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PubMed1994

Chylothorax associated with right-sided heart failure in five cats.

Chylothorax associated with right-sided congestive heart failure was diagnosed in 5 cats. One cat had restrictive pericardial disease, with mild pericardial effusion, and a heart-base chemodectoma. Two other cats had congestive cardiac disease (tetralogy of Fallot and tricuspid regurgitation in 1 cat, and endocardial cushion defect and tricuspid dysplasia in the other), and 2 cats had idiopathic cardiomyopathy. All cats had jugular venous distention, and echocardiographic evaluation helped define the nature of the cardiac disease in these cats. Subtotal pericardiectomy resulted in resolution of the chylothorax in the cat with the heart-base tumor, whereas medical management of the right-sided heart failure temporarily decreased pleural effusion in the cat with tetralogy of Fallot and in the 2 cats with cardiomyopathy.

Animals↗
PubMed1993

Humoral immune responses in cats with dermatophytosis.

The IgG and IgM classes of antibodies to a water-soluble antigen preparation derived from Microsporum canis were determined by ELISA in the sera of 79 cats with dermatophytosis confirmed by results of fungal culture, and of 46 specific-pathogen-free-derived, barrier-maintained cats with no previous exposure to dermatophytes. Of the 79 cats with dermatophytosis, the species isolated were: M canis from 72, M gypseum from 6, and Trichophyton mentagrophytes from 1. Concentrations of soluble M canis antigen-specific IgG and IgM were significantly (P < 0.05) higher in the cats with dermatophytosis than in the control cats. The IgG concentration was > or = 2.0 ELISA units/ml ml in 71% of the cats with dermatophytosis and in 9% of the control cats, whereas IgM concentration was > or = 4.0 ELISA units/ml in 38% of the cats with dermatophytosis and in 11% of control cats. There was no significant difference in either IgG or IgM values between the cats with M canis infection and those with other non-M canis dermatophyte infections.

Animals↗
PubMed1993

Prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavages and of mycoplasmal recovery from pharyngeal swab specimens in cats with or without pulmonary disease.

The prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavage specimens and prevalence of mycoplasmal recovery from pharyngeal swab specimens from cats with (28) or without (18) pulmonary disease were determined. Mycoplasmas were recovered from tracheobronchial lavage specimens in 21% of cats with pulmonary disease, but in no cats without pulmonary disease; this difference is significant (P = 0.04). Mycoplasmal recovery from tracheobronchial lavage specimens was not significantly associated with concurrent Pasteurella spp isolation, septic inflammation, or bronchitis. Ureaplasmas were only isolated from a tracheobronchial lavage specimen in 1 cat with pulmonary disease and in no cats without pulmonary disease. Similar mycoplasmal recovery rates were found for pharyngeal swab specimens from cats with (39%) or without (35%) pulmonary disease. Seemingly, mycoplasmas are part of the normal pharyngeal flora in approximately a third of the feline population, but mycoplasmas are not normal inhabitants of the lower respiratory tract in cats. It is unknown whether mycoplasmas isolated from tracheobronchial lavage specimens in cats with pulmonary disease are primary pathogens or opportunistic invaders. Seemingly, ureaplasmas are seldom associated with pulmonary disease in cats, and are not normal inhabitants of the trachea and bronchi of cats.

Age Factors↗
PubMed1995

Long-term antibody responses of cats fed toxoplasma gondii tissue cysts.

