Modality independent coding of spatial layout in the human brain

eblackwood — Tue, 07 Jun 2011 16:00:42 +0000

Abstract: In many nonhuman species, neural computations of navigational information such as position and orientation are not tied to a specific sensory modality [1, 2]. Rather, spatial signals are integrated from multiple input sources, likely leading to abstract representations of space. In contrast, the potential for abstract spatial representations in humans is not known, because most neuroscientific experiments on human navigation have focused exclusively on visual cues. Here, we tested the modality independence hypothesis with two functional magnetic resonance imaging (fMRI) experiments that characterized computations in regions implicated in processing spatial layout [3]. According to the hypothesis, such regions should be recruited for spatial computation of 3D geometric configuration, independent of a specific sensory modality. In support of this view, sighted participants showed strong activation of the parahippocampal place area (PPA) and the retrosplenial cortex (RSC) for visual and haptic exploration of informationmatched scenes but not objects. Functional connectivity analyses suggested that these effects were not related to visual recoding, which was further supported by a similar preference for haptic scenes found with blind participants. Taken together, these findings establish the PPA/RSC network as critical in modality-independent spatial computations and provide important evidence for a theory of highlevel abstract spatial information processing in the human brain.

Citation: Wolbers, T.*, Loomis, J.M., Klatzky, R.L., Wutte, M., & Giudice, N.A.* (2011). Modality independent coding of spatial layout in the human brain. Current Biology. 21(11), 984-989 (* equal contribution of authors)

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Decoding the direction of auditory motion in blind humans

eblackwood — Sun, 15 May 2011 16:00:30 +0000

Abstract: Accurate processing of nonvisual stimuli is fundamental to humans with visual impairments. In this population, moving sounds activate an occipito-temporal region thought to encompass the equivalent of monkey area MT+, but it remains unclear whether the signal carries information beyond the mere presence of motion. To address this important question, we tested whether the processing in this region retains functional properties that are critical for accurate motion processing and that are well established in the visual modality. Specifically, we focussed on the property of ‘directional selectivity’, because MT+ neurons in non-human primates fire preferentially to specific directions of visual motion. Recent neuroimaging studies have revealed similar properties in sighted humans by successfully decoding different directions of visual motion from fMRI activation patterns. Here we used fMRI and multivariate pattern classification to demonstrate that the direction in which a sound is moving can be reliably decoded from dorsal occipito-temporal activation in the blind. We also show that classification performance is at chance (i) in a control region in posterior parietal cortex and (ii) when motion information is removed and subjects only hear a sequence of static sounds presented at the same start and end positions. These findings reveal that information about the direction of auditory motion is present in dorsal occipito-temporal responses of blind humans. As such, this area, which appears consistent with the hMT+ complex in the sighted, provides crucial information for the generation of a veridical percept of moving non-visual stimuli.

Citation: Wolbers, T., Zahorik, P., & Giudice, N.A. (2010). Decoding the direction of auditory motion in blind humans. Neuroimage, special issue on Multivariate decoding and Brain Reading, 56(2), 681-687.

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Wolbers, T. – VEMI Lab

Modality independent coding of spatial layout in the human brain

Decoding the direction of auditory motion in blind humans