Task-specific reversal of visual hemineglect following bilateral reversible deactivation of posterior parietal cortex: A comparison with deactivation of the superior colliculus

Abstract

The purpose of the present study was to compare and contrast behavioral performance on three different tasks of spatial cognition during unilateral and bilateral reversible deactivation of posterior parietal cortex. Specifically, we examined posterior middle suprasylvian (pMS) sulcal cortex in adult cats during temporary and reversible cooling deactivation. In Task 1, the cats oriented to a high-contrast, black visual stimulus moved into the visual field periphery. In Task 2, the cats oriented to a static light-emitting diode (LED). Task 3 examined the cats' ability to determine whether a black-and-white checkered, landmark box was closer to the right or left side of the testing apparatus. Following training on all tasks, cryoloops were implanted bilaterally within the pMS sulcus. Unilateral deactivation of pMS sulcal cortex resulted in virtually no responses to either moved or static stimuli and virtually no responses to landmarks presented in the contralateral hemifield, and a profound contralateral hemifield neglect was induced. Responses to stimuli and landmarks presented in the ipsilateral hemifield were unimpaired. Additive, bilateral cooling of the homotopic region in the contralateral hemisphere, but not an adjacent region, resulted in reversal of the initial hemineglect for the moved stimulus, yet induced a complete failure to orient to peripheral static LED stimuli. Bilateral cooling also reversed the contralateral neglect of the landmark, but then cats could not accurately determine position of the landmark anywhere in the visual field because performance was reduced to chance levels for all landmark loci in both hemifields. In this instance, as the contralateral neglect disappeared during bilateral cooling of pMS cortex, a new spatial discrimination deficit was revealed across the entire visual field. We conclude that pMS cortex contributes in multiple ways to the analyses of space, and that these contributions cannot be safely predicted from analyses of unilateral deactivations or from one task to another. Moreover, it is clear that other structures are capable of guiding orienting to high contrast, moved targets when pMS cortex is eliminated from brain circuitry. However, these same structures are incapable of supporting either orienting to static stimuli or analyses of spatial relations as tested with the landmark task. The impact of reversible deactivation of the superior colliculus on these same tasks is discussed.

Cerebral areas mediating visual redirection of gaze: Cooling deactivation of 15 loci in the cat

“…This region corresponds to all of areas PMLS and PLLS, dorsalmost DLS, the posteriormost portion of areas AMLS and ALLS (Palmer et al, 1978), and all of areas LS and PEV, the descriptors given by Grant and Shipp (1991) for the same region. This deactivation locus is illustrated in Lomber and Payne (2001a). Cooling of the PS cryoloops deactivated the anterior (dorsal) and posterior (ventral) banks of the posterior suprasylvian sulcus, which include areas DLS and VLS of Palmer et al (1978; Fig.…”

Localization of Function via Lesion Analysis

“…A classical example of such an interaction was given by Sprague (1966) resulting from large cortical visual lesions, can be reversed through additional removal of contralateral areas. This has been known as the Sprague effect, or paradoxical lesioning (Hilgetag, Lomber, & Payne, 2000;Lomber & Payne, 2001). To address these challenges, we have generalized the FCA to include high-dimensional, context-dependent interactions.…”

“…Although still infrequent, multiple lesion studies are now being performed in an increasing frequency in neuroscienti c studies of reversible inactivation (Lomber & Payne, 2001). However, these data are still of fairly limited magnitude.…”

Fabrication of an inexpensive, implantable cooling device for reversible brain deactivation in animals ranging from rodents to primates

“…The loops can be shaped to conform to the brain curvature and can be implanted within sulci, an important advantage. This device has been successfully utilized in studies of visual (Ponce et al 2008;Rushmore et al 2006), auditory Lomber et al 2007;Malhotra et al 2008;Meredith et al 2011;Payne and Lomber 1999), somatosensory (Alvarado et al 2007;Jiang and Stein 2003), and posterior parietal cortex (Lomber and Payne 2001) to examine alterations in both neural response and behaviors when a target field is deactivated.…”