Visual discrimination defects in cats with temporal or occipital decortications.

Investigated performance on visual discrimination problems by 7 control (C) cats, 8 cats with lesions in the posterior temporal (PT) cortex, and 8 with destruction of the central 3-20° of the retina's projection to the marginal (M) gyrus. Group PT was impaired on 7/11 initial learning and transfer tests and on 0/3 retention tests with pattern stimuli and was inferior to Group C on 1/7 object discrimination tasks. No discrimination contingency was more likely than the others to reveal a significant deficit in Group PT. Group M was not impaired relative to Group C on any individual discrimination task. However, it made significantly more total errors on 7 discriminations between complex patterns (embedded or masked figures) than Group C. On 3 discriminations between simple patterns (unmasked figures), Group M made fewer errors than Group C. This pattern of loss is qualitatively similar to but milder than that observed in previous cats with M lesions, probably because the present M lesions were relatively small. Findings indicate that M and PT ablations produce differential impairments in cats, a selective difficulty in differentiating complex patterns after M lesions and a nonselective disruption of pattern discrimination learning after PT lesions. (34 ref) (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)     

Learning deficits in lab-reared cats

Data obtained by the author and his colleagues on deficits in learning in cats reared in the lab breeding colony are reviewed. As compared with cats who lived free in a farm during the first 3-4 months of life, the lab-reared cats showed a dramatic impairment of delayed response learning to visual and auditory stimuli. They also showed some impairment of visual discrimination learning: they commited more errors than farm-reared cats when a discrimination apparatus had a partition between the stimuli, their reaction times were longer, and after lesions of the superior colliculus-pretectum complex their relearning was impaired. Thus, even moderate impoverishment of environment can considerably affect later learning ability.     

Temporal neocortical injuries in rats impair attending but not complex visual processing.

The effects of variations of the distance between the relevant stimuli and the animals' response sites were observed upon the performances of a black–white discrimination habit for normal rats or subjects prepared with either bilateral injuries to the visual or temporal neocortex. In addition, the animals were given a strict test of visual form perception. Subjects with injuries to the visual cortex failed the test of visual form perception but performed like normals in discriminating a spatially discontiguous problem. In contrast, subjects with temporal injuries exhibited enormous performance deficits when trained on a spatially discontiguous problem but performed like normals on the test of form perception. The findings parallel the results of studies using primates and suggest that bitemporal injuries result in impairments of attending and not of complex visual processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rhinal cortex lesions produce mild deficits in visual discrimination learning for an auditory secondary reinforcer in rhesus monkeys.

Aspiration, but not neurotoxic, lesions of the amygdala impair performance on a visual discrimination learning task in which an auditory secondary reinforcer signals which of 2 stimuli will be reinforced with food. Because aspiration lesions of the amygdala interrupt projections of the rhinal cortex traveling close to the amygdala, it was hypothesized that damage to the rhinal cortex would severely impair learning in this task. Rhesus monkeys (Macaca mulatta) were trained to solve visual discrimination problems based on an auditory secondary reinforcer, were given lesions of the rhinal cortex or the perirhinal cortex alone, and were then retested. The monkeys displayed a reliable, albeit mild, deficit in postoperative performance. It is concluded that the aspiration lesions of the amygdala that produced a severe impairment did so because they interrupted connections of temporal cortical fields beyond the rhinal cortex that are also involved in learning in this task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posterior extramarginal cortex and visual learning by cats.

Reports results of 3 experiments with a total of 59 mongrel and 11 Siamese cats. Extensive ablations of posterior cortex which spared the primary visual areas severely impaired visual pattern discrimination, detour learning, and spatial reversal performance. Lesions in the posterior ecto- and suprasylvian gyri (EP) produced significant deficits in learning multiple object discrimination problems, repeated reversals on spatial or visual cues, and successive visual discriminations. Ss with cortical ablations that did not invade the EP region but did cause damage to the optic radiations were not impaired in reversal learning and were deficient in successive discriminations only when tested with nonsalient cues. Thus, some of the defects shown by EP cats are qualitatively different from the losses in cats with damage to the geniculostriate system. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

Cortical lesions and auditory discrimination.

