Overt orienting in the rat: Parametric studies of cued detection of visual targets.

Covert shifts of visual attention in space have been quantified by measuring the effects of visual cues on the detection of visual targets in humans and monkeys maintaining visual fixation. These observations of "covert orienting" have provided important information regarding the neurobiology of visual attention in primates. This article describes a cued spatial target detection task for physically unrestrained rats. Valid cues (spatially contiguous with the target) enhanced target detection, and invalid cues (spatially discontiguous with the target) degraded target detection. Both visual and auditory cues were effective. These validity effects could not be explained by stimulus additivity or response preparation mechanisms, whereas a cue-independent "alerting effect" appeared to reflect response preparation. The effects compare favorably with primate work and suggest that this method may enable assessment of visual attention shifts in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of serial unilateral and serial bilateral visual cortex lesions on brightness discrimination relearning in rats.

In Exp I, 32 male Long-Evans hooded rats with serial unilateral (SU), serial bilateral (SB), or 1-stage bilateral (B) visual cortex lesions were compared in their retention of a preoperatively learned brightness discrimination. Groups SU and SB showed substantial savings of the brightness discrimination after the completed bilateral visual cortex removals, while Group B showed a complete postoperative loss. In Exp II with 34 rats, the effects of 2 additional types of serial bilateral visual cortex lesions were investigated. These involved the medial and then lateral aspects of visual cortex in 2 stages (ML), or vice versa (LM). Once again, the serial bilateral lesion groups (SB, ML, and LM) showed substantial savings of the discrimination after the completed lesion, while Group B showed a complete postoperative loss. Results indicate that the serial lesion effect is not specific to interhemispheric relationships. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of unilateral and bilateral caudate lesions on side preferences and timing behavior in rats.

Trained 24 female Sprague-Dawley rats to barpress on a DRL-16 sec schedule for water reinforcement. Ss were allowed to barpress on either of 2 levers (left and right). All Ss showed consistent side preferences. For the nonsignaled condition, normal rates were related to the strength of side preferences; lower rates and better timing performance were significantly correlated with greater preferences. Unilateral lesions in the caudate nucleus ipsilateral to side preferences facilitated performance during nonsignaled test sessions and increased side preferences during both. Unilateral lesions contralateral to side preferences impaired performance during nonsignaled test sessions and decreased side preferences during all sessions. Bilateral lesions transiently depressed response rates without significantly affecting timing performance or side preferences. It is suggested that side preferences are intimately involved in the control of behavior by internal stimuli and that an inherent asymmetry in nigrostriatal function underlies side preferences; the effect of a unilateral striatal lesion will depend on whether the lesion is placed in the more or less active striatum. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral vigilance following infusions of 192 IgG-saporin into the basal forebrain: Selectivity of the behavioral impairment and relation to cortical AChE-positive fiber density.

Rats were trained in a previously validated behavioral vigilance task that required them to detect visual signals of variable length and to discriminate signal from nonsignal events. Baseline performance was characterized by a signal length-dependent ability to score hits. a decline in hits over time, and a correct rejection rate of approximately 70% After the rats reached criterion performance in this task, the immunotoxin 192 IgG-saporin or its vehicle was infused into the area of the nucleus basalis/substantia innominata of the basal forebrain. Postoperative performance in lesioned rats was characterized by a decrease in their ability to detect signals while their ability to correctly reject nonsignals remained unaffected. The effect of the lesion did not recover in the course of over 180 sessions of postlesion testing. The overall performance of the rats correlated with acetylcholinesterase (AChE)-positive fiber density in all cortical areas measured except the cingulate and pyriform cortex. These findings help to elucidate the nature of the attentional impairments resulting from the loss of cortical cholinergic inputs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of patient recovery following unilateral and bilateral endoscopic preperitoneal herniorrhaphy

This study examined the effects of prenatal ethanol exposure on hippocampal theta activity in adult rats. Subjects were randomly selected from four prenatal treatment conditions: untreated, 0, 3, or 5 g/kg/day ethanol. At approximately 90 days of age, all subjects were surgically implanted with a bipolar electrode in the CA1 region of the hippocampus. Four epochs of hippocampal theta rhythm activity were recorded while the subjects were moving and four more while still, and a normalized theta score was computed and compared among groups. The 5 g/kg male group demonstrated a significantly higher theta score than controls, indicating either an increase in type I (movement-associated) theta and/or a decrease in type II (information-processing) theta activity. These results are consistent with prior reports that prenatal ethanol exposure alters hippocampal function and support clinical indications that monitoring the EEG of children may prove to be useful in the diagnosis of fetal alcohol syndrome and/or the detection of alcohol-related birth defects.     

