doi:10.1016/j.neunet.2003.08.002 
Copyright © 2003 Published by Elsevier Science Ltd.
2003 Special Issue
Language evolution: neural homologies and neuroinformatics
*1
a Neuroscience Program and USC Brain Project, University of Southern California, Los Angeles, CA 90089-2520, USA
b Department of Computer Science, University of Southern California, Los Angeles, CA 90089-2520, USA
Received 5 December 2002;
revised 14 August 2003;
accepted 14 August 2003. ;
Available online 22 October 2003.
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Abstract
This paper contributes to neurolinguistics by grounding an evolutionary account of the readiness of the human brain for language in the search for homologies between different cortical areas in macaque and human. We consider two hypotheses for this grounding, that of Aboitiz and García [Brain Res. Rev. 25 (1997) 381] and the Mirror System Hypothesis of Rizzolatti and Arbib [Trends Neurosci. 21 (1998) 188] and note the promise of computational modeling of neural circuitry of the macaque and its linkage to analysis of human brain imaging data. In addition to the functional differences between the two hypotheses, problems arise because they are grounded in different cortical maps of the macaque brain. In order to address these divergences, we have developed several neuroinformatics tools included in an on-line knowledge management system, the NeuroHomology Database, which is equipped with inference engines both to relate and translate information across equivalent cortical maps and to evaluate degrees of homology for brain regions of interest in different species.
Author Keywords: Brain evolution; Broca's area;Cortical maps; Homologies; Neural; Language; Neural mechanisms; Mirror neurons; NeuroHomology Database; Neuroinformatics; Neurolinguistics; Wernicke's area
Fig. 1. (A, B) Architectonic areas considered by Aboitiz and García in comparing the human (A) and the macaque (B). Numbers correspond to Brodmann's classification. AG, angular gyrus; AS, arcuate sulcus; CS, central sulcus; IPS, intra-parietal sulcus; PCS, precentral sulcus; PS, principal sulcus; SF, sylvian fissure; SMG, supramarginal gyrus; STS, superior temporal sulcus. (C). A side view of the left hemisphere of the macaque brain. Area 7b is also known as area PF. ((A) and (B) adapted from [Aboitiz and García, 1997]; (C) adapted from [Jeannerod, 1995].)
Fig. 2. Network of connectivity for language in the human brain proposed by [
Aboitiz and García, 1997], emphasizing the connection, which may largely correspond to the arcuate fasciculus, between SMG (supramarginal gyrus) and Broca's area. Area TE, which projects to area 45, may also participate in language processing. Connections between Tpt and Broca's area, and between Tpt and SMG (direct or indirect) have not been substantially confirmed in the monkey but (especially the latter) are proposed by Aboitiz and García to have developed in the hominid line. FGC, frontal granular cortex.
Fig. 3.
(A) Partial view of the FARS model: This emphasizes the role of IT (inferotemporal cortex; it includes areas like the TE of
Fig. 1C) and PFC (prefrontal cortex) in modulating F5's selection of an affordance. The idea is that AIP does not ‘know’ the identity of the object, but can only extract affordances (opportunities for grasping for the object consider as an unidentified solid); prefrontal cortex uses the IT identification of the object, in concert with task analysis and working memory, to help F5 select the appropriate action from ‘the AIP menu’. (B) ‘FARS modificato’ (based on the anatomy reviewed by [
Luppino and Rizzolatti, 2001]) suggests that FARS be modified to have PFC influence AIP rather than F5.
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Fig. 4. The MNS (Mirror Neuron System) model. (i) Top diagonal: Object features are processed by AIP to extract grasp affordances, these are sent on to the canonical neurons of F5 that choose a particular grasp. (ii) Bottom right: Recognizing the location of the object provides parameters to the motor programming area F4 which computes the reach. The information about the reach and the grasp is taken by the motor cortex M1 to control the hand and the arm. (iii) Essential elements for the mirror system: Bottom left are two schemas, one to recognize the shape of the hand of the actor being observed by the monkey whose brain we are interested in, and the other to recognize how that hand is moving. Just to the right of these is the schema for hand-object spatial relation analysis. It takes information about object features, the motion of the hand and the location of the object to infer the relation between hand and object. Just above this is the schema for associating object affordances and hand state. Together with F5 canonical neurons, this last schema (in PF=7b) provides the input to the F5 mirror neurons.
Fig. 5. (A) A recasting and extension (in part) of FARS Modificato (
Fig. 3B) designed for maximal congruence with the Aboitiz–García schematic of
Fig. 2. (B) A high-level view of the cumulative emergence of three fronto-parietal systems: choosing an action→recognizing an action→describing an action (in multiple modalities). This schematic builds on and modifies the schematic presented in [
Arbib, 2001] to maximize its congruence with (A).
Fig. 6. Cytoarchitectonic map of the caudal part of the macaque frontal lobe and possible homologies with human frontal cortex analysis (adapted from [
Rizzolatti and Arbib, 1998]). (A) Areas F7, 8 and 45 are areas mostly related to orienting behavior, while areas F2, F4, and F5 are areas mostly related to interactions with the external world. (B) Parcellation of portions of the human frontal cortex. The homologies based on cytoarchitectonics and electrical stimulation presented here are (F7,8,45)≈(6aα,8), (F2,F4)≈(6aβ,Inf.6), and F5≈(44,45). Sulcal equivalences based on data on the anatomical and functional organization of the premotor cortices in the two species are described in the text.
Fig. 7. Six different parcellation schemes of the agranular frontal cortex in the macaque, (a) the parcellation scheme provided by [
Brodmann, 1909] for Cercopithecus, (b) the parcellation scheme of [
Vogt and Vogt, 1919], (c) the map provided by Barbas and Pandya (1987), (d) the map of the macaque cortex of [
von Bonin and Bailey, 1947], (e) the cortical map of [
Preuss and Goldman-Rakic, 1991a] and (f) the parcellation map of Matelli (1985). [Adapted from Barbas and Pandya (1987), [
Matelli et al., 1991,
Vogt and Vogt, 1919,
Preuss and Goldman-Rakic, 1991a and
Rizzolatti et al., 2002].]
Fig. 8. The object-relationship schema (OR) of the NHDB systems.
Table 1. Ventral area 6: equivalent parcellation schemes
Table 2. Summary of homologies
Column 1 human; column 2 our canonical parcellation of macaque; column 3 criteria used to ground the homology; column 4+ or − for agreement with A&G; Column 5 + or − for agreement with MSH.
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