Dissociation of visual and auditory pattern discrimination functions within the cat's temporal cortex

In ablation-behavior experiments performed in adult cats, a double dissociation was demonstrated between ventral posterior suprasylvian cortex (vPS) and temporo-insular cortex (TI) lesions on complex visual and auditory tasks. Lesions of the vPS cortex resulted in deficits at visual pattern discrimination, but not at a difficult auditory discrimination. By contrast, TI lesions resulted in profound deficits at discriminating complex sounds, but not at discriminating visual patterns. This pattern of dissociation of deficits in cats parallels the dissociation of deficits after inferior temporal versus superior temporal lesions in monkeys and humans.     

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)     

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)     

Monkeys with rhinal cortex damage or neurotoxic hippocampal lesions are impaired on spatial scene learning and object reversals

Rhesus monkeys (Macaca mulatta) with lesions of the rhinal cortex or parahippocampal gyrus (made by aspiration) or hippocampus (made with ibotenic acid) and unoperated controls were tested on object discrimination and reversal, place discrimination and reversal, and spatial scene learning to determine the contribution of these temporal lobe structures to these forms of learning and memory. Rhinal cortex lesions produced a severe deficit in object reversal learning; hippocampal lesions produced a milder deficit. Monkeys with rhinal cortex removals and those with hippocampal lesions were equally impaired on spatial scene learning. None of the lesions impaired place discrimination or reversal. These results argue against the idea that the mnemonic contributions of the rhinal cortex and hippocampus are limited to object and spatial domains, respectively.     

Effects of inferior temporal lesions on visual discrimination performance in monkeys with complete and incomplete striate cortex ablations.

Eight male cynomolgus monkeys (Macaca fascicularis) were retrained to perform 2 preoperatively acquired discriminations (brightness-flux and brightness-area) after receiving bilateral striate cortex lesions to determine whether the inferior temporal cortex participates in the relearning of visual discriminations following striatectomy. Ss were then retested in the same tasks after bilateral inferior temporal surgery. After inferior temporal surgery, Ss with histologically verified total ablation of the striate cortex showed little or no impairment in relearning the discriminations, whereas Ss with remnants of intact striate cortex were severely impaired. Findings suggest that the inferior temporal cortex is of minor importance in relearning brightness-flux and brightness-area discriminations in the absence of striate cortex. This interpretation is consistent with the view that the contribution of the inferior temporal cortex to visual discrimination performance depends on input from striate cortex. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impairment in object-in-place scene learning after uncinate fascicle section in macaque monkeys.

Three previous experiments have shown that a disconnection of frontal cortex from inferior temporal cortex in monkeys impairs a variety of visual learning tasks but leaves concurrent object discrimination learning intact. In the present experiment, three monkeys were trained on an object-in-place task where concurrent object discrimination learning took place within unique background scenes. After surgery to transect the uncinate fascicle, the monosynaptic route between prefrontal cortex and inferior temporal cortex, all three monkeys showed an impairment relative to their preoperative performance. Combined with previously reported impairments after uncinate fascicle transection, the interaction between frontal cortex and inferotemporal cortex is likely to be important in discrimination learning in background scenes because learning depends on associating the visual elements of a scene together with the appropriate choice object. This result adds to recent evidence showing that tasks such as object-in-place learning and conditional learning are impaired after disconnection of frontal cortex from inferior temporal cortex because those tasks require the representation of temporally extended events. (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)     

Effect of superior colliculus, striate, and prestriate lesions on visual sampling in rhesus monkeys.

27 male rhesus monkeys were tested for pattern discrimination retention and for color discrimination learning, with and without stimulus-response (S-R) separation, following superior colliculus lesions, partial striate cortex lesions, foveal prestriate lesions, or control lesions involving cortical or subcortical structures. Only the prestriate Ss were reliably impaired in pattern retention and in color discrimination tasks without S-R separation. In color discriminations involving S-R separation, collicular Ss were deficient compared either with the controls or with those with striate lesions. These findings suggest that the primate superior colliculus, like prestriate cortex, is involved in visual sampling behavior required by S-R separation, and thus participates in orientation to visual stimuli. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Triple dissociation of anterior cingulate, posterior cingulate, and medial frontal cortices on visual discrimination tasks using a touchscreen testing procedure for the rat.

