The effects of posterior parietal and posterior temporal cortical lesions on multimodal spatial and nonspatial competencies in rats.

Neuronal correlates of signal detection in the posterior parietal cortex of rats performing a sustained attention task

Ablations and local intracerebral infusions were used to determine the role of rat temporal association cortex (area Te2) in object recognition memory, so that this role might be compared with that of the adjacent perirhinal cortex (PRH). Bilateral lesions of Te2 impaired recognition memory measured by preferential exploration of a novel rather than a familiar object at delays ≥20 min but not after a 5-min delay. Local infusion bilaterally into Te2 of (1) CNQX to block AMPA/kainate receptors or (2) lidocaine to block axonal transmission or (3) AP5, an NMDA receptor antagonist, impaired recognition memory after a 24-h but not a 20-min delay. In PRH all these manipulations impair recognition memory after a 20-min as well as a 24-h delay. UBP302, a GluK1 kainate receptor antagonist, impaired recognition memory after a 24-h but not a 20-min delay, contrasting with its action in PRH where it impairs only shorter-term (20 min) recognition memory. Also in contrast to PRH, infusion of the muscarinic receptor antagonist scopolamine was without effect. The Te2 impairments could not readily be ascribed to perceptual deficits. Hence, Te2 is essential for object recognition memory at delays >5 or 20 min. Thus, at long delays both area Te2 and PRH are necessary for object recognition memory.

/pdf/contributions-of-area-te2-to-rat-recognition-memory-1fsqnay2fy.pdf

Contributions of area Te2 to rat recognition memory

The hypothesis to be discussed in this review is that posterior parietal cortex is directly involved in selecting relevant stimuli and filtering irrelevant distractors. The posterior parietal cortex receives input from several sensory modalities and integrates them in part to direct the allocation of resources to optimize gains. In conjunction with prefrontal cortex, nucleus accumbens, and basal forebrain cholinergic nuclei, it comprises a network mediating sustained attentional performance. Numerous anatomical, neurophysiological, and lesion studies have substantiated the notion that the basic functions of the posterior parietal cortex are conserved from rodents to humans. One such function is the detection and selection of relevant stimuli necessary for making optimal choices or responses. The issues to be addressed here are how behaviorally relevant targets recruit oscillatory potentials and spiking activity of posterior parietal neurons compared to similar yet irrelevant stimuli. Further, the influence of cortical cholinergic input to posterior parietal cortex in learning and decision-making is also discussed. I propose that these neurophysiological correlates of attention are transmitted to frontal cortical areas contributing to the top down selection of stimuli in a timely manner.

/pdf/posterior-parietal-cortex-dynamically-ranks-topographic-2z93c0sd5q.pdf

Posterior parietal cortex dynamically ranks topographic signals via cholinergic influence

Low frequency oscillations in rat posterior parietal cortex are differentially activated by cues and distractors.

Rats with sham, unilateral, or bilateral aspiration lesions of the posterior parietal cortex (PPC) were trained in a water T-maze to use flashing lights located along the starting alley (two each) and inner walls of the goal alleys (two each) to find a hidden escape platform. Thereafter, the performance of the spatial response was tested under several conditions. Rats with bilateral PPC lesions were significantly inferior to unilateral- and sham-injured rats in learning the “turn-signal” cued spatial task. Also, left-PPC-injured rats committed significantly more errors than did the control animals. After mastering the task, cue saliency was reduced and the amount of spatial discontiguity between the stimuli and escape site was increased in two stages. That is, the flashing light closest to the escape platform was turned off for one testing session. On the following day, animals were required to rely on information located within the starting alley to make the correct spatial response at the choice point. Animals with bilateral or left PPC lesions were significantly impaired on the task with cues located only in the starting alley. The animals were then tested with competing constant illumination of the lights on the side of the apparatus opposite the flashing-light cues. The performance of all animals dropped to chance and failed to improve with training. Finally, three of the sham-operated controls were retrained to criterion on the original discrimination and prepared with bilateral PPC injuries. Substantial savings was observed. The results reveal a greater role of the left PPC than the right in the use of local sensory cues for spatial navigation, and they show that the PPC is not the repository of the “engram” for this learned visuospatial behavior.

/pdf/turn-signal-utilization-by-rats-with-either-unilateral-or-4ki7ju2mx2.pdf

Turn-signal utilization by rats with either unilateral or bilateral posterior parietal cortex injuries

Previous research has shown that injuries of the inferotemporal cortex in monkeys result in impaired visual “categorical” perception. The goal of this project was to explore the possibility that a similar deficit might accompany injuries of the visual portions of the temporal cortex in rat, namely area TE2. Rats were prepared with bilateral TE2, partial striate, or sham cortical lesions and trained to discriminate between 17- (S+) and 3-cm (S−) diameter circles in a Y-shaped water maze. After criterion on this discrimination was reached, tests of relational perception were conducted with intermediate-size stimuli. The larger of the two stimulus pairs consistently cued the location of a submerged escape platform. Not only did rats with TE2 lesions learn the original discrimination as rapidly as normal rats and rats with partial striate lesions, but their performance paralleled that of the other groups on all tests of relational perception with intermediate stimuli. Several possible explanations for the discrepancy between the results observed here with rats and those observed with nonhuman primates are discussed.

https://link.springer.com/content/pdf/10.3758%2FBF03332127.pdf

Laura B. Williams

Papers

Turn-signal utilization by rats with either unilateral or bilateral posterior parietal cortex injuries

Visual relational (“categorical”) learning and performance by rats with temporal or partial striate cortical lesions