Selective immunotoxic lesions of basal forebrain cholinergic cells: Effects on learning and memory in rats.

Male Long-Evans rats were given injections of either 192 IgG-saporin, an apparently selective toxin for basal forebrain cholinergic neurons (LES), or vehicle (CON) into either the medial septum and vertical limb of the diagonal band (MS/VDB) or bilaterally into the nucleus basalis magnocellularis and substantia innominata (nBM/SI). Place discrimination in the Morris water maze assessed spatial learning, and a trial-unique matching-to-place task in the water maze assessed memory for place information over varying delays. MS/VDB-LES and nBM/SI-LES rats were not impaired relative to CON rats in acquisition of the place discrimination, but were mildly impaired relative to CON rats in performance of the memory task even at the shortest delay, suggesting a nonmnemonic deficit. These results contrast with effects of less selective lesions, which have been taken to support a role for basal forebrain cholinergic neurons in learning and memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lesions in four parts of the basal forebrain change basic behaviour in rats

Subdivisions of the basal forebrain (BF) are postulated to be differently involved in the regulation of behavioural functions. We compared 16 parameters of rat open field behaviour before, 10 days and 60 days after lesions in four BF subdivisions, the anterior and the posterior nucleus basalis magnocellularis (NBMa, NBMp), the vertical and the horizontal diagonal band nucleus (VDB, HDB) with sham-operated control rats. Every lesion type caused a significantly different pattern of significant behavioural changes. VDB and NBMp lesions both produced different patterns of ambulatory and exploratory hyperactivity, whereas NBMa lesions caused hypoactivity. Changes after HDB lesions were relatively small. The rate of habituation also shared changes that differed according to the lesion site. These changes in basic unlearned behaviour are likely to interact with more complex functions such as cognitive processes, learning and memory.     

A comparison of the effects of depth rotation on visual and haptic three-dimensional object recognition.

A sequential matching task was used to compare how the difficulty of shape discrimination influences the achievement of object constancy for depth rotations across haptic and visual object recognition. Stimuli were nameable, 3-dimensional plastic models of familiar objects (e.g., bed, chair) and morphs midway between these endpoint shapes (e.g., a bed–chair morph). The 2 objects presented on a trial were either both placed at the same orientation or were rotated by 90° relative to each other. Discrimination difficulty was increased by presenting more similarly shaped objects on mismatch trials (easy: bed, then lizard; medium: bed, then chair; hard: bed, then bed–chair morph). For within-modal visual matching, orientation changes were most disruptive when shape discrimination was hardest. This interaction for 3-dimensional objects replicated the interaction reported in earlier studies presenting 2-dimensional pictures of the same objects (Lawson & Bülthoff, 2008). In contrast, orientation changes and discrimination difficulty had additive effects on within-modal haptic and cross-modal visual-to-haptic matching, whereas cross-modal haptic-to-visual matching was orientation invariant. These results suggest that the cause of orientation sensitivity may differ for visual and haptic object recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of estrogen replacement on choline acetyltransferase and trkA mRNA expression in the basal forebrain of aged rats

Testosterone reversed the age-related increase in glial fibrillary acidic protein (GFAP) in the male rat cerebellum, a brain region not generally associated with gonadal steroid hormone sensitivity. This supports the hypothesis that a decrease in circulating testosterone contributes to age-related increase in GFAP. These data also suggest that reductions in circulating gonadal steroids during aging could render the brain more susceptible to neurodegeneration and that hormone replacement therapy might have value in neurodegenerative disease intervention.     

Decrease in effects of muscimol on the dorsal root after repeated administration of diazepam in rats

In in situ experiments on spinal rats transected at the C1 level and on non-spinal rats, muscimol (3 mg/kg, i.v.) depolarized the primary afferent fibers and diazepam (3 mg/kg, i.v.) potentiated this effect of muscimol. When diazepam was given for 14 days, the effect of muscimol was significantly reduced in non-spinal rats. These findings suggest that diazepam probably interacts with GABA-ergic mechanisms more closely in supraspinal regions of the rat.     

A comparison of discrimination and reversal learning for olfactory and visual stimuli in aged rats.

