Visual scan paths in first-episode schizophrenia and cannabis-induced psychosis

Philip John Benson, Ute Leonards, Robert M Lothian, David M St Clair, Marco C G Merlo

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


Objective: Patterns of successive saccades and fixations ( scan paths) that are made while viewing images are often spatially restricted in schizophrenia, but the relation with cannabis- induced psychosis has not been examined. We used higher- order statistical methods to examine spatiotemporal characteristics of scan paths to determine whether viewing behaviour was distinguishable on a continuum. Methods: Patients with early acute first- episode paranoid schizophrenia ( SCH; n = 11), cannabis- induced psychosis ( CIP; n = 6) and unaffected control subjects ( n = 22) undertook a task requiring free viewing of facial, fractal and landscape images for 5 seconds while their eye movements were recorded. Frequencies and distributions of saccades and fixations were calculated in relation to image regions examined during each trial. Results: Findings were independent of image category, indicating generalized scanning deficits. Compared with control subjects, patients with SCH and CIP made fewer saccades and fewer fixations of longer duration. In turn, the spatial distribution of fixations in CIP patients was more clustered than in SCH and control subjects. The diversity of features fixated in subjects with CIP was also lower than in SCH patients and control subjects. Conclusion: A continuous approach to characterizing scan path changes in different phenotypes suggests that CIP shares some of the abnormalities of SCH but can be distinguished with measures that are sensitive to cognitive strategies active or inhibited during visual exploration.

Original languageEnglish
Pages (from-to)267-274
Number of pages8
JournalJournal of Psychiatry and Neuroscience
Issue number4
Publication statusPublished - 1 Jul 2007


  • adult
  • cannabis
  • Eye Movements
  • female
  • fixation, Ocular
  • Humans
  • male
  • photic Stimulation
  • psychiatric Status Rating Scales
  • psychoses, substance-induced
  • schizophrenia
  • schizophrenic Psychology
  • smooth-pursuit
  • swedish conscripts
  • affective-disorder
  • performance
  • recognition
  • scanpaths
  • deficits
  • bipolar
  • risk


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