Hemodynamic differences in the activation of the prefrontal cortex: attention vs. higher cognitive processing.
Both simple attention tasks (e.g. letter cancellation) and most tasks of higher cognitive processing (e.g. word generation) are known to activate the dorsolateral prefrontal cortex (PFC). While attention and higher cognitive processing differ phenomenologically, with attention tasks requiring great subjective effort despite their simplicity, possible physiological differences in the activation of the PFC between the two types of cognitive processing have remained uninvestigated. Hemodynamic changes in the PFC during activation due to tasks of attention and those of higher cognitive processing were examined using near-infrared spectroscopy in 10 Japanese and 10 American healthy adults. In tasks of higher cognitive processing, which included both verbal and non-verbal tasks, the concentration of oxygenated hemoglobin ([HbO2]) increased, and that of deoxygenated hemoglobin ([HbR]) decreased, with an increase in the tissue hemoglobin saturation (THS). In tasks of attention, which consisted of the letter cancellation and continuous performance test, both [HbO2] and [HbR] increased, with no significant changes in the THS observed. The distinctive patterns of hemodynamic changes were not affected by the factors of task difficulty or language. The change in [HbR] may be a physiological marker of the prefrontal lobe activation that discriminates between attention and higher cognitive processing. The increase in [HbR] suggests increased oxygen consumption of the PFC during tasks of attention, which might be related to the disproportionately great subjective effort associated with sustained attention. The physiological alteration in hemodynamic patterns according to changes in cognition needs to be examined in subjects with prefrontal lobe dysfunction, such as schizophrenia and mood disorder.
Toichi
Motomi
M
Division of Child and Adolescent Psychiatry, Case Western Reserve University/University Hospitals of Cleveland, Cleveland, OH, USA. motomi@mbj.ocn.ne.jp
Findling
Robert L
RL
Kubota
Yasutaka
Y
Calabrese
Joseph R
JR
Wiznitzer
Max
M
McNamara
Nora K
NK
Yamamoto
Kokichi
K
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D008297:Male; D010108:Oxyhemoglobins / Q000378:metabolism; D017397:Prefrontal Cortex / Q000098:blood supply / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013055:Spectrophotometry, Infrared / Q000379:methods
D006454:Hemoglobins; D010108:Oxyhemoglobins