Rhinal cortex lesions and object recognition in rats.

Tested 11 male rats with bilateral lesions of lateral entorhinal cortex and perirhinal cortex on a nonrecurring-items delayed nonmatching-to-sample (DNMS) task resembling the one that is commonly used to study object recognition (OR) in monkeys. The rats were tested at retention delays of 4, 15, 60, 120, and 600 sec before and after surgery. After surgery, they displayed a delay-dependent deficit: They performed normally at the 4-sec delay but were impaired at delays of 15 sec or longer. The addition of bilateral amygdala lesions did not increase their DNMS deficits. The present finding of a severe DNMS deficit following rhinal cortex damage is consistent with the authors' previous finding that bilateral lesions of the hippocampus cause only mild DNMS deficits in rats unless there is also damage to rhinal cortex (D. G. Mumby et al, 1992). These findings add to accumulating evidence that the rhinal cortex, but not the amygdala, plays a critical role in OR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scopolamine impairs object exploration but not habituation in rats

Memory of a novel object was examined in saline (Sal) and scopolamine (Scopo) treated rats (1.0 mg/kg). Scopo rats showed lower overall exploration time than Sal rats, resulting mainly from shorter durations per contact. In a second exposure to the same object, after 1 min or 20 min interval, both groups displayed marked decrease of exploration indicating between-session habituation. The shorter time spent by Scopo rats on investigation of an object during a single approach might be interpreted as a deficit in maintenance of attention. Nevertheless, Scopo rats were able to acquire sufficient information for the retention during 20 min interval, as indicated by habituation, which is an elementary index of memory.     

MPTP lesion causes neuroinflammation and deficits in object recognition in Wistar rats.

Animal models of Parkinson’s disease with dementia would greatly facilitate research into the underlying causes of this disorder. Here, we showed that bilateral infusion of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into the substantia nigra pars compacta (SNc) of Wistar rats caused degeneration of nigrostriatal dopaminergic neurons, cell loss in the hippocampal CA1 area, as well as microglial activation and increase of interleukin-2 levels in several brain regions. In addition, increase of anxiety-like behavior and impairment of object recognition were observed in the MPTP-lesioned rats. These findings suggest that neuroinflammation may contribute to MPTP-induced neurodegeneration and behavioral deficits, which is suggested as an animal model of Parkinson’s disease dementia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Coordinate transformations in object recognition.

A basic problem of visual perception is how human beings recognize objects after spatial transformations. Three central classes of findings have to be accounted for: (a) Recognition performance varies systematically with orientation, size, and position; (b) recognition latencies are sequentially additive, suggesting analogue transformation processes; and (c) orientation and size congruency effects indicate that recognition involves the adjustment of a reference frame. All 3 classes of findings can be explained by a transformational framework of recognition: Recognition is achieved by an analogue transformation of a perceptual coordinate system that aligns memory and input representations. Coordinate transformations can be implemented neurocomputationally by gain (amplitude) modulation and may be regarded as a general processing principle of the visual cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perirhinal cortex ablation in rats selectively impairs object identification in a simultaneous visual comparison task.

In Experiment 1, rats discriminated among computer-generated visual displays (scenes) comprising 3 different shapes (objects). One constant scene (unrewarded) appeared on every trial together with a trial-unique variable scene (rewarded). Four types of variable scene were intermingled: (a) unfamiliar objects in different positions from the constant; (b) unfamiliar objects in same positions as the constant; (c) same objects as the constant in different positions; (d) same objects and positions, recombined. Aspiration lesions of perirhinal cortex impaired performance with type (b) only. Experiment 2 tested spatial delayed nonmatching-to-sample. The perirhinal group were impaired nonsignificantly, and less than fornix-transected rats in an earlier study. Rats' perirhinal cortex, like monkeys', subserves object identification in the absence of memory requirement but does not contribute substantially to hippocampal system spatial memory function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired object recognition memory in rats following ischemia-induced damage to the hippocampus.

