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Brain Struct Funct. 2016 Jan;221(1):463-72. doi: 10.1007/s00429-014-0918-2. Epub 2014 Oct 25.

A frontal but not parietal neural correlate of auditory consciousness.

Author information

1
Section of Experimental Psychology, Department of Psychological Sciences, Humanities and the Territory, "G. d'Annunzio" University of Chieti and Pescara, Via dei Vestini 31, 66100, Chieti Scalo, Italy. alfredo.brancucci@unich.it.
2
Section of Experimental Psychology, Department of Psychological Sciences, Humanities and the Territory, "G. d'Annunzio" University of Chieti and Pescara, Via dei Vestini 31, 66100, Chieti Scalo, Italy.
3
Department of Neuroscience and Imaging, "G. d'Annunzio" University of Chieti and Pescara, Via dei Vestini 31, 66100, Chieti Scalo, Italy.
4
ITAB, Institute for Advanced Biomedical Technologies, "G. d'Annunzio" University of Chieti and Pescara, Via dei Vestini 31, 66100, Chieti Scalo, Italy.

Abstract

Hemodynamic correlates of consciousness were investigated in humans during the presentation of a dichotic sequence inducing illusory auditory percepts with features analogous to visual multistability. The sequence consisted of a variation of the original stimulation eliciting the Deutsch's octave illusion, created to maintain a stable illusory percept long enough to allow the detection of the underlying hemodynamic activity using functional magnetic resonance imaging (fMRI). Two specular 500 ms dichotic stimuli (400 and 800 Hz) presented in alternation by means of earphones cause an illusory segregation of pitch and ear of origin which can yield up to four different auditory percepts per dichotic stimulus. Such percepts are maintained stable when one of the two dichotic stimuli is presented repeatedly for 6 s, immediately after the alternation. We observed hemodynamic activity specifically accompanying conscious experience of pitch in a bilateral network including the superior frontal gyrus (SFG, BA9 and BA10), medial frontal gyrus (BA6 and BA9), insula (BA13), and posterior lateral nucleus of the thalamus. Conscious experience of side (ear of origin) was instead specifically accompanied by bilateral activity in the MFG (BA6), STG (BA41), parahippocampal gyrus (BA28), and insula (BA13). These results suggest that the neural substrate of auditory consciousness, differently from that of visual consciousness, may rest upon a fronto-temporal rather than upon a fronto-parietal network. Moreover, they indicate that the neural correlates of consciousness depend on the specific features of the stimulus and suggest the SFG-MFG and the insula as important cortical nodes for auditory conscious experience.

KEYWORDS:

Auditory perception; Deutsch’s octave illusion; Dichotic stimuli; Functional magnetic resonance imaging (fMRI); Multistable perception; Neural correlates of consciousness (NCC)

PMID:
25344118
DOI:
10.1007/s00429-014-0918-2
[Indexed for MEDLINE]

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