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5.0 Discussion

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Outline 5.0 Discussion

5.0 Discussion

5.1 Resting-State Evidence for a Supramodal Prefrontal Architecture

Our central objective of this study was to examine whether the prefrontal hubs known to govern top-down attentional control in the visual domain extend their functional architecture into the auditory system. Our resting-state connectivity patterns are consistent with this hypothesis. Applying single-seed partial correlation analyses, we observe a functional dissociation between the FEF and the IFJa: the FEF shows preferential resting-state coupling with auditory-spatial and motion-sensitive cortical regions, whereas the IFJa couples selectively with temporal-semantic and language-related areas. This pattern supports our primary hypothesis (Section 1.3) that the auditory where-stream connects preferentially to FEF and the what-stream to IFJa. The observed dissociation is analogous to the spatial–non-spatial segregation previously established for these regions in the visual domain by Bedini & Baldauf (2021), who characterized the FEF as a spatial attention hub embedded in the dorsal attention system and the IFJa as anchoring for non-spatial, object-level processing. That our auditory connectivity profiles mirror this division suggests a prefrontal organization that may not be modality-specific but supramodal in its logic.

5.1.1 The FEF as an Auditory-Spatial Controller

The partial correlation profile of the FEF is consistent with its established role as a spatial attention controller, now extended to the auditory domain. Rather than projecting to the superior parietal lobule regions typically associated with visuospatial attention (7PC, 7Am, 7AL) — connections that vanish when shared ROI variance is partialled out — the FEF couples selectively with the inferior parietal lobule, specifically PF (left ; right ) and PFcm, as well as with the motion-sensitive area MST (bilateral, ) and multimodal convergence zones including STV and TPOJ1. Crucially, the FEF shows no significant effect-size connectivity with any temporal regions of the ventral “what” stream (e.g., TE1a, TA2, TGd), suggesting a topographically clean dissociation.

This pattern aligns with the functional logic described by Rauschecker & Scott (2009), who demonstrated that the posterior-dorsal auditory stream links posterior superior temporal cortex and parietal areas for spatial processing, with activation in regions adjacent to MT/MST specifically for auditory motion. Our resting-state data extend this framework to the prefrontal level by showing that the FEF — a node absent from classical auditory stream models — shows functional coupling with these motion-tracking areas, suggesting it may exert top-down control over auditory spatial orienting via the inferior parietal lobule. This stands in contrast to the superior parietal lobule route that characterizes visuospatial FEF connectivity Bedini & Baldauf (2021), a shift that may reflect the inherently multimodal nature of auditory spatial processing: auditory spatial localization operates within a distributed, multisensory reference frame rather than a retinotopic, egocentric one Rauschecker & Scott (2009).

5.1.2 The IFJa as a Semantic-Auditory Controller

The partial correlation profile of the IFJa reveals a complementary picture. After controlling for shared ROI variance, IFJa couples robustly with superior temporal sulcus regions central to auditory object identity processing (STSdp: left , right ; STSda: left , right ), with the Broca’s area subregions BA44 (bilateral ) and BA45 (bilateral ), and with early auditory association areas A4 and A5, while showing no substantial coupling with parietal spatial areas. In direct contrast to the FEF, the IFJa’s partial connectivity profile is predominantly language- and identity-oriented, and spatially disjoint from the parietal networks that define the dorsal where-stream.

This selectivity is consistent with the IFJa’s network membership and functional characterization. Per the resting-state fMRI parcellation of Ji et al. (2019, as reviewed in Bedini & Baldauf (2021)), the IFJa belongs to the language network, while the FEF is assigned to the cingulo-opercular network in that same partition — a classification our data directly support for the IFJa: its strongest auditory couplings are with the STS and Broca’s area. The concurrent coupling with early auditory association areas A4 and A5 suggests that IFJa may exert top-down modulation at an early stage of auditory feature extraction, biasing the processing of spectrotemporal features relevant to auditory object identity. The coupling with Broca’s area suggests coordination with the language working memory system, consistent with the IFJa’s proposed role in feature- and object-based attention encoding Bedini & Baldauf (2021). This pattern further resonates with the broader finding that top-down prefrontal control over auditory cortex is implemented via anticipatory alpha oscillations in object-based attention tasks De Vries & Baldauf (2021).

5.1.3 A Supramodal Prefrontal Architecture

Taken together, the complementary dissociation between FEF and IFJa connectivity profiles is consistent with a supramodal organization of prefrontal attentional control. The connectivity patterns suggest that the brain may not deploy dedicated, modality-specific attention controllers for each sensory stream; instead, the same two prefrontal hubs — FEF for spatial and IFJa for non-spatial control — appear to couple preferentially with corresponding auditory cortical regions in ways that parallel their known functional roles in the visual domain.