As part of a long-term study on immunity to oocyst shedding, 12 4-6-mo-old cats were inoculated orally with tissue cysts of the ME-49 strain (6 cats) or the TS-2 strain (6 cats) of Toxoplasma gondii. Two cats fed the ME-49 strain died or were killed because of acute toxoplasmosis 12 and 13 days after inoculation (DAI), respectively. On day 39 after primary infection, 5 cats (2 infected with the ME-49 strain and 3 infected with the TS-2 strain) were challenged orally with tissue cysts of the ME-49 strain. One cat died following rechallenge infection due to causes unrelated to toxoplasmosis. Seventy-seven months after primary infection, the remaining 9 cats were challenged orally with tissue cysts of the P89 strain of T. gondii. Blood samples were obtained weekly or monthly and sera were analyzed for antibodies to T. gondii using the modified agglutination test (MAT), the Sabin-Feldman dye test (DT), and the enzyme-linked immunosorbent assay (ELISA) for IgM (IgM-ELISA) or IgG (IgG-ELISA). The MAT was performed using both formalin-fixed (FF) and acetone-fixed (AF) tachyzoites. The MAT (FF) was the most sensitive test; cats seroconverted within 14 DAI and high titers (> 10,000) persisted > 6 yr, although cats had no clinical signs. The MAT titers using the AF detected recent exposure and titers declined sharply after 2 mo postinoculation. DT and ELISA titers were lower and developed slower than MAT titers. Fluctuations in antibody titers were limited to 8-fold during the 6-yr observation period. Anamnestic serum antibody responses were seen in 2 cats after the final challenge, but not after first challenge.

Agglutination Tests↗
PubMed1996

Factors affecting treatment decisions and satisfaction of owners of cats with cancer.

Cancer in cats is being diagnosed with increasing frequency. Euthanasia or an active intervention such as chemotherapy, radiation therapy, or surgery are treatment choices for the owner at diagnosis of the cat's disease. In this study, 2 interviews with cat owners, one soon after diagnosis of cancer in the cat and one 6 months later, were used to identify owner characteristics associated with a decision of euthanasia or intervention, to identify factors associated with an owner's satisfaction with euthanasia or intervention, and to evaluate inappropriate expectations of the owners who selected an intervention. The study included 89 owners from 3 referral hospitals. In logistic regression analysis, significant factors were not found that affected the owner's decision to euthanatize the cat versus intervene. Satisfaction with the decision to euthanatize the cat was associated with the ability of the cat to groom itself, eat, and play at the first interview. Among owners who selected an intervention, 4 combinations of factors were associated with being satisfied. The first combination was clinic of origin (CLIN), having a live cat at the 6-month follow-up interview (LIVE), and understanding the number of return visits required for the intervention. The second was CLIN, LIVE, and type and frequency of adverse effects from the intervention at the 6-month interview. The third was CLIN, LIVE, and feeling guilty at the 6-month interview. The fourth was CLIN, LIVE, and whether the cat had a good or excellent quality of life at the first interview. Thirty percent (21/69) of the owners tended to overestimate their cats' life expectancy. Owners also felt they had reasonably accurate estimations of adverse effects of treatment and number of return visits, but underestimated the costs required for an intervention. For owners who elect an intervention, a reminder from the veterinarian that emotional upheavals may develop even after the decision has been made is important. To provide optimal patient care and client education, veterinarians must find a middle ground between being knowledgeable, practical, and informed, and being compassionate and approachable.

Animals↗
PubMed1997

Diagnostic evaluation of cats with seizure disorders: 30 cases (1991-1993).

OBJECTIVE: To investigate causes of seizure disorders in cats. DESIGN: Case series. ANIMALS: 30 cats referred to the Ontario Veterinary College for recurrent seizures. PROCEDURES: Signalment and seizure pattern were evaluated. Diagnostic procedures included physical, neurologic, and fundic examinations; CBC; serum biochemical analyses, including determination of pre- and postprandial bile acid concentrations; urinalysis; serologic assays for FeLV and feline immunodeficiency virus, feline infectious peritonitis, and Toxoplasma gondii, magnetic resonance imaging of the brain; CSF analysis; and neuropathologic examination of euthanatized cats and of surgical biopsy specimens. RESULTS: All cats were found to have structural brain diseases; nonsuppurative meningoencephalitis of unknown cause was found in 14 cats, feline ischemic encephalopathy in 6, meningioma in 2, polycythemia vera with secondary brain lesions in 2, posttraumatic epilepsy in 1, and cerebral abscess in 1. A definitive diagnosis could not be reached in 4 cats. CLINICAL IMPLICATIONS: The most common cause of seizures in cats is structural brain disease. Structural brain lesions often can be detected on the basis of seizure pattern and results of neurologic examination. Cerebrospinal fluid analysis and brain imaging are essential to determine the cause of these lesions. Causes of seizures found in the cats of this study differ from those reported to be the most common. Nonsuppurative meningoencephalitis of unknown origin appears to be a frequent cause of neurologic disorders in cats, including seizure disorders. Feline ischemic encephalopathy appears to exist in a milder form than the classic disease and may be a common cause of seizures in cats.

