Visual discrimination by cats given lesions of visual cortex in one or two stages in infancy or in one stage in adulthood.

Sparing of visual function was studied in cats with bilateral cortical damage to Areas 17 and 18 and most of Area 19. Cats with lesions made in 2 stages, on Postnatal (P) Days 3 and 6, in 1 stage on P6, or in 1 stage in adulthood were compared with sham-operated controls on 10 visual discrimination tasks. On some tasks, both groups of cats that underwent surgery as infants showed considerable sparing of function compared with cats that had surgery as adults; the latter group showed a marked impairment. However, on several of the discriminations, 2-stage lesions permitted almost total sparing of pattern vision, whereas 1-stage lesions made neonatally were almost as debilitating as those incurred in adulthood. The findings suggest that differential behavioral consequences can follow physiological or anatomical changes, or both, that occur within a 4-day neonatal interoperative period. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual depth discrimination in animals.

"The capacity to react discriminatively to the distance of visual stimulus appears to characterize a great many species, ranging from insects to primates. Especially in the case of insects, birds, and rats, it is evident that displacement of the images on the retinal mosaic is a very important factor in depth discrimination." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual cortex role in object discrimination in cats deprived of pattern vision from birth

Bacteria incorporate two atoms of molecular oxygen into aromatic hydrocarbons with the formation of cis dihydrodiols. The production of cis dihydrodiols has been demonstrated for substrates that range in size from benzene to benzo[a]pyrene. These results are in direct contrast to the mechanisms utilized by mammals, and possibly all eucaryotic organisms, for the oxidation of aromatic hydrocarbons. Thus, mammals incorporate one atom of molecular oxygen into these substrates to form arene oxides. Hydration of the latter compounds produces dihydrodiols that have a trans stereochemistry.     

Interocular transfer of lateral mirror-image discrimination by cats.

Interocular transfer of mirror-image discriminations has been shown to be paradoxical in split-chiasm monkeys tested in a lighted Wisconsin General Test Apparatus (WGTA) with 3-dimensional forms, but veridical in split-chiasm cats tested in a darkened 2-choice discrimination box with transilluminated patterns. In the present study, 8 split-chiasm cats showed veridical interocular transfer of a mirror-image and a non-mirror-image discrimination in a WGTA or a 2-choice discrimination box. On the basis of the testing parameters used, it is argued that the discrepancy in the literature arises from a species difference (having a behavioral rather than a gross neurological basis) and not from differences in behavioral testing apparatus or mode of stimulus presentation. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual neglect in pretrigeminal cats with lateral suprasylvian lesions

11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) is a microsomal enzyme present in the peripheral tissues of the rat, including the liver, and is mediated by a number of factors in animal in vivo studies. However, the effect of peptide hormones and glucocorticoids on the activity of 11 beta-HSD in isolated rat hepatocytes is not clear. To investigate these effects, we determined 11 beta-HSD activity in a primary culture of rat hepatocytes by adding various concentrations of growth hormone, insulin and dexamethasone (Dex). 11 beta-HSD activity increased significantly after treatment with Dex (10(-9)M-10(-6)M) for 48h. Dex (100nM) treated hepatocytes, incubated for 12h to 48h, resulted in a significant two-to four-fold rise in 11 beta-HSD activity compared to control (p < 0.01), which was in contrast to GH (10(-9)M-10(-6)M) and insulin (10(-8)M-10(-5)M), which inhibited 11 beta-HSD activity (p < 0.05). These results suggest that the 11 beta-HSD of rat hepatocytes is under multifactorial regulation; Dex stimulates and GH and insulin inhibit 11 beta-HSD activity in primary cultures of rat hepatocytes.     

Visual discrimination in adult dairy bulls

Adult Holstein-Friesian dairy bulls were trained to recognize a black disk and then to discriminate between that disk and smaller ones. The bulls learned these tasks, but much more slowly than did dairy calves. Achievement of a consistently high percentage of correct choices varied among bulls because of daily variation in the disposition of the bull, which seemed to affect willingness to concentrate on the experimental task. Nevertheless, all bulls demonstrated learning, and each bull remembered very well what he once had learned. A 36-cm disk was easily detected and discriminated from smaller disks. However, bulls were not able to discriminate between two disks that differed in area by less than a factor of 4. The ability to use visual cues, such as shapes and size of shapes, suggested that the visual system is important in the biology of bulls. The slow learning rate and the variability in the percentages of correct responses were not considered to be an indication of cognitive disabilities in general but rather a reflection of the daily disposition of the bull, which affected his willingness to cooperate.     

Spared discrimination and impaired reversal eyeblink conditioning in patients with temporal lobe amnesia.

