title: Reduced Frontal Activations at High Working Memory Load in Mild Cognitive Impairment: Near-Infrared Spectroscopy.
abstract: Some functional magnetic resonance imaging studies have reported altered activations in the frontal cortex during working memory (WM) performance in individuals with mild cognitive impairment (MCI), but the findings have been mixed. The objective of the present study was to utilize near-infrared spectroscopy (NIRS), an alternative imaging technique, to examine neural processing during WM performance in individuals with MCI.
  
  
  
  Twenty-six older adults with MCI (7 males; mean age 69.15 years) were compared with 26 age-, gender-, handedness-, and education-matched older adults with normal cognition (NC; 7 males; mean age 68.87 years). All of the participants undertook an n-back task with a low (i.e., 0-back) and a high (i.e., 2-back) WM load condition while their prefrontal dynamics were recorded by a 16-channel NIRS system.
  
  
  
  Although behavioral results showed that the two groups had comparable task performance, neuroimaging results showed that the MCI group, unlike the NC group, did not exhibit significantly increased frontal activations bilaterally when WM load increased. Compared to the NC group, the MCI group had similar frontal activations at low load (p > 0.05 on all channels) but reduced activations at high load (p < 0.05 on 4 channels), thus failing to demonstrate WM-related frontal activations (p < 0.05 on 9 channels). In addition, we found a positive correlation between the left WM-related frontal activations and WM ability primarily in the NC group (rs = 0.42, p = 0.035), suggesting a relationship between frontal hypoactivation and WM difficulties.
  
  
  
  The present findings suggest the presence of frontal dysfunction that is dependent on WM load in individuals with MCI.
authors: Department of Psychology, The Chinese University of Hong Kong, New Territories, Hong Kong, SAR, China.
authors: Michael K
authors: MK
authors: Yeung
authors: Sophia L
authors: SL
authors: Sze
authors: Jean
authors: J
authors: Woo
authors: Timothy
authors: T
authors: Kwok
authors: David H K
authors: DH
authors: Shum
authors: Ruby
authors: R
authors: Yu
authors: Agnes S
authors: AS
authors: Chan
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000523:psychology; D005260:Female; D005625:Frontal Lobe / Q000000981:diagnostic imaging* / Q000503:physiopathology; D007839:Functional Laterality; D059907:Functional Neuroimaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders; D008570:Memory, Short-Term; D008875:Middle Aged; D059906:Neuroimaging; D019265:Spectroscopy, Near-Infrared; D013647:Task Performance and Analysis