Removal Of Cortex Research Articles

Both striate cortex and superior colliculus contribute to visual properties of neurons in superior temporal polysensory area of macaque monkey.

Although the tectofugal system projects to the primate cerebral cortex by way of the pulvinar, previous studies have failed to find any physiological evidence that the superior colliculus influences visual activity in the cortex. We studied the relative contributions of the tectofugal and geniculostriate systems to the visual properties of neurons in the superior temporal polysensory area (STP) by comparing the effects of unilateral removal of striate cortex, the superior colliculus, or of both structures. In the intact monkey, STP neurons have large, bilateral receptive fields. Complete unilateral removal of striate cortex did not eliminate visual responses of STP neurons in the contralateral visual hemifield; rather, nearly half the cells still responded to visual stimuli in the hemifield contralateral to the lesion. Thus the visual properties of STP neurons are not completely dependent on the geniculostriate system. Unilateral striate lesions did affect the response properties of STP neurons in three ways. Whereas most STP neurons in the intact monkey respond similarly to stimuli in the two visual hemifields, responses to stimuli in the hemifield contralateral to the striate lesion were usually weaker than responses in the ipsilateral hemifield. Whereas the responses of many STP neurons in the intact monkey were selective for the direction of stimulus motion or for stimulus form, responses in the hemifield contralateral to the striate lesion were not selective for either motion or form. Whereas the median receptive field in the intact monkey extended 80 degrees into the contralateral visual field, the receptive fields of cells with responses in the contralateral field that survived the striate lesions had a median border that extended only 50 degrees into the contralateral visual field. Removal of both striate cortex and the superior colliculus in the same hemisphere abolished the responses of STP neurons to visual stimuli in the hemifield contralateral to the combined lesion. Nearly 80% of the cells still responded to visual stimuli in the hemifield ipsilateral to the lesion. Unilateral removal of the superior colliculus alone had only small effects on visual responses in STP. Receptive-field size and visual response strength were slightly reduced in the hemifield contralateral to the collicular lesion. As in the intact monkey, selectivity for stimulus motion or form were similar in the two visual hemifields. We conclude that both striate cortex and the superior colliculus contribute to the visual responses of STP neurons. Striate cortex is crucial for the movement and stimulus specificity of neurons in STP.(ABSTRACT TRUNCATED AT 400 WORDS)

Phaco-Ersatz: cataract surgery designed to preserve accommodation.

Phaco-Ersatz represents a new approach to cataract surgery and the correction of aphakia. The procedure involves the removal of the cataractous cortex and nucleus while preserving the lens capsule and its zonular attachments. The empty lens capsule is then refilled with biocompatible and optically suitable clear gel. A physiologic lens is recreated in situ. Experimental work with human cadaver eyes and rabbit and cat eyes in vivo demonstrates this surgical feasibility. A review of the literature reveals contradicting theories regarding the physical laws and lens properties governing accommodation. The accommodative potential of the ersatz lens has not been tested, but it may be speculated that this recreated lens may, in fact, possess some accommodative properties. Experimental investigations in this area represent the logical extension of intraocular lens implant development.

Somatosensory evoked potentials after removal of somatosensory cortex in man

Somatosensory evoked potentials (SEPs) to median nerve, ulnar nerve, thumb, middle finger, and posterior tibial nerve stimulation were recorded in a patient with a discrete resection of part of the postcentral somatosensory cortex as a treatment for focal epilepsy. Comparison of the different stimulation sites confirmed electrophysiologically the restricted locus of the lesion. The results strongly suggest that the early negative component (N20) and subsequent components recorded postcentrally are of cortical origin and depend upon postcentral gyrus cytoarchitectonic areas 3, 2, and 1. Moreover, these postcentral SEPs are distinct from precentrally recorded activity.

Cross-modal recognition by the monkey: Can the experience in the first modality be reduced to a single trial?

Using the cross-modal recognition procedure previously described, but now progressively reducing the number of learning trials given in the first sense modality, three unselected and unoperated rhesus monkeys (and one with bilateral removals of frontal, temporal and parietal polysensory cortex) were able to maintain an average level of 75% correct cross-modal recognition with only 1–3 learning trials. The pool size seemed less important than the familiarity of the objects. No discontinuity between single-trial and multiple-trial learning procedures was detected. Instead, the number of objects available at one time during learning was regarded as critical for distinguishing between these two kinds of learning procedure.