Transient cerebral ischemia can produce irreversible neuronal damage and permanent learning and memory impairments in humans. This study examined whether ischemia-induced brain damage in rats results in impairments on the delayed nonmatching-to-sample (DNMS) task, a nonspatial recognition task analogous to tests on which amnesic patients display impairments. Male Wistar rats received either sham surgery or 20-min forebrain ischemia induced by bilateral carotid occlusion and hypotension. Four weeks after surgery, ischemic rats were significantly impaired in both learning and performing the DNMS task at retention intervals up to 5 min. Extensive presurgical training did not reduce this impairment. Observable cell loss in ischemic rats was limited to CA1 pyramidal neurons and a subset of cells in the dentate gyrus. Results indicate that ischemic damage to the hippocampus in rats results in recognition memory deficits similar to those produced by ischemic damage in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Causality of parenchymal and vascular changes in rats with experimental thiamine deficiency encephalopathy

The causality of vascular and parenchymal damage to the central nervous system (CNS) was examined in rats with thiamine deficiency. Male Sprague-Dawley rats were divided into two groups; one was given a thiamine-deficient diet (TDD) and injected intraperitoneally with 10 micrograms/100 g bodyweight pyrithiamine (PT) in order to analyze morphometrically the topographical and sequential relationship between vascular and parenchymal changes and vasodilatation, and the other was given a TDD and 50 micrograms/100 g bodyweight PT in order to determine hemorrhagic sites using serial sections. Histological examination showed that spongiotic change occurred selectively in the inferior colliculus (100%) from day 19, and thereafter in the thalamus (95%), mammillary body (50%) and nuclei olivaris and vestibularis of the pons (25%), with or without hemorrhage. Simultaneously, glycogen accumulation was also observed in these regions at a frequency similar to that of hemorrhage. Ultrastructurally, however, hydropic swelling of astrocytic and neuronal processes without glycogen accumulation was observed as early as day 9 in the inferior colliculus, at which time an increase of glial fibrillary acidic protein-positive processes was also recognized. The superior colliculus was completely spared. From day 22 vasodilatation of the inferior colliculus occurred, concomitantly with bodyweight loss and neurological symptoms. Twenty-two examined hemorrhages, which occurred in the thalamus and inferior colliculus, were distributed along the arterioles or capillaries on the arterial side. In conclusion, the morphological CNS changes caused by thiamine deficiency with administration of low-dose PT in rats begin as hydropic swelling of neuronal and astrocytic processes, followed by hemorrhage and, thereafter, by vasodilation. The predilection for hemorrhage on the arterial side without parenchymal changes suggests that petechial hemorrhage is not simply secondary to parenchymal changes, but is due to hemodynamic change resulting from thiamine deficiency-induced vascular dysfunction.     

Biochemical measures of thiamine deficiency

Human T cell lymphotropic virus type I (HTLV-I)-induced immunosuppression has been suggested to explain the occurrence of crusted scabies in HTLV-I-infected patients. HTLV-I is the etiologic agent of adult T cell leukemia/lymphoma (ATL). Crusted scabies diagnosed in 6 HTLV-I-seropositive patients was studied to look for an association with ATL. Four of the 6 either had concomitant ATL when crusted scabies was diagnosed or developed ATL a few months later. These findings suggest that the occurrence of crusted scabies in patients seropositive for HTLV-I could represent a sign of marked immunosuppression related to ATL.     

Effects of outline shape in object recognition.

The use of outline shape in recognizing objects was investigated in 4 experiments. In Experiment 1, participants matched a shaded image to either another shaded image or a silhouette. In Experiment 2, they initially named shaded images; later they named either shaded images or silhouettes. Performance in both experiments was predicted by changes in the outline shape of the stimuli. The same matching (Experiment 3) and priming (Experiment 4) paradigms were then used to investigate recognition with objects that were rotated between presentations so as to change the outline shape of the object. Recognition was predicted by changes to outline shape. These results place constraints on models of object recognition and are most compatible with viewpoint-dependent models of recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of amygdaloid and amygdaloid-hippocampal lesions on object recognition and spatial working memory in rats.

