Auditory and visual connectivity gradients in frontoparietal cortex

Abstract

A frontoparietal network of brain regions is often implicated in both auditory and visual information processing. Although it is possible that the same set of multimodal regions subserves both modalities, there is increasing evidence that there is a differentiation of sensory function within frontoparietal cortex. Magnetic resonance imaging (MRI) in humans was used to investigate whether different frontoparietal regions showed intrinsic biases in connectivity with visual or auditory modalities. Structural connectivity was assessed with diffusion tractography and functional connectivity was tested using functional MRI. A dorsal–ventral gradient of function was observed, where connectivity with visual cortex dominates dorsal frontal and parietal connections, while connectivity with auditory cortex dominates ventral frontal and parietal regions. A gradient was also observed along the posterior–anterior axis, although in opposite directions in prefrontal and parietal cortices. The results suggest that the location of neural activity within frontoparietal cortex may be influenced by these intrinsic biases toward visual and auditory processing. Thus, the location of activity in frontoparietal cortex may be influenced as much by stimulus modality as the cognitive demands of a task. It was concluded that stimulus modality was spatially encoded throughout frontal and parietal cortices, and was speculated that such an arrangement allows for top–down modulation of modality‐specific information to occur within higher‐order cortex. This could provide a potentially faster and more efficient pathway by which top–down selection between sensory modalities could occur, by constraining modulations to within frontal and parietal regions, rather than long‐range connections to sensory cortices. Hum Brain Mapp 38:255–270, 2017. © 2016 Wiley Periodicals, Inc.

Sensory-biased attention networks in human lateral frontal cortex revealed by intrinsic functional connectivity

“…On the other hand, human-based functional MRI (fMRI) studies of visual and auditory sensory processing in lateral frontal cortex (LFC) typically report either a relative lack of sensitivity to sensory modality (Lewis et al, 2000; Johnson and Zatorre 2006; Ivanoff et al, 2009; Karabanov et al, 2009; Tark and Curtis 2009; Tombu et al, 2011; Braga et al, 2013) or a bias for a single sensory modality (Crottaz-Herbette et al, 2004; Jantzen et al, 2005; Rämä and Courtney 2005; Salmi et al, 2007). However, consistent with non-human primate studies, two recent human fMRI studies (Michalka et al, 2015; Mayer et al, 2017) and one study combining functional and structural connectivity (Braga et al, 2017) found that distinct regions of LFC exhibit strong biases for vision or audition. Another study also reported sensitivity to sensory modality within LFC (Tamber-Rosenau et al, 2013).…”

“…Topographic differences related to using primary sensory or secondary association cortex as seeds for calculating connectivity with LFC remain to be fully investigated. The second study used structural connectivity and rsFC analyses to propose a dorsal-to-ventral gradient of visual-to-auditory bias in frontal cortex (Braga et al, 2017). This study also used seeds that differ substantially from those used here and are more similar to that of Mayer et al (2017).…”

A cortical wiring space links cellular architecture, functional dynamics and hierarchies in humans

“…The structural manifold identified here captured both sensory-fugal and anterior-posterior processing streams, two core modes of cortical organisation and hierarchies established by seminal tract-tracing work in non-human primates 36,59 . The anterior-posterior axis combines multiple local gradients and functional topographies, such as the ventral visual stream running from the occipital pole to the anterior temporal pole that implements a sensory-semantic dimension of perceptual processing 60,61 and a rostrocaudal gradient in the prefrontal cortex that describes a transition from high-level cognitive processes supporting action preparation to those tightly coupled with motor execution 59,[62][63][64] . The sensory-fugal axis represents an overarching organisational principle that unites these local processing streams.…”

Domain-general brain regions do not track linguistic input as closely as language-selective regions

“…Perhaps MD regions are biased towards visual information (or audio-visual integration) in movies compared to the auditory information of stories (Michalka et al, 2015;Braga et al, 2016). Alternatively, MD regions may track both movies and stories, but fluctuations in MD activity during movie viewing could simply be slower, and thus more reliably measured, compared to the fast fluctuations during story comprehension.…”