Trace conditioning: Abolished by cerebellar nuclear lesions but not lateral cerebellar cortex aspirations

The trace conditioning paradigm in which the conditioned stimulus-unconditioned stimulus (CS-US) interval is longer and the US and CS do not overlap requires retention of a ‘trace’ of the CS to associate it with the US. This task is difficult, requiring for learning about 5 times the number of trials to criterion as the standard delay task. The present study was undertaken to determine if: (1) the cerebellar interpositus nucleus is essential in trace as well as in delay conditioning; and (2) the lateral cerebellar cortex is involved when CS-US association over longer time intervals is required. Sixteen adult male New Zealand white rabbits had recording and in some cases lesion electrodes surgically implanted before training. They were trained daily with 126 paired trials of tone CS and airpuff US. The trace period between CS offset and US onset was 500 ms. Mean number of trials to criterion of 8/9 CRs was 466.9 trials. After a day of overtraining the animals had one of 3 surgeries: (1) electrolytic lesion of the left cerebellar interpositus nucleus ( n= 3); (2) aspiration of the left lateral cerebellar cortex (HVI and HVIIA) and underlying cerebellar nuclei ( n= 4); or (3) aspiration of HVI and HVIIA only ( n= 9). Rabbits with only HVI and HVIIA removed exhibited a transient decrease in CRs but relearned with significant savings. The amplitude, area and latency of pre- and postlesion conditioned responses (CRs) was similar. When the interpositus nucleus was damaged, the animals' capacity for CRs on the side ipsilateral to the lesion was permanently abolished. It is concluded that the cerebellar interpositus nucleus but not the overlying lateral cerebellar cortex is essential for retention of trace classical conditioning. Nevertheless, the temporary abolition of CRs by removal of lateral cerebellar cortex suggests that the cerebellar cortex does play an important role in learning and retention of the trace conditioned response.

Pathways through cingulate, neo-and entorhinal cortices mediate atropine-resistant hippocampal rhythmical slow activity

Rats prepared with a lesion separating the entorhinal cortex from the neocortex and cingulate cortex displayed apparently normal hippocampal rhythmical slow activity (RSA) with a frequency of 6–12 Hz in both CA1 and dentate gyrus during Type 1 behavior (locomotion, head movements, changes in posture). Variations in the commissural average evoked potential (AEP) and increased power in the 30–100 Hz range (fast waves) also correlated with Type 1 behavior. Urethane did not abolish the RSA. However, systemic administration of atropinic drugs eliminated all RSA and eliminated or attenuated the Type 1 behavior-related variations in the AEP and fast waves. Thus, the normally present atropine-resistant RSA was eliminated by the cortical lesion while atropine-sensitive RSA remained intact. Removal of cingulate cortex alone was partially effective in suppressing atropine-resistant RSA but a lesion of the neocortex only, sparing cingulate cortex, had a minimal effect on it. Lesions of the amygdala, the anterior or medial thalamus or the cerebellum had little or no effect on atropine-resistant RSA. Previous work has shown that lesions of the entorhinal cortex or lateral hypothalamus eliminate atropine-resistant RSA. We suggest that atropine-resistant RSA is mediated by a somewhat diffuse pathway which traverses the hypothalamus, cingulate cortex, and neocortex before reaching the hippocampus via the entorhinal cortex.

Visuo-motor behaviour after bilateral removal of the visual cortex in the rabbit

Visuo-motor behaviour after bilateral removal of the visual cortex in the rabbit

Survival of the ganglion cell population in the rabbit retina following neonatal visual cortex ablation

Unilateral visual cortex ablations in neonatal rabbits produced no detectable loss of ganglion cells in the contralateral retina following a survival period of 3, 4 or 8 months. Analysis of neuron size distributions and neuron densities from whole-mounted retinas indicate that transneuronal retrograde degeneration does not occur in the rabbit following neonatal visual cortex removal. The results support the hypothesis that axon collaterals play a role in retinal ganglion cell survival in neonatally operated animals. The paradoxical relationship between functional sparing and ganglion cell survival is discussed.

Cortex removal system for manual extracapsular cataract extraction

An irrigation/aspiration (I/A) system for cortex removal has been developed. It consists of an I/A cannula, connecting silicone tube, a handle with an aspiration cut-off device for the silicone tube, and an aspirating device. The aspirating pressure is produced by a fixed syringe, the cylinder of which is pulled by a weight. In addition, the aspirating system can be equipped with a small battery-operated pump. The aspiration cut-off device located in the handle enables aspiration with one hand so the other hand is free for another instrument. Flushing back, if necessary, is possible.