Reviews studies investigating the effects of lesions of the auditory cortex upon auditory discriminations. Discriminations studied include frequency, intensity, duration and other temporal cues, complex spectral differences, and changes in temporal patterning. Factors determining the effectiveness of lesions are (a) size and completeness of lesion, (b) whether the lesion involved 1 or both hemispheres, (c) nature of the testing procedure, (d) size of the signal differences to be discriminated, and (e) nature of the discrimination. In view of the numerous factors, comparison of different studies is often difficult because of confounding. In terms of the factors listed above, (a) patterning changes, in which signals are not changed but merely rearranged in order of presentation, suffer more than do tasks involving the detection of new signals or the recognition of different signals; and (b) discrimination tasks requiring recognition suffer more than do tasks requiring only the detection of a new signal. It appears probable that the nature of the discrimination task interacts with the locus of the lesion and that failures on different types of tasks reflect different deficits. (58 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral analyses of visual cortex of the Galago..

To examine the function of primate visual cortex, the performance of 1 normal control group and 3 operated groups of Galago senegalensis (n?=?12) having bilateral cortical lesions in area 17, the middle temporal area (MT), or areas 18 and 19 (XS) was assessed on tasks measuring visual sensory capacity, search, and learning. Striate lesions produced a reduction in foveal vision and were responsible for deficits only on a complex visual learning task. The lesions of Group MT extended beyond the MT and involved the optic radiations. This resulted in impairments on all visual problems. Ss in Group XS had subtotal lesions of prestriate cortex and were also impaired on each task, but they showed less severe deficits in sensory capacity than Ss in Group MT. It is suggested that the Galago striate cortex plays a major role in the identification and utilization of relevant visual information and that areas 18 and 19 are important in both visual learning and visuospatial analyses. Evidence is provided that the MT is involved in visual search. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociable contributions of the prefrontal and neocerebellar cortex to time perception

We report a series a three psychophysical experiments designed to differentiate the contributions of the neocerebellar and prefrontal cortex to time perception. Comparison of patients with focal, unilateral neocerebellar or prefrontal lesions on temporal discrimination of 400-ms and 4-s intervals (Expt. 1) indicated that neocerebellar damage impaired timing in both millisecond and seconds ranges, whereas prefrontal damage resulted in deficits that were robust only at the longer duration. Patients with prefrontal lesions, however, also exhibited working memory deficits on a non-temporal task (Expt. 2), biases in point of subjective equality indicative of attentional deficits, and were disproportionately sensitive to strategic manipulations in a long-duration discrimination task (Expt. 3). In contrast, the pervasive timing deficits of cerebellar patients were relatively insensitive to strategic support and could not be readily explained by general deficits in working memory or attention. These findings support the hypothesis that neocerebellar regions subserve a central timing mechanism, whereas the prefrontal cortex subserves supportive functions associated with the acquisition, maintenance, monitoring and organization of temporal representations in working memory. Such functions serve to bridge the output of the central timing mechanism with behavior. Together, these regions appear to participate in a working memory system involved in discrimination of durations extending from a few milliseconds to many seconds.     

Involvement of the entorhinal cortex in a process of attentional modulation: Evidence from a novel variant of an IDS/EDS procedure.

Novel behavioral assays were used to assess the role of the entorhinal cortex in modulating attention to components of stimulus compounds. In Stage 1, rats received discrimination training with compounds constructed from 3 dimensions (auditory, visual, and tactile); in each compound the combination of components from 2 dimensions (e.g., auditory and visual) were relevant to the solution of the discrimination, and the remaining dimension (e.g., tactile) was irrelevant. In Stage 2, rats received a different discrimination in which the relevant dimensions were either congruent (auditory and visual) or incongruent (auditory and tactile) with those that were relevant in Stage 1. Sham-operated rats acquired the congruent discrimination more rapidly than the incongruent discrimination—a finding indicative of a process of attentional modulation—whereas rats with excitotoxic lesions of the entorhinal cortex acquired both discriminations equally readily. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Different effects on learning ability after injection of the cholinergic immunotoxin ME20.4IgG-saporin into the diagonal band of Broca, basal nucleus of Meynert, or both in monkeys.