Neurotoxic lesions of the amygdala did not affect the postoperative acquisition of a nonspatial test of object recognition (delayed nonmatching to sample) even when retention delays were increased from 0 sec to 20 or 60 sec, or when test stimuli were deliberately repeated within a session. Although these amygdaloid lesions did not alter forced-choice spatial alternation, they slightly increased neophobic responses to novel foods and environments. In contrast, combined amygdalohippocampal (A?+?H) lesions impaired performance on the object recognition task when the retention intervals were increased beyond 0 sec and when test stimuli were repeated within a session. The A?+?H rats were also severely impaired on the spatial alternation task, and they showed reduced neophobia. Comparisons with a previous study show that damage to the amygdala or hippocampus does not affect object recognition, whereas A?+?H damage produces clear deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object recognition and object orientation in Alzheimer's disease.

There are a wide variety of neuropsychological deficits in Alzheimer's disease (AD), among which are disorders of visual perception and spatial cognition. The present study investigated the ability of 20 mildly to moderately deteriorated patients with AD (and 174 age- and education-matched controls) on tasks that required them to visually identify, provide the canonical orientation of, and mentally rotate common objects. Some 85% of the AD patients performed poorly on all tasks. The authors were able to identify a small number of individual patients whose pattern of performance represented double dissociations between recognizing objects and knowing their canonical orientation. These findings are interpreted in the context of previous findings, especially as to whether information relating to an object's orientation and identity is independently coded. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of perceptual load in object recognition.

Predictions from perceptual load theory (Lavie, 1995, 2005) regarding object recognition across the same or different viewpoints were tested. Results showed that high perceptual load reduces distracter recognition levels despite always presenting distracter objects from the same view. They also showed that the levels of distracter recognition were unaffected by a change in the distracter object view under conditions of low perceptual load. These results were found both with repetition priming measures of distracter recognition and with performance on a surprise recognition memory test. The results support load theory proposals that distracter recognition critically depends on the level of perceptual load. The implications for the role of attention in object recognition theories are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired allocentric spatial working memory and intact retrograde memory after thalamic damage caused by thiamine deficiency in rats.

Rats were tested on an allocentric-spatial working-memory task—delayed matching-to-place (DMTP) in a water maze—before and after either pyrithiamine-induced thiamine deficiency (PTD) or electrolytic lesions of the lateral internal medullary laminae (IML), an area damaged by PTD. DMTP trials consisted of paired swims, with the escape platform in a new location on each trial. PTD rats were impaired at retention delays of 300 s, but not at delays of 4 or 60 s. Rats with IML lesions performed normally at all delays. Both groups displayed normal retention of object-discrimination problems that they had learned at different intervals before treatment (5 weeks, 3 weeks, and 1 week). The results suggest that PTD causes delay-dependent deficits of allocentric spatial working memory and that damage outside the IML is probably responsible. Neither PTD-induced diencephalic damage nor restricted IML lesions appear to produce a global retrograde amnesia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perirhinal cortex ablation impairs visual object identification

Impairments in both recognition memory and concurrent discrimination learning have been shown to follow perirhinal cortex ablation in the monkey. The pattern of these impairments is consistent with the hypothesis that the perirhinal cortex has a role in the visual identification of objects. In this study we compared the performance of a group of three cynomolgus monkeys with bilateral perirhinal cortex ablation with that of a group of three normal controls in two tasks designed to test this hypothesis more directly. In experiment 1 the subjects relearned a set of 40 familiar concurrent discrimination problems; the stimuli in each trial were digitized images of real objects presented in one of three different views. After attaining criterion they were tested on the same problems using similar, but previously unseen, views of the objects. In experiment 2 the subjects were tested on their ability to perform 10 of these familiar discriminations with each problem presented in the unfamiliar context of a digitized image of a unique complex scene. The subjects with ablations were significantly impaired on both tasks. These results demonstrate that the role of the perirhinal cortex is not restricted to memory, and they support the hypothesis that the perirhinal cortex is involved in visual object identification. We suggest that the perirhinal cortex is crucially involved in processing coherent concepts of individual objects. A deficit of this nature could underlie the pattern of impairments that follow perirhinal cortex damage in both visual object recognition memory and visual associative memory.     