Four experiments examined effects of quinolinic acid-induced lesions of the anterior cingulate, posterior cingulate, and medial frontal cortices on tests of visual discrimination learning, using a new "touchscreen" testing method for rats. Anterior cingulate cortex lesions impaired acquisition of an 8-pair concurrent discrimination task, whereas posterior cingulate cortex lesions facilitated learning but selectively impaired the late stages of acquisition of a visuospatial conditional discrimination. Medial frontal cortex lesions selectively impaired reversal learning when stimuli were difficult to discriminate; lesions of anterior and posterior cingulate cortex had no effect. These results suggest roles for the anterior cingulate, posterior cingulate, and medial frontal cortex in stimulus-reward learning, stimulus-response learning or response generation, and attention during learning, respectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral effects of early rearing conditions and neonatal lesions of the visual cortex in kittens.

16 mongrel kittens with neonatal lesions of the marginal and posterolateral gyri and 20 unoperated controls were reared either in an enriched environment or in laboratory cages. Ss with lesions were inferior to controls with respect to learning mazes and discriminating forms and gratings. This held regardless of whether they were raised in enriched or impoverished conditions. Enrichment did not facilitate form or grating discrimination by either normal or lesioned Ss, although such experience facilitated maze learning by both groups. It is concluded that early enrichment of sensorimotor experience was probably not the cause of the complete sparing of pattern vision after neonatal damage of the visual cortex reported in earlier studies. Task variables and completeness of the lesions are discussed as reasons for sparing of vision. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preoperative overtraining protects against form learning deficits after lateral occipital lesions in Galago senegalensis

Bushbabies (Galago senegalensis) trained on a form discrimination task in a two-choice apparatus prior to partial disruption of the central field representation of vision in striate cortex were found to be protected from postoperative deficit. These same animals were deficient in learning novel form discriminations. Pre- and postoperative tests of these subjects on discrimination of fine stripe patterns and of small food objects gave no evidence of reduced epicritic visual capacities. Results are discussed in terms of an interpretive role in form learning for areas of central field representation in primary visual cortex.     

Extent of recovery from neonatal damage to the cortical visual system in cats.

Cats that received either marginal or marginal plus extramarginal lesions as 3-day-old kittens were assessed on a series of tests of visually guided behavior. These Ss were not conspicuously different from normal controls in avoiding obstacles or in activity level. Yet these same operated Ss were severely impaired in performance on the visual cliff and in visual discrimination learning, even when lesions were limited to the geniculocortical portion of the visual system. Maximum losses in pattern and form discrimination learning were observed only in Ss with severe retrograde degeneration in both the lateral geniculate nucleus and the complex of the pulvinar and nucleus lateralis posterior. Photically evoked potentials were recorded in the lateral regions of the neocortex more reliably from operated Ss that had made fewer errors in discrimination learning than from more severely debilitated cases; this relation was present even among cases with nearly equivalent amounts of retrograde degeneration in the visual thalamus. These findings suggest that in the cat (a) recovery of vision is incomplete after neonatal lesions of the visual cortex, and (b) a cortical system lateral to the geniculocortical projections may be involved in pattern vision. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual control of the arm, the wrist and the fingers: pathways through the brain

Sperry and his colleagues had shown that section of the corpus callosum blocks the normally strong interocular transfer of visual learning in chiasma sectioned monkeys. Although interhemispheric transfer of learning was blocked, monkeys could be readily trained to use any combination of eye and hand in a task that required rapid visually guided responses. Sperry suggested that there must be a subcortical pathway linking sensory to motor areas of the brain. We tested monkeys in a task which required them to orient their wrist and fingers correctly in order to remove a morsel of food from a slotted disc. Animals in which we made lesions of the dorsal extrastriate visual areas of the parietal lobe were profoundly impaired in performing this task, but showed no deficit in visual discrimination learning. A monkey with an extensive lesion of the ventral, temporal lobe extrastriate areas showed no deficit in the visuomotor task but was profoundly impaired in visual discrimination learning. Lesions of peri-arcuate cortex, a major cortical target of parietal lobe visual areas, produced only a mild deficit which was motor in character. We suggest that the visuomotor deficit caused by parietal lobe lesions is brought about by depriving the cerebellum of its cortical visual input.     

Reversal set formation in the visually decorticate rat.

Results of 4 experiments with 32 male black-hooded rats show that Ss given large visual cortex lesions demonstrated a simultaneous task reversal deficit previously reported by R. C. Gonzales et al (1964) to follow more extensive cortical ablation. However, no deficit appeared in an operant discrimination that deemphasized visuospatial cues, and the simultaneous task deficit vanished when translucent eye occluders were applied to eliminate spatial, but not intensity, cue use. Because the lesion Ss showed an impairment only when visuospatial cues were available and relevant to correct reversal performance, they seemed hindered by their incompetent processing of visuospatial information. Results support spatial rather than learning approaches to visual cortex function. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrasting effects of lateral striate and superior colliculus lesions on visual discrimination performance in rhesus monkeys.

