Dissociation of letter and picture naming resulting from callosal disconnection

BACKGROUND: Detailed mapping of the corpus callosum for functional fractionation in humans remains incomplete. OBJECTIVE: To examine separable interhemispheric transfer of visual information by callosal fibers, especially in the splenium. METHODS: We examined callosal disconnection signs in a 14-year-old boy with a lesion confined to the posterior part of the splenium and reviewed reported cases with callosal lesions. RESULTS AND CONCLUSION: The patient presented with left hemialexia as the only manifestation of callosal disconnection syndrome. The only difficulty demonstrated was in reading aloud or copying letters, which were presented tachistoscopically to the left visual field, with his right hand. He could copy letters presented to his left visual field with his left hand, however. Therefore, left hemialexia was not due to hemiamblyopia or hemineglect. There was no anomia for pictures and colors in the left visual field. MRI revealed that the lesion was limited to the ventroposterior end of the splenium. Review of 40 reported patients with callosal lesions suggests that the anterior to middle part of the splenium is involved in transferring picture information from the language-nondominant hemisphere to the language-dominant hemisphere and that the ventroposterior part is involved in transferring letter information.     

The role of the anterior commissure in callosal agenesis.

Two individuals with callosal agenesis (J.P. and M.M.) and 10 neurologically normal participants were tested on tasks requiring interhemispheric visual integration. M.M., whose anterior commissure was within normal limits, was much worse at matching colors and letters between visual fields than within visual fields, whereas J.P., whose anterior commissure was greatly enlarged, showed no evidence of interhemispheric disconnection. This suggests that in some cases of callosal agenesis, probably a minority, an enlarged anterior commissure may compensate for the lack of the corpus callosum. Neither acallosal participant showed interhemispheric disconnection on tasks requiring integration of location and orientation, however, suggesting that the anterior commissure plays no role in such tasks. These tasks may depend on subcortical commissures, such as the intertectal commissure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A two-process view of Facebook use and relatedness need-satisfaction: Disconnection drives use, and connection rewards it.

Does using Facebook help people to meet their relatedness needs? Study 1 shows that more frequent Facebook usage paradoxically correlates with more relatedness satisfaction (connection) and more relatedness dissatisfaction (disconnection). Study 2 supports a 2-process explanation of this finding, showing that disconnection motivates greater usage as a coping strategy, whereas connection results from greater usage. Study 3 examines the effects of depriving participants of Facebook use for 48 hr. Further supporting the 2-process view, connection decreased, but disconnection was unaffected during the deprivation period; however, those who became more disconnected during the deprivation period engaged in more Facebook use during a 2nd, unconstrained 48-hr period, whereas changes in connection did not predict later use. In Study 4, participants set a Facebook reduction goal; initial disconnection interfered with and predicted worse performance in this goal. Implications for theories of psychological needs, behavioral motives, and adaptive coping are considered. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Transient axonal branching in the developing corpus callosum

During development, there is a transient overproduction of axons in the corpus callosum; this overproduction of axons is due, in part, to a transient excess of neurons that send an axon through the corpus callosum. However, transient axonal branching could also contribute to the developmental overproduction of callosal axons. To investigate this possibility, we filled developing callosal axons in the Syrian hamster with the carbocyanine dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil). Light microscopic analysis showed that, indeed, developing callosal axons branch transiently in the hamster: branching was robust on postnatal day 0 (P0) and P3 (P0 = the first 24 hr after birth), less prominent on P6 and P8, and absent by P11. Immature callosal axons branched before or after crossing the midline and at all rostral-caudal and medial-lateral levels within the corpus callosum. The majority of callosal axon collaterals that were contained within individual 100-micron-thick sections were relatively short (mean = 15.1 microns) but some collaterals extended up to approximately 135 microns from the main axon trunk before passing out of the section in which they were observed. Nearly all of the collaterals emanated from the main axon trunk; higher-order collaterals were rare. Some callosal axon trunks had multiple collaterals. Branching callosal axons originated from multiple cortical areas, including area 17. Electron microscopic observations indicated that the processes designated as axon collaterals by light microscopic criteria would have been included in electron microscopic counts of developing callosal axons. Some callosal axon trunks and branches had ultrastructural features that suggested they were degenerating. In cats, developing callosal axons branch on embryonic day 57 (E57; the first 24 hr after conception = E0) and P0. Thus, it is likely that transient branching of immature callosal axons is a generalized feature of mammalian cortical development and that it contributes to the overproduction of callosal axons, albeit perhaps to varying degrees, in multiple species.     

