Biomedical subjects

M Podell

Publications and source records attributed to M Podell.

At least 37 records · Page 2Linked to original sources

PubMed1997

Generalized tremors in dogs: 24 cases (1984-1995).

OBJECTIVE: To characterize clinical features, diagnostic evaluation, and treatment outcome for dogs with generalized tremors. DESIGN: Retrospective case series. ANIMALS: 12 white purebred and 12 nonwhite mixed-breed and purebred dogs. PROCEDURE: Medical records of dogs examined for tremors between January 1984 and July 1995 were reviewed. History, signalment, abnormalities on physical and neurologic examinations, results of diagnostic testing, and diagnosis were recorded for each dog. Results were divided into the following 3 categories on the basis of the cause of the tremors: inflammatory, noninflammatory, and idiopathic. Cause was determined by results of CSF analyses or a history of toxin exposure. RESULTS: The only noninflammatory cause of generalized tremors identified in these dogs was mycotoxin ingestion. Steroid-responsive tremor syndrome had developed in 22 of 24 dogs, half of which had abnormal results of CSF analyses. Most dogs were young adults between 1 and 5 years old. More than half of the dogs were nonwhite mixed-breeds and all weighed < 15 kg (33 lb). Eighty percent of the dogs responded to immunosuppressive treatment within 3 days. CLINICAL IMPLICATIONS: Inflammatory and noninflammatory causes for generalized tremors in dogs result in similar clinical signs, so a logical diagnostic and treatment approach is needed. Steroid-responsive tremor syndrome should be considered in small- to medium-breed, young adult dogs, regardless of coat color. A rapid and complete response to immunosuppressive treatment is expected.

Administration, Oral↗

PubMed1997

Progressive encephalopathy associated with CD4/CD8 inversion in adult FIV-infected cats.

Experimental intravenous challenge of five adult cats with the feline immunodeficiency virus Maryland isolate (FIV-MD) was investigated for its ability to induce neurologic abnormalities associated with the onset of immunodeficiency. Five 8-month-old cats were inoculated with 1000 median tissue culture infective dose of FIV-MD isolate, with five age-matched cats serving as uninfected controls. All FIV-MD-infected cats tested positive for serum antiviral antibodies and plasma viral DNA as detected by polymerase chain reaction at 2, 4, 10, and 16 months postinfection (PI). At 10 and 16 months PI, there was a significant reduction in the CD4/CD8 lymphocyte ratio, with all cats having a CD4/CD8 ratio of 1 or less. Total protein electrophoretic analysis of cerebrospinal fluid demonstrated a significantly increased albumin quotient at 4 and 16 months PI, representing a disrupted blood-brain barrier (BBB). At 16 months PI, all cats demonstrated a preferential increase in frontal cortical slow-wave activity compared with control cats. Serial evaluation of brainstem auditory evoked potential recordings revealed a prolongation of the interpeak latencies times over the study time. At least one abnormality was found over time in visual and somatosensory evoked potential testing in three and four infected cats, respectively. Comparing lymphocyte subtype ratios with neurologic testing revealed that every FIV-MD-infected cat exhibited an abnormality in at least one neurologic functional test with a concurrent CD4/CD8 count ratio of 1 or less. Overall, this study demonstrated that FIV-MD infection in adult cats results in a delayed-onset, progressive encephalopathy that parallels the decline in the CD4/CD8 lymphocyte ratio. Compared with prior information from pediatric FIV-MD-infected cats, these results indicate that age of infection influences the onset and severity of disease and may be associated with CD4 cell depletion in FIV-MD-infected cats, as seen in HIV-1-infected humans.

Analysis of Variance↗

PubMed1997

Cerebrospinal fluid gamma-aminobutyric acid and glutamate values in dogs with epilepsy.