Tested 3 rhesus monkeys with lesions of lateral striate cortex (LSC), 4 monkeys with superior colliculus (SC) lesions, and 3 unoperated monkeys for retention of a preoperatively acquired pattern discrimination. The 3 groups of monkeys were then tested in 2-choice, color discrimination tests, 1 involving varying degrees of stimulus–response (S–R) separation and the other, administered several months later, involving various directions of S–R separation. Ss were also tested in a series of 2-choice pattern discriminations, following each of which they were tested for relearning when the patterns were masked with bars or circles. LSC lesioned Ss were moderately retarded in retention of the pattern discrimination, whereas those with SC lesions were not. SC lesioned Ss, but not those with LSC lesions, were impaired in both S–R separation tests, which demonstrates that their deficit was not transient or solely due to a difficulty in shifting the gaze in 1 direction. The LSC Ss, unlike those with SC lesions, were deficient in relearning discriminations between masked patterns. Findings suggest that SC and LSC may be involved in 2 different aspects of attention, respectively: shifting attention (and orientation) from 1 spatial locus to another and maintaining attention on fixated stimuli. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Promoter/repressor system of Lactobacillus plantarum phage og1e: characterization of the promoters pR49-pR-pL and overproduction of the cro-like protein cng in Escherichia coli

Previous studies have shown that extensive damage to the medial prefrontal cortex (mPFC) of rats causes reversal learning deficits. The mPFC of rats, however, consists of several subareas that are different from each other in both cytoarchitecture and neural connectivity, suggesting a functional dissociation among the mPFC subareas. In the present study, selective lesions of the mPFC of rats were made with a specially designed microknife whose intracranial placement could be controlled stereotaxically. Restricted lesions were made to each of the 3 parts of the mPFC: the anterior cingulate area (AC) (including the medial precentral area, PrCm), the prelimbic area (PL), and the infralimbic area (IL). One week after surgery, rats were trained in an aversively motivated visual discrimination task in a novel rotating T-maze. After reaching the acquisition criterion, rats were trained in a reversal task in the same maze. No difference was found in acquisition between control and mPFC lesioned rats. However, lesions of either the PL or the IL produced a marked deficit in the reversal task. This behavioral deficit was not found in rats with lesions of the AC. The results indicate that the mPFC of rats is not essential for discrimination learning, but that each of the 2 ventral subareas of the mPFC, PL, and IL, plays a critical role in reversal learning.     

Responsiveness of neurons in the posterior inferotemporal cortex to visual patterns in the macaque monkey

Using anesthetized and immobilized monkeys, responses of neurons in the posterior inferotemporal cortex to visual patterns were examined. Response properties were compared between the sulcus and the gyrus, extending between the anterior tip of the posterior middle temporal sulcus and the inferior occipital sulcus. Of 682 neurons tested, 37% in the sulcus (134/365) and 36% in the gyrus (113/317) responded to one or more patterns. The preference of neurons for patterns varied from neuron to neuron; some neurons responded selectively to one particular pattern, whereas others responded to two or more patterns. To evaluate response properties of neurons, two indices were calculated (the pattern preference index and the pattern selectivity index). The distributions of these indices in the sulcus did not differ significantly from those of the gyrus. Furthermore, the relationship between the pattern preference index and the pattern selectivity index for each neuron was almost the same in these two portions; most neurons responding to a small number of patterns showed inhibitory or weak responses to the worst pattern. In both portions, most neurons had receptive fields with small eccentricities and receptive field sizes were almost the same. These results suggest that the cortex in the sulcus in the posterior inferotemporal cortex is involved in the detection of features of visual patterns, similarly to the cortex in the gyrus.     

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.     

Ventrolateral prefrontal cortex lesions in rats impair the acquisition and retention of a tactile-olfactory configural task.

Rats with aspirative lesions of the ventrolateral frontal cortex were tested on acquisition and postsurgical retention of an associative learning task that required that they learn a tactile–olfactory configural discrimination. The task required that they pull up a string to obtain attached food and that they identify the correct string using a compound of string size and odor. The rats were not impaired in initial learning or reversal of the olfactory elements of the discrimination. They were impaired in acquisition and retention of the compound, and their deficit was proportional to lesion size. The results confirm that the ventrolateral frontal cortex is involved in processing of olfactory information and imply that the prefrontal cortex is involved in at least certain types of cross-modal configural associative learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)