title: Material-dependent activation in prefrontal cortex: working memory for letters and texture patterns--initial observations.
abstract: OBJECTIVE
  To prospectively evaluate whether a distinction between verbal and nonverbal short-term memory systems, as predicted with the multicomponent working memory model, is reflected in the material-specific patterns of activation in the prefrontal cortex.
  
  
  METHODS
  Informed written consent was obtained from all participants, and the institutional review board approved the study protocol. Echo-planar MR imaging was performed in 12 healthy subjects (five female and seven male subjects), with a mean age of 23.52 years +/- 2.52 (standard deviation) and a range of 20-29 years. A two-back task was used in the verbal and nonverbal versions. In the first version, letters were used as stimuli, and in the second version, the stimuli were abstract texture patterns. Timing parameters for both versions were the same. Statistical analysis of the functional data involved a fixed-effects general linear model. Regions of activation were identified from specific t-statistic contrasts between baseline and active tasks (corrected for whole-brain multiple comparisons).
  
  
  RESULTS
  The following suprathreshold voxels for the verbal condition were observed predominantly in the left hemisphere (middle frontal gyrus, precentral gyrus, middle temporal gyrus, and occipital cortex). Bilateral activations were in inferior frontal gyri, insulae inferior, superior parietal lobules, and cingulate gyri. In the nonverbal condition, suprathreshold voxels were located mostly bilaterally in the following regions: inferior, middle, and medial frontal gyri and inferior parietal lobules. Active regions were also found in the precentral gyrus and precuneate gyrus in the left parietal lobe and the occipital cortex in the right hemisphere.
  
  
  CONCLUSIONS
  Results of this study are consistent with the multicomponent model of working memory.
authors.affiliation: Department of Psychophysiology, Institute of Psychology, Jagiellonian University, 19 Kopernika St, 31-501 Kraków, Poland.
authors.forename: Marek
authors.initials: M
authors.lastname: Binder
authors.forename: Andrzej S
authors.initials: AS
authors.lastname: Urbanik
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping / Q000379:methods; D017352:Echo-Planar Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D010775:Photic Stimulation; D017397:Prefrontal Cortex / Q000033:anatomy & histology* / Q000502:physiology; D011446:Prospective Studies