Immunotoxic lesions of the diagonal band of Broca (VDB) in monkeys disrupted cholinergic input to the hippocampus, producing impaired learning of visuospatial conditional discriminations but not simple visual discriminations. Immunotoxic lesions of the basal nucleus of Meynert (NBM) deprived the cortex of most of its cholinergic input, producing impaired learning of simple visual discriminations but not visuospatial conditional discriminations. Combined lesions of the NBM?+?VDB resulted in impaired learning of both types of task. The impairment after NBM lesions ameliorated with time but could be reinstated by a low dose of the glutamate blocking drug MK801, which, at this dose, did not impair simple visual discrimination learning in normal monkeys. The cholinergic projections from the NBM and VDB may sustain the function of the glutamatergic pyramidal cell pathways within the cortex and hippocampus, respectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of restricted cortical lesions on absolute thresholds and aphasia-like deficits in Japanese macaques.

The effect of small bilateral cortical lesions on pure-tone audiograms and on the ability to discriminate between two types of Japanese macaque coo vocalizations was determined in 4 Japanese macaques. A lesion that included the middle portion of the superior temporal gyrus of both hemispheres, that is, the primary and secondary auditory areas, resulted in a partial hearing loss as well as an inability to discriminate the vocalizations. Lesions that included the ventral portions of the superior temporal gyrus of both hemispheres but spared auditory cortex on one side also resulted in a partial hearing loss but had either a small effect or no effect on the ability to discriminate the vocalizations. Bilateral ablation of the dorsal superior temporal gyrus and adjacent parietal and occipital areas did not result in a hearing loss and had no effect on the ability to discriminate the vocalizations. Results suggest that a hearing loss may be produced by lesions that involve small portions of the ventral two-thirds of the superior temporal gyrus bilaterally although the resulting loss is not as great as that observed with larger lesions. However, the aphasia-like deficit appears to result from a lesion of primary and/or secondary auditory cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intersensory redundancy guides attentional selectivity and perceptual learning in infancy.

This study assessed an intersensory redundancy hypothesis, which holds that in early infancy information presented redundantly and in temporal synchrony across two sense modalities selectively recruits attention and facilitates perceptual differentiation more effectively than does the same information presented unimodally. Five-month-old infants' sensitivity to the amodal property of rhythm was examined in 3 experiments. Results revealed that habituation to a bimodal (auditory and visual) rhythm resulted in discrimination of a novel rhythm, whereas habituation to the same rhythm presented unimodally (auditory or visual) resulted in no evidence of discrimination. Also, temporal synchrony between the bimodal auditory and visual information was necessary for rhythm discrimination. These findings support an intersensory redundancy hypothesis and provide further evidence for the importance of redundancy for guiding and constraining early perceptual learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Grooming behavior in cats with pontile lesions and cats with tectal lesions.

Because an abnormal grooming behavior that is mediated by the superior colliculi is elicited from cats with pontile lesions, an ablation study of these structures was conducted in 40 cats to specify quantitatively the changes in grooming behavior. Ss that underwent the surgical procedure except for the lesion and Ss with lesions of the auditory and visual cortices served as controls. Time-lapse motion pictures of the Ss in their home cages were taken, and statistical analyses of the grooming behavior shown on the films indicated that Ss with pontile lesions and those with tectal lesions spent less time grooming, had shorter grooming bouts, and failed to exhibit the normal temporal pattern of grooming behaviors. Other studies revealed that Ss with pontile or tectal lesions were deficient in removing tapes stuck on their fur. A sensory-loss hypothesis appeared to account for some of the changes, but a deficit in endogenous control of the grooming behaviors also was indicated. The literature on grooming behavior related to peripheral vs endogenous control is reviewed, and the role of the superior colliculi as a higher order integrative center for complex behaviors is emphasized. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of the medial prefrontal cortex in the play fighting of rats.

