structured feature storage account of VSTM (Brady, Konkle, & Alvarez, 2011) and draw attention to the need to characterize retrieval processes in VSTM.

Correction to: Reduced Value-Driven Attentional Capture among Children with ADHD Compared to Typically Developing Controls

The authors would like to correct a few minor errors in our article, none of which change the conclusions or interpretations presented.

Structural, not spectral, representation of shape in lateral occipital complex

Neural recording studies in monkeys have shown that shape representation in high-level ventral pathway cortex (including inferotemporal cortex or IT) is structural: ensembles of neurons encode shapes as spatial configurations of structural fragments. The putative homologue for IT in the human brain is the lateral occipital complex (LOC), which is defined by differential responses to intact and scrambled object photographs. Here, we used fMRI to test whether shape representation in human LOC is similarly structural, or is better explained by spatial frequency tuning, which has been the standard quantitative model for shape sensitivity in human cortex. Our stimuli were letter-like combinations of medial axis fragments (straight and curved line segments). Stimuli were presented in random order while subjects performed a one-back shape-matching task. We used a generalized linear model (GLM) to estimate the response pattern of each LOC voxel across stimuli. We parameterized the stimuli as combinations of medial axis fragments, defined by their curvatures, orientations, and object-relative positions. For each voxel, we used stepwise regression to fit a structural tuning model that explained stimulus responses in terms of sensitivity to component fragments. Model complexity was limited to components that explained at least 5% additional variance. Typical models comprised 3-6 components and explained 45-65% of the response variance across stimuli. In contrast, comparable spectral models, based on components from a Gabor wavelet pyramid decomposition of the stimuli, typically explained only 5-15% of the response variance. The explanatory power of the structural models suggests that LOC represents shapes as configurations of structural components. These results also support the homology between human LOC and monkey IT, where neural mechanisms of shape coding can be studied in detail. Meeting abstract presented at VSS 2015.

Attentional Orienting Expectations Broaden and Constrain the Window of Spatial Selection

Individuals adjust preparatory attentional control settings according to environmental statistical regularities such that the behavioral cost in response time associated with shifting attention is reduced when shifting is likely (Sali, Anderson, & Yantis, under review). This learned flexibility may reflect a readiness to update the spatial locus of attention. Alternatively, the spread of attention may be variable such that when a shift of attention is anticipated, the region of space encompassed by attentional selection broadens. We, therefore, investigated whether the breadth of selection varied based on block-by-block changes in the likelihood of shifting attention. Participants held and shifted attention between two rapid serial visual presentation (RSVP) streams of alphanumeric characters in response to visual cues and made speeded parity judgments for target stimuli appearing in the cued stream. Three distractor streams flanked each of the two task-relevant streams. We manipulated the frequency of attention shift and hold cues across blocks of 40 trials each. To test whether these changes in cue frequency modulated the breadth of attentional selection, we varied the response congruency of stimuli appearing in the three distractor RSVP streams surrounding the to-be-attended location. Consistent with previous studies, the behavioral cost in RT associated with shifting attention was smallest for blocks in which shifting was most frequent. When examining shift trials alone, there was a significant interaction of block type and flanker congruency. Participants were slower for incongruent shift trials than for congruent shift trials only in blocks with frequent shift cues. A similar trend existed such that the congruency effect for hold trials was larger when holding was frequent. Our results suggest that increased likelihood of shifting attention is associated with increases in the breadth of attentional selection to include the to-be-attended spatial location, not simply a faster shift at the time of the cue. Meeting abstract presented at VSS 2015.