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PubMed1994

Actions of sciatic nerve ligature on sexual behavior of sexually experienced and inexperienced male rats: effects of frontal pole decortication.

The action of the hyperalgesia produced by the loose ligature of the sciatic nerve on the sexual behavior of two groups of sexually experienced and inexperienced male rats was studied. The putative changes in the behavior induced by this manipulation were attempted to be counteracted by the removal of the anterior frontal cortex. Independently of the sexual experience, the ligature of the sciatic nerve did not modify any parameter of the sexual behavior, except for a slight prolongation of the intromission latency. Surprisingly, the removal of the cortical frontal pole resulted in drastic changes in the sexual behavior of sexually inexperienced male rats such as an increase in the intromission and ejaculation latencies and the postejaculatory interval. These changes were not observed in the sexually experienced group. Interestingly, the sciatic nerve ligature prevented the changes in the copulatory behavior produced by the frontal cortex removal. These results suggest that the hyperalgesia induced by the sciatic nerve ligature was unable to alter the sexual behavior. By contrast, the frontal cortex removal produced important changes in the sexual behavior that depend upon the previous sexual experience. All results are discussed on the bases of the neural control underlying the possible relationships between algesia and male sexual behavior.

Animals↗
PubMed1987

Visual discrimination in the absence of visual cortex.

Normal rats and rats with devascularization lesions ranging from subtotal removals of striate cortex (Area 17) to complete removal of neocortex were trained in a horizontal/vertical stripe discrimination for a liquid reinforcer. Subgroups of animals were identified on the basis of size and location of lesion (with particular reference to striate cortex) as Subtotal, Striate, Posterior and Decorticate. Some animals in all of the lesion groups were able to acquire the discrimination, but there was a direct relationship between lesion size and number of training trials. Those animals which reached criterion on the original discrimination were trained on a second horizontal/vertical discrimination under either transfer or reversal conditions using 'rotated obliques' stimuli. Performance on this second discrimination indicated that animals from all lesion groups had been using visual stimuli based on stripe orientation in the original problem. Members of all lesion groups solved the rotated obliques problem under the transfer condition, though the speed and completeness with which they did so was again inversely related to lesion size. These data show high levels of visual competence in the absence of visual cortex even when stimuli thought to detect form discrimination are used and thus reinforce the view that superior colliculus may be a more significant visual area for the rat than was previously assumed. They also support other observations that animals do not use residual visual capacities without extensive experience and appropriate motivation.

Animals↗
PubMed1997

Spatiotemporal patterns of spindle oscillations in cortex and thalamus.

Spindle oscillations (7-14 Hz) appear in the thalamus and cortex during early stages of sleep. They are generated by the combination of intrinsic properties and connectivity patterns of thalamic neurons and distributed to cortical territories by thalamocortical axons. The corticothalamic feedback is a major factor in producing coherent spatiotemporal maps of spindle oscillations in widespread thalamic territories. Here we have investigated the spatiotemporal patterns of spontaneously occurring and evoked spindles by means of multisite field potential and unit recordings in intact cortex and decorticated animals. We show that (1) spontaneous spindle oscillations are synchronized over large cortical areas during natural sleep and barbiturate anesthesia; (2) under barbiturate anesthesia, the cortical coherence is not disrupted by transection of intracortical synaptic linkages; (3) in intact cortex animals, spontaneously occurring barbiturate spindle sequences occur nearly simultaneously over widespread thalamic territories; (4) in the absence of cortex, the spontaneous spindle oscillations throughout the thalamus are less organized, but the local coherence (within 2-4 mm) is still maintained; and (5) spindling propagation is observed in intact cortex animals only when elicited by low intensity cortical stimulation, applied shortly before the initiation of a spontaneous spindle sequence; propagation velocities are between 1 and 3 mm/sec, measured in the anteroposterior axis of the thalamus; increasing the intensity of cortical stimulation triggers spindle oscillations, which start simultaneously in all leads. We propose that, in vivo, the coherence of spontaneous spindle oscillations in corticothalamic networks is attributable to the combined action of continuous background corticothalamic input initiating spindle sequences in several thalamic sites at the same time and divergent corticothalamic and intrathalamic connectivity.