Although decorticated rats are able to engage in play, their play is abnormal in three ways. First, decorticates do not display the normal, age-related shifts in defensive strategies during development. Second, decorticates do not modify their defensive tactics in response to the social identity of their partners. Third, decorticates display a global shift in defensive tactics from more complex to less complex strategies. It has been shown that lesions of the motor cortex (MC) selectively produce the abnormal developmental effects on play, and that lesions of the orbitofrontal cortex (OFC) selectively produce the deficits in behavioral discrimination between social partners. In the current set of experiments, we demonstrate that lesions of the medial prefrontal cortex (mPFC) produce the shift from more complex to less complex defensive tactics, while leaving intact the age-related and partner-related modulation of defensive strategies. Thus, we have evidence for a triple dissociation of function between the MC, the OFC, and the mPFC with respect to social play behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of dorsal versus ventral hippocampal, total hippocampal, and parietal cortex lesions on memory for allocentric distance in rats.

To test for the contribution of the parietal cortex and hippocampus to memory for allocentric spatial cues, the authors trained rats on a go/no-go task that required the rat to remember the distance between two visual cues. Total hippocampal lesions impaired working-memory representation for allocentric distance, whereas parietal cortex lesions resulted in only a transient impairment. In a second experiment, neither hippocampal nor parietal cortex lesions impaired allocentric distance discrimination. A third experiment showed that both the dorsal and ventral areas of the hippocampal formation must be destroyed to impair working memory for allocentric distance information. There appears to be a dissociation between the hippocampus and parietal cortex in mediating memory for allocentric distance information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alterations in receptive field properties of superior colliculus cells produced by visual cortex ablation in infant and adult cats

To determine if functional alterations in the superior colliculus might account for recovery of visual behaviors following visual cortex removal in infant cats, the receptive field characteristics of single units in the superior colliculus of cats whose visual cortex was removed within the first week of life were compared with those of cats which sustained visual cortex lesions in adulthood and with those of normal cats. In the normal superior colliculus, 90% of all cells responded to moving stimuli irrespective of shape or orientation. Sixty-four percent of these units were directionally selective, responding well to movement in one direction but poorly or not at all to movement in the opposite direction. Ninety percent of units were binocular, the vast majority of these responding equally to stimulation of either eye or showing only slight preference for stimulation of the contralateral eye. Responses to stationary flashes of light were observed in only 33% of all visually activated cells in the normal superior colliculus. After visual cortex ablation in adult cats, only six percent of movement sensitive cells were directionally selective. Binocular preference was shifted following adult visual cortex lesions such that sixty percent of all cells responded exclusively or predominantly to stimulation of the contralateral eye. Seventy-one percent of all visually responsive units responded to stationary lights flashed on or off within their receptive field boundaries. Lesions limited primarily to area 17 had the same effect as larger lesions of visual cortex. Infant visual cortex lesions resulted in receptive field alterations similar to those observed after adult ablation. Only fifteen percent of motion sensitive units were directionally selective. Seventy-one percent responded exclusively or predominantly to stimulation of the contralateral eye. Seventy-six percent of visually responsive cells were activated by stationary light. Lesions largely confined to area 17 produced the same alterations as more extensive lesions of visual cortex. Thus, no evidence was found that the superior colliculus is involved in the functional reorganization presumed to occur following visual cortex ablation in infant cats. Recovery of visual behaviors following neonatal injury may therefore not involve alterations in the receptive fields of single cells.     

Subdivisions of inferior temporal cortex in squirrel monkeys make dissociable contributions to visual learning and memory.

Inferior temporal cortex of squirrel monkeys consists of caudal (ITC), intermediate (ITI), and rostral (ITR) subdivisions, possibly homologous to TEO, posterior TE, and anterior TE of macaque monkeys. The present study compared visual learning in squirrel monkeys with ablations of ITC; ITI and ITR (group ITRd); or ITI, ITR, and more ventral cortex, including perirhinal cortex (group ITR+), with visual learning in unoperated controls. The ITC monkeys had significant impairments on pattern discriminations and milder deficits on delayed nonmatching to sample (DNMS) of objects. The ITRd monkeys had deficits on some pattern discriminations but not on DNMS. The ITRd monkeys were significantly impaired on DNMS and some pattern discriminations. These results are similar to those found in macaques and support the proposed homologies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)