Spontaneous Recovery of Excitation but Not Inhibition.

Five magazine approach experiments with rats and 1 sign-tracking experiment with pigeons explored the possibility of an analogue to spontaneous recovery of excitatory conditioning from extinction: spontaneous recovery of inhibitory conditioning from training. Stimuli were 1st treated as conditioned inhibitors and then as conditioned exciters or as irrelevant to reinforcement. At issue was whether the passage of time after the 2nd treatment would allow partial restoration of the initial conditioned inhibition. The experiments differed in the design used to study recovery, the manner of reinforcing the inhibitor, the means of testing for recovery, the time interval allowed for recovery, and the species used. None of the experiments found evidence for recovery of the inhibitory learning with time, despite the concurrently measured presence of spontaneous recovery of excitatory conditioning after extinction. These experiments suggest that changes with time may be preferential to the learning that occurs during extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of catalase inhibitor 3-amino-1,2,4-triazole on coupled oxidative phosphorylation and the state of adenyl system in liver mitochondria of albino rats

Blepharoptosis is a recognized complication of cataract extraction and other ocular procedures. A 6-month waiting period is recommended before repairing postcataract ptosis because most cases resolve during this time. We report the course of a patient who developed spontaneous recovery of eyelid function 11 months after cataract surgery. She had previously undergone successful ptosis repair 8 months after cataract extraction, but developed overcorrection 3 months later as her levator function returned to normal. We recommend at least a 1-year waiting period before repair of postcataract ptosis. If corrective surgery is undertaken earlier than 1 year due to visual obstruction or for aesthetic reasons, we suggest two guidelines. The levator should be plicated rather than resected and patients should be forewarned of the possibility for a revisionary procedure if spontaneous return of levator function occurs.     