Anesthesia↗
PubMed1984

[Active selection of afferent information--the principle underlying peripheral correction of the function of spinal generators of rhythmic movements].

The paper presents data obtained in experiments on the study of primary afferent depolarization and retuning of segmental reactions to afferent signals during fictitious locomotion and fictitious scratching in immobilized decorticated, decerebrated and spinal cats. Fictitious locomotion was accompanied by sustained hyperpolarization, while fictitious scratching--by sustained depolarization of primary afferent central terminals. On the background of tonic changes periodic waves of primary afferent depolarization coinciding with the rhythm of efferent activity were observed. In different ipsilateral lumbosacral segments these periodic waves occurred in phase. The data are presented about the groups of afferent fibres in which central endings display tonic and phasic changes of primary afferent depolarization. Fictitious locomotion led to tonic increase and fictitious scratching--to tonic decrease in a number of evoked segmental reflex reactions. These tonic changes served as the background on which segmental reactions were modulated with the rhythm of locomotor and scratching generators. It is shown that the modulation of polarization of central primary endings by locomotor and scratching generators is the reason for many changes in reflex reactions. The conclusion is made that due to modulation of presynaptic inhibition the generators perform an active tonic and phase-dependent selection of afferent information. The role of such active selection in the peripheral correction of the function of locomotor and scratching generators is discussed.

Animals↗
PubMed1979

Auditory cortex lesions and interaural intensity and phase-angle discrimination in cats.

1. A currently unresolved question concerning the effects of auditory decortication on sound localization is whether or not operated animals have a normal capacity for discriminating the small interaural differences in phase angle or intensity that result from the spatial separation of sound sources relative to the head. The present experiment was designed to provide data relevant to this question. 2. Four normal and three operated cats (bilateral ablations of AI, AII Ep, SII, I-T), wearing stereo headsets, were tested with an active avoidance procedure to detect reversals in the interaural phase-angle or intensity relations of binaural 1-kHz tones. For both groups of cats, the detection thresholds for interaural intensity and phase angle were found to be close to 1 dB and 5 degrees, respectively. 3. In addition, we found that both unoperated and operated cats exhibited positive transfer from the original lateralization task involving the detection of interaural reversals of phase angle or intensity to a new test, which required the cats to identify, in an absolute sense, which ear received the leading or louder signals. 4. Thus, the present investigation provides additional evidence that the neocortex has no primary sensory role in sound localization.

Animals↗
PubMed1983

Evidence for respiratory and locomotor pattern generators in the rabbit cervico-thoracic cord and for their interactions.

In addition to the wellknown fictive locomotion, a fictive respiration can also be obtained in decorticate, unanaesthetized rabbit preparations after curarization and vagotomy. Both patterns were abolished after high spinal (C2 or C3) transection. Spinal rhythmic capabilities could be disclosed after administration of nialamide and DOPA: together with the earlier demonstrated locomotor-like bursting in hindlimb and forelimb muscle nerves, two different types of phrenic bursting patterns could be observed, depending on endtidal CO2 levels: (1) short lasting phrenic bursts (SLPBs), coordinated with locomotor bursts, result of a locomotor driving process; (2) when end-tidal CO2 was slightly increased (4.5 instead of 4.0%), long lasting phrenic bursts (LLPBs) developed: they have no causal link with the locomotor bursts. Intraspinal interactions were shown to operate between these rhythmic patterns: (1) the already mentioned caudo-rostral driving from hindlimb or posterior locomotion generators (pLGs) onto forelimb bursting and onto phrenic activity too (providing SLPBs in the latter case); (2) the rostro-caudal inhibition of fore- and hindlimb locomotor activity throughout each LLPB. Since forelimb locomotor-like bursting and LLPBs could still be obtained after functional isolation of the cervico-thoracic cord (through C2 and Th12 spinal transections) with comparable interactions as before Th12 transection, it is concluded that: two categories of generators, forelimb or anterior locomotion generators (aLGs), and chemosensitive respiration generators (RGs) are both present in this part of the cord, on the one hand; interactions between RGs and pLGs are likely to be achieved via aLGs on the other.

Animals↗
PubMed1996

Orientation discrimination in the cat: its cortical locus II. Extrastriate cortical areas.

