Auditory Spatial Coding Flexibly Recruits Anterior, but Not Posterior, Visuotopic Parietal Cortex

Abstract

Audition and vision both convey spatial information about the environment, but much less is known about mechanisms of auditory spatial cognition than visual spatial cognition. Human cortex contains >20 visuospatial map representations but no reported auditory spatial maps. The intraparietal sulcus (IPS) contains several of these visuospatial maps, which support visuospatial attention and short-term memory (STM). Neuroimaging studies also demonstrate that parietal cortex is activated during auditory spatial attention and working memory tasks, but prior work has not demonstrated that auditory activation occurs within visual spatial maps in parietal cortex. Here, we report both cognitive and anatomical distinctions in the auditory recruitment of visuotopically mapped regions within the superior parietal lobule. An auditory spatial STM task recruited anterior visuotopic maps (IPS2-4, SPL1), but an auditory temporal STM task with equivalent stimuli failed to drive these regions significantly. Behavioral and eye-tracking measures rule out task difficulty and eye movement explanations. Neither auditory task recruited posterior regions IPS0 or IPS1, which appear to be exclusively visual. These findings support the hypothesis of multisensory spatial processing in the anterior, but not posterior, superior parietal lobule and demonstrate that recruitment of these maps depends on auditory task demands.

Keywords: attention; intraparietal sulcus; retinotopy; short-term memory; working memory.

Figure 1.

Auditory spatial and temporal change-detection tasks. Each trial included a target stimulus (2350 ms), a 900-ms delay, and a probe stimulus (2350 ms). Each stimulus comprised 4 sequentially presented, spatialized, complex tones (370 ms duration) with irregular BTIs (120–420 ms). Subjects attempted to detect a change in the location (spatial task) or onset-timing pattern (temporal task) of the tones.

Figure 2.

Comparison of auditory spatial and temporal task activations. Average percent signal change relative to sensorimotor control within (A) visuotopic ROIs and (B) nonvisuotopic parietal dorsal attention network ROIs for the spatial (dark gray) and temporal (light gray) tasks. N = 10 for IPS0, IPS1, IPS2, IPS3, latIPS, antIPS, and mSPL; N = 9 for IPS4, and SPL1. Error bars reflect SEM. (C) Summary of functional organization of posterior parietal cortex with respect to auditory spatial and temporal processing.