In the Light of Evolution Volume VI: Brain and Behavior (2013) / Chapter Skim
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15 Integration of Faces and Vocalizations in Ventral Prefrontal Cortex: Implications for the Evolution of Audiovisual Speech--Lizabeth M. Romanski
15 Integration of Faces and Vocalizations in Ventral Prefrontal Cortex: Implications for the Evolution of Audiovisual Speech--Lizabeth M. Romanski
Pages 273-292
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From page 273... ...
Anterograde and retrograde tracing studies show that macaque VLPFC receives afferents from the superior and inferior temporal gyrus, which provide complex auditory and visual information, respectively. Moreover, physiological studies have shown that single neu rons in VLPFC integrate species-specific face and vocal stimuli.
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From page 274... ...
VENTRAL PFC: ANATOMICAL CONSIDERATIONS Organization of VLPFC The frontal lobe of the macaque monkey has been studied extensively with anatomical, electrophysiological, and functional methodologies compared with other primate species. The area of the VLPFC, also referred to as the inferior convexity of the PFC, in the macaque monkey, includes the cortical region ventral to the principal sulcus and anterior to the inferior limb of the arcuate sulcus (Fig.
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From page 275... ...
(B) Map of the human brain color-coded to match the corresponding homologous regions in the macaque brain shown in D
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From page 276... ...
mulatta individuals. As explained later, the IPD is the primary location in which auditory responsive neurons and audiovisual responsive cells have been reliably located in several studies, and may be a critical landmark for delineating the functional auditory responsive prefrontal region in macaques.
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From page 277... ...
, which covers the surface of the ventrolateral convexity and extends onto the lateral orbital surface as far as the lateral orbital sulcus, can be distinguished from area 46 by its more heavily myelinated appearance. The disappearance of the large layer III pyramidal cells marks the transition from area 45 to area 12vl.
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From page 278... ...
Auditory Projections to PFC In contrast to the visual pathways, the prefrontal targets of central auditory pathways have not been studied as extensively despite the accepted role of the frontal lobe in language. In early anatomical studies, lesion/degeneration techniques were used to reveal projections from the caudal superior temporal gyrus (STG)
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From page 279... ...
They determined that rostral and ventral PFC receives projections from the anterior auditory association cortex (areas AL and anterior parabelt) and caudal prefrontal regions are innervated by posterior auditory cortex (areas CL and caudal parabelt; Fig.
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From page 280... ...
Rostral and VLPFC receives stronger innervation from the anterior belt and adjacent parabelt regions whereas dorsolateral PFC receives the greatest innervation from caudal auditory belt and parabelt regions. Adapted from Romanski et al.
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From page 281... ...
(1993) showed that DLPFC neurons were selectively engaged by visuospatial memory tasks and VLPFC neurons were selective for color, shape, or type of visual objects.
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A B 282 Q C D 70 spike/sec 0 -500 0 1000 1500 2000 Q
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From page 283... ...
and ventral premotor cortex are more active during phonological processing and speech production. The precise neuronal mechanisms that occur in the frontal lobe during the processing of complex auditory information are unknown but might be indirectly assessed with neurophysiological recordings in animals with similar ventral frontal lobe regions, such as macaque monkeys.
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From page 285... ...
The localization of this auditory processing area to the ventral prefrontal region of Old World monkeys suggests a functional similarity between it and human language FIGURE 15.4 Auditory responsive neurons in VLPFC. A single-cell example of responses to four different vocalization stimuli is shown in the top part of the figure.
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From page 286... ...
Any overlap in these auditory and visual responsive zones could thus be sites for multisensory integration of complex auditory and visual information. As neurons in this region are face- and vocalizationresponsive, multisensory neurons in the macaque VLPFC might integrate face and vocal information.
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From page 287... ...
Cell in A exhibited multisensory enhancement and cell in B exhibited multisensory suppression. Locations where multisensory stimuli (open squares)
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From page 288... ...
have noted responsive neurons within this arcuate region as well as in the more commonly recorded principal sulcus region. A smaller, potentially more specialized pool of multisensory neurons is located in VLPFC, anterior and lateral to the first pool (Fig.
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From page 289... ...
The linking, or integrating of face and vocal information, in the macaque monkey frontal lobe could be seen as a precursor to the more complex functions that the IFG performs in the human brain whereby abstract concepts are united with images and sounds. In the human brain, words, sounds, gestures, and visual images are each integrated with meaning and with each other (Xu et al., 2009)
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From page 290... ...
. Recordings of macaque VLPFC neurons show that incongruent stimuli also evoke an increase or a decrease in neuronal activity depending on the original response to bimodal stimuli (Romanski and Diehl, 2011)
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From page 291... ...
VLPFC cells respond optimally to face and vocalization stimuli and exhibit multisensory enhancement or suppression when facevocalization stimuli are combined. Thus, the ventral frontal lobe of nonhuman primates may have some basic functional homologies to the human frontal lobe, although more evidence from additional primate species is needed.
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