Influence of Pleasant and Unpleasant Auditory Stimuli on Cerebral Blood Flow and Physiological Changes in Normal Subjects

Abstract

The prefrontal cortex (PFC) plays an important role in emotion and emotional regulation. The valence asymmetry hypothesis, proposes that the left/right asymmetry of the PFC activity is correlated with specific emotional responses to stressors. However, this hypothesis still seems to leave room for clarifying neurophysiological mechanisms. The purpose of the present study was to investigate the effects of stimuli with positive and negative valence sounds (hereafter PS, NS) selected from the International Affective Digitized Sounds-2 on physiological and physiological responses, including PFC activity in normal participants. We studied the effect of both stimuli using 12 normal subjects (mean age 26.8 years) on cerebral blood oxygenation in the bilateral PFC by a multi-channel NIRS, alpha wave appearance rate in theta, alpha, beta by EEG, autonomic nervous function by heart rate, and emotional conditions by the State-Trait Anxiety Inventory (STAI) and the visual analogue scale (VAS). PS was selected over 7.00 and NS were fewer than 3.00 in the Pleasure values. Sounds were recorded during 3 s and reproduced at random using software. Every task session was designed in a block manner: seven rests with Brown Noise (30 s) and six tasks (30 s) blocks. All participants performed each session in random order with eyes closed. A paired Student's t-test was used for comparisons (P<0.05). PFC activity showed increases bilaterally during both stimuli with a greater activation of the left side in PS and a tendency of more activation by NS in the right PFC. Significantly greater alpha wave intensity was obtained in PS. Heart rate tended to show smaller values in PS. The STAI level tended to show smaller values in PS, and a significantly greater VAS score was obtained in PS which indicated 'pleasant'. Despite the limitations of this study such as the low numbers of the subjects, the present study indicated that PS provided pleasant psychological and physiological responses and NS unpleasant responses. The PFC was activated bilaterally, implying a valence effect with the possibility of a dominant side.

Uncovering electrophysiological and vascular signatures of implicit emotional prosody

“…This could be due to the fact that the fNIRS mostly measures cortical layers of the brain, not reaching deeper structures like the amygdala, which is known to be predominantly involved in emotional processing in general 35 , but also emotional prosody processing in particular 36 . Nevertheless, fMRI studies showed that the cortex is indeed also involved when it comes to emotional (prosody) processing 13,33,37 and effects were also found in previous fNIRS studies 20,[40][41][42] . However, also in those fNIRS studies, effects are sometimes reported as mere tendencies as statistical analyses reveal only marginally significant results.…”

Speech Prosodies of Different Emotional Categories Activate Different Brain Regions in Adult Cortex: an fNIRS Study

“…Also, ventral frontal channels and channels across the midline of the frontal cortex (the influence of cerebrospinal fluid) did not show significant deactivation when prosody was contrasted to silence condition. Second, in order to provide comparable results for the on-going neonatal study, the adult subjects in the current study were required to passively listen to the prosodies (see also in other studies 12 , 27 , 42 , 58 , 59 ). This task setting is suitable and may be the only feasible task for neonates, but may generate unnecessary voluntary perception and evaluation of emotional prosodies in adult’s brain.…”

“…In addition, fMRI studies on the effects of emotional sounds are unavoidably interfered with the gradient noise of the scanner so the fMRI-based results are necessary to be verified and complemented by a silent imaging method such as functional near-infrared spectroscopy (fNIRS) 25 . However, so far as we know, speech prosody has never been investigated using the fNIRS technique; and there are only three relevant fNIRS studies that examined nonverbal expressions or nonhuman sounds 25 – 27 . Therefore, the first aim of the present study was to provide an fNIRS-based knowledge of how speech prosodies of different emotional categories elicit activation in adult brain.…”

Simultaneous functional near-infrared spectroscopy and electroencephalography for monitoring of human brain activity and oxygenation: a review

“…Part of the combined fNIRS–EEG studies focused on characterizing brain activity during external sensory stimulation (auditory or visual) 69 – 71 …”