OBJECTIVES: To investigate changes in CSF concentrations of inhibitory and excitatory neurotransmitters in dogs with confirmed idiopathic epilepsy, and to evaluate them with regard to the clinical characteristics of the sample population and of the seizures. ANIMALS: 13 (8 male and 5 female) drug-naive dogs with an initial generalized seizure, 6 (4 male and 2 female) drug-naive dogs with an initial partial seizure, and 10 clinically normal (5 male and 5 female) control dogs. PROCEDURE: At least 24 hours after the last observed seizure, CSF was collected aseptically from the cisterna cerebellomedullaris, and a portion was immediately aliquoted into vials, placed on dry ice, then stored at -80 C. The CSF glutamate (GLU) and gamma-aminobutyric acid (GABA) concentrations were estimated by use of HPLC with electrochemical detection. Cerebellomedullary cisternal CSF glutamate and GABA values were analyzed in dogs with noninduced idiopathic epilepsy. Comparisons were determined for differences attributable to weight, sex, age at first seizure, seizure type, and total time of past seizure history. RESULTS: Mean (range) age at onset of the first seizure was 3.33 (0.1 to 11), 3.5 (0.1 to 11), and 3.25 (0.5 to 9) years for all dogs, dogs with initial partial seizure, and dogs with initial generalized seizure, respectively. Low GABA and high GLU values were found in the CSF of epileptic dogs, and were independent of time elapsed between the first observed seizure and CSF sample collection. The GABA value was inversely related to body weight in epileptic dogs, independent of age. Changes in GABA and GLU concentrations were not related to seizure type. CONCLUSIONS: Altered GABA and GLU values in CSF might be indicative of a state of chronic overexcitation in the brain of dogs with primary or idiopathic epilepsy. CLINICAL RELEVANCE: CSF GABA and GLU may serve as important markers in epileptic dogs for potential response to antiepileptic drugs.

Aging↗

PubMed1996

Methylmalonic and malonic aciduria in a dog with progressive encephalomyelopathy.

A 12 week old female Labrador retriever dog with signs of progressive diffuse degeneration of the brain and spinal cord was found to have methylmalonic and malonic aciduria. Over a 5 month period, the dog developed neurologic signs compatible with disease of the central nervous system with predominant diffuse cerebral and right lateralizing brainstem deficits. Gross pathological examination of the brain showed that the lateral, third, and fourth ventricles of the brain were markedly enlarged and associated with white and grey matter atrophy. Syringomyelia and hydromyelia of the central canal into the dorsal funiculus of the spinal cord beginning at the level of the cervical intumescence and extending to the lumbar intumescence was also present. Significant biochemical abnormalities include methylmalonic and malonic aciduria, mild lactic and pyruvic aciduria. There was also accumulation of citric acid cycle intermediates including succinic, aconitic, and fumaric acids. Disordered fatty acid oxidation was suggested by increased excretion of adipic, ethylmalonic, suberic and sebacic acids. Neither ketoacidosis nor hyperammonemia were present, and serum cobalamin levels were normal. Overall, this dog demonstrates an inborn error of metabolism resulting in abnormal organic acid accumulation associated with a neurodegenerative disease.

Animals↗

PubMed1996

Benefits of calcitriol therapy and serum phosphorus control in dogs and cats with chronic renal failure. Both are essential to prevent of suppress toxic hyperparathyroidism.

Daily oral calcitriol at low doses is safe and effective in the control of renal secondary hyperparathyroidism in dogs and cats. Low doses of calcitriol are most effective when started early in uremia before the advanced stages of renal secondary hyperparathyroidism. At early stages calcitriol both diminishes PTH synthesis in the parathyroid cells present and prevents the hyperplasia that, if unchecked, results in the most extensive an difficult-to-control hyperparathyroidism. The salutary effects on the dog's or cat's sense of well being, appetite, activity, strength, and lifespan as reported by the veterinarians of our survey are attributed primarily to keeping PTH levels below a toxic threshold. Additionally, some of the benefits achieved by calcitriol are likely a direct consequence of calcitriol interacting with the vitamin D receptor in a wide variety of tissues throughout the body. Phosphorus restriction through a combination of diet and intestinal phosphate binders is important to allow calcitriol therapy to successfully lower PTH levels, but it likely has no direct effects that are independent of interactions involving calcitriol. Phosphorus restriction is also important to minimize chances for adverse tissue mineralization. Calcitriol therapy can be considered for treatment of chronic renal failure after serum phosphorus has been decreased to less than 6.0 mg/dL in patients in whom it was initially elevated. Calcitriol supplementation to dogs and cats with chronic renal failure makes good endocrinologic sense. Calcitriol deficits cause increased PTH and, as these two hormones are designed to maintain calcium and phosphorus homeostasis, the PTH increase is initially adaptive. One of the important effects of PTH is to stimulate additional calcitriol formation as a powerful means to raise blood calcium through increased calcium absorption from the diet. With too great an increase in PTH, however, its effects become harmful to many tissues due to the widespread distribution of the PTH receptor in many cell types that are likely normally responsive only to the paracrine PTH-related peptide that shares the PTH receptor. Exogenous supplemental calcitriol administration allows concentrations of calcitriol in the bloodstream to remain normal without the toxic consequences of excessive PTH secretion that would otherwise be provoked. Studies involving young dogs with subtotal nephrectomy may not parallel those on older dogs and cats with spontaneous chronic renal failure. In particular, higher doses are needed to effect PTH change in these young dogs than we have found necessary for older dogs and cats. Because survey participants agreed most strongly with the idea that their calcitriol-treated dogs and cats were living longer than comparably uremic animals they had treated previously, further studies to evaluate the ability of calcitriol to retard the progression of renal lesions and loss of excretory renal function seem warranted. Additional studies to document the beneficial effects of calcitriol on the many organs adversely affected by excess PTH during uremia are also needed because findings thoroughly documented and proven in humans and rats may not always extrapolate to dogs and cats.

