Mirror asymmetry of Category and Letter fluency in traumatic brain injury and Alzheimer's patients

Erminio Capitani, Chiara Rosci, Maria Cristina Saetti, Marcella Laiacona

Research output: Contribution to journalArticlepeer-review


In this study we contrasted the Category fluency and Letter fluency performance of 198 normal subjects, 57 Alzheimer's patients and 57 patients affected by traumatic brain injury (TBI). The aim was to check whether, besides the prevalence of Category fluency deficit often reported among Alzheimer's patients, the TBI group presented the opposite dissociation. According to some recent claims, in fact, the deficit of TBI would be equally severe for both fluency types. The inquiry followed different approaches for data analysis, including the evaluation of a unique index (Fluency Type Index or FTI), independent of the overall fluency and aimed at expressing at individual subject level the relationship between Category and Letter fluency. The results confirmed that Alzheimer's patients are more defective on Category than Letter fluency, and also clearly indicated that an opposite pattern applies to TBI patients. TBI seems to cause a relatively more severe impairment of Letter than Category fluency, probably due to its impact on the frontal lobe structures. We discuss whether, on the basis of the statistical distribution of our data, it is worth considering as homogeneous populations broadly defined groups as Alzheimer's or TBI patients.

Original languageEnglish
Pages (from-to)423-429
Number of pages7
Issue number2
Publication statusPublished - Jan 2009


  • Alzheimer's disease
  • Traumatic brain injury
  • Verbal fluency

ASJC Scopus subject areas

  • Behavioral Neuroscience
  • Cognitive Neuroscience
  • Experimental and Cognitive Psychology


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