Frontal Cortex Activation During CLFT | Photon Cap C20 Analysis

A recent study by Krukow et al. (2025), published in Scientific Reports 1 presented a comparative analysis of a Combined Letter Fluency Task (CLFT)—newly introduced version of the verbal fluency test (VFT)—and a typical Initial Letter Fluency Task (ILFT), using fNIRS technology for data obtaining and its further analysis. Introduction. The verbal fluency tests (VFT) are widely used to study frontal cortex activity in clinical groups and cognitive neuroscience research. Traditionally, these tasks are analyzed using functional magnetic resonance imaging (fMRI), but there is growing interest in using fNIRS to measure oxygenated (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) in brain tissue. Commonly, VFTs are combined with fNIRS to study individuals with schizophrenia, depression, and bipolar disorder, as well as research on aging and dementia. These tests usually last up to 1 minute and are divided into phonemic fluency , focused on pronouncing words with particular letter(s) and semantic fluency – naming words within a particular category (animals, fruits etc). This division elicits hemodynamic responses in the corresponding brain regions involved in task performance. However, Krukow et al. (2025) consider that recent research has highlighted the limitations of standard VFTs. The cognitive and linguistic specificity of VFT remains unclear. Studies have shown that phonemic VFT activates the frontal cortex more strongly than semantic VFT. Moreover, factors such as processing speed, verbal intelligence, executive functioning, and education level significantly influence performance.