Unilateral injury of posterior parietal cortex and spatial learning in hooded rats

The influences of bilateral or unilateral injuries within the posterior parietal cortex (PPC) upon spatial learning in a water maze were examined in three experiments. Place-learning and response-learning were investigated in a four-alley 'Greek-cross' shaped water maze with extra-maze visual cues available. No differences were detected on any of several measures sensitive to learning between the lesion groups on the place-learning task. Microanalysis of behavior within trials revealed that animals with either bilateral or right unilateral PPC injuries committed significantly more total errors, initial alley entrance ('reference memory') errors, and re-entry ('working memory') errors in the response-learning paradigm than did either the control or left PPC-injured rats. No differences were detected between the latter two groups on these measures. Unilateral lesions resulted in asymmetrical placing responses ipsilateral to the injury 10 days after surgery whereas bilateral injuries resulted in asymmetrical placing with mixed directionality. The acquisition of the response-learning problem in the absence of visual cues was studied on animals prepared with unilateral lesions and housed post-operatively either in isolation or in a 'complex environment.' In the absence of visual cues both right and left PPC-injured rats committed more errors than sham controls, and differential post-surgical housing did not attenuate these impairments. These same animals were trained on the landmark navigation task. Although no differences appeared between the lesion groups, a generalized but transient facilitation of learning was observed in animals housed in the 'complex' environment. Unilateral injuries placed in sham controls failed to disturb retention of the landmark navigation strategy. Because none of the PPC-injured animals were deficient in the landmark task, a result which is contrary to observations in other laboratories, the influence of post-surgical recovery interval upon acquisition of the landmark navigation strategy was explored. Animals were prepared with right PPC injuries and trained following either a 5 or 35 day recovery interval. Only those animals limited to the short recovery interval proved to have a spatial deficit in the landmark task. It is concluded that injuries in the PPC of either hemisphere disturb egocentric spatial functions. However, animals with left PPC injuries are able to compensate by using allocentric visual cues if they are available. It is due to the special role played by the right PPC in complex visuospatial functions that animals with this injury are unable to compensate.     

Lateralization of emotionality in right parietal cortex of the rat.

Lesions of right parietal cortex in the rat increase activity in the open field compared with left parietal lesions, especially after section of the corpus callosum. Left or right motor or medial frontal cortex lesions do not have a lateralized effect. This evidence of a localized asymmetry between the cerebral hemispheres strongly implies that right parietal cortex has a role in emotionality in this species. Our findings suggest a functional similarity to right parietal cortex in man. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Digital agnosia and lesions of the parietal lobe

130 patients with focal brain damage have been submitted to non-verbal finger identification tasks. The results of this research can be summarized as follows: -when bilateral finger agnosia is studied with non-verbal tasks, no difference can be shown between right and left parietal lesions; -in left brain damaged patients the bilateral form of finger agnosia is generally due to large lesions involving the parietal lobe; -in right brain damaged patients the unilateral form of finger agnosia is almost always due to lesions centered on the parietal region.     

Deficits in landmark navigation and path integration after lesions of the interpeduncular nucleus.

Experiments were designed to determine the role of the interpeduncular nucleus (IPN) in 3 forms of navigation: beacon, landmark, and path integration. In beacon navigation, animals reach goals using cues directly associated with them, whereas in landmark navigation animals use external cues to determine a direction and distance to goals. Path integration refers to the use of self-movement cues to obtain a trajectory to a goal. IPN-lesioned rats were tested in a food-carrying task in which they searched for food in an open field, and returned to a refuge after finding the food. Landmark navigation was evaluated during trials performed under lighted conditions and path integration was tested under darkened conditions, thus eliminating external cues. We report that IPN lesions increased the number of errors and reduced heading accuracy under both lighted and darkened conditions. Tests using a Morris water maze procedure indicated that IPN lesions produced moderate impairments in the landmark version of the water task, but left beacon navigation intact. These findings suggest that the IPN plays a fundamental role in landmark navigation and path integration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial callosotomy and left-right response differentiation in the rat: Separate anterior and posterior facilitatory effects.