Animals↗
PubMed1997

Clinical management and outcome of cats with seizure disorders: 30 cases (1991-1993).

OBJECTIVE: To determine outcome of clinical management of cats with seizure disorders. DESIGN: Case series. ANIMALS: 30 cats referred to the Ontario Veterinary College for recurrent seizures. PROCEDURES: Treatment was dictated by the cat's seizure frequency and by the underlying cause. Cats that were having cluster seizures or status epilepticus at the time of admission were treated orally with phenobarbital and with constant IV administration of diazepam. The other cats were treated with long-term oral administration of phenobarbital if the frequency of their seizures justified it. Follow-up included evaluation of seizure frequency, serum antiepileptic drug concentrations, and hematologic and serum biochemical values. Outcome was documented on the basis of survival and seizure frequency at the end of the followup period, which ranged from 3 to 21 months. RESULTS: 6 cats were euthanatized without any therapeutic attempts at the owners' request. Twenty of the remaining 24 cats were alive at the time of final follow-up. Seventeen had a good outcome; 11 were not having any more seizures and 6 were having a low frequency of seizures. For 3 other cats, seizures were not well controlled. Four cats had been euthanatized (2 because of intractable seizures, 1 because of postcraniotomy complications, and 1 because the owners did not want to pursue treatment). CLINICAL IMPLICATIONS: Results suggest that severity of seizure disorder in cats is not a good predictor of outcome and that aggressive treatment is often rewarding, even in the most severe cases.

Administration, Oral↗
PubMed1996

Acute gastric dilatation in cats: a case series.

Acute gastric dilatation (AGD) is a well-known, acute, life-threatening disease in dogs but its feline counterpart is much less known. This paper provides descriptions of 2 cases of AGD in cats that the authors have seen. Including these a total of 10 cases of feline AGD have been reported. No breed or sex predilection was found among the cases. Age distribution ranged from 11 weeks to 13 years. All 10 cats with AGD had enlarged abdomens on presentation. In 3 of the cases this was the only presenting sign and all 3 were simple, uncomplicated gastric dilatations, that were easily corrected by gastric decompression. Four of the 10 cats with AGD had dyspnea in addition to enlarged abdomens and only one of these cats survived, suggesting that this combination of clinical signs might indicate a guarded prognosis. Five out of the 10 cats with AGD had gastric torsion, 2 of these with concomitant diaphragmatic hernia. Four of the 5 cats with gastric torsion survived after appropriate surgery. Diaphragmatic hernia was a concurrent condition in 3 cats with signs of AGD. A mortality of 30% was observed in cats with AGD. Treatment was successful in 7 out of 10 cases and consisted of shock therapy combined with gastric decompression or surgery. Prognosis seems favorable once the initial acute stage has been overcome. Recurrence has only been recorded in one cat. Conclusions drawn from the available material are: 1) clinical signs and therapeutical management of AGD are similar in cats and dogs, 2) the age of the patients seem to differ between feline and canine AGD, 3) more information is needed to fully assess the prognosis and recurrence rate of feline AGD.

Animals↗
PubMed1998

Prevalence and risk factors for odontoclastic resorptive lesions in cats.

OBJECTIVE: To determine prevalence of, and risk factors for, odontoclastic resorptive lesions in cats seen in a private veterinary practice population. DESIGN: Population-based cross-sectional study. ANIMALS: 145 cats more than 1 year of age that underwent anesthesia for various procedures. PROCEDURE: Cats were evaluated under anesthesia for odontoclastic resorptive lesions. Lesions were graded, using a published classification system. Clients completed a standardized survey on signalment, indoor-outdoor status, medications, diet during the past year, number of daily feedings, treat feeding, source of water, and oral hygiene practices. RESULTS: 48% of cats had resorptive lesions. Lesions were most commonly mandibular, and premolars were more often affected. Compared with cats without oral lesions, cats with oral lesions were more likely to be older, female, taking medications, drinking city (vs well) water, and playing less often with toys. In addition, cats without oral lesions were more likely to have owners who cleaned their teeth daily or twice a week and to be fed diets with higher magnesium, calcium, phosphorus, and potassium contents. Frequency of teeth cleaning was inversely related to the development of odontoclastic resorptive lesions. Variables significantly associated with oral lesions were age and magnesium content of diet. CLINICAL IMPLICATIONS: Older cats should be examined closely for odontoclastic resorptive lesions. Clients should be advised on methods and frequency of teeth cleaning in cats to prevent lesions. Dietary nutrients may play a role in the development of odontoclastic resorptive lesions in cats.