Removal and reimplantation of the parietal cortex of the neonatal mouse: Consequences for the barrelfield

The barrelfield, i.e., the cortical representation of the contralateral whiskerpad, develops in the mouse between postnatal days 4 and 6 (P4 and P6). The pattern of barrels in the barrelfield is dependent on that of the whiskers on the whiskerpad. We removed (unilaterally) and reimplanted, with normal orientation (n = 23) or after 180° rotation (n = 23), that part of the pallium where the barrelfield is to develop. These operations were made at birth (P0), at P1 or at P3. Our aim was to know whether a homeomorphic representation of the periphery would be established, by regeneration or by retarded growth of surviving thalamic fibers into the cortex, and if so, whether it could be modified in its orientation. Of group (i) 16 animals survived of which 14 killed between P26 and P29 could be analyzed. We operated 11 at P0 and 4 of these had a normal barrelfield, two a rotated one (by about 30°) with some barrels in odd positions, one a wildly disorganized one and 4 no barrels at all. Three mice operated at P3 presented a normal barrelfield. In group (ii) operated at PO, the 17 survivors, killed between P13 and P68, had no barrels. The results indicate that a homeomorphic representation of the periphery may be established in the somatosensory cortex after an early, complete and massive interruption not only of all its afferent and efferent fibers, but also of its vascularization. With respect to animals of group (ii) we cannot rule out the ingrowth of thalamic afferents into the implant. The absence of barrels here may point to the existence of a certain degree of target-specificity of thalamic fibers which would fail to induce the formation of barrels when confronted with a wrong domain of parietal cortex.

Prefrontal cortex and the sequencing of movement in monkeys (macaca mulatta)

There have been suggestions that the prefrontal cortex may play a role in the regulation of higher-order sequences of behaviour. In this experiment monkeys were taught a sequence of three movements. After removal of either sulcus principalis or the superior prefrontal convexity monkeys were able to perform the sequence normally. After removal of arcuate cortex (areas 8 and 6) monkeys were slow to learn the task; but it is argued that their impairment may not be one of sequencing per se.

Critical periods for functional and anatomical compensation in lateral suprasylvian visual area following removal of visual cortex in cats.

Previous experiments have found that neurons in the cat's lateral suprasylvian (LS) visual area of cortex show functional compensation following removal of visual cortical areas 17, 18, and 19 on the day of birth. Correspondingly, an enhanced retino-thalamic pathway to LS cortex develops in these cats. The present experiments investigated the critical periods for these changes. Unilateral lesions of areas 17, 18, and 19 were made in cats ranging in age from 1 day postnatal to 26 wk. When the cats were adult, single-cell recordings were made from LS cortex ipsilateral to the lesion. In addition, transneuronal autoradiographic methods were used to trace the retino-thalamic projections to LS cortex in many of the same animals. Following lesions in 18- and 26-wk-old cats, there is a marked reduction in direction-selective LS cortex cells and an increase in cells that respond best to stationary flashing stimuli. These results are similar to those following visual cortex lesions in adult cats. In contrast, the percentages of cells with these properties are normal following lesions made from 1 day to 12 wk of age. Thus the critical period for development of direction selectivity and greater responses to moving than to stationary flashing stimuli in LS cortex following a visual cortex lesion ends between 12 and 18 wk of age. Following lesions in 26-wk-old cats, there is a decrease in the percentage of cells that respond to the ipsilateral eye, which is similar to results following visual cortex lesions in adult cats. However, ocular dominance is normal following lesions made from 1 day to 18 wk of age. Thus the critical period for development of responses to the ipsilateral eye following a lesion ends between 18 and 26 wk of age. Following visual cortex lesions in 2-, 4-, or 8-wk-old cats, about 30% of the LS cortex cells display orientation selectivity to elongated slits of light. In contrast, few or no cells display this property in normal adult cats, cats with lesions made on the day of birth, or cats with lesions made at 12 wk of age or later. Thus an anomalous property develops for many LS cells, and the critical period for this property begins later (between 1 day and 2 wk) and ends earlier (between 8 and 12 wk) than those for other properties.(ABSTRACT TRUNCATED AT 400 WORDS)

