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At least 19 recordsLinked to original sources
PubMed1982

Lateralized effects of monocular training on dendritic branching in adult split-brain rats.

A number of experimental approaches have indicated differential interneuronal connectivity following differential experience during both development and adulthood. In Golgi preparations, prolonged maze training was reported to alter dendritic branching of distal apical dendrites of Layer IV and V pyramidal neurons in adult rat occipital cortex. To determine the specificity of this effect to direct involvement in the visual aspects of training, the effects of monocular maze training, using a split-brain procedure and opaque contact occluders, was examined in the present study. Rats were maze trained with unilateral or alternating monocular occlusion, while nontrained rats with unilateral or alternating monocular occlusion were handled briefly and given water reward. There was no within-animal effect of fixed occluder position in non-trained controls. In unilaterally-occluded trained rats, Layer V pyramidal neurons in occipital cortex opposite the open eye had greater oblique dendritic length in the distal region of the apical dendrite than did those opposite the occluded eye. Similarly, rats trained with alternating occlusion had greater distal apical oblique dendritic length in Layer V occipital pyramidal neurons than did nontrained controls. This indicates that morphological sequelae of training are concentrated in areas processing information associated with visual aspects of the training and renders unlikely general metabolic or hormonal causation of such effects.

Animals↗
PubMed1977

Cerebral commissurotomy for control of intractable seizures.

Cerebral commissurotomy or the "split-brain" procedure may be a valuable adjunct to anticonvulsants for the control of seizures in people whose epilepsy cannot be relieved by anticonvulsants alone, and who are not candidate for the standard methods of surgery. Corpus callosotomy, a revised form of the usual division of many commissures, is a safer operation and appears to be equally effective. The complex clinical aspects of cure and treatment are emphasized.

Adolescent↗
PubMed1978

Division of the corpus callosum for uncontrollable epilepsy.

Cerebral commissurotomy, the "split-brain" procedure, has been employed for the control of intractable seizures, in conjunction with moderate doses of anticonvulsant drugs. The results have been encouraging in several small series. The use of microsurgical techniques and the restriction of surgery to one commissure, the corpus callosum, has reduced morbidity without apparent change in result. The eight patients in our first series who underwent the prescribed division of several forebrain commissures are compared to the four patients in our second series who underwent division of the corpus callosum alone. The technique of callosotomy is described.

Adult↗
PubMed1981

Memory in split-brain patients: a comparison with organic amnesic syndromes.

Acquisition of pictorial information and its retention over a one week retention interval were examined in 3 split-brain patients using the titration procedure developed by Huppert and Piercy (1978, 1979). Split-brain patients were found to have a normal ability to retain information once learnt. However, two of the patients required longer than normal presentation rates to reach the desired level of learning, suggesting the presence of an acquisition defect. In contrast, the youngest patient (L.B.) showed normal acquisition as well as normal retention. These findings are compared with those obtained for two classes of amnesic patients, i.e. Korsakoff patients and H.M., who show functionally different forms of organic amnesia. The results suggest that inter-hemispheric co-operation is relatively unimportant for normal retention although co-operation may be necessary for normal learning. The possibility of recovery of memory following commissurotomy is raised.

Adult↗
PubMed2000

Conditioned changes in ultrasonic vocalizations to an aversive olfactory stimulus are lateralized in 6-day-old rats.

Using a soft rubber plug to block airflow in one naris, Kucharski, Johanson, and Hall (1986) found that some forms of olfactory memory (e.g., odor preferences) were lateralized in young rats while other forms (e.g., conditioned activation and mouthing) were not. The present experiments extended that research by showing that conditioned increases in ultrasonic vocalizations were also lateralized. That is, when exposed to an odor that was previously paired with footshock, 6-day-old rats significantly increased their rate of vocalizing. This response only occurred, however, when the naris open at training was also open at test. The use of the developing rat as a natural split-brain preparation appears to be an effective procedure with which to broaden current approaches to the analysis of learning, memory, and emotion.

Age Factors↗
PubMed1975

Split-brain rat: transfer and interference of kindled amygdala convulsions.

Rats were subjected to varying degrees of commissurotomy, followed by implantation of a bipolar electrode into each amygdala. After the kindling of six convulsions at one electrode (primary site), the procedure was applied to the contralateral amygdala (secondary site). Convulsions were observed to develop more rapidly, independent of the degree or kind of transection. After 6 secondary site convulsions, the primary site was re-tested and convulsion-triggering was blocked, except in animals with transection of the rostral portion of the corpus callosum (CC). Collectively, the data indicate: (i) amygdala kindling develops a lasting trace which operates through the midbrain or brainstem; (ii) kindling from a second site utilizes this trace; (iii) a series of 6 convulsions produces negative after-effect which manifests itself at the convulsion level via the anterior CC; (iv) the anterior CC is important in determining the laterality of the forelimb clonus; and (v) the inter-amygdala propagation of after-discharge is blocked by the combined sectioning of the anterior CC and the anterior commissure.