The effect of medial temporal lobe damage on a 2-tone delay discrimination and reversal paradigm was examined in human classical eyeblink conditioning. Eight medial temporal lobe amnesic patients and their demographically matched controls were compared. Amnesic patients were able to distinguish between 2 tones during the initial discrimination phase of the experiment almost as well as control participants. Amnesic patients were not able to reverse the previously acquired 2-tone discrimination. In contrast, the control participants showed improved discrimination performance after the reversal of the tones. These findings support the hypothesis that the hippocampus and associated temporal lobe regions play a role in eyeblink conditioning that becomes essential in more complex versions of the task, such as the reversal of an acquired 2-tone discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficits in visual learning produced by posterior temporal lesions in cats.

Eight cats with lesions in the posterior temporal (PT) cortex, 7 cats with lesions in the basolateral amygdala (BLA), and 8 intact controls were observed on 8 tests of visual discrimination learning and spontaneous responses to salient visual stimuli. The effects of the 2 lesions were somewhat dissociable. The PT lesions were accompanied by a severe deficit in pattern discrimination learning but no loss in visual tracking or orientation to the silhouette of a threatening cat. The BLA lesions produced a milder and less consistent loss in pattern discrimination but serious defects in tracking and response to the cat silhouette. Both operated groups performed well on the visual cliff. The deficit from PT lesions appeared independent of damage to the geniculocortical system. The parallel of symptoms from PT lesions in cats and inferotemporal lesions in monkeys is discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Marginal and extramarginal cortical lesions and visual discrimination by cats.

75 mongrel cats learned a shape discrimination with 0, 1, or 2 irrelevant cues. They were then subjected to either sham operations, ablation of the marginal and splenial gyri, or lesions in the extramarginal (EM) cortex. The 32 EM cats comprised 4 groups, 3 with small (EM1), intermediate (EM2), large (EM3) decortications, and a 4th group with both EM lesions and heavy degeneration in the lateral geniculate nucleus (LGN). Ss with marginal or extensive extramarginal lesions were severely impaired in shape and size discrimination. Results show the following: (a) The errors made by marginal gyrus cases increased sharply as a function of the number of irrelevant cues present in shape discrimination training; no other group, including Group EM3, was affected by this variable. (b) Ss with extramarginal ablations and strong LGN degeneration were no more severely impaired than were Ss with comparable extramarginal damage and little or no LGN degeneration. While the nature of the 2 kinds of deficits remains unclear, they seem parallel to those following posterior cortical lesions in monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual angle of the mind's eye before and after unilateral occipital lobectomy.

Do mental images occur in a spatially mapped (i.e., analog, or array-format) representational medium? S. M. Kosslyn's (1978) method was used to measure the visual angle of "the mind's eye" to estimate the extent of the imagery medium before and after unilateral occipital lobectomy. It was found that the overall size of the largest possible image was reduced following the surgery. In addition, only the horizontal extent, and not the vertical extent, of the imagery medium was reduced. Finally, it was determined that the S understood the tasks, was not aware of any predictions, and was unaffected by a strong demand characteristic in a different imagery task. These results are consistent with the hypothesis that imagery occurs in a spatially mapped representational medium dependent on occipital cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus dynamics and temporal discrimination: Implications for pacemakers.

The purpose of the present study was to observe the functional relationship between stimulus dynamics and stimulus duration judgments in humans. Stimulus duration was defined as the length of time that a spinning sphere appeared on a computer screen. Stimulus dynamics were defined by how quickly the sphere rotated on its y-axis. Using a logarithmic scale, a psychophysical bisection task was used to divide stimulus durations into two categories, short and long. Across three experiments, participants’ duration judgments were longer the faster the sphere was rotated. This effect was observed over both a long and short temporal scale and over a wide range of stimulus dynamics despite the fact that the reinforcement contingencies penalized participants for this effect. The results are discussed in terms of perceived change as the possible basis of temporal duration estimation. This hypothesis was investigated through applications of the leading quantitative models of temporal discrimination to the present data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual learning suppressed by cooling the temporal pole.

Three female Macaca fasicularis were trained to remember colored photographs of objects over delays of 0, 15, 30, and 45 sec. Then 2 pairs of cooling devices were implanted bilaterally over the anterior 9 mm of the temporal lobe. One pair (anterior pair) covered the medial part of the temporal tip (area TG), starting at the rhinal sulcus and extending 3 mm laterally. The 2nd pair (posterior pair) was placed 3 mm lateral to the anterior pair, covering the rest of TG and the anterior extreme of the inferotemporal gyri, anterior TE. Cooling either pair of probes produced a deficit at all delays, but the deficit was greater at the longest delays. Cooling the anterior pair greatly increased the disruption of recall produced by an interfering stimulus. When all 4 probes were cooled, which suppressed the function of the entire temporal tip, performance dropped to chance at all delays. Under this condition, Ss could not learn new visual discriminations but could perform previously learned visual discriminations. Results are consistent with the suggestion that the temporal pole is the store for the brief anterograde memory that is available to the medial temporal amnesics. (64 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual discrimination and detection of configurational invariance in 3-month infants.