Animals↗

PubMed1996

Seizures in dogs.

Epileptic seizures are the most common neurologic problem of the dog. The ability of a clinician to start proper management does not require elaborate equipment or specialized skills. What is needed is a thorough assessment of the history and examination findings. Dogs with a history of seizures at less than 1 or greater than 7 years of age, a history of behavioral changes, an initial interictal interval of less than 4 weeks, or an initial partial seizure should be suspected of having an identifiable underlying cause for the seizures. As such, an appropriate diagnostic evaluation should be done. Once a cause has been determined, PB is the AED of choice for dogs without underlying liver disease. Factors that enhance successful PB therapy are early initiation of therapy and proper monitoring of trough serum concentrations. Dogs that develop functional tolerance to PB should be given oral potassium bromide as the second AED. Diazepam per rectum can be used as an at-home therapy to stop cluster seizure activity. Overall, improved seizure control can be achieved by establishing a well-thought out therapeutic monitoring schedule. This approach will lead to improved quality of life for the patient, resulting in greater client satisfaction and less clinician frustration.

Animals↗

PubMed1995

Seizure classification in dogs from a nonreferral-based population.

On initial evaluation for onset of seizure disorders at nonreferral veterinary practices, 50 previously healthy dogs were enrolled in a study to determine the probability of identifying a specific cause for the seizures. Treatment was not administered prior to entry of dogs in the study. On the basis of antemortem and postmortem test results, 22 dogs (44%) were classified as having primary epileptic seizures (PES; idiopathic or without identifiable cause), 23 (46%) had secondary epileptic seizures (SES; identifiable intracranial cause), and 5 (10%) had reactive epileptic seizures (RES; metabolic or transient noxious cause). Forty-one dogs (82%) had 2 or more seizures before evaluation, with 37 (90%) of these dogs classified as having epilepsy on the basis of an underlying chronic brain disorder. For these 41 dogs, 17 (41%) had PES, 20 (49%) had SES, and 4 (10%) had RES. Among the 9 dogs (18%) with nonrecurring seizures, 5 had PES, 3 had SES, and 1 had RES. Generalized seizures were the most common first-observed seizure type associated with all etiologic classifications in all dogs with recurring and nonrecurring seizures. Diagnosis of SES was statistically more probable when the dog was less than 1 or more than 7 years old at the first seizure, when the first seizure was a partial seizure, or when the first seizure occurred between midnight and 8 AM. A diagnosis of RES was statistically more probable only when the interval between the first and second seizure was brief (< or = 4 weeks).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1993

Systemic mycosis caused by Acremonium sp in a dog.

A 4-year-old female German Shepherd Dog was examined to determine the cause of ataxia, progressive head tilt, anorexia, lethargy, and weight loss of 3 weeks' duration. A vestibular syndrome, generalized lymphadenopathy, bilateral uveitis, and chorioretinitis with complete detachment of the left retina were detected. Abnormal clinicopathologic findings were isosthenuria and hyperglobulinemia. The non-functional left eye was enucleated and fungal organisms resembling Aspergillus spp were identified on histologic examination. Microbial culture of a urine sample yielded Acremonium sp, which was initially considered a contaminant. The dog was considered to have systemic aspergillosis and was treated with itraconazole for 7 months, until it was euthanatized because of persistent vomiting and anorexia. Postmortem examination revealed multisystemic pyogranulomatous and necrotizing inflammation of the myocardium, pericardium, liver, and kidneys; and granulomatous splenitis, lymphadenitis, retinitis, endometritis, and meningoencephalitis. Fungal culture of affected organs yielded Acremonium sp. These findings indicated that Acremonium spp can be pathogenic and should not be ignored when cultured.

Acremonium↗

PubMed1993

AIDS-associated encephalopathy with experimental feline immunodeficiency virus infection.

Experimental intravenous challenge of 8-week-old kittens with the feline immunodeficiency virus Maryland isolate (FIV-MD) was investigated for its ability to infect the central nervous system (CNS) and induce neurologic abnormalities. Six cats were inoculated with 1,000 TCID50 units of FIV-MD isolate, with six age-matched cats serving as uninfected controls. Clinical and immunological evaluation documented that challenged cats developed immunodeficiency and growth delay. Neurologic examination revealed an abnormal stereotypic motor behavior consisting of repetitive, compulsive roaming that developed as early as 4 weeks postinfection (PI) and persisted throughout the 16-month study in three cats. Serial neuroelectrodiagnostic evaluation revealed persistent abnormal electroencephalographic recordings in three infected cats. Serial evoked potential (EP) recordings at 3, 8, and 12 months PI demonstrated significantly prolonged interpeak latencies III-V at 3 months PI and I-III at 12 months PI for brainstem EP recordings. Alterations of visual EPs were detected only at the 3-month time period. Retinocortical time, however, was significantly different from that in control cats at 3 and 12 months PI. Magnetic resonance imaging evaluation of FIV-MD-infected cats at 12 months PI revealed cortical atrophy, mild ventricular enlargement, and discrete white matter lesions. At 16 months PI, however, histopathological examination of brain tissue indicated only mild lesions limited to satellitosis and perivascular lymphocytic infiltrates. Virus was detected in the CNS by reverse transcriptase, immunofluorescence, and antigen capture. Evaluation of the cerebrospinal fluid revealed intrathecal anti-FIV-MD antibody despite lack of detectable viremia in five challenged cats. Collectively, these findings demonstrate the induction of virus-associated neurologic disease following parenteral FIV challenge in conjunction with an immunodeficiency state. The nature of the nervous system infection is analogous to HIV-1 pediatric encephalopathy.

Animals↗

PubMed1992

Polycystic kidney disease and renal lymphoma in a cat.

A 2-year-old castrated domestic shorthair cat was determined to have polycystic kidney disease (PKD) and renal lymphoma. History and examination findings consisted of progressive lethargy, asymmetric renomegaly, thick segments of small intestine, and anisocoria. Initial diagnostic tests revealed nonregenerative anemia, mild azotemia, and multiple, round anechoic cysts in both kidneys. Renal cystic fluid contained many mature lymphocytes, and results of biochemical analysis indicated that the fluid was consistent with proximal tubular fluid. Stage-3 lymphoma was diagnosed on the basis of histologic evidence of unresectable lymphoma in multiple abdominal organs. Chemotherapy with vincristine sulfate, cytarabine, cyclophosphamide, and prednisone was unsuccessful. Morphologic association between PKD and lymphoma could not be identified after histologic evaluation of the kidneys.

Animals↗

PubMed1992

Characterization of cerebral infarction by multicomponent analysis of transverse magnetization decay curves.

RATIONALE AND OBJECTIVES: Individual components of the transverse magnetization decay curve (TDC) were assessed for their ability to characterize ischemia in photochemically induced cerebral infarcts. METHODS: Fifty rats were randomly divided into equal-sized experimental and control groups, which were subdivided into groups studied at five different time points, ranging from 6 hours to 22 days. All the rats received transcalvarial irradiation with 560-nm light. Five rats in each time group also received a sensitizing dye before irradiation. In these latter animals, lesions of uniform size and location developed. Lesions were compared with tissue of similar volume and location from the contralateral cortex of the experimental animals and with tissue from both hemispheres of the control animals. TDCs of all the samples were measured and fit with mono- and bi-exponential functions. RESULTS: Unlike the control tissue, infarcted tissue displayed definitive two-component TDC behavior. The time course of the bi-exponential parameters yielded information unavailable from mono-exponential analyses. CONCLUSIONS: Bi-exponential analysis of TDCs may have diagnostic use as a more sensitive indicator of cerebral infarction than mono-exponential analyses.

Animals↗

PubMed1990

Canine hypoadrenocorticism. Diagnostic dilemmas associated with the "great pretender".

Canine hypoadrenocorticism (HAC) is often a difficult disease to diagnose in the early course of presentation because of the multitude of associated vague clinical signs. Frequently, the disease is considered only after the patient presents in an acute crisis after an undetected or ignored ongoing, slowly progressive deterioration over the previous several weeks. Although not a common clinical disorder, HAC is still present in the canine population to a degree that merits a full diagnostic workup in all cases of suspicion. The purpose of this chapter is to alert the clinician to the underlying pathophysiology of adrenal insufficiency to better understand the clinical and biochemical abnormalities of this syndrome. By recognizing early signs of HAC, the potential for advanced detection is raised. From this detection, the acute crisis situation may be averted. Of equal importance in the diagnosis of HAC is the fact that other disease states may be mimicked by its presentation. This chapter reviews the common differential diagnoses for the presenting clinical signs, along with establishing a differential list for the expected biochemical abnormalities. In particular, special emphasis is placed on the discussion of potassium homeostasis and hyperkalemia. Finally, a brief overview of the treatment of both acute and nonacute adrenal insufficiency is mentioned.

Adrenal Insufficiency↗

PubMed1988

Meningioma in a woodchuck exhibiting central vestibular deficits.

An 11-yr-old captive-raised male woodchuck (Marmota monax) presented with ataxia, poor balance, left-sided weakness, circling to the left and nystagmus with the fast-phase directed towards the left. The clinical signs were compatible with a central vestibular deficit syndrome. Necropsy and histologic findings revealed a meningotheliomatous meningioma centered over the ventrolateral left pons and medulla along with acute bronchopneumonia, chronic glomerulopathy, interstitial nephritis, and phthisis bulbi.

Aging↗

PubMed1988

The deafferented visual cortex and interhemispheric relationships: a physiological approach.

A condition of asymmetrical activation in the visual system, induced by unilateral optic tract section (OTX) was examined in nine adult cats, four of which had been reared after early onset of monocular deprivation (MD-OTX) during the critical developmental period. Their results were compared to those of monocularly deprived (MD) and normal control cats. Extracellular single-unit recordings from areas 17, 18 and their border were performed at various intervals after OTX to study the effects of this isolation of one hemisphere from direct geniculo-cortical input. Electrophysiological results from the isolated hemispheres of both OTX and MD-OTX cats revealed that contralateral input via the corpus callosum was virtually undetectable in the majority of cats. Only in the cats in which the deprivation was ipsilateral to the OTX, 3.5% of the cells exhibited visual activity in the isolated hemisphere. In the intact hemisphere of the OTX group, binocularity was unaffected overall in comparison to the normal control animals, except for a slight decrease within the 0-4 degrees region from the vertical meridian. In the MD-OTX group, the cats with onset of deprivation prior to natural eye opening possessed an increase in deprived eye responsiveness compared to the control MD cats. No such an increase was seen in later onset of deprivation (3-4 weeks following natural eye opening) in the MD-OTX cats. Overall, visual responsiveness was reduced in all of the OTX and MD-OTX cats, with a return towards normal control values seen only in one animal with extended recovery (6 months). Orientation and direction selectivity were dramatically decreased in the OTX and MD-OTX cats. As the majority of receptive fields mapped from the OTX cats were in the ipsilateral visual field to the section, the remaining small number of receptive fields in the contralateral "blind" visual fields adds further support for a nasotemporal overlap in the retina of the cat. The conclusion from these results is that an asymmetrical level of direct geniculo-cortical input in the visual system of the adult cat yields a physiological bidirectional inactivation of the callosal pathway for the transfer of visual information. Thus, activation of the callosal pathway connecting the cortical visual areas has been postulated to be dependent upon simultaneous, reciprocal interaction between the two hemispheres.

Animals↗

PubMed1987

Unilateral visual cortex deafferentation induces changes in receptive field properties of cortical cells in the intact hemisphere of normal and of monocularly deprived cats.

Receptive field properties and the selectivity of cortical cells to visual stimulation were studied in the visual cortices (the boundary between areas 17 and 18) of both hemispheres following unilateral deafferentation in normal and in early monocularly deprived cats. Almost no visual activity was encountered in the deafferented hemisphere and a considerable diminution in visual responsiveness was found in the intact hemisphere of all experimental cats. Responsiveness had increased with recovery time; unresponsive cells had consisted 44.6% of the cells in the intact hemisphere of the acute, 34.7% in the 3-month chronic and 14.5% in the normal cats. Disregarding the bias due to an early monocular deprivation, the ocular dominance distribution of the cells in the intact hemispheres of these cats was unaffected. Selectivity was markedly reduced in the intact hemisphere of the deafferented cats as expressed mainly in the increased orientation tuning range and in the proportion of orientation-selective cells. The proportion of these cells was 45.5% in the deafferented cats, 38.6% in the deafferented monocularly deprived cats, 65.3% in the monocularly deprived and 81.9% in the normal control cats. A similar trend, although less prominent, was found in respect to the proportion of direction-selective cells. The size of receptive fields was only slightly affected in the deafferented deprived cats. Receptive fields were considerably larger in size (length) in the deafferented cats in comparison to their respective normal and monocularly deprived controls. It is concluded that the absence of visual input from the deafferented hemisphere is bidirectionally affecting the corpus callosum.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗

PubMed1987

Temporal encoding of two-dimensional patterns by single units in primate inferior temporal cortex. I. Response characteristics.

We seek a general approach to determine what stimulus features visual neurons are sensitive to and how those features are represented by the neuron's responses. Because lesions of inferior temporal (IT) cortex interfere with a monkey's ability to perform pattern discrimination tasks we studied IT neurons. Previous single-unit studies have shown that IT neurons sometimes respond more strongly to complex stimuli (brushes, hands, faces) than to simple stimuli (bars, slits, edges). However, it is not known how specific stimulus parameters are represented by responses. We studied the responses of IT neurons in alert behaving monkeys to a large set of two-dimensional black and white patterns. The stimulus set was based on 64 Walsh functions that can be used to represent any picture with a resolution of one part in eight along each of two dimensions. The responses to these stimuli spanned a continuum from inhibition to strong excitation. A statistical test showed that the spike count was determined by which Walsh stimulus was presented. Hence, these stimuli form an adequate set for testing IT neurons. The responses showed temporal modulation of the spike train that could not be represented by a change in the spike count alone. Examples of this modulation were changes in latency, changes in the duration of the response, and alternating periods of excitation and inhibition. This temporal modulation may be important in representing stimulus parameters. The next paper in this series develops a method for quantifying this temporal modulation and shows that it is dependent on the stimulus. The third paper in this series shows that this temporal modulation contains more information about stimulus parameters than is contained in the spike count alone.

Animals↗

PubMed1987

The deafferented visual cortex: neuronal activity and visual evoked potentials.

The callosal transfer of information to the visual cortex following its unilateral deafferentation from its geniculate input was studied in both hemispheres. Deafferentation was performed in adult cats by sectioning the optic tract. Action potentials of single cortical cells and visual evoked potentials were recorded from area 17-18 boundary in acute and chronic operated cats. In the deafferented hemisphere, cortical cells were usually visually inactive. However, some recovery of function took place in this hemisphere in the chronic cats, as expressed by the increase in the proportion of S-cells. In the intact hemisphere diminution of responsiveness and reduction of selectivity to the stimulus orientation and direction were found. The responsiveness and selectivity level in the intact hemisphere increased with postoperative time. The ocular dominance distribution in this hemisphere was similar to that of our normal control cats. The characteristics of the visual evoked potentials were in keeping with the hemispheric dominance of the cortical cells found in the experimental cats. It was concluded that a plasticity related mechanism is involved in the recovery of callosal activation of visual cortical cells following deafferentation.

Animals↗

PubMed1984

Properties of visual cortical cells of the intact and the deafferented hemisphere of unilateral optic tract sectioned acute and chronic adult cats.

Single unit recording from visual cortex areas 17 and 18 and in the border region between them was performed on adult cats with unilateral optic tract section (OTX) either on the day of the operation (acute) or three to six months postoperatively (chronic). Visual activity from both hemispheres was analyzed with respect to the responsiveness level, the ocular dominance distribution and selectivity to orientation and direction. The results showed almost a complete absence of visual responsiveness in the deafferented hemisphere and a considerable reduction of responsiveness in the intact hemisphere. Following surgery an increase in visually responsive cells was found in the intact hemisphere as postoperative recovery continued. In addition, a reduction in the proportion of cells selective for orientation and direction was also found in the intact hemisphere of the OTX animals as compared to the control cats. Furthermore, cortical binocularity was not affected in the intact hemisphere of all OTX cats. We conclude that an almost total absence of interhemispheric callosal transfer of visual functions from the intact to the deafferented hemisphere is induced as a result of the unilateral OTX in adult cats. Moreover, the fact that the absence of cortical binocularity in the hemisphere receiving direct geniculate input was not disrupted, indicates the absence of callosal transfer from the deafferented to the intact hemisphere.

Animals↗