Ever since the advent of cognitive and neuro-science, the line between ‘mere’ thought and actual perception of the outside world has been blurry to say the least.
What is the correlation of subjective perception of sound and actual events in the world? How individuated are they? Questions such as these abound.
Now, a new study conducted by a group of researchers from NYU Shanghai and New York University, entitled ‘Imagined Speech Influences Perceived Loudness of Sound’ suggests that ‘loudness’ of our inner speech dampens our perception of ‘real’ sounds originating in the proximal environment.
Using an imagery-perception repetition paradigm, the study has found that auditory imagery, which could be likened to inner monologue, tune down the perception of actual, subsequent sounds. The finding was also supported by behavioural ratings, and magnetoencephalography (MEG) and electroencephalography (EEG) results.
“This is because imagery and perception activate the same auditory brain areas. The preceding imagery activates the auditory areas once, and when the same brain regions are needed for perception, they are ‘tired’ and will respond less,” said professor of neural and cognitive science Tian Xing of NYU Shanghai.
According to Xing, the study leads credence to the idea that perception is the result of both top-down (e.g., cognitive) and bottom-up (e.g., sensory processing of external stimuli) functions. In other words, the human auditory system both receives external stimuli (passive) and interprets and manipulates them (active), which leads to perception.
“The results suggest that the internal reconstruction of neural representations without external stimulation is flexibly regulated by task demands, and that such top-down processes can interact with bottom-up information at an early perceptual stage to modulate perception,” wrote the authors in their paper.
The study is part of a larger body of work the team has been pursuing to investigate speech monitoring and control in the production process, which can help explain such low-level auditory attributes as loudness.
“Combining perception and speech production monitoring and control, this study can implicate the mechanisms of mental disorders. The most relevant one is auditory hallucination mostly in schizophrenia,” said Xing.