Animals↗
PubMed1998

Protein and calorie effects on progression of induced chronic renal failure in cats.

OBJECTIVE: To determine effects of dietary protein and calories on progression of induced chronic renal failure in cats. ANIMALS: 28 young adult female cats. PROCEDURE: Renal mass was reduced surgically, and glomerular filtration rate (GFR) was determined. Cats were alloted to 4 groups of 7 with similar mean GFR (1.52 to 1.55 ml/min/kg of body weight). Diets were formulated to provide: low protein and calorie (diet A), low protein and high calorie (diet B), high protein and low calorie (diet C), and high protein and calorie (diet D) intakes. Cats were fed their prescribed diet for 12 months, then blood and urine biochemical variables were measured, after which kidney specimens were examined microscopically. RESULTS: Protein intake by cats of groups C and D (9.0 g/d/kg) was substantially greater than that by cats of groups A and B (5.3 and 5.2 g/d/kg, respectively). Caloric intake by cats of groups B and D (73 and 71 calories/d/kg, respectively) was greater than that by cats of groups A and C (58 and 55 calories/d/kg, respectively). Renal glomerular lesions were mild and not affected by protein, calories or their interactions. Nonglomerular lesions, though mild, were significantly influenced by calorie intake, but not by protein or calorie-protein interactions. The GFR did not decrease in any group. Urine protein-to-creatinine ratio increased significantly in all groups after reduction of renal mass, but values from all groups remained within the reference range (0 to 0.3). CONCLUSIONS AND CLINICAL RELEVANCE: Diets replete in protein were not associated with increased severity of glomerular or nonglomerular renal lesions, increased proteinuria, or decreased GFR. Diets replete in calories were not associated with increased severity of glomerular lesions, but were associated with mild increase of nonglomerular lesions. Factors other than protein and calorie intake must be considered potential causes of progression of renal failure in cats. Results raise questions about the practice of restricting quantity of protein in the diet of cats with chronic renal failure, with the intention of ameliorating development of further renal damage.

Adipose Tissue↗
PubMed1979

The effect of the sequence of contralateral cortical and collicular lesions on the rate of relearning a visual discrimination by cats.

Visual field deficits which follow ablation of the posterior two-thirds of one cerebral hemisphere in the cat have been shown to be ameliorated by ablation of the contralateral superior colliculus. The present study was designed to determine whether the sequence in which contralateral cortical and collicular lesions are made is a significant factor affecting the rate of monocular relearning through the eye ipsilateral to the cortical lesion. Nine adult cats had the optic chiasm sectioned, were trained to criterion monocularly on a dark-light discrimination, and were divided into two groups. Four cats (Group S) had one superior colliculus ablated, followed one month later by ablation of the contralateral two-thirds of the neocortex. Five cats (Group C) had the same lesions in the reverse order. One month after the second brain lesion, each cat was retrained monocularly through each eye on the dark-light discrimination for food reward in a Y-maze. Through the eye ipsilateral to the cortical lesion, all cats in Group S relearned to criterion more rapidly than cats previously reported with only unilateral neocortical lesions. Four of the five cats in Group C were severely retarded in relearning and two of these cats failed to relearn. The results show that when chiasm-sectioned cats are trained monocularly in a Y-maze on a dark-light discrimination, ablation of the superior colliculus prior to ablation of the contralateral neocortex facilitates relearning through the eye ipsilateral to the cortical ablation. When ablation of the superior colliculus follows the neocortical lesion, learning occurs but is not facilitated by the additional lesion.