Luminance-defined edges or bars are among the basic units of visual analysis: a "primitive" component of perception. We have utilized this stimulus in a psychophysical study of bar orientation discrimination in the cat before and after selective lesions in visual cortical areas. The cortices have been divided on the basis of their connectivity into three tiers. Tier I refers to areas 17 and 18, tier II includes areas that receive directly from tier I, and tier III includes those areas that receive directly from tier II. Previous studies (Vandenbussche et al. [1991] J. Comp. Neurol. 305:632-658) have shown that the discrimination of bar orientation depends heavily upon the integrity of areas 17 and 18 (tier I). The present study indicates that several extrastriate areas in tiers II and III contribute to this discrimination task. Our data suggest that the anterior medial lateral suprasylvian, the posterior lateral lateral suprasylvian (tier II), and the anterior lateral lateral suprasylvian (tier III) areas are most likely to contribute to bar orientation discrimination.

Animals↗
PubMed1977

Cerebral necrosis following radiotherapy of extracranial neoplasms.

We have examined 6 patients with delayed cerebral necrosis following irradiation of extracranial neoplasms. Four of the 6 patients received 1,760 rets (or less) tumor dose. The initial symptoms attributable to radiation necrosis appeared 4 to 31 months after irradiation and were those of a focal supratentorial mass. Cerebral angiography delineated an avascular frontal or temporal lesion in all 6 patients; in 1 case a magnification study revealed narrowing, irregularity, and occlusion of small cortical vessels. Four of our 6 patients underwent craniotomy with partial or complete surgical extirpation of necrotic brain tissue. Two operated patients are alive and without disabling neurological symptoms 30 and 25 months, respectively, after the operation. The characteristic neuropathological features of delayed radiation necrosis of brain suggest that vascular injury rather than neuronal or glial damage is of primary pathogenetic significance.

Adult↗
PubMed1986

Multidisciplinary prediction of seizure relief from cortical resection surgery.

Preoperative variables from a full range of medical specialties were used to predict degree of seizure relief from cortical resection surgery as treatment for epilepsy in 100 patients. General, seizure history, electroencephalographic (EEG), radiological, surgical, and psychological/neuropsychological data were considered. The patients were divided into one large predictive group (n = 75) and a smaller independent cross-validation sample (n = 25). Eight predictive variables emerged: single EEG focus; anterior-midtemporal lobe discharges; discharges only from the side of surgery; rate of occurrence of discharges in surgical area; Wechsler Adult Intelligence Scale Digit Symbol subtest; Marching Test, preferred hand, time; Minnesota Multiphasic Personality Inventory (MMPI) Hysteria scale score; and MMPI Paranoia scale score. By use of multivariate procedures, increased predictability of surgical outcome was obtained not only with the predictive group but with the independent cross-validation sample. The results demonstrate that predictions of seizure relief from epilepsy surgery can be made with 80% accuracy using multiple, rather than single, predictors.

Adolescent↗
PubMed1988

Functional hemispherectomy for treatment of epilepsy associated with hemiplegia: rationale, indications, results, and comparison with callosotomy.

Hemispherectomy is effective in arresting seizures associated with maximal or near maximal hemiparesis. This procedure, however, carries an unacceptable 33% risk of late complications due to cerebral hemosiderosis. Anatomically partial but functionally complete hemispherectomy was devised to avoid these complications. The frontal or occipital lobes, or both, were left in place with the blood supply intact but with connections to commissures and brainstem divided. The central strip and parietal and temporal lobes were removed. Twenty patients were so treated with a follow-up of 4 to 13 years (average, 7.3 years) in 14. Ten of these are seizure free, 1 had a single nocturnal seizure, 1 had occasional focal twitching, and 2 had a worthwhile but lesser reduction in the seizure tendency. None has developed cerebral hemosiderosis, to date. In appropriately selected patients, functional hemispherectomy is an effective procedure preferable to callosotomy or to partial hemispherectomy. When there is no independent ictal discharge from the opposite hemisphere, arrest of seizures may be expected, leading to improvement in cognitive functioning (mean increase, 10 IQ points), social behavior, and a reduction in or discontinuation of anticonvulsant medication. In these patients, gait and hand use remain unchanged.

Adolescent↗