Disconnections in the breathing system

Modern anaesthesia is considered as relatively safe. Nevertheless, incidents happen which result in harm for the patient. Incidents which cause hypoxia are especially grave. One of the most frequent incidents in anaesthesia and intensive care is of this nature: disconnection in the ventilatory apparatus. DEFINITION. Unintentional separation--partial or complete--of two manually connected components in a ventilatory apparatus. INCIDENCE. About 5% of incidents during narcosis are likely to be caused by disconnections in the ventilatory apparatus. CAUSES. Axially directed force of as little as 15 N may cause disconnection. It may result from active or passive movements of the patient, high pressure in the apparatus or unintentional traction on the breathing hoses. Conically moulded couplings are mostly used for connections. The stability of these so-called taper fit connections is decisively determined by the effort and technique of the user when coupling the two components. On the other hand the use of unsuitable materials may lead to an inadequate connection. Another possibility is damage by mechanical, chemical or thermal influences. Additionally, differences from the standard specifications of the components may occur. MOST COMMON SITES. Disconnections are found predominantly (in around 70% of cases) at the connection between the tube connector and the adapter or Y-piece. This joint represents a weak point, especially during surgical treatment in the head and neck region, when it cannot be controlled and in most cases is not accessible by hand because it is covered. CONSEQUENCES. The consequences of disconnection depend on different factors: relaxation of the patient, depth of narcosis, duration and localization of the disconnection, constitution and current oxygenation of the patient. An undetected disconnection may lead to hypoxia within a few minutes and then to irreversible brain damage and finally death. Serious incidents have been decreased in number in recent years by the application of improved monitoring procedures. DETECTION. Measurements of airway pressure, minute volume and expiratory CO2 by capnography ensure rapid detection of disconnections using appropriate adjustments of alarm limits. A disconnection may not be detected by pulse oximetry before a latent period, i.e. after a significant decrease of the oxygenation saturation of the patient. PREVENTION. Standardized specifications exist for technical dimensions of connectors, but "reliability" of connectors has not yet been defined in terms of technical requirements. Disconnection is currently prevented by application of various mechanical methods and devices, not all of which fulfil the conditions required of an ideal system: (1) Simple and fast connection ("single-handed operation"); (2) connection independent of the torsional angle between the two parts; (3)safe connection which cannot be detached unintentionally; (4) 360 degrees torsion possible after connection; (5) tight connection; (6) fast and easy deliberate disconnection; (7) intentional disconnection possible independent of the torsional angle between the two parts; (8) compatibility with conventional systems; (9) user's comfort and convenience (when ventilating with mask, etc.) as good as with conventional systems. DISCONNECTION OR EXTUBATION? There is a heated debate on the theme "disconnection". Some authors suspect that the development of reliable locking connections could lead to an increased frequency of unwanted extubations. To prevent unwanted extubations with consequent harm to patients, some developers propose a mechanical fuse, i.e. a defined site of fracture with an additional adequate monitoring device for reliable detection of disconnections. CONCLUSIONS. There are many approaches to the "disconnection" problem. In principle the problem requires a fundamental decision for each connection in the breathing system: safe prevention of disconnection (lock connection) or reliable mechanical f     

Callosal transfer in schizophrenia: Too much or too little?

Evidence from diverse sources has pointed to an abnormality in callosal transfer in schizophrenia. To examine this further, a test was devised that measures Stroop interference and facilitation within and between the cerebral hemispheres. 46 heterogeneous schizophrenic patients were tested, and it was found that lateralized Stroop effects were equivalent in the left and right hemispheres and did not differ from normal or psychiatric (affective disorder) control Ss. In control Ss, Stroop effects that required interhemispheric transfer of coded information were reduced relative to those requiring intrahemispheric transfer, whereas among schizophrenic Ss, greater Stroop effects were found in the interhemispheric condition, presumably reflecting increased callosal connectivity. An index of callosal transfer did not correlate with gender, age, or IQ in any of the groups, nor did it relate to clinical characteristics in the schizophrenic Ss. The results support a specific functional abnormality of excessive callosal transfer in schizophrenia, though its role in pathogenesis remains unspecified. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Alien hand syndrome: influence of neglect on the clinical presentation of frontal and callosal variants

Three patients with mesial frontal and extensive callosal lesions due to anterior cerebral artery infarction manifested an alien hand syndrome (AHS) with varied features. Patient 1 with left hemispheric lesion showed right hand's impulsive reaching and grasping and left hand's antagonistic movements to the right (intermanual conflict; IMC). Patients 2 and 3 with right hemispheric lesion manifested a left hemihypokinesia which was thought to have suppressed the frequency and amplitude or even the occurrence of left hand's reaching and grasping. IMC and other left hand's non-antagonistic, irrelevant movements to the right remained. Because the term "IMC" is often misused and not strictly defined, its association with right hand's reaching and grasping is quite uncommon, its significance as a sign of callosal disconnection is not well validated, and because left hand's reaching and grasping tend to be suppressed by motor neglect, a trend may then develop for the right hand to be the sole focus of pathological behaviour in patients with the so-called frontal AHS (Feinberg, Schindler, Flanagan et al., 1992).     

Strain-dependent recovery of spontaneous hindlimb movement in spinal cord transected mice (CD1, C57BL/6, BALB/c).

