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At least 1,261 records · Page 70Linked to original sources
PubMed2003

A neural basis for the perception of voices in external auditory space.

We used functional imaging of normal subjects to identify the neural substrate for the perception of voices in external auditory space. This fundamental process can be abnormal in psychosis, when voices that are not true external auditory objects (auditory verbal hallucinations) may appear to originate in external space. The perception of voices as objects in external space depends on filtering by the outer ear. Psychoses that distort this process involve the cerebral cortex. Functional magnetic resonance imaging was carried out on 12 normal subjects using an inside-the-scanner simulation of 'inside head' and 'outside head' voices in the form of typical auditory verbal hallucinations. Comparison between the brain activity associated with the two conditions allowed us to test the hypothesis that the perception of voices in external space ('outside head') is subserved by a temperoparietal network comprising association auditory cortex posterior to Heschl's gyrus [planum temporale (PT)] and inferior parietal lobule. Group analyses of response to 'outside head' versus 'inside head' voices showed significant activation solely in the left PT. This was demonstrated in three experiments in which the predominant lateralization of the stimulus was to the right, to the left or balanced. These findings suggest a critical involvement of the left PT in the perception of voices in external space that is not dependent on precise spatial location. Based on this, we suggest a model for the false perception of externally located auditory verbal hallucinations.

Acoustics↗
PubMed2004

Length perception and production of normal subjects in proximal versus distal peripersonal space.

We investigated whether the perception or production of a given line length in normal subjects varies according to where in peripersonal space the line is perceived or produced. We also investigated the influence of the direction of movement used to make the line. In Experiment 1, blindfolded normal subjects were asked to estimate distances while the examiner moved the subject's hand in proximal (medial) or distal (lateral) space, moving centripetally or centrifugally. The subjects showed a spatial effect, perceiving the same length as shorter in proximal space than distal space. This result could be related to either a proximal spatial attentional bias or an anisometric representation of spatial distances. In Experiment 2, we attempted to dissociate these hypotheses by studying blindfolded normal subjects, who were requested to produce horizontal lines of a given length (100 or 200 mm) in proximal versus distal peripersonal space using centripetal or centrifugal movements. Centrifugal movements in proximal space were the longest; centrifugal movements in distal space were the shortest: in between were the proximal centripetal and distal centripetal movements which did not differ from each other. These results suggest that in peripersonal space the perception of length in normal subjects is most consistent with anisometric mental representation where the size of mental representations of length units decreases as a function of the distance from the subject's midsagittal plane. Length production, however, may depend on an interaction of the anisometric mental representation and the premotor/intentional factors.

Adult↗