Development of tactile discrimination capacity in Macaca mulatta. II. Effects of partial removal of primary somatic sensory cortex (SmI) in infants and juveniles

Four infant macaques between the ages of 2.7 and 6.7 weeks and 5 juvenile macaques between the ages of 78.6 and 108.3 weeks received partial, unilateral lesions of the hand projection in primary somatic sensory cortex (SmI) (either Brodmann's area 3 or areas 1 and 2 combined). Following these partial SmI lesions, both infants and juveniles showed some impairment on acquisition and slightly inferior performance on the size-ALL task. Both infants and juveniles were able to discriminate smaller size differences with the contralateral hand than partial SmI-lesioned adult macaques with similar SmI lesions in previous studies. After partial SmI lesions, infants and juveniles were markedly retarded in the acquisition of texture discriminations indicating that, as in adult macaques, these separate SmI areas contribute jointly to texture discrimination capacity. However, in contrast to adult animals, all infants and most juveniles were able to master all levels of texture tasks after 2–4 months of training. On the texture-ALL task, the performance of partial SmI-lesioned infants was slightly inferior to that of normal infants with the contralateral hand but significantly better than normal infants on the ipsilateral hand. Lesioned juveniles showed impairment on both contralateral and ipsilateral hands. Recovery of near-normal tactile function in both partial SmI-lesioned infants and juveniles is seen although mature levels of function are typical of normal infants over this same age range.

Development of tactile discrimination capacity in Macaca mulatta. III. Effects of total removal of primary somatic sensory cortex (SmI) in infants and juveniles

Four infant macaques between the ages of 3.0 and 5.1 weeks and three juvenile macaques between the ages of 79.9 and 109.3 weeks received unilateral lesions of all cytoarchitectural fields (Brodmann's areas 3, 1 and 2) in the hand area of the postcentral gyrus. These total SmI-lesioned infants acquired the size and texture tasks within the same time period and with the same efficiency as normal infants. On some size- and texture-ALL tasks they actually performed significantly better than partial SmI-lesioned or normal infants. The normal acquisition and ALL performance of the infants with total SmI lesions contrasts with that of the juveniles with comparable lesions. On size acquisition and ALL tasks, with the contralateral hand, total SmI-lesioned juveniles were significantly inferior to normal and total SmI-lesioned infants and to partial SmI-lesioned juveniles. During texture acquisition with the contralateral hand, the total SmI-lesioned juveniles made significantly more errors than normal and total SmI-lesioned infants. The capacity to recover from partial SmI lesions extends into the second year of life and is a gradual process which may be mediated by remaining SmI subdivisions. By contrast, the capacity to recover from total SmI lesions is restricted to infants and is a rapid process which must depend on other areas within the damaged, or possibly the intact, hemisphere.

Experiments on functional role of peripheral input to motor cortex during voluntary movements in the monkey.

The functional role of sensory input to the motor cortex was studied by interrupting two major input pathways. One was the dorsal column, which sends the input directly through the thalamus to the motor cortex, and the other was the sensory cortex, which transfers its input through association fibers. Removal of the sensory cortex produced very little motor disturbances and the function recovered within a week. Section of the dorsal column produced some motor deficit, but the deficit was not severe and the animals recovered nearly completely within 2 wk. Combination of dorsal column section and sensory cortex removal produced severe motor deficits. These consisted of loss of orientation within extrapersonal space and loss of dexterity of individual fingers. These deficits never recovered within the duration of observation, which lasted 4-5 wk. It is concluded that the direct sensory input from the thalamus plays an important role in the control of voluntary movements, but loss of its function can be compensated by the input from the sensory cortex. The possible neuronal basis for the observed motor deficits is discussed and it is proposed that the sensory input functions by selectively changing the excitability of cortical efferent zones before and during the execution of voluntary movements. Recovery of motor function following dorsal column section occurred in parallel with the recovery of sensory input to the motor cortex. The recovered function and sensory input disappeared again following section of the association fibers from the sensory cortex. Neuronal mechanism for this observation is also discussed.

Superior temporal lesions and delayed auditory matching in monkeys

This study considers whether or not unilateral removal of superior temporal cortex in monkeys disrupts performance of a nonspatial delayed auditory matching task. Preliminary evidence of such an impairment has been suggested. Monkeys were evaluated before and after unilateral and serial bilateral removal of superior temporal cortex. No significant