Reorganization and plasticity after spinal cord injury have been recently shown to take place in sublesional neuronal networks, but the possibility of strain-dependent changes at that level has never been explored. The authors studied the spontaneous return of hindlimb movement in low-thoracic spinal cord transected (Tx) mice from 3 commonly used strains. Without intervention, most CD1, C57BL/6, and BALB/c mice displayed some hindlimb movement recovery after Tx. Although all assessment methods unanimously reported that CD1 displayed higher recovery levels than did the C57BL/6 and BALB/c, higher scores were generally found with the Antri-Orsal-Barthe (M. Antri, D. Orsal, & J. Y. Barthe, 2002) and the Average Combined Score (P. A. Guertin, 2005a) methods. Such spontaneous recovery in low-thoracic Tx mice is likely the result of neuronal plasticity at the lumbosacral spinal cord level, suggesting that these sublesional changes are strain dependent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fertility results after ovarian transposition for pelvic malignancies treated by external irradiation or brachytherapy

The spontaneous recovery of nigrostriatal dopaminergic neurons was quantitatively analyzed with tyrosine hydroxylase (TH)-immunocytochemistry in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated C57BL/6 young mice. A substantial reduction of striatal dopamine (DA) level was observed until 24 days following MPTP treatment. The TH-immunoreactive (IR) fibers and number of TH-positive cell bodies were also markedly reduced at 3 days after the toxin treatment. Thereafter, TH-IR fiber densities showed to progressively recover through the examining period. The number of TH-positive cell bodies in substantia nigra pars compacta were not changed during the recovery period. These results indicate that MPTP-treated mice have a potential for spontaneous regenerative sprouting in nigrostriatal dopaminergic system.     

Extent and limits of callosal plasticity: presence of disconnection symptoms in callosal agenesis

Although earlier studies have emphasized the absence of 'split-brain' symptoms in callosal agenesis patients, the notion of an 'asymptomatic' acallosal brain has lately been challenged. We report a number of findings that are indicative of an interruption of interhemispheric communication and integration in individuals lacking the corpus callosum. Several groups of patients with callosal pathology (acallosals, patients with commissurotomy or callosotomy, either complete or partial) were compared to matched controls. Interhemispheric transfer was tested in two different experiments involving pointing to a light source while maintaining central fixation. In the first experiment, a learning paradigm was used to measure transfer of a motor skill from the trained to the untrained hand. In the second experiment, subjects pointed to visual targets at different locations on a perimeter. Midline fusion, a recurrent theme when describing callosal function, was assessed using tasks which included depth perception with binocular and/or monocular cues, two-point discrimination thresholds and sound localization in the peri-central and lateral fields. Subjects with callosal pathology were impaired on all tasks involving transfer of motor and visuo-spatial skills and on some of the tasks requiring sensory integration of visual and tactile information across the body midline. We conclude that these functions require an intact corpus callosum since none of these deficits were seen in controls equated for IQ.     

Relative importance of informational units and their role in long-term recall by closed-head-injured patients and control groups.

Applied qualitative analysis to the information recalled by control Ss and closed-head-injured (CHI) patients. The Logical Memory subtest of the Wechsler Memory Scale (WMS) was administered to 40 CHI and 40 control Ss. Recall was tested immediately after administration, 40 min later, and 24 hrs later. The analysis took into account the importance of recalled information as determined by a prior rating according to 3 levels of importance. Results suggest that CHI patients have difficulty selectively retrieving the most important information after a long delay. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Callosal dysfunction in schizophrenia and schizo-affective disorder.

