Eye-Centered, Head-Centered, and Complex Coding of Visual and Auditory Targets in the Intraparietal Sulcus

Abstract

The integration of visual and auditory events is thought to require a joint representation of visual and auditory space in a common reference frame. We investigated the coding of visual and auditory space in the lateral and medial intraparietal areas (LIP, MIP) as a candidate for such a representation. We recorded the activity of 275 neurons in LIP and MIP of two monkeys while they performed saccades to a row of visual and auditory targets from three different eye positions. We found 45% of these neurons to be modulated by the locations of visual targets, 19% by auditory targets, and 9% by both visual and auditory targets. The reference frame for both visual and auditory receptive fields ranged along a continuum between eye- and head-centered reference frames with approximately 10% of auditory and 33% of visual neurons having receptive fields that were more consistent with an eye- than a head-centered frame of reference and 23 and 18% having receptive fields that were more consistent with a head- than an eye-centered frame of reference, leaving a large fraction of both visual and auditory response patterns inconsistent with both head- and eye-centered reference frames. The results were similar to the reference frame we have previously found for auditory stimuli in the inferior colliculus and core auditory cortex. The correspondence between the visual and auditory receptive fields of individual neurons was weak. Nevertheless, the visual and auditory responses were sufficiently well correlated that a simple one-layer network constructed to calculate target location from the activity of the neurons in our sample performed successfully for auditory targets even though the weights were fit based only on the visual responses. We interpret these results as suggesting that although the representations of space in areas LIP and MIP are not easily described within the conventional conceptual framework of reference frames, they nevertheless process visual and auditory spatial information in a similar fashion.

Idiosyncratic and systematic aspects of spatial representations in the macaque parietal cortex

“…Monkey S had a left hemisphere chamber and showed a median weight of 0.80 with 43% gaze-centered, 17% hand-centered, and 24% intermediate cells. Finally, we applied three previously published classification schemes (7,(23)(24)(25) for distinguishing gaze-and hand-centered frames of reference, and these confirmed our conclusion that PRR shows a broad range of representations, from gaze-centered to hand-centered, with a bias for gaze-centered cells (Fig. 3B, Fig.…”

“…For example, cells in the superior colliculus code auditory stimuli using complex representations that are idiosyncratic to individual cells and neither purely gazenor purely head-centered (18,19). Similar complex and nonuniform coding may occur in the ventral intraparietal area (VIP) (20), the dorsal medial superior temporal area (MSTd) (21), the lateral intraparietal area (LIP) (22,23), and PMd (24,25). Modeling work suggests that these complex coding schemes may help convert reference frames, optimally combine sensory information from different modalities, or perform nonlinear computations (15,17,26,27).…”

Auditory Spatial Perception Dynamically Realigns with Changing Eye Position

“…Transient eccentric eye position (Ͻ5 s) has also been shown to modulate the spatial responses of auditory neurons in the inferior colliculus (Groh et al, 2001;Zwiers et al, 2004), superior colliculus (Jay and Sparks, 1987;Hartline et al, 1995;Peck et al, 1995;Zella et al, 2001;Populin et al, 2004), auditory cortex (WernerReiss et al, 2003;Fu et al, 2004), and the intraparietal sulcus (Stricanne et al, 1996;Mullette-Gillman et al, 2005). These short-term effects may reflect a step in the eye-to-head-centered transformation of sound source coordinates, their associated errors, or an early component of the auditory spatial adaptation reported here.…”

A parietal–temporal sensory–motor integration area for the human vocal tract: Evidence from an fMRI study of skilled musicians

“…Thus Spt is defined as a region with the posterior portion of the Sylvian fissure that exhibits both auditory and motor response properties. al., 1996), as well as the observation that sensory input from multiple modalities can drive neurons in PPC sensory-motor fields (Cohen, Batista, & Andersen, 2002;Mullette-Gillman, Cohen, & Groh, 2005). In sum, the response properties of area Spt -particularly that it shows both sensory and motor responses -are consistent with the hypothesis that it is a sensory-motor integration region similar to those found in the primate intraparietal sulcus (Buchsbaum et al, 2005b).…”

“…These areas are organized around particular motor-effector systems (Andersen 1997;Colby et al, 1999;Simon et al, 2002). While these areas can take input from multiple sensory modalities Mullette-Gillman et al, 2005;Xing & Andersen, 2000), these systems may nonetheless be biased towards certain sensory modalities depending on the demands of the particular action systems involved. For example, manual action systems may be biased towards visual input in most individuals because of visually-guided reaching/ grasping functions, whereas vocal tract systems may be biased toward auditory input for reasons discussed in the Introduction.…”