The present study investigated age-related differences in discrimination and reversal learning for olfactory and visual stimuli in 6-month and 24-month-old rats. Rats were trained to discriminate between two pseudo-randomly selected odors or objects. Once each animal reached a criterion on discrimination trials, the reward contingencies were reversed. Young and aged rats acquired the olfactory and visual discrimination tasks at similar rates. However, on reversal trials, aged rats required significantly more trials to reach the learning criterion on both the olfactory and visual reversal tasks than young rats. The deficit in reversal learning was comparable for odors and objects. Furthermore, the results showed that rats acquired the olfactory task more readily than the visual task. The present study represents the first examination of age-related differences in reversal learning using the same paradigm for odors and objects to facilitate cross-modal comparisons. The results may have important implications for the selection of memory paradigms for future research studies on aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extensive reinnervation of the hippocampus by embryonic basal forebrain cholinergic neurons grafted into the septum of neonatal rats with selective cholinergic lesions

The immunodominant surface antigen of Toxoplasma gondii, surface antigen 1 (SAG1), was expressed in Escherichia coli as a fusion protein containing a majority of the SAG1 protein supplied with six histidyl residues in the N-terminal end. The recombinant protein was purified on a Ni-chelate column and then on a fast-performance liquid chromatography column and was in a nonreduced condition. It was recognized by T. gondii-specific human immunoglobulin G (IgG) and IgM antibodies as well as by a mouse monoclonal antibody (S13) recognizing only nonreduced native SAG1. Antibodies induced in mice by the recombinant SAG1 recognized native SAG1 from the T. gondii RH isolate in culture. Recombinant SAG1 is suitable for use in diagnostic systems for detecting anti-SAG1-specific IgG and IgM antibodies.     

Kynurenic acid protects against the neurochemical and behavioral effects of unilateral quinolinic acid injections into the nucleus basalis of rats.

Investigated whether unilateral coinjections of kynurenic acid (KYN) and quinolinic acid (QUIN) into the rat nucleus basalis magnocellularis (nbm) antagonized the effects of QUIN alone. Food-deprived rats were pretrained on an 8-arm radial maze, with four arms baited, until choice accuracy stabilized to ≥87% correct. Postoperatively, rats were tested on the radial maze for 32 consecutive days. Feeding behavior and locomotor activity were also measured to determine if nonassociative factors accounted for any observed behavioral deficits. QUIN lesions resulted in significantly more working and reference memory errors compared with sham-operated and coinjected animals, which did not differ significantly from each other. There were no reliable group differences in amount of food eaten or locomotor activity. The QUIN group had a reliable decrease in cortical choline acetyltransferase, with no significant changes for the sham and coinjected groups. Results confirm that KYN antagonizes the neurotoxic and mnemonic effects of QUIN alone and suggest that the memory deficits induced by nbm lesions cannot be solely attributed to changes in feeding or locomotor activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contribution of the cholinergic basal forebrain to proactive interference from stored odor memories during associative learning in rats.

E. De Rosa and M. E. Hasselmo (see record 2000-13470-003) demonstrated that 0.25 mg/kg scopolamine (SCOP) selectively increased proactive interference (PI) from stored odor memories during learning. In the present study, rats with bilateral cholinergic lesions limited to the horizontal limb of the diagonal band of Broca, made with 192 IgG-saporin, were not impaired in acquiring the same olfactory discrimination task relative to control rats. Rats with bilateral IgG-saporin lesions to all basal forebrain cholinergic nuclei (BF) also showed no impairment in acquisition of this task. However, the BF-saporin rats were hypersensitive to oxotremorine-induced hypothermia and demonstrated an increased sensitivity to PI following a low dose of SCOP (0.125 mg/kg) relative to control rats. The results suggest that weaker cholinergic modulation after cholinergic BF lesions makes the system more sensitive to PI during blockade of the remaining cholinergic elements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A possible role for cholinergic neurons of the basal forebrain and pontomesencephalon in consciousness

