Article

Interactions of Top-Down and Bottom-Up Mechanisms in Human Visual Cortex

Princeton Neuroscience Institute, Department of Psychology, Princeton University, Princeton, New Jersey 08544, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.75). 01/2011; 31(2):587-97. DOI: 10.1523/JNEUROSCI.3766-10.2011
Source: PubMed

ABSTRACT Multiple stimuli present in the visual field at the same time compete for neural representation by mutually suppressing their evoked activity throughout visual cortex, providing a neural correlate for the limited processing capacity of the visual system. Competitive interactions among stimuli can be counteracted by top-down, goal-directed mechanisms such as attention, and by bottom-up, stimulus-driven mechanisms. Because these two processes cooperate in everyday life to bias processing toward behaviorally relevant or particularly salient stimuli, it has proven difficult to study interactions between top-down and bottom-up mechanisms. Here, we used an experimental paradigm in which we first isolated the effects of a bottom-up influence on neural competition by parametrically varying the degree of perceptual grouping in displays that were not attended. Second, we probed the effects of directed attention on the competitive interactions induced with the parametric design. We found that the amount of attentional modulation varied linearly with the degree of competition left unresolved by bottom-up processes, such that attentional modulation was greatest when neural competition was little influenced by bottom-up mechanisms and smallest when competition was strongly influenced by bottom-up mechanisms. These findings suggest that the strength of attentional modulation in the visual system is constrained by the degree to which competitive interactions have been resolved by bottom-up processes related to the segmentation of scenes into candidate objects.

Full-text

Available from: Stephanie A Mcmains, Jun 11, 2014
0 Followers
 · 
151 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Area V5 of the visual brain, first identified anatomically in 1969 as a separate visual area, is critical for the perception of visual motion. As one of the most intensively studied parts of the visual brain, it has yielded many insights into how the visual brain operates. Among these are: the diversity of signals that determine the functional capacities of a visual area; the relationship between single cell activity in a specialized visual area and perception of, and preference for, attributes of a visual stimulus; the multiple asynchronous inputs into, and outputs from, an area as well as the multiple operations that it undertakes asynchronously; the relationship between activity at given, specialized, areas of the visual brain and conscious awareness; and the mechanisms used to " bind " signals from one area with those from another, with a different specialization, to give us our unitary perception of the visual world. Hence V5 is, in a sense, a microcosm of the visual world and its study gives important insights into how the whole visual brain is organized—anatomically, functionally and perceptually.
    Frontiers in Integrative Neuroscience 05/2015; 9. DOI:10.3389/fnint.2015.00021
  • [Show abstract] [Hide abstract]
    ABSTRACT: When making decisions, individuals tend to systematically prefer information that supports their a priori views over information that conflicts with them. This phenomenon is known as confirmatory information processing. The present research investigated whether contextual disorder-a factor that is typically irrelevant to a given decision case yet can significantly influence decision quality-affects confirmatory information processing. In Study 1, decision makers in untidy environments evinced less confirmatory information processing than decision makers in tidy environments. Study 2 replicated this finding and demonstrated that divergent thinking is an important precondition of the relationship between disorder and confirmatory information processing.
    Basic and Applied Social Psychology 05/2014; 36(3):199-208. DOI:10.1080/01973533.2014.890621 · 0.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The brain constantly creates perceptual predictions about forthcoming stimuli to guide perception efficiently. Abundant studies have demonstrated that perceptual predictions modulate sensory activities depending on whether the actual inputs are consistent with one particular prediction. In real-life contexts, however, multiple and even conflicting predictions might concurrently exist to be tested, requiring a multiprediction coordination process. It remains largely unknown how multiple hypotheses are conveyed and harmonized to guide moment-by-moment perception. Based on recent findings revealing that multiple locations are sampled alternatively in various phase of attentional rhythms, we hypothesize that this oscillation-based temporal organization mechanism may also underlie the multiprediction coordination process. To address the issue, we used well established priming paradigms in combination with a time-resolved behavioral approach to investigate the fine temporal dynamics of the multiprediction harmonization course in human subjects. We first replicate classical priming effects in slowly developing trends of priming time courses. Second, after removing the typical priming patterns, we reveal a new theta-band (∼4 Hz) oscillatory component in the priming behavioral data regardless of whether the prime was masked. Third, we show that these theta-band priming oscillations triggered by congruent and incongruent primes are in an out-of-phase relationship. These findings suggest that perceptual predictions return to low-sensory areas not continuously but recurrently in a theta-band rhythm (every 200-300 ms) and that multiple predictions are dynamically coordinated in time by being conveyed in different phases of the theta-band oscillations to achieve dissociated but temporally organized neural representations. Copyright © 2015 the authors 0270-6474/15/352830-08$15.00/0.