Earlier research demonstrated that complete section of the corpus callosum in the rat reduced the number of trials required to acquire a left–right response differentiation (LRRD). This study was designed to investigate whether the facilitatory effect on LRRD could be produced by section of an anatomical subdivision of the callosum. Rats with sections of the anterior or posterior corpus callosum mastered the LRRD task faster than sham Ss, but more slowly than rats with total callosal section; section of the middle portion of the callosum had no such effect. The partial facilitatory effects of anterior and posterior callosotomy appear to be independent and suggest that the callosal intermixing of lateral information, which contributes to left–right confusion, occurs at both the sensory and motor levels of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unilateral cortical lesions and paw preferences in cats.

Conducted 3 experiments to examine the effects of unilateral cortical lesions on the paw preferences of a total of 30 laboratory-reared mongrel and 3 Siamese 6-146 mo. old cats. Results show that paw preferences were reversed by ablations of the sensorimotor cortex contralateral to the preferred paw. These shifts in manual preferences remained constant throughout several mo. of postoperative testing. Ss with lesions in sensorimotor cortex, tested only after the acute effects of the cortical lesion subsided, showed a permanent reversal in their responses on object-displacement tasks, but not on simpler retrieval tasks. Extensive ablations of the posterior cortex, alone or in combination with section of the corpus callosum, had no significant effect upon paw preferences when the sensorimotor cortex was spared. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Recovery of sensorimotor function after frontal cortex damage in rats: Evidence that the serial lesion effect is due to serial recovery": Correction.

Reports an error in "Recovery of sensorimotor function after frontal cortex damage in rats: Evidence that the serial lesion effect is due to serial recovery" by John M. de Castro and Mark C. Zrull (Behavioral Neuroscience, 1988[Dec], Vol 102[6], 843-851). The plate for this article appears on page 996. The information should read, "Plate B. Photographs of the dorsal side of the brains showing the minimum (top) and maximum (bottom) extent of the lesion produced unilaterally in the sham group (left) and bilaterally in the single- and two-stage groups (right)." (The following abstract of the original article appeared in record 1989-28759-001.) Multiple-staged brain lesions produce fewer and smaller behavioral effects than single surgery (the serial lesion effect, SLE). Two hypotheses were tested: the reduced deficit hypothesis and the serial recovery hypothesis. Effects of lesions of the medial frontal cortex on sensorimotor behavior were investigated in 7 rats that received bilateral damage in single surgery, 16 in 2 unilateral stages separated by 3 wks, or 5 with unilateral damage followed 3 wks later by sham surgery. Unilateral damage produced deficits on the contralateral side in response to visual, tactile, and olfactory stimuli and impairments in roll-over and paw withdrawal responses. All impairments except visual placement recovered over the next 3 wks. A 2nd unilateral lesion on the contralateral side produced the same symptoms on the opposite side. Bilateral damage incurred in a single stage produced the same deficits on both sides. Because the effects of the 2nd unilateral lesion in the 2-stage group produced comparable contralateral effects to those produced in the single-stage group, but no reinstatement of ipsilateral deficits, the reduced deficit hypothesis was rejected. It was concluded that SLE occurred as a result of serial recovery of the deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mental space travel: Damage to posterior parietal cortex prevents egocentric navigation and reexperiencing of remote spatial memories.