Studies of corpus callosum dysfunction in schizophrenia have typically relied on measures that reveal impairment in commissurotomy patients, but measures that distinguish people with callosal agenesis may be more appropriate. Four of these indexes were included in the present study. Tests of associated movements, cross-localization of touch, interocular transfer of spiral aftereffect, and transfer of blind formboard learning were administered to 18 chronic schizophrenics, 19 schizo-affectives, and 20 normal volunteers. Both schizophrenics and schizo-affectives were impaired on all measures except transfer of blind formboard learning. Schizophrenics also made significantly more associated movements than schizo-affectives and exhibited a different pattern of cross-localization deficit. These results support the hypothesis of developmental callosal dysfunction in schizophrenia and schizo-affective disorder, although the nature of this dysfunction differs in part from that exhibited by acallosals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unilateral aplasia of the cerebellum in Aicardi's syndrome

A case of unilateral aplasia of the cerebellum in a girl with Aicardi's syndrome is described. Aplasia of an entire hemisphere is one of the least frequent malformations of the cerebellum. Hypoplasia, partial hemispheric defects of the cerebellum and, rarely, complete absence of one hemisphere have been described in Aicardi's syndrome, which is associated with multiple systemic and CNS malformations. In our patient, who presented the characteristic trial of infantile spasms, callosal agenesia and retinal lacuna, we also saw right cerebellar aplasia along with other CNS malformations using magnetic resonance. We discuss the possibility that this aplasia arises as the result of a developmental defect of the posterior arterial system of Willis's polygon.     

Intermanual transfer in the monkey as a function of amount of callosal sparing

The effects of commissure section, task difficulty and overtraining on the intermanual transfer of tactile learning have been examined. Twenty-one rhesus monkeys were allocated to 4 groups. One group was subjected to complete transection of the corpus callosum, massa intermedia and posterior commissure. Some of this group also sustained a cerebellar section. A second group received a similar division of the commissures but with part of the posterior body of the corpus callosum left intact. A third group received similar division of the commissures but with the posterior commissure left intact. The fourth group formed an unoperated control group. Animals with only the posterior commissure left intact showed little or no transfer. Animals with partial callosal lesions showed significantly greater transfer than animals with total transections, but were impaired relative to the unoperated controls. Estimates have been made of the number of callosal fibres left intact in the animals with partial callosal lesions. These estimates have been correlated with transfer. The correlation was significant on only one task. Neither task difficulty nor overtraining were found to affect transfer significantly. The comparison of transfer of the submodalities of size and roughness was inconclusive.     

Protamine sulfate enhances lipid-mediated gene transfer

OBJECTIVE: To analyze myoelectric activity of the cecum and proximal loop of the ascending colon (PLAC) in cows after spontaneous cecal dilatation/dislocation (CDD) and compare it with that in healthy cows after surgical evacuation of the cecum. ANIMALS: 12 cows with spontaneous CDD and 6 healthy cows (group C). Cows with spontaneous CDD were retrospectively assigned to 2 groups: delayed recovery from surgery or recurrence (group A; n = 3), and normal recovery (group B; n = 9). PROCEDURE: After surgical evacuation of the cecum, 8 pairs of bipolar, retrievable electrodes were implanted in the ileum, cecum, and PLAC. Cows were evaluated daily from postoperative day 1 to 7, using routine clinical methods and computer-based analysis of myoelectric activity of the cecum, and PLAC. Parameters of myoelectric activity included rate of spike bursts, duration of individual spike bursts, duration of overall spike burst activity per electrode, rate of propagated spike burst sequences, and ratio of orally propagated spike burst sequences. RESULTS: Rate of spike bursts, duration of cecocolic spike burst activity, and ratio of orally to aborally propagated spike burst sequences did not vary among groups during the 7-day recording period. However, cows with delayed recovery had a typical, uniform pattern of myoelectric activity of the cecum and PLAC at days 1 and 2 after surgery that consisted of repeated, propagated spike burst sequences, made up of spike bursts of significantly (P < 0.05) increased duration at postsurgical day 1 and substantially prolonged duration at postsurgical day 2, interrupted by periods of little or no activity. CONCLUSION: Delayed recovery and recurrence of CDD in cows after spontaneous CDD is not caused by hypomotility of the cecum and PLAC. CLINICAL RELEVANCE: Postoperative treatment, intended to reduce recurrence of CDD or delayed recovery after surgical evacuation of the cecum, should address propagation of digesta in the spiral colon.     

