Manipulation of affective speech and hemoglobin changes: A case study

Abstract

Despite the wide use of functional near-infrared spectroscopy (fNIRS) in various cognitive research, it is under-investigated whether fNIRS can offer neural evidence of emotion vocalization, especially in older adults. In this study, an 74-year-old male participant without a cognitive or physical difficulty completed two speech tasks while an fNIRS device recorded Changes in Oxy-hemoglobin (HbO) and total hemoglobin (HbT) levels in the pre-frontal cortex. The three speech tasks were (1) affective speech (i.e., talking about happy and sad life events) and (2) neutral speech (i.e., explaining how to make a peanut butter and jelly sandwich). The speech tasks were audio recorded which was acoustically analyzed using Praat for frequency and amplitude measures. In general, the frequency measures were highest when talking about sad life event while amplitude measures were highest when producing neutral speech. The HbO and HbT levels were positive and highest during the happy speech manipulation. During the other two speech tasks, the HbO levels were all negative with neutral being the lowest. The HbT levels showed a more complex change. More data are needed to confirm the pre-frontal lobe (de)activation associated with manipulation of affective prosody. This case study will facilitate future research in this line.