The ability to navigate in a familiar environment depends on both an intact mental representation of allocentric spatial information and the integrity of systems supporting complementary egocentric representations. Although the hippocampus has been implicated in learning new allocentric spatial information, converging evidence suggests that the posterior parietal cortex (PPC) might support egocentric representations. To date, however, few studies have examined long-standing egocentric representations of environments learned long ago. Here we tested 7 patients with focal lesions in PPC and 12 normal controls in remote spatial memory tasks, including 2 tasks reportedly reliant on allocentric representations (distance and proximity judgments) and 2 tasks reportedly reliant on egocentric representations (landmark sequencing and route navigation; see Rosenbaum, Ziegler, Winocur, Grady, & Moscovitch, 2004). Patients were unimpaired in distance and proximity judgments. In contrast, they all failed in route navigation, and left-lesioned patients also showed marginally impaired performance in landmark sequencing. Patients' subjective experience associated with navigation was impoverished and disembodied compared with that of the controls. These results suggest that PPC is crucial for accessing remote spatial memories within an egocentric reference frame that enables both navigation and reexperiencing. Additionally, PPC was found to be necessary to implement specific aspects of allocentric navigation with high demands on spontaneous retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amygdalar Lateralization in Fear Conditioning: Evidence for Greater Involvement of the Right Amygdala.

The relative contribution of left and right amygdalae in the acquisition and retention of fear conditioning was investigated in rats. Pretraining bilateral electrolytic lesions blocked the acquisition of conditioned fear to tone and context, whereas unilateral lesions induced partial impairments with no left-right amygdala differences. In contrast, posttraining bilateral and unilateral lesions produced significant deficits in the retention of conditioned fear to tone and context. Although no left-right difference was observed to tone, the right amygdala lesions generated greater deficits in contextual fear than the left amygdala lesions. These results indicate that fear conditioning is partially disrupted with unilateral amygdalar lesions, but that the right amygdala has greater involvement than the left amygdala when conditioning occurs under a normal brain state. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovery of sensorimotor function after frontal cortex damage in rats: Evidence that the serial lesion effect is due to serial recovery.

[Correction Notice: An erratum for this article was reported in Vol 103(1) of Behavioral Neuroscience (see record 2008-10623-002). The plate for this article appears on page 996. The information should read, "Plate B. Photographs of the dorsal side of the brains showing the minimum (top) and maximum (bottom) extent of the lesion produced unilaterally in the sham group (left) and bilaterally in the single- and two-stage groups (right)."] Multiple-staged brain lesions produce fewer and smaller behavioral effects than single surgery (the serial lesion effect, SLE). Two hypotheses were tested: the reduced deficit hypothesis and the serial recovery hypothesis. Effects of lesions of the medial frontal cortex on sensorimotor behavior were investigated in 7 rats that received bilateral damage in single surgery, 16 in 2 unilateral stages separated by 3 wks, or 5 with unilateral damage followed 3 wks later by sham surgery. Unilateral damage produced deficits on the contralateral side in response to visual, tactile, and olfactory stimuli and impairments in roll-over and paw withdrawal responses. All impairments except visual placement recovered over the next 3 wks. A 2nd unilateral lesion on the contralateral side produced the same symptoms on the opposite side. Bilateral damage incurred in a single stage produced the same deficits on both sides. Because the effects of the 2nd unilateral lesion in the 2-stage group produced comparable contralateral effects to those produced in the single-stage group, but no reinstatement of ipsilateral deficits, the reduced deficit hypothesis was rejected. It was concluded that SLE occurred as a result of serial recovery of the deficits. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

The importance of fiber biopersistence and lung dose in determining the chronic inhalation effects of X607, RCF1, and chrysotile asbestos in rats

Rats were taught 1 of 3 types of multiple-object scene discrimination. Manipulations included either replacing (object based), displacing (space based), or replacing and displacing (object/space based) 1 object in the scene. Once trained, rats received hippocampal, parietal cortex, or cortical control lesions and then were retested. Parietal cortex- and hippocampal-lesioned rats displayed deficits on both the space and object/space tasks but not the object task. The hippocampal-lesioned group's deficit on the object/space task was only transient, whereas the impairments of the parietal cortex-lesioned rats were stable for both tasks. The parietal cortex-lesioned rats sustained difficulty with the object/space task may indicate an inability to switch cognitive strategies.     