Animals↗
PubMed1980

Receptive field properties of simple and complex striate neurons in Siamese cats.

Responses of striate cortical cells in Midwestern Siamese cats to moving slits and stationary flashed spots were recorded and compared to similar data in common cat controls obtained under identical experimental conditions. Over 90% of the neurons sampled had receptive fields within 10 degrees of the area centralis. The proportion of binocularly excited cells in Siamese striate cortex was less than that found in the control cats, but more than has previously been reported, and was inversely related to the extent of convergent misalignment exhibited by each animal. Those striate neurons which could be driven by either eye had normal binocular receptive fields and demonstrated normal binocular interaction effects except facilitation. Receptive field dimensions (length, width, area) were significantly larger in Siamese than in common cats. For the simple cells, strabismic Siamese cats had larger receptive fields than orthophoric Siamese cats. Average spontaneous activity in Siamese cats was significantly higher than in the controls. However, similar encounter rates of simple, complex, and hypercomplex units were observed in both Siamese and common cats, and peak responses were not different. Velocity preference in complex Siamese units was shifted to slower velocities compared to common cat complex cells. A loss of direction selectivity was also revealed in the Siamese simple and complex neurons. Finally, sharpness of orientation tuning was dramatically reduced in Siamese complex cells, and this reduction was directly related to the extent of convergent squint exhibited by each animal. The results are discussed in terms of developmental anomalies and neurophysiological retinal abnormalities in Siamese cats.

Animals↗
PubMed1980

Development of the dorsal lateral geniculate nucleus in normal and visually deprived Siamese cats.

Neuronal cell bodies in the lateral geniculate nucleus of normal and of monocularly-deprived Siamese cats have been measured. Seventeen normally reared Siamese cats, ranging in age between 20 and 120 days, were used to determine rates of normal geniculate cell growth. A second group of five adult Siamese cats reared from bith with the lids of one eye closed were used to study the effects of monocular visual deprivation upon geniculate cell size. For each of the normal and visually deprived Siamese cats, the cross-sectional areas of 600 lateral geniculate cells were measured from camera lucida drawings of Nissl preparations. During normal development the geniculate cells rapidly increase in size during the first postnatal month of life and reach their adult size sometime between days 28 and 56. While this course of geniculate cell growth is similar to that seen in normally pigmented cats, the pattern of change seen after monocular deprivation is quite different in Siamese cats from that found in normally pigmented cats. In Siamese cats the regions of the nucleus receiving a contralateral projection from the deprived eye appear to be shielded from the effects of binocular competition. Cells throughout lamina A and in the abnormal, contralaterally innervated segment of lamina A1 show only about a 10% reduction in cell size. There are no noticeable differences between the parts of lamina A in the binocular and monocular segments of the nucleus. Cells in the ipsilaterally innervated segment of lamina A1, in contrast, show deprivation-induced changes that average 27.1%. Two mechanisms are proposed to explain why some geniculate cells in Siamese cats appear to be shielded from binocular competition: one depends on possible interactions between geniculo-cortical cells lying in adjacent parts of the same geniculate lamina, and the other depends on an anatomical segregation of the cell type ("Y-cells") most heavily affected by the binocular competition. Each proposed mechanism is related to earlier observations on monocularly deprived, normally pigmented cats.

Animals↗
PubMed1981

Differences in binocular interactions between cortical areas 17 and 18 and superior colliculus of Siamese cats.