Excitation at widely dispersed loci in the cerebral cortex may represent a neural correlate of consciousness. Accordingly, each unique combination of excited neurons would determine the content of a conscious moment. This conceptualization would be strengthened if we could identify what orchestrates the various combinations of excited neurons. In the present paper, cholinergic afferents to the cerebral cortex are hypothesized to enhance activity at specific cortical circuits and determine the content of a conscious moment by activating certain combinations of postsynaptic sites in select cortical modules. It is proposed that these selections are enabled by learning-related restructuring that simultaneously adjusts the cytoskeletal matrix at specific constellations of postsynaptic sites giving all a similar geometry. The underlying mechanism of conscious awareness hypothetically involves cholinergic mediation of linkages between microtubules and microtubule-associated protein-2 (MAP-2). The first reason for proposing this mechanism is that previous studies indicate cognitive-related changes in MAP-2 occur in cholinoceptive cells within discrete cortical modules. These cortical modules are found throughout the cerebral cortex, measure 1-2 mm2, and contain approximately 10(3)-10(4) cholinoceptive cells that are enriched with MAP-2. The subsectors of the hippocampus may function similarly to cortical modules. The second reason for proposing the current mechanism is that the MAP-2 rich cells throughout the cerebral cortex correspond almost exactly with the cortical cells containing muscarinic receptors. Many of these cholinoceptive, MAP-2 rich cells are large pyramidal cell types, but some are also small pyramidal cells and nonpyramidal types. The third reason for proposing the current mechanism is that cholinergic afferents are module-specific; cholinergic axons terminate wholly within individual cortical modules. The cholinergic afferents may be unique in this regard. Finally, the tapering apical dendrites of pyramidal cells are proposed as primary sites for cholinergic mediation of linkages between MAP-2 and microtubules because especially high amounts of MAP-2 are found here. Also, the possibility is raised that muscarinic actions on MAP-2 could modulate microtubular coherence and self-collapse, phenomena that have been suggested to underlie consciousness.     

Opioidlike effects of intraoral infusions of corn oil and polycose on stress reactions in 10-day-old rats.

The effects of intraoral infusions of corn oil and the polysaccharide Polycose on behavioral reactions to pain and to social isolation were studied in 10-day-old albino rat pups. Both substances significantly increased paw-lift latencies (a measure of pain response) and reduced the number of ultrasonic vocalizations (a measure of isolation distress). Moreover, elevated pain thresholds were normalized by naltrexone (0.25 mg/kg) pretreatment, and the quieting of vocalizations was abolished by pretreatment. These findings indicate an interaction between ingestion, pain, and distress systems in neonatal rats and suggest that fats and polysaccharides influence these systems via endogenous opioids. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Plastic changes in the cholinergic innervation of the rat cerebral cortex after unilateral lesion of the nucleus basalis with alpha-amino-3-OH-4-isoxozole propionic acid (AMPA): effects of basal forebrain transplants into neocortex

Since the beginning of the twentieth century, different methods to control the quality of analyses have been in use. The advent of modern analytical instruments has prompted the need for such controls. In a modern clinical chemistry laboratory, quality control is an important tool to maintain the high predictive value of the methods in use. In this article the most important aspects of quality control are outlined. For further study, I recommend the references listed at the end of this article.     

Neonatal 192 IgG-saporin lesions of basal forebrain cholinergic neurons selectively impair response to spatial novelty in adult rats.

The role of the developing cholinergic basal forebrain system on cognitive behaviors was examined in 7 day-old rats by giving lesions with intraventricular injections of 192 IgG-saporin or saline. Rats were subjected to passive avoidance on postnatal days (PND) 22–23, water maze testing on PND 50–60, and a open-field test (in which reactions to spatial and object novelty were measured) on PND 54. Behavioral effects of the lesions were evident only in the open-field test with 5 objects. Unlike controls, the lesioned rats did not detect a spatial change after a displacement of 2 of the 5 objects. Control and lesioned rats, however, showed comparable novelty responses to an unfamiliar object. Lesion effectiveness was confirmed by 75% and 84% decreases in choline acetyltransferase activity in cortex and hippocampus. These results suggest that the developing cholinergic system may be involved in spatial information processing or attention to spatial modifications. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Frames of reference in unilateral neglect and visual perception: A computational perspective.

Neurological patients with unilateral neglect fail to orient and respond to stimuli on one side, typically the left. A key research issue is whether neglect is exhibited with respect to the left side of the viewer or of objects. When deficits in attentional allocation depend not merely on an object's location with respect to the viewer but on the object's intrinsic extent, shape, or movement, researchers have inferred that attention must be operating in an object-based frame of reference. Simulations of a view-based connectionist model of spatial attention prove that this inference is not logically necessary: Object-based attentional effects can be obtained without object-based frames. The model thus explains away troublesome phenomena for view-based theories of object recognition. (PsycINFO Database Record (c) 2011 APA, all rights reserved)