Distal dorsal forearm flap

Reinstatement and spontaneous recovery of previously extinguished nicotine-taking behavior were examined in rats. Male subjects were trained to self-administer nicotine (30 microg/kg per infusion, IV; one 60-min session per day for 3 weeks). Extinction sessions were then given for 5-10 days during which saline was substituted for nicotine. Subsequently, in the first set of tests for nicotine seeking, the reinstatement of lever presses that previously delivered nicotine was examined after priming injections of saline and nicotine (75, 150 and 300 microg/kg, SC; and 30 and 60 microg/kg, IV). In the second set of tests for nicotine-seeking, rats were tested after an additional 21-day drug-free period during which they were not exposed to the self-administration chambers (a test for the spontaneous recovery of drug seeking), and after priming injections of nicotine (150 and 300 microg/kg, SC). Reinstatement of extinguished food-reinforced behavior after exposure to nicotine was also determined. Priming injections of nicotine reinstated nicotine seeking regardless of the route of administration. In addition, previously extinguished nicotine seeking recovered spontaneously after a 21-day period during which rats were not exposed to the drug-taking environment. Nicotine also reinstated extinguished food-reinforced behavior in rats with a history of nicotine self-administration, but not in drug-naive rats. The present results extend previous work with opioid and stimulant drugs on reinstatement of drug seeking by the self-administered drug. It also appears that, as with other positive reinforcers, the mere passage of time is a sufficient condition for the spontaneous recovery of extinguished nicotine seeking.     

Social disintegration and the spread of AIDS--II. Meltdown of sociogeographic structure in urban minority neighborhoods

An elementary model of sociogeographic network structure in an urban minority community suggests externally applied stress, particularly that which triggers frequent individual or family moves of increasing distance, may cause a sudden 'phase change' resulting in disconnection of previously integrated subgroups from the community. Such 'community meltdown' would seriously disrupt mechanisms for social control, economic opportunity and socialization of youth, while intensifying substance abuse and indiscriminate and frequent sexual activity, particularly among the very young. 'Phase change' of this nature would seem to preclude success of programs to control spread of HIV infection, particularly in heterosexual populations. The possibility is explored that programs of 'community recrystalization' in disintegrated urban area might likewise need to exceed some threshold of investment and organizing activity before becoming effective. However, if supported to levels above threshold, this work implies such programs might have very great impact in a very short time. The possibility of interaction between behavioral pathologies resulting from the initial meltdown and further consequent deterioration in sociogeographic network structure leads to speculation that the threshold for recrystalization may become significantly and progressively greater than for meltdown. Implications of these matters for diffusion of HIV into the general population are discussed.     

Timing of extinction relative to acquisition: A parametric analysis of fear extinction in humans.

Fear extinction is a reduction in conditioned fear following repeated exposure to the feared cue in the absence of any aversive event. Extinguished fear often reappears after extinction through spontaneous recovery. Animal studies suggest that spontaneous recovery can be abolished if extinction occurs within minutes of acquisition. However, a limited number of human extinction studies have shown that short interval extinction does not prevent the return of fear. For this reason, we performed an in-depth parametric analysis of human fear extinction using fear-potentiated startle. Using separate single-cue and differential conditioning paradigms, participants were fear conditioned and then underwent extinction either 10 min (Immediate) or 72 hr (Delayed) later. Testing for spontaneous recovery occurred 96 hr after acquisition. In the single cue paradigm, the Immediate and Delayed groups exhibited differences in context, but not fear, conditioning. With differential conditioning, there were no differences in context conditioning and the Immediate group displayed less spontaneous recovery. Thus, the results remain inconclusive regarding spontaneous recovery and the timing of extinction and are discussed in terms of performing translational studies of fear in humans. (PsycINFO Database Record (c) 2010 APA, all rights reserved)