In Siamese cats most retinal projections are crossed and almost all neurons in cortical areas 17 and 18 respond exclusively to the contralateral eye. However, neurons in visual areas in the suprasylvian sulci (LSA) can be activated from both eyes, since the input from the ipsilateral eye is relayed to them by the corpus callosum (Marzi et al., '80). This study shows that the superior colliculus (SC) is also the site of binocular interactions in Siamese cats with a predominantly monocular organization of areas 17 and 18. In 8 unanesthetized, brainstem-sectioned Siamese cats, identified as "Boston" on the basis of the pattern of visual field representation in areas 17 and 18 (Hubel and Wiesel, '71; Shatz, '77a), only 25 out of 140 neurons in these areas could be driven from both eyes, whereas as many as 124 out of 143 SC neurons showed a clear binocular input. The input from each eye to the ipsilateral SC and the resulting binocular interactions in our Siamese cats might have depended on corticotectal projections from LSA. If so, since a posterior callosal section abolishes the input from each eye to ipsilateral LSA, the SC should similarly be affected by callosotomy. The posterior half of the corpus callosum was sectioned acutely in three Siamese cats after recording from SC; the input from the ipsilateral eye to SC was suppressed by this operation in one cat (which, however, also had an unintended interruption of the posterior, habenular, and anterior intertectal commissures), and drastically reduced in the other two. In a fourth cat, in which callosotomy was performed three weeks before recording from SC, the number of SC neurons responsive to the ipsilateral eye was significantly inferior to that of Siamese cats with an intact corpus callosum. These findings indicate the importance of the corpus callosum for ipsilateral eye-SC relations, as well as for SC binocularity, in Siamese cats. At the same time they imply that noncallosal routes can also transmit information from each eye to the ipsilateral SC in callosotomized Siamese cats.

Animals↗
PubMed1987

Effects of corpus callosum section on functional compensation in the posteromedial lateral suprasylvian visual area after early visual cortex damage in cats.

A visual cortex lesion made in adult cats leads to a loss of direction selectivity and a loss of response to the ipsilateral eye among cells in posteromedial lateral suprasylvian (PMLS) cortex of cats. However, a visual cortex lesion made in young cats results in normal direction selectivity and normal ocular dominance in PMLS cortex. Thus cats with an early lesion demonstrate functional compensation in PMLS cortex. The present experiment determined whether the functional compensation depends upon an intact corpus callosum. Cats received a unilateral visual cortex lesion on the day of birth (day 1) or at 8 weeks of age. When the cats were adult, the corpus callosum was sectioned and 24 hours later recordings were made in PMLS cortex ipsilateral to the visual cortex lesion. Results were compared to cats with a similar lesion and an intact corpus callosum. In cats with a lesion made on day 1, a corpus callosum section did not affect receptive-field properties or ocular dominance in PMLS cortex. Therefore, functional compensation is not dependent on input via the corpus callosum in these animals. However, in cats with a lesion made at 8 weeks. a corpus callosum section resulted in a decrease in the percentage of direction-selective cells and in the percentage of cells driven by the ipsilateral eye. Despite the decrease, the percentage of direction-selective cells still was greater than in cats with an adult unilateral visual cortex lesion. Thus, while partly dependent on callosal inputs, some functional compensation for direction selectivity remains on the basis of ipsilateral inputs.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1992

"Activation" of alveolar leukocytes isolated from cats fed taurine-free diets.

Taurine is a ubiquitous amino sulfonic acid in mammals, present in high concentrations in tissues, including those exposed to elevated levels of oxidants. Experiments were designed to examine the consequences of taurine deficiency on production of ROI in leukocytes isolated from the lungs and blood of cats fed taurine-deficient diets. Cats were maintained on taurine-free or taurine-supplemented diets for at least 12 months at which time taurine deficiency was evident. To analyze alveolar cells, lungs were lavaged to recover lung macrophages and PMNs. Lung lavage fluid from cats contained macrophages and PMNs, although taurine deficiency was associated with a decrease in the percentage of PMNs in the lungs. This is similar to our findings in blood that taurine deficiency reduced the proportion of PMNs. Taurine measurements revealed 2.1 +/- 1.6 mumol/g wet wt of taurine in the lungs from cats fed a taurine-deficient diet versus 8.3 +/- 2.6 in lungs from cats fed a diet supplemented with taurine (n = 16). The effects of taurine deficiency on the functional activity of lung macrophages and PMNs were analyzed including the production of ROI. Alveolar leukocytes from cats fed taurine-deficient diets produced more superoxide anion in response to phorbol myristate acetate than cats fed taurine supplemented diets. Similar results were obtained using a chemiluminescence assay. Using the highly specific H2O2 indicator dye, dichlorofluorescin, and flow cytometry we found that alveolar leukocytes made more H2O2 than cells from cats fed taurine-supplemented diets. Forty-two percent of the cells from cats fed a taurine-supplemented diet expressed class II antigens. In contrast, 72% of cells from the taurine-deficient cats expressed this antigen. We hypothesize that taurine functions to prevent terminal activation and release of cytotoxic mediators by lung macrophages. Thus, a deficiency of taurine will indeed cause an activation of leukocytes, as evidenced by our data which show an increase in ROI, as well as an increase in class II antigen.