Amygdala↗
PubMed2003

One or two: an examination of the recent case of the conjoined twins from Malta.

The article questions the assumption that conjoined twins are necessarily two people or persons by employing arguments based on different points of view: non-personal vitalism, the person as a sentient being, the person as an agent, the person as a locus of narrative and valuation, and the person as an embodied mind. Analogies employed from the cases of amputation, multiple personality disorder, abortion, split-brain patients and cloning. The article further questions the assumption that a conjoined twin's natural interest and wish is separation. I first contend that separation is such a radical procedure as to render the post-separation person different from the pre-separation one. Therefore, it is not possible to benefit the pre-separation twin by the act of separation. The article concludes with a critical evaluation of the tendency in bioethics to regard ethical challenges as rivalry between individuals competing for scarce resources.

Abortion, Induced↗
PubMed1989

Duplex perception: some initial findings concerning its neural basis.

Duplex perception is the simultaneous perception of a speech syllable and of a nonspeech "chirp," and occurs when a single formant transition and the remainder (the "base") of a synthetic syllable are presented to different ears. The current study found a slight but nonsignificant advantage for correct labeling of the fused syllable when the chirp was presented to the left ear. This advantage was amplified in the performance of a "split-brain" subject. A subject with a left pontine lesion performed at chance level when the chirp was presented to her left ear. These findings suggest that some, if not complete, ipsilateral suppression does occur in the dichotic fusion procedure, and that identification of the fused syllable is maximal when the left hemisphere fully processes the linguistic characteristics of the base (through contralateral presentation), and at least minimally processes the frequency transition information of the chirp (through ipsilateral presentation).

Adult↗
PubMed1998

Hemispheric differences in serial reversal learning: a study with commissurotomy patients.

A serial reversal learning task involving tactile-proprioceptive discrimination and manual responses was presented alternately to the left and the right hemisphere of four "split-brain" patients. In each trial, one of two rods that differed in both diameter and surface texture was placed in the patient's hand out of view. The patient was trained to match it to samples according to either size or texture and non-verbal audio visual feedback was used to signal the correctness of each response. After reaching five consecutively correct responses, the feature to be matched was switched. When the patient again made five consecutively correct responses, the feature to be matched was reversed back. This procedure was repeated until the end of a 200-trial training run. The two hemispheres learned equally readily on the first learning task. The right hemisphere had much greater difficulty in learning the reversals than the left hemisphere and this was not attributable to a strong tendency to stay with a previously correct match. Learning with the left hemisphere showed relatively stable performance across successive reversals, whereas that with the right hemisphere showed high lability. Control trials showed that the hemispheres were equally competent in making the basic tactile-proprioceptive discriminations. Comparisons with the findings on (a) three control patients and (b) training with unrestricted visual input showed that learning with two hemispheres was easier than learning with either one alone; performance regulated by both hemispheres was also more stable.

Adult↗
PubMedDate not supplied

An investigation of the line motion effect in a callosotomy patient.

When a line is flashed instantaneously between two markers it can appear to propagate from one marker to the other. This illusion is known as the line motion effect. We investigated this effect in the two hemispheres of a callosotomy ("split-brain") patient. We found that both hemispheres perceived the line motion effect, and that flashing one of the markers biased the direction of motion away from that marker regardless of which hemisphere received the stimulus. In contrast, matching the width of the line to the width of one of the markers biased the direction of motion away from the marker only when it appeared in the left visual hemifield. This suggests that multiple mechanisms can contribute to the line motion effect, and that some of these mechanisms rely on different neural structures.

Corpus Callosum↗
PubMed2001

Failure to remap visuotactile space across the midline in the split-brain.

We examined the effect of posture change on the representation of visuotactile space in a split-brain patient using a cross-modal congruency task. Split-brain patient J.W. made speeded elevation discrimination responses (up versus down) to a series of tactile targets presented to the index finger or thumb of his right hand. We report congruency effects elicited by irrelevant visual distractors placed either close to, or far from, the stimulated hand. These cross-modal congruency effects followed the right hand as it moved within the right hemispace, but failed to do so when the hand crossed the midline into left hemispace. These results support recent claims that interhemispheric connections are required to maintain an accurate representation of visuotactile space.

Attention↗
PubMed2000

Interhemispheric comparisons in a man with complete forebrain commissurotomy.