Investigated 40 3-mo-old infants' discrimination of simple visual arrangements of discrete elements, using an operant high-amplitude sucking technique in a stimulus familiarization–novelty paradigm. In Exp I, response recovery was found following changes in the arrangement of 3-dot patterns. To rule out contour density and position as possible cues, Ss were familiarized in Exp II with sets of stimuli varying in size and position but of constant arrangements. Response recovery was found following new arrangements of similar size and position, but Ss failed to recover to the familiarized arrangement presented in novel sizes and positions. Results of Exp III indicate the ability of infants to discriminate changes in size and position similar to the variations received during familiarization in Exp II. Results suggest sensitivity to pattern configuration and the ability to detect pattern invariance. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Toluene and temporal discrimination behavior in the rat

Fifteen rats were trained to perform a temporal discrimination between two signal durations using a standard Skinner box with two levers. When a 2-s tone signal was presented, rats were required to press one lever ("SHORT" response), and when an 8-s tone signal was presented, they were required to press another lever ("LONG" response). Then five intermediate tone signals were introduced and all signals were pseudorandomly presented. In the case of 2- and 8-s signals, rats could gain a food reward if they pressed the correct lever. When five intermediate signals were presented, neither response was reinforced. After stable performance was established, percentages of "LONG" responses to the seven signals were calculated. The percentages increased as a function of signal durations. Then three dosages of toluene were intraperitoneally administered. Treatment with 100 mg/kg toluene increased the gradient of the psychophysical function between signal durations and percentages of "LONG" responses, and accuracy of performance improved. There was no clear change in the rats injected with 200 mg/kg. However, 400 mg/kg toluene decreased the gradient. The temporal gradient reflects discriminability of signal durations. Therefore, it was proposed that treatment with 100 mg/kg toluene improved discriminability and enhanced accuracy of temporal discrimination in the rats. The treatment with 400 mg/kg toluene reduced the accuracy of temporal discrimination.     

Visual discrimination impairments in rhesus monkeys with combined lesions of superior colliculus and striate cortex.

To test the hypothesis that posterior inferotemporal cortex and the adjoining foveal prestriate cortex contribute to vision by combining inputs from striate cortex and superior colliculus, a total of 18 rhesus monkeys with combined collicular and partial striate lesions, foveal prestriate-posterior inferotemporal lesions, or subcortical lesions (controls) were tested in a series of visual discrimination tasks. Prestriate-inferotemporal lesions, unlike striate-collicular lesions, consistently impaired retention of a pattern discrimination and produced partial impairments in a size discrimination test. However, prestriate-inferotemporal and striate-collicular lesions produced similar deficits in pattern discrimination learning and no deficits in brightness discrimination learning. The deficits of the striate-collicular monkeys are discussed with regard to the "input-combining" hypothesis and alternative views. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inferior temporal lesions do not impair discrimination of rotated patterns in monkeys.

Ablation of inferior temporal cortex in the rhesus monkey produces a visual discrimination learning deficit. The severity of this deficit has often been found to be a function of task difficulty. The present paper reports 2 experiments with 25 Macaca mulatta and M. fascicularis on a type of visual discrimination problem that, although difficult, is not sensitive to inferior temporal lesions. Ss with anterior, posterior, and complete inferior temporal lesions were repeatedly unimpaired or only slightly impaired in learning to discriminate a pattern from the same pattern rotated 90° or 180°; yet they were very severely impaired in learning equally or more difficult discriminations of 2 different patterns. This demonstration that discrimination of orientation of patterns is relatively spared after inferior temporal lesions helps specify the pattern-rcognition processes that require inferior temporal cortex. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual marking: Selective attention to asynchronous temporal groups.

In visual search, when a subset of distractors is previewed 1 s before the target and the remaining distractors, search speed is independent of the number of previewed items. This is visual marking. What allows old items to be marked? Four experiments show that marking is disrupted if the onset of the new items is accompanied by synchronous changes to the old items, but it is not disrupted by changes restricted to the background or by asynchronous changes to the old items. Further, behaviorally relevant old items can be prioritized over new items. Visual marking is based on temporal asynchrony between new and old items, which allows segregation of these items into 2 temporal groups. Attention is then selectively applied to 1 group. (PsycINFO Database Record (c) 2010 APA, all rights reserved)