Effects of hippocampal and parietal cortex lesions on memory for egocentric distance and spatial location information in rats

To assess the working memory system for egocentric distance and place information, delayed matching-to-sample (DMTS) go/no-go tasks were run for each rat. To assess the reference memory system, and to serve as a control for nonmemory deficits, successive discrimination go/no-go tasks were then conducted using the same rats. Rats with hippocampal, but not parietal cortex, lesions were impaired relative to controls in the working memory (DMTS) task for both egocentric distance and place information, although the deficit observed in the working memory task for egocentric distance information by rats with hippocampal lesions was mild. Neither hippocampal nor parietal cortex lesioned rats were impaired relative to controls in the reference memory (successive discrimination) task for either cue. The hippocampus appears to be involved in working memory for egocentric distance and in spatial location information, whereas the parietal cortex is not.     

Effects of hippocampal and parietal cortex lesions on the processing of multiple-object scenes.

Rats were taught 1 of 3 types of multiple-object scene discrimination. Manipulations included either replacing (object based), displacing (space based), or replacing and displacing (object/space based) 1 object in the scene. Once trained, rats received hippocampal, parietal cortex, or cortical control lesions and then were retested. Parietal cortex- and hippocampal-lesioned rats displayed deficits on both the space and object/space tasks but not the object task. The hippocampal-lesioned group's deficit on the object/space task was only transient, whereas the impairments of the parietal cortex-lesioned rats were stable for both tasks. The parietal cortex-lesioned rats sustained difficulty with the object/space task may indicate an inability to switch cognitive strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sound localizations after kainic acid lesions of the dorsal nucleus of the lateral lemniscus in the albino rat.

The ability of rats to localize sounds in space was determined before and after kainic acid lesions of the dorsal nucleus of the lateral lemniscus (DNLL). The rats were trained to approach a 45-msec noise burst delivered from loudspeakers on the right or left of midline. Lesions were made by local injection of kainic acid into the DNLL. Rats with unilateral lesions of DNLL were impaired in their postoperative ability to localize a single noise burst. Rats with bilateral lesions also had deficits in postoperative performance, but the severity of the impairment was not substantially greater than that expected from a unilateral lesion. The mean pre- and postoperative minimum audible angles were 14.8° and 40.4° for rats with complete unilateral lesions and 13.5° and 36.0° for rats with bilateral lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of unilateral hypothalamic manipulations on the sexual behaviors of rats.

Four experiments that assessed the contributions of each side of the hypothalamus to the control of sexual behavior found the following: (1) Exposing the left, but not the right, ventromedial nucleus to estrogen neonatally defeminized sexual behavior in female rats. This asymmetry did not reverse as sexual differentiation progressed. (2) Unilateral cuts lateral to the medial preoptic area disrupted mounting in females that had mounted regularly before surgery, when given testosterone. The deficits were greater when the cuts were on the left side, but a third of the females with unilateral cuts showed severe deficits regardless of the side. (3) Comparable cuts did not impair masculine sexual behavior in gonadally intact males. In fact, left-side cuts seemed to accelerate copulation in males. (4) Unilateral lesions of the ventromedial nucleus disrupted lordosis in female rats in an essentially all-or-none fashion. This effect did not vary with side. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recovery from a partial Kluver-Bucy syndrome in the monkey produced by disconnection.

Gave 6 rhesus monkeys a unilateral temporal lobectomy, contralateral occipital lobectomy, and section of the splenium of the corpus callosum. These operations produced some of the components of the Kluver-Bucy syndrome, particularly the hypoemotionality and visual defects. The visual defects recovered only to the objects tested. With the presentation of new objects the deficits reappeared and subsequently recovered. Cutting the optic tract on the side of the occipital lobectomy had varying consequences. Subsequent removal of the remaining temporal lobe did not produce a return of recovered visual deficits. Comparison was made with 2 bilateral temporal lobectomies and 2 normals on all tasks. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial attention deficits in humans: A comparison of superior parietal and temporal-parietal junction lesions.