J. Sergent (1991) claimed that split-brained people are highly accurate in judging which is the larger of 2 circles in opposite visual hemifields but are relatively poor at judging whether circles in the 2 hemifields are of the same size. The discrepancy could be due, at least in part, to an artifact. A split-brained man, L.B., was markedly worse than normals at judging which was the larger of 2 circles or the longer of 2 horizontal lines in opposite hemifields, and his performance could be largely accounted for without assuming any interhemispheric transfer. L.B. also judged whether a single flashed line extended further into the left or right hemifield and, as in a previous study (M. C. Corballis, 1995), was strongly biased to respond "right longer." This bias was not observed in the judgments about the circles or the separated lines, suggesting that it is not due to a compression of perceived space in the left hemifield.

Adult↗
PubMed1988

Corpus callosum section and other disconnection procedures for medically intractable epilepsy.

Corpus callosum section for carefully selected patients with uncontrolled epilepsy has become more acceptable as operative complications have decreased. From consideration of anatomical pathways utilized in the spread of seizure discharges, section of the corpus callosum is expected to decrease, but not abolish, bilaterally synchronous EEG abnormalities arising from most cerebral locations, perhaps excluding the temporal lobe. Clinical experience confirms this expectation. Persistence of some bilateral synchrony, presumably through subcortical relays, does not usually diminish the effectiveness of corpus callosum section on clinically generalized seizures that are eliminated or markedly decreased in 85% of patients after total corpus callosum section. Generalized seizure types that respond include tonic, atonic, tonic-clonic, and absence seizures. Patients who continue to have generalized seizures usually have low IQ and perhaps extensive bilateral cerebral involvement increases the extent to which subcortical structures participate in generalization. Complex partial seizures may cease, usually in patients with well-circumscribed, often extratemporal seizure foci. Focal seizures intensify in 25% of patients; a predictable consequence of sectioning interhemispheric inhibitory connections. Permanent disconnection syndromes, which are only rarely symptomatic, include sensory disconnection after posterior section, and split-brain syndrome after total section. A small percentage of patients develop impairments in language, motor, or memory functions. Language and motor deficits are predicted by pre-existing unilateral mild or moderate central nervous system damage. Partial section of the corpus callosum produces control of generalized seizures half as frequently as complete section. Neurologic sequelae of partial section occur nearly as frequently but are less severe.

Cerebral Cortex↗
PubMed2002

Selective zif268 mRNA induction in the perirhinal cortex of macaque monkeys during formation of visual pair-association memory.

To elucidate the molecular basis of cognitive memory formation in the primate, transcriptional activation during learning of a visual pair-association (PA) task was evaluated systematically along the occipito-temporo-hippocampal pathway in the macaque monkey brain. Split-brain monkeys were used for intra-animal comparison, which enables elimination of animal-to-animal variation in gene expression. We found that the expression of the mRNA of an immediate-early gene (IEG), zif268, was up-regulated selectively in the perirhinal cortex (area 36) during the formation of PA memory compared to that during learning of a visual control task. The mRNA expression levels of another IEG, c-jun, were not up-regulated during the PA learning in any cortical areas examined. We also showed that cells strongly expressing zif268 mRNA accumulated in patches in area 36 during learning of the PA task. As the zif268 gene encodes a transcription factor, these results suggest that the activation of zif268 mRNA in area 36 may function as a trigger of the cascade of gene activation that leads to cellular events underlying neuronal reorganization for visual long-term memory formation.

Animals↗
PubMed1976

The split-brain neonate: a surgical method for corpus callosum section in newborn kittens.

One way to determine the importance of interhemispheric interaction in the development of adaptive and acquired behavior is to section completely the corpus callosum about the time of birth before myelination commences and before any significant hemispheric interaction takes place. Therefore, we developed a technique for commissurotomy in the neonatal kitten 36 to 72 hr of age. A specially designed "commissurotomy knife" was used which eliminated retraction of the hemispheres. Histology showed completeness of corpus callosum section as well as commissure of the fornix without any apparent damage to cortical or subcortical structures. This technique meets the following criteria: (1) reproducibility or lesions without additional nonspecific damage; (2)minimal exposure and manipulation of the delicate newborn brain: (3) brief operational procedure minimizing risk of infection; and (4) low mortality rate.

Anesthetics↗
PubMed1981

[Monocular enucleation causes a deficit in visual learning in rats].

Behavioral effects of monocularity were assessed in rats, by means of visual discrimination training in a jumping box. The results showed that the experimental subjects did not differ from controls in brightness discrimination, however, were significantly inferior on a conditional discrimination task. This particular test involves the association of present cues with previously learned ones. Since previous work proposes the consideration of the rat's brain as a functional split-brain, and in our condition the visual information was highly lateralized only to the contralateral hemisphere, we suggest that our results may be due to an impairment produced by the reduction of the brain mass available for the discrimination.

Animals↗