The Intraparietal Sulcus of the Macaque and Connected Cortical Regions: Anatomical Parcellation and Connections Throughout the Hemisphere

Author: Lewis, James William

Year: 1997

Degree: Dissertation (Ph.D.)

Advisor: Van Essen, David C.

Committee Members: Bower, James M.; Van Essen, David C.; Allman, John Morgan; Andersen, Richard A.; Konishi, Masakazu

Option: Neurobiology

DOI: 10.7907/wsgr-wz25

Abstract

The general aim of this thesis was to better characterize anatomical connections of cortical areas of the intraparietal sulcus (IPS) in the macaque monkey, which is a region implicated in visual and somatosensory integration and motor intention. The anatomical organization of the IPS and regions with which it is connected was investigated with structural and connectional methods. The structure of the JPS and most other portions of the cortical hemisphere were analyzed with myelin and Nissl stains, plus immunohistochemical staining with the SMI-32 antibody. Primarily utilizing architectonic criteria defined in previous studies (with some refinements), parcellation maps were derived including up to 90 distinct cortical areas and zones. Retrograde tracers were injected into selected areas of the IPS (LIP, VIP, and AIP), superior temporal sulcus (MT and MST) and parietal lobule (7a and 7b), and the distribution of labeled cells was charted in relation to the architectonic parcellation maps. These data, together with geographical landmarks (sulcal curvature) were all displayed on computer-generated three-dimensional reconstructions and on cortical flat maps .

The analysis of architecture in the JPS revealed two newly identified regions : the lateral occipito-parietal zone, LOP, previously considered part of V3A; plus 7t, characterized by strong SMJ-32 immunoreactivity (previously considered part of area 7b or area 2). Additionally, medial and lateral subdivisions of area VIP are proposed (VIPm and VIPI), and significant modifications were introduced along portions of the superior temporal sulcus, and for somatosensory area 2.

Injections centered in visual area LIPv led to connections mainly with extrastriate visual areas, whereas injections centered in neighboring area VIP (VIPl and VIPm) led to stronger connections with somatosensory, polysensory, and motor areas. The visual-related connections of VIP! largely overlapped the patterns seen in LIPv injections. Sensorimotor projections to VIP included several somatotopically organized areas or regions, predominantly from the estimated hand, arm, and to a lesser extent the face representations. Strong connections originated from several bimodal and polysensory areas, supporting its involvement in multiple highly distributed hierarchical networks relating to the integration of visual, somatosensory (sensorimotor), vestibular, and possibly auditory information .

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