title: Visual demand and visual field presentation influence natural scene processing.
abstract: BACKGROUND
  Bottom-up and top-down processes are involved in visual analysis of scenes. Here we examined the influence of top-down visual demand on natural scene processing.
  
  
  METHODS
  We measured accuracy and response time in adults performing two stimuli-equivalent tasks. Unfiltered, low or high spatial frequency (SF) natural scenes were presented in central, left, or right visual fields (CVF, LVF, RVF). The tasks differed only by the instructed visual demand. In the detection task, participants had to decide whether a scene was present or not. In the categorization task, they had to decide whether the scene was a city or a forest.
  
  
  RESULTS
  Higher accuracy was seen for the LVF in the detection task, but for categorization, greater accuracy was seen for the RVF. The interaction between Task and SF revealed coarse-to-fine processing in the categorization task for both accuracy and reaction time, which nearly disappeared in the detection task. Considering the interaction of Task, VF and SF, a left-hemisphere specialisation (i.e., RVF advantage) was observed for the categorisation of HSF scenes for accuracy alone, whereas a LVF advantage was seen for all SFs in the detection task for both accuracy and reaction time.
  
  
  CONCLUSIONS
  Our results revealed that the nature of top-down visual demand is essential to understanding how visual analysis is achieved in each hemisphere. Moreover, this study examining the effects of visual demand, visual field presentation, and SF content of stimuli through the use of ecological stimuli provides a tool to enrich the clinical examination of visual and neurovisual patients.
authors.affiliation: ERT TREAT Vision & Laboratoire de Psychologie et NeuroCognition, UMR 5105 CNRS-Université Pierre Mendès France, 1251 avenue Centrale, 38040, Grenoble, France. olivier.coubard@gmail.com
authors.forename: Olivier A
authors.initials: OA
authors.lastname: Coubard
authors.forename: Céline
authors.initials: C
authors.lastname: Perez
authors.forename: Seta
authors.initials: S
authors.lastname: Kazandjian
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gaudry
authors.forename: Christian
authors.initials: C
authors.lastname: Marendaz
authors.forename: Nathalie
authors.initials: N
authors.lastname: Guyader
authors.forename: Carole
authors.initials: C
authors.lastname: Peyrin
authors.forename: Sylvie
authors.initials: S
authors.lastname: Chokron
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005556:Form Perception / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013647:Task Performance and Analysis; D013997:Time Factors; D014793:Visual Cortex / Q000502:physiology; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult