Arousal response to electrical stimulation of the cerebral cortex in cats.

Questions the belief that the arousal response produced by stimulation at various sites in the cortex is due to direct stimulation of the cortical component of a central arousal system. 3 observations of 9 female and 2 male cats were not consistent with this interpretation. Fractionation of the arousal response, subtotal parts of the reaction being produced by varying the intensity of cortical stimulation, occurred only when the S was in the resting state, and the arousal response habituated during repeated cortical stimulation. These observations on the arousal response to cortical stimulation were duplicated closely by the arousal response to an auditory stimulus. In agreement with a 1967 study by H. Ursin, K. Wester, and R. Ursin, it is suggested that the arousal response to stimulation of the cortex is a reflex to a sensory experience created by cortical stimulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory modality distribution in the anterior ectosylvian cortex (AEC) of cats

Modality specificity of neuronal responses to visual, somesthetic and auditory stimuli was investigated in the anterior ectosylvian cortex (AEC) of cats, using single-unit recording techniques. Seven classes of neurons were found, and according to their responsiveness to sensory stimuli regrouped into three categories: unimodal, bimodal and trimodal. Unimodal cells that responded to only one of the three stimulus modalities formed 59% of the units; 30.2% were bimodal, in that they showed a clear increase of neuronal discharges to two of the three stimulus types; 10.8% were defined as trimodal because they responded to all three stimulus modalities. Although the different categories of cells were intermingled within the AEC, indicating a certain degree of overlap between sensory modalities, some clustering of cell types was nonetheless evident. Thus, the somatosensory responsive cells were mainly located in the anterior two-thirds of the dorsal bank of the anterior ectosylvian sulcus. Visually responsive cells were concentrated on the ventral bank of the sulcus, whereas neurons with an auditory response occupied the banks and fundus of the posterior three-quarters of the sulcus. The histological distribution and physiological properties of AEC neurons suggest that this cortical region is a higher-order associative area whose function may be to integrate information from different sensory modalities.     

Long-term potentiation of the neuronal activity in the motor cortex induced by simultaneous stimulation of the thalamus and somatosensory cortex in cats

Long-lasting potentiation of the cat motor cortex units induced by tetanic stimulation of the VL + SCx led to an increase of the motor cortex unit discharge rate. The findings suggest that co-activation of cortico-cortical and thalamo-cortical afferents modifies neuronal activity of the motor cortex at the specific site which receives convergent sensory input from the thalamus and the somatosensory cortex.     

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)     

Association cortex lesions and umweg behavior in cats.

Three groups of 7 cats were subjected to anterior or posterior association cortex lesions or sham lesions. Both anterior and posterior preparations were impaired in performance on the Hebb-Williams maze task, but did not differ significantly, thus supporting the argument of R. F. Thompson et al (1963) that structurally distinct association fields are equivalent parts of a general functional system. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Methylmercury intoxication and histochemical demonstration of NADPH-diaphorase activity in the striate cortex of adult cats

Primary pulmonary hypertension is characterized by elevated pulmonary arterial pressure and vascular resistance, frequently producing right heart failure and death. Therefore, the Doppler right ventricular (RV) index, which is a measure of global RV function, could be a useful predictor of outcome in primary pulmonary hypertension. The Doppler RV index, defined as the sum of isovolumic contraction time and isovolumic relaxation time divided by ejection time, was retrospectively measured in 53 patients (38 women, aged 45 +/- 14 years) with primary pulmonary hypertension. Ejection time was measured from the pulmonary outflow velocity signal. The sum of isovolumic contraction time and isovolumic relaxation time was obtained by subtracting ejection time from the duration of tricuspid regurgitation. The Doppler RV index tended to be elevated (median 0.83) compared with normal ranges. Normal Doppler RV index was 0.28 +/- 0.04. After a mean follow-up duration of 2.9 years, 4 patients underwent lung transplantation and 30 patients died; the cause was cardiac in 28, noncardiac in 1, and uncertain in 1. Univariately, the Doppler RV index (chi-square 20.7, p <0.0001), severity of tricuspid regurgitation (chi-square 8.2, p = 0.004), treatment with calcium blockers (chi-square 6.6, p = 0.01), heart rate (chi-square 5.1, p = 0.02), and symptom status (chi-square 4.9, p = 0.03) were associated with adverse outcome (cardiac deaths and lung transplantation). However, only the Doppler RV index and treatment with calcium blockers were independent predictors within the multivariate model. Our results indicate that the Doppler RV index is a useful predictor of adverse outcome in patients with primary pulmonary hypertension.     

Functional specificity of long-range intrinsic and interhemispheric connections in the visual cortex of strabismic cats

The development of both long-range intracortical and interhemispheric connections depends on visual experience. Previous experiments showed that in strabismic but not in normal cats, clustered horizontal axon projections preferentially connect cell groups activated by the same eye. This indicates that there is selective stabilization of fibers between neurons exhibiting correlated activity. Extending these experiments, we investigated in strabismic cats: (1) whether tangential connections remain confined to columns of similar orientation preference within the subsystems of left and right eye domains; and (2) whether callosal connections also extend predominantly between neurons activated by the same eye and preferring similar orientations. To this end, we analyzed in strabismic cats the topographic relationships between orientation preference domains and both intrinsic and callosal connections of area 17. Red and green latex microspheres were injected into monocular iso-orientation domains identified by optical imaging of intrinsic signals. Additionally, domains sharing the ocular dominance and orientation preference of the neurons at the injection sites were visualized by 2-deoxyglucose (2-DG) autoradiography. Quantitative analysis revealed that 56% of the retrogradely labeled cells within the injected area 17 and 60% of the transcallosally labeled neurons were located in the 2-DG-labeled iso-orientation domains. This indicates: (1) that strabismus does not interfere with the tendency of long-range horizontal fibers to link predominantly neurons of similar orientation preference; and (2) that the selection mechanisms for the stabilization of callosal connections are similar to those that are responsible for the specification of the tangential intrinsic connections.     

Interrelationship between differently spaced neurons in the auditory and motor zones of the cerebral cortex in cats

Multineuronal activity was studied in unrestrained cats with bundles of seven electrodes (tips dia. 50 mcm) chronically implanted in the auditory and motor cortex. Spikes of the highest and lowest amplitude were isolated from each neurogram by an amplitude discriminator. Functional connections between neurones located under different electrodes at a distance of up 540 mcm were defined by statistical dependence of the isolated spike series. In the auditory cortex, the distance at which it was possible to detect connections between high amplitude neurones (H-H) did not exceed 450 mcm, while between low amplitude neurones (L-L) it was 270 mcm. In the motor cortex, dependent relations for similar pairs of neurones (H-H) and (L-L) were found at all the studied distances up to 540 mcm. For mixed neuronal pairs (H-L and L-H) functional connections at different distances were differently expressed at various distances.     

Receptive-field properties and neuronal connectivity in striate and parastriate cortex of contour-deprived cats

An attempt was made to relate the alterations of cortical receptive fields as they result from binocular visual deprivation to changes in afferent, intrinsic, and efferent connections of the striate and parastriate cortex. The experiments were performed in cats aged at least 1 jr with their eyelids sutured closed from birth. The results of the receptive-field analysis in A17 confirmed the reduction of light-responsive cells, the occasional incongruity of receptive-field properties in the two eyes, and to some extent also the loss of orientation and direction selectivity as reported previously. Other properties common to numerous deprived receptive fields were the lack of sharp inhibitory sidebands and the sometimes exceedingly large size of the receptive fields. Qualitatively as well as quantitatively, similar alterations were observed in area 18. A rather high percentage of cells in both areas had, however, preserved at least some orientation preference, and a few receptive fields had tuning properties comparable to those in normal cats. The ability of area 18 cells in normal cats to respond to much higher stimulus velocities than area 17 cells was not influenced by deprivation. The results obtained with electrical stimulation suggest two main deprivation effects: 1) A marked decrease in the safety factor of retinothalamic and thalamocortical transmission. 2) A clear decrease in efficiency of intracortical inhibition. But the electrical stimulation data also show that none of the basic principles of afferent, intrinsic, and efferent connectivity is lost or changed by deprivation. The conduction velocities in the subcortical afferents and the differentiation of the afferents to areas 17 and 18 into slow- and fast-conducting projection systems remain unaltered. Intrinsic excitatory connections remain functional; this is also true for the disynaptic inhibitory pathways activated preferentially by the fast-conducting thalamocortical projection. The laminar distribution of cells with monosynaptic versus polsynaptic excitatory connections is similar to that in normal cats. Neurons with corticofugal axons remain functionally connected and show the same connectivity pattern as those in normal cats. The nonspecific activation system from the mesencephalic reticular formation also remains functioning both at the thalamic and the cortical level. We conclude from these and several other observations that most, if not all, afferent, intrinsic, and efferent connections of areas 17 and 18 are specified from birth and depend only little on visual experience. This predetermined structural plan, however, allows for some freedom in the domain of orientation tuning, binocular correspondence, and retinotopy which is specified only when visual experience is possible.     

Time-discrimination performance in cats with lesions in prefrontal cortex and caudate nucleus.

Conducted 2 experiments with 16 mongrel cats. Ss were trained on a time-discrimination task in which different periods of bodily confinement served as discriminanda for go-left-go-right responding. Lesions of gyrus proreus or the associated anteroventral part of nucleus caudatus impaired relearning in this situation. After reacquisition, Ss with caudate lesions received proreal ablations, and Ss with cortical damage received caudate lesions; both additional lesions caused reappearance of the deficit. The absence of external stimuli to signal locus of reinforcement at the moment of spatial choice may have been crucial for eliciting the deficit. The data support the notion that the prefrontal cortex and the anatomically related part of the caudate nucleus participate in similar behaviors. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

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

Amphetamine accelerates recovery of locomotor function following bilateral frontal cortex ablation in cats.

Prior work has demonstrated that d-amphetamine hastens recovery of beam-walking ability following unilateral sensorimotor or frontal cortex ablation (D. A. Hovada and D. M. Feeney; see record 1985-11540-001). In this study, after bilateral frontal cortex ablation, cats given injections of d-amphetamine showed an enduring acceleration of recovery of beam-walking ability relative to saline controls. In general, rates of spontaneous and drug-induced recovery in cats with bilateral lesions were similar to those previoulsy reported for cats with unilateral ablations. These results indicate that the bilateral corticostriate and corticothalamic projections from the contralateral homotopic cortex do not mediate the beneficial effects of d-amphetamine on locomotor recovery after unilateral cortical ablation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric interrelationships in the visual cortex of cats following unilateral polarization and photic stimulation of different intensity

Anodic polarization of the parastriate area in the right hemisphere causes in symmetric regions of cat's visual cortex dynamic changes in EPs, interhemispheric functional asymmetry and interhemispheric relations, depending on the intensity of photic stimulation. The sequence of phases of interhemispheric callosal relations and characteristics of interaction between callosal and extracallosal influences were traced in different periods of polarization excitation. It was found that interhemispheric callosal and extracallosal influences lead either to stabilization of initial EP levels and interhemispheric asymmetry or to their change depending on conditions of photostimulation and on the stage in the formation of polarization site.     

Monocular enucleation prevents retinal ganglion-cell loss following neonatal visual cortex damage in cats

Studies were conducted to assess the utility of free solution capillary electrophoresis (CE) for monitoring the effects of selected excipients on the thermal denaturation of a model protein (Ribonuclease A, RNase A) at low pH. Thermal denaturation/unfolding experiments were conducted via temperature-controlled CE using a run buffer of 20 mM citric acid in the pH range of 2.3-3.1, with a marker peptide incorporated to correct for temperature-induced changes in endoosmotic flow. The effects of selected excipients on the thermal unfolding of RNase A were then evaluated by adding either sorbitol, sucrose, polyethylene glycol 400 (PEG 400) or 2-methyl-2,4-pentanediol (MPD) to the electrophoretic run buffer (pH 2.3). Confirmatory denaturation experiments were conducted under the same solution conditions using circular dichroism (CD) spectropolarimetry. Using temperature-controlled CE, an increase in solution pH from 2.3 to 2.7 and 3.1 resulted in an increase in transition temperatures of RNase A by approximately 8 and 13 degrees C, respectively. Similar shifts in transition temperatures were observed when thermal denaturation transitions were monitored by far-UV CD. Sorbitol (0.55-1.1 M) and sucrose (0.55 M) each shifted the denaturation transition temperatures of RNase A to higher values, whereas PEG 400 and MPD had minimal effect on the unfolding transition midpoint at the concentrations evaluated (0.55 M for each). The observed changes in the transition temperatures for RNase A as a function of pH and selected excipients were similar when measured by either CE or far-UV CD. These results support the utility of CE for monitoring the effects of neutral excipients on the thermal denaturation of a model protein under selected conditions. The widespread utility of the technique may be limited by the narrow temperature range of most commercial CE instruments and the need to use extreme pH conditions to monitor the complete denaturation transition.     

Distribution and localization of NMDA receptor subunit 1 in the visual cortex of strabismic and anisometropic amblyopic cats

ACTIVATION of NMDA (N-methyl-D-aspartate) receptors has recently been proposed as a prerequisite for the induction of experience-dependent modification of visual cortical neurones seen during early postnatal development. A new monoclonal antibody to the NMDA receptor subunit 1 (NMDA-R1) has been used to localize and compare the distribution of the receptors in the primary visual cortex of normal cats and those raised with either amblyopia induced by monocular optical blur or monocular esotropic strabismus. Although all three groups showed densest labelling in layers II-III, a comparison of immunopositive cells at any depth below the cortical surface showed a significantly lower frequency in strabismic and anisometropic cats than in normal cats, but a greater frequency in anisometropic cats that in strabismic animals. There appears to be no direct relationship between the expression of NMDA-R1 receptors and the level of excitability, binocularity or neuronal acuity known to exist in either of these two cat models of amblyopia, thus raising further questions as to the precise nature of the role of NMDA receptors in the processes of visual cortical plasticity.     

Fos expression during the critical period in visual cortex: differences between normal and dark reared cats

BACKGROUND: Height of portal pressure correlates with severity of alcoholic cirrhosis. Portal pressure indices are not however used routinely as predictors of survival. AIMS: To examine the clinical value of a single portal pressure measurement in predicting outcome in cirrhotic patients who have bled. METHODS: A series of 105 cirrhotic patients who consecutively underwent hepatic venous pressure measurement were investigated. The main cause of cirrhosis was alcoholic (64.8%) and prior to admission all patients had bled from varices. RESULTS: During the follow up period (median 566 days, range 10-2555), 33 patients died, and 54 developed variceal haemorrhage. Applying Cox regression analysis, hepatic venous pressure gradient, bilirubin, prothrombin time, ascites, and previous long term endoscopic treatment were the only statistically independent predictors of survival, irrespective of cirrhotic aetiology. The predictive value of the pressure gradient was much higher if the measurement was taken within the first or the second week from the bleeding and there was no association after 15 days. A hepatic venous pressure gradient of at least 16 mm Hg appeared to identify patients with a greatly increased risk of dying. CONCLUSIONS: Indirectly measured portal pressure is an independent predictor of survival in patients with both alcoholic and non-alcoholic cirrhosis. In patients with a previous variceal bleeding episode this predictive value seems to be better if the measurement is taken within the first two weeks from the bleeding episode. A greater use of this technique is recommended for the prognostic assessment and management of patients with chronic liver disease.     

Emotional behavior in feral cats with ablations of prefrontal cortex and subsequent lesions in amygdala.

Bilateral ablations of gyrus proreus in 6 cats did not significantly alter either the intensity or the pattern of flight behavior during confrontation with a human. The scores for defense behavior were reduced in only 2 Ss. Subsequent lesions in the rostral part of the basolateral nuclei of amygdala reduced flight and transiently decreased defense scores in all Ss. It is concluded that the prefrontal cortex does not seem necessary for the flight and defense responding observed in feral cats. The role of amygdala in the regulation of these behaviors is confirmed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)