Although clinical evidence of spatial attention deficits, such as neglect and extinction, is typically associated with lesions of the right temporal-parietal junction, recent evidence has suggested an important role for the superior parietal lobe. Two groups of patients, selected for lesions at the temporal-parietal junction including the superior temporal gyrus (TPJ group), or for lesions involving the parietal but not the superior temporal region (PAR group), performed cued-target detection tasks in 2 experiments. An extinction-like response time pattern was found for the TPJ but not the PAR group. In addition, both groups were able to use expectancy information, in the form of cue predictiveness, suggesting that separate mechanisms mediate exogenous and endogenous processes during attention shifts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The “good” limb makes the “bad” limb worse: Experience-dependent interhemispheric disruption of functional outcome after cortical infarcts in rats.

Following stroke-like lesions to the sensorimotor cortex in rats, experience with the ipsi-to-lesion (ipsilesional), “nonparetic”, forelimb worsens deficits in the contralesional, “paretic”, forelimb. We tested whether the maladaptive effects of experience with the nonparetic limb are mediated through callosal connections and the contralesional sensorimotor cortex. Adult male rats with proficiency in skilled reaching with their dominant (for reaching) forelimb received ischemic bilateral sensorimotor cortex lesions, or unilateral lesions, with or without callosal transections. After assessing dominant forelimb function (the paretic forelimb in rats with unilateral lesions), animals were trained with their nonparetic/nondominant forelimb or underwent control procedures for 15 days. Animals were then tested with their paretic/dominant forelimb. In animals with unilateral lesions only, nonparetic forelimb training worsened subsequent performance with the paretic forelimb, as found previously. This effect was not found in animals with both callosal transections and unilateral lesions. After bilateral lesions, training the nondominant limb did not worsen function of the dominant limb compared with controls. Thus, the maladaptive effects of training the nonparetic limb on paretic forelimb function depend upon the contralesional cortex and transcallosal projections. This suggests that this experience-dependent disruption of functional recovery is mediated through interhemispheric connections of the sensorimotor cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory, response selection, and effortful processing in rats with medial prefrontal lesions.

Examined the effects of lesions of the prelimbic area of the prefrontal cortex on acquisition and retention of nonmatching (NMTS) and matching-to-sample (MTS) tasks. 64 male rats participated. Both tasks involved a reference and a working memory component, but only working memory was impaired by the lesions. A comparison of the 2 tasks revealed quantitatively similar deficits in postoperatively trained rats. In preoperatively trained rats, however, the deficits were more important in the MTS task than in the NMTS task. In addition, an effect of interference between successive trials was observed in the NMTS task but not in the MTS task. Perseverative tendencies were observed in the MTS task only. Results suggest that prefrontal lesions induce working memory deficits as a result of poor temporal encoding and increased susceptibility to interference, and impair effortful processing, such as that engaged in response selection mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Entorhinal cortex lesions disrupt the transition between the use of intra- and extramaze cues for navigation in the water maze.

[Correction Notice: An erratum for this article was reported in Vol 117(5) of Behavioral Neuroscience (see record 2007-16848-001). The definitions "Present = intramaze landmark present during Stage 2" and "Absent = intramaze landmark absent during Stage 2" appear incorrectly in the caption to Figure 3. These terms and definitions should appear in the caption to Figure 4.] This study with rats examined the effects of excitotoxic lesions to the entorhinal cortex (EC) and hippocampus (HPC) on using extramaze and intramaze cues to navigate to a hidden platform in a water maze. HPC lesions resulted in a disruption to the use of extramaze cues, but not intramaze cues, whereas EC lesions had no effect on the use of these cues when they were encountered for the fast time. However, prior navigation training in which 1 type of cue was relevant disrupted navigation with the other type in rats with EC lesions. Results show that the EC contributes to the processing of spatial information, but that this contribution is most apparent when there is a conflict between 2 sources of navigational cues in the water maze. (PsycINFO Database Record (c) 2010 APA, all rights reserved)