Outline 2.2 The Auditory Where (“Dorsal”) Stream
- 2.2.1 Debate
- Rauschecker vs Hickock&Poeppel (where vs how)
- beide modelle erklären
- 2.2.2 Anatomical Definition & Evidence
- Glasser area A4, A5, Parietal Cortex
- Rolls Group 3
- 7Am, 7PC und so anschauen und verbindung mit FEF
- PF, PFcm, PFop connections anschauen
- 2.2.3 Synthesis
- Defining the where-stream as spatial/motion stream (maybe motor?)
To-Do’s
- [x]
2.2 The Auditory Where (“Dorsal”) Stream
In contrast to the ventral ‘what’-stream, the dorsal pathway has no single, universally accepted functional definition. Depending on the theoretical framework, the dorsal stream has been characterized as a spatial localization system (Rauschecker & Scott (2009) - Nature Neuroscience), a sensorimotor integration pathway for speech (Hickok & Poeppel 2007 - Nature), or a system for processing affective prosody (Frühholz (2015) - NeuroImage). These accounts are not mutually exclusive — they reflect different levels of description of the same anatomical pathway. For the purposes of this thesis, the dorsal stream is treated as a spatial-motor system subserving both spatial orienting and audiomotor integration, with the FEF as its prefrontal top-down control hub.
2.2.1 Spatial Processing and Audio-Motor Integration
The spatial-motor characterization of the dorsal stream focuses on converging evidence across species and methodologies. Early support came from non-human primate studies demonstrating posterior auditory cortex sensitivity to sound location (Rauschecker & Afsahi (2023) - Journal of Comparative Neurology), complemented by neuroimaging showing right-lateralized temporo-parietal activation for spatial processing and the clinical observation that spatial neglect is more severe after right-hemisphere damage.
Ahveninen et al. (2006) extended this account by reporting a double dissociation between anterior ‘what’ and posterior ‘where’ processing, with dorsal stream responses emerging at 70–150ms post-stimulus onset. Rauschecker (2011) further noted a cross-species shift: whereas non-human primates recruit the dorsal stream primarily for spatial localization, humans appear to repurpose it for sensorimotor integration in speech.
This sensorimotor dimension was elaborated by Hickok and Poeppel (2004, 2007), who proposed that the dorsal stream maps acoustic speech signals onto articulatory representations, projecting from the STG via the Sylvian parietal temporal area (Spt) to frontal regions including Broca’s area. Rather than contradicting the spatial account, this suggests that the dorsal pathway supports a broader spatial-motor function — localizing sounds in space and coupling that information with motor action plans.
2.2.2 Anatomical Definition and Evidence
The auditory dorsal “where”-stream originates posterior to Herschl’s Gyrus in the planum temporale and STG (Ahveninen et al. (2006) - PNAS), and extends through auditory association areas before reaching parietal and frontal regions. A4 and A5 have EC to motion-sensitive areas MT and MST, which connect to superior parietal regions (7AL, 7Am, 7PC), consistent with a dorsal “where”-stream (Rolls et al. (2023) - Cerebral Cortex).
Further, the stream is characterized by Rolls’ (2022) Group 3, with connectivity to auditory belt regions, motion-sensitive visual areas, and somatosensory cortex.
The Frontal Eye Field (FEF), located in the caudal middle frontal gyrus ventral to the junction of the superior precentral sulcus (sPCS) and superior frontal sulcus (SFS), serves as a primary prefrontal node of the dorsal stream. The FEF contains a full topographic map of contralateral space, predominantly encodes spatial information (cited from Bedini (2023) - Brain Structure: Wang et al., 2015) and is a core node of the Dorsal Attention Network (DAN), mediating covert spatial attention, oculomotor control, and spatial working memory (Bedini & Baldauf (2021)). It is structurally connected via SLF1 and SLF2 to posterior parietal (LIPd) and temporoparietal cortices, embedding FEF anatomically in the “where”-stream.
The inferior parietal cortex (specifically PF, PFop and PFcm) corresponds to the gyrus of the classical IPL (Baker (2018)) and forms a critical relay station within the “where”-stream. Consistent with both Rauschecker & Scott (2009) - Nature Neuroscience and Hickok & Poeppel 2007 - Nature/Hickok & Poeppel (2004) - Cognition, the “where”-pathway projects from posterior superior temporal cortex (pST) through parietal cortex before reaching prefrontal regions. These inferior parietal areas function as higher-level coordinator between auditory and somatosensory areas such as OP1-4 and FOP1 (Glasser et al. (2016) - Nature). Additionally, posterior parietal areas may serve as a relay station to the premotor cortex (PMC).
Importantly, the IPL does not appear to be driven by acoustic stimuli (Rauschecker & Scott (2009) - Nature Neuroscience), rather the angular gyrus is involved in higher-order speech processing - along with clear prefrontal activation. This suggests, the inferior parietal cortex is involved in domain-general, language-related speech comprehension, rather than low-level auditory processing (Rauschecker & Scott (2009) - Nature Neuroscience).
Superior parietal regions 7AM, 7PC, 7AL receive direct auditory input from A4 and PBelt and may support tracking moving objects in space (Rolls et al. (2023) - Cerebral Cortex).
Finally, A5 shows additional connectivity to IFJa and IFSp (Rolls et al. (2023) - Cerebral Cortex), suggesting a partial overlap between “where” and “what” - a boundary that will be explored in the analyses in Chapter 4.
2.2.3 The “Where”-Stream as a Spatial-Motor System
Taken together the evidence reviewed in 2.2.1 and 2.2.2 suggests that the auditory “where”-stream does not map on one functional label only, but rather has a spatial-processing (Rauschecker & Scott (2009) - Nature Neuroscience) and a sensori-motor-integration (Hickok & Poeppel 2007 - Nature) function and reflect different levels within the same dorsal pathway.
Spatial processing in the temporo-parietal cortex is predominantly right-lateralized, consistent with the well-documented asymmetry of spatial neglect in patients with right-hemispheric damage (Rauschecker & Scott (2009) - Nature Neuroscience). In contrast, Hickok & Poeppel’s dorsal language model that links area Spt to Broca’s area is strongly left-dominant (Hickok & Poeppel 2007 - Nature). This hemispheric dissociation suggests that the “where”-stream operates in parallel in both hemispheres with different functional emphases: right-lateralized spatial and motion processing, and left-lateralized sensorimotor integration.
Further findings support this account, with caudal auditory belt area receiving somatosensory input (Rauschecker & Scott (2009) - Nature Neuroscience) and the inferior parietal cortex - especially PF, PFcm, PFop - serving as an interface between auditory, somatosensory and motor signals.
A related question concerns the dorsal language pathway, Rolls et al. (2023) - Cerebral Cortex report that connections of PBelt, A4 and A5 with BA44 may form a language-related dorsal pathway. However, this is not in conflict with a spatial-motor property: The same stream seems to perform spatial processing and sensorimotor feedback in the right hemisphere and articulatory and phonological processing on the left.
For the purpose of this thesis, the “where”-stream is therefore treated as a spatial-motor system: primarily organized around spatial and motor processing, with a left-dominant component that extends into speech production. The FEF serves as a primary prefrontal node, embedded anatomically in the DAN and structurally connected to the posterior parietal regions.
Notes & Scrapbook
Hier Dinge abladen, die noch keinen Platz im Text haben, damit der Schreibfluss nicht stoppt.
see also
2.0 Theoretical Background
2.1 The Auditory What (“Ventral”) Stream