Amino Acids↗
PubMed1986

Detection performance of normal cats and those lacking areas 17 and 18: a behavioral approach to analyse pattern recognition deficits.

The ability of cats to discriminate between two geometrical outline patterns in the presence of superimposed Gaussian visual noise was tested before and after bilateral removal of cortical area 17 and parts of area 18. The detection probability PD was measured as a function of the signal-to-noise ratio for the parameters: noise bandwidth, spatial frequency content and rate of movement of patterns. In both normal and lesioned cats a broadband noise was found to be most effective in masking the large patterns while two other types of noise, a medium frequency noise and a high frequency noise had little or no masking effect. For recognition of the smaller patterns in normal cats the medium frequency noise was found to be more effective than the broadband noise. The performance of the lesional cats was disturbed severely at low signal-to-noise ratios and was significantly inferior to that of normal cats-especially for small patterns. However, at high S/N ratios and for large patterns the performance of the lesioned cats was comparable to that of normals while for the small patterns they reached PD values inferior to those of normal cats. It is concluded that although pattern recognition can be performed successfully by cats lacking areas 17 and 18, these cortical areas probably make an essential contribution to this function under natural conditions in two ways: because of the X-type input of area 17, they increase the acuity of the system by making it more sensitive to higher spatial frequencies, and they permit detection of patterns at much lower S/N ratios i.e. they lower the signal-to-noise ratio at which the system is able to detect the presence of a pattern in a background of statistical visual noise. The latter effect is not limited to the higher spatial frequencies but also affects the very low spatial frequencies which are normally used for pattern detection. Previous failures to demonstrate clear deficits in pattern discrimination after 17/18 lesions in cats may be attributed to the fact that the patterns presented for discrimination were not masked by visual noise. Movement of patterns led to a slight, but not significant improvement of the performance in both normal and lesioned cats, but the deficits found for stationary and moving patterns were more or less equal.

Animals↗
PubMed1984

Effects of neonatally induced strabismus on binocular responses in cat area 18.

Responses to binocular visual stimulation were compared in cortical area 18 of normal cats and in cats in which one eye was exodeviated by surgery early in postnatal life. In contrast to normal cats where most units (58%) were binocularly activated, relatively few units (10%) in strabismic cats were activated well by stimulation of either eye. Rather individual units were driven mainly via one eye or the other but not both. In addition, there was a tendency for more units to be driven well via the unoperated eye than via the exodeviated eye. Fewer cells preferring vertically oriented than horizontally oriented stimuli were found in area 18 of strabismic cats. This trend was observed for cells driven by either the normal or deviated eye and was especially marked among the small number of binocularly activated cells. Generally binocular responses and binocular interactions were found with stimulation at corresponding retinal points. In a few striking instances, however, the receptive fields of binocular neurons were located on noncorresponding retinal points at loci which would enable the cat to correlate the two images of an external object despite the large divergent strabismus. Quantitative responses to binocular stimuli presented at varied disparities and to stimuli with varied directions of motion in depth were compared in normal and strabismic cats. Despite the large strabismus, a reduced fraction of cortical neurons displayed substantial binocular interactions. In fact, binocular facilitation was as marked in the population of cells studied in strabismic cats as it was in normal animals. The major effect of strabismus was a reduction in the strength of binocular inhibition when units were tested with sideways motion. Disparity-specific responses to motion toward or away from the organism were little affected by strabismus. The degree of binocular facilitation and binocular inhibition among the cell population was similar in normal and strabismic cats. A subpopulation of units encountered in strabismic cats showed strong disparity-specific interactions for motion toward or away from the animal without equivalent modulation for sideways moving stimuli. Units with these properties were not found in normal animals and may, therefore, represent a special adaptation of the strabismic animals.

Animals↗