This is compatible with the view that the lateral prefrontal cortex organizes top-down attention according to a spatial/non-spatial axis that cuts across sensory modalities. Such a supramodal architecture would be computationally efficient — allowing a single prefrontal control system to flexibly coordinate attention across vision, audition, and potentially other modalities — and would be consistent with the evolutionary argument that visuospatial attention systems, which are phylogenetically older, are preserved in primates and subsequently recruited for the control of other sensory domains Bedini & Baldauf (2021). Whether these resting-state coupling patterns reflect genuine top-down control signals remains to be established with directed connectivity methods.

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5.2 Re-evaluating the auditory where stream

As Hickock und Poeppel proposed a How pathway which might be the language oatheway rolls talked about

1. Neighboring Areas

The Resulkts frm 4.5 show another dissoctation within the where stream where FEF and 55b share the labour of this stream.

  • this could

2. Subheading

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Notes & Scrapbook

Hier Dinge abladen, die noch keinen Platz im Text haben, damit der Schreibfluss nicht stoppt.

Where stream

This connectivity might be running via the SLF2 (Superior Longitudinal Fasculus), partly SLF3 (Bedini (n.d.)), which mediates spatial-motor and auditory communication.

PSL

While Dureux et al. (2024) demonstrate an absence of primary acoustic responsiveness in PSL, effective connectivity models (Rolls et al., 2023) reveal directional information flow from semantic temporal regions (STS) into PSL. This directional integration supports the conclusion that PSL does not process acoustic features, but rather receives fully abstracted semantic inputs…

FEF vs 55b

The isolated partial connectivity of Area 55b to early auditory association areas A4 and A5 reveals a functional fractionation within the dorsal prefrontal network. While the FEF relies on higher-order parietal (PF) and supramodal (STV) hubs for spatial coordinates, Area 55b maintains direct access to early acoustic features. This divergence perfectly aligns with the dual nature of the dorsal stream (Hickok & Poeppel, 2007): Area 55b acts as the ‘how’ relay for direct auditory-motor integration (e.g., vocal feedback), whereas the FEF acts as the pure ‘where’ controller, remaining decoupled from low-level acoustic features to operate on an abstract spatial map.

The Fractionation of the Dorsal Stream: Spatial vs. Language Sub-Networks

könnte zeigen, dass spatial stream und language zwei verschiedene sind, weil eben auch 55b mehr mit A4/A5 redet als FEF.

This prefrontal dissociation offers a refined perspective on the dorsal auditory pathway. While effective connectivity models (Rolls et al., 2023) and classical dual-stream theories (Hickok & Poeppel, 2007) postulate a dorsal sensorimotor and language-related stream, our data suggests this pathway is not functionally monolithic.

Instead, the dorsal stream bifurcates into distinct sub-networks in the prefrontal cortex. Area 55b acts as the primary sensorimotor interface for auditory-language processing, maintaining direct access to early auditory nodes (A4/A5) and classical language output regions. Concurrently, it communicates extensively with the FEF. Thus, the FEF remains an isolated, pure spatial controller, supplying abstract spatial coordinates to Area 55b without getting entangled in low-level acoustic or articulatory processing. This structural segregation allows the dorsal stream to manage complex language-motor feedback and spatial attention simultaneously, yet independently.

Resolving the A4/A5 Ambiguity: Semantic vs. Spatial Pathways

Within the dual-stream framework, the affiliation of early auditory association areas like A4 and A5 is frequently debated. Rolls et al. (2023) classify A5 as functionally ambiguous, noting its effective connectivity to spatial nodes (MT/MST), while simultaneously grouping it with semantic and language-related areas (STGa, PSL) that project to Broca’s area 44 (Rolls, 2022).

Our isolated prefrontal analysis effectively resolves this ambiguity. Despite their structural potential to feed into dorsal pathways via MT/MST, A4 and A5 lack any direct partial connectivity to the prefrontal spatial controller (FEF). Instead, their massive and exclusive coupling with the IFJa indicates that their primary top-down recruitment serves the ventral “what” stream. The IFJa likely targets these specific early auditory regions to extract auditory identity features and facilitate short-term working memory (Rolls et al., 2023), completely bypassing the spatial orienting network.

Limitations SFL

While the current analysis focused on the primary hubs FEF and IFJa, the prefrontal auditory-motor interface likely involves a broader cluster of dorsal regions, including the Superior Frontal Language Area (SFL) and Area 55b. Future studies should employ high-dimensional partial correlation models to investigate whether SFL provides a distinct contribution to syntactic processing that is independent of the spatial-motor control established by the FEF.