Spatiotemporal dynamics of visual vertical judgments: early and late brain mechanisms as revealed by high-density electrical neuroimaging

Abstract

Abstract-Constructing and updating an internal model of verticality is fundamental for maintaining an erect posture and facilitating visuo-spatial processing. The judgment of the visual vertical (VV) has been intensively studied in psychophysical investigations and relies mainly on the integration of visual and vestibular signals, although a contribution of postural and somatosensory signals has been reported. Here we used high-density 192-channel evoked potential (EP) mapping and distributed source localization techniques to reveal the neural mechanisms of VV judgments. VV judgments (judging the orientation of visual lines with respect to the subjective vertical) were performed with and without a tilted visual frame. EP mapping revealed a sequence of neural processing steps (EP maps) of which two were specific for VV judgments. An early EP map, observed at ϳ75-105 ms post-stimulus, was localized in right lateral temporo-occipital cortex. A later EP map (ϳ260 -290 ms) was localized in bilateral temporo-occipital and parieto-occipital cortex. These data suggest that early VV-related neural processing involves the lateral and ventral visual stream and is related to visual processing concerning orientation, attention and comparison. The later, more dorsal, activation involves multimodal cortex subtending a constantly available and updated internal model of the vertical that we can refer to for the control of one's posture, actions, and visuo-spatial processing.

Dorsal and ventral stream contributions to form-from-motion perception in a patient with form-from motion deficit: a case report

“…These dependent variables were then subjected to statistical analysis using unpaired t tests with single trials as repeated measures. A similar analysis procedure has previously been applied to study a wide variety of cognitive processes in healthy subjects [such as perception (Lopez et al 2011), attention (Plomp et al 2009), social interaction (Thirioux et al 2010(Thirioux et al , 2014] as well as in clinical populations (Michel and Murray 2012).…”

Early and late activity in somatosensory cortex reflects changes in bodily self-consciousness: An evoked potential study

“…In the second analysis step we performed statistical analysis and verified the presence of a given EP map as identified in the group-averaged data in the EPs of the individual participants. This is done by means of a fitting procedure based on the spatial correlation between template maps obtained from the group-averaged EPs data and the individual participants' data (Lopez et al, 2011). Thus, the dominant EP maps, as identified by the segmentation procedure in the group-averaged data (analysis step 1), were fitted to the EPs of each individual participant (analysis step 2).…”

Influence of Spatial Neglect, Hemianopia and Hemispace on the Subjective Vertical

“…For the effect of hemianopia, we have previously considered two main hypotheses, which could be either specific [12] or related to the presence of an associated posterior lesion. The importance of the posterior cortex in the SV task has been confirmed by a recent study in healthy subjects [28]. High-density electrical neuroimaging revealed that the SV task elicited early activation of the temporo-occipital area and later activation of both the temporo-occipital and parieto-occipital regions.…”