Context- but not familiarity-dependent forms of object recognition are impaired following excitotoxic hippocampal lesions in rats.

Dual-process models of recognition memory in animals propose that recognition memory is supported by two independent processes that reflect the operation of distinct brain structures: a familiarity process that operates independently of the hippocampus and a context-dependent (episodic) memory process that is dependent on the hippocampus. A novel variant of an object recognition procedure was used to examine this proposal. Healthy rats showed a preference for exploring a novel object rather than a familiar object: a familiarity-dependent recognition effect. They also showed a preference for exploring a familiar object that was presented in a different spatiotemporal context rather than a familiar object that was presented either in a different spatial or temporal context: a context-dependent form of recognition that is sensitive to "what" object has been presented "where" and "when." Rats with excitotoxic hippocampal lesions showed the familiarity-dependent but not the context-dependent form of recognition. The results provide support for dual-process theories of recognition memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Color improves object recognition in normal and low vision.

Does color improve object recognition? If so, is the improvement greater for images with low spatial resolution in which there is less shape information? Do people with low visual acuity benefit more from color? Three experiments measured reaction time (RT) and accuracy for naming food objects displayed in 4 types of images: gray scale or color, and high or low spatial resolution (produced by blur). Normally sighted Ss had faster RTs with color, but the improvement was not significantly greater for images with low spatial resolution. Low vision Ss were also faster with color, but the difference did not depend significantly on acuity. In 2 additional experiments, it was found that the faster RTs for color stimuli were related to objects' prototypicality but not to their color diagnosticity. It was concluded that color does improve object recognition, and the mechanism is probably sensory rather than cognitive in origin. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic versus perceptual influences of color in object recognition.

The influence of color as a surface feature versus its influence as stored knowledge in object recognition was assessed. Participants decided whether a briefly presented and masked picture matched a test name. For pictures and words referring to similarly shaped objects, semantic color similarity (SCS) was present when picture and word shared the same prototypical color (e.g., purple apple followed by cherry). Perceptual color similarity (PCS) was present when the surface color of the picture matched the prototypical color of the named object (e.g., purple apple followed by blueberry). Response interference was primarily due to SCS, despite the fact that participants based similarity ratings on PCS. When uncolored objects were used, SCS interference still occurred, implying that the influence of SCS did not depend on the presence of surface color. The results indicate that, relative to surface color, stored color knowledge was more influential in object recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Peripheral nerve changes in thiamine deficiency and starvation. An electron microscopic study

The treatment of iatrogenic esophageal perforation is still today subject of discussion. The present work relates our experience on 16 cases seen between 1955 and 1976, and compares the results with the 1,310 collected by French and English literature. The etiology of perforation is: endoscopy (50.5%), dilatation (19.5%), foreign bodies (14%), surgery and other causes (16%). The mortality rate of cervical perforations is 14.5% (7.3% with medical treatment, 18% with drainage, 12.6% with suture). In the thoracic esophagus it is 32.5% (50% with medical treatment, 40% with drainage, 18% with suture). The data demonstrate that the best results are obtained with surgical treatment, that may be simple drainage when the perforation is cervical, but must be the suture in the thoracic esophagus. We must emphasize that the operation must be performed within 24 hours, because, in the cases operated on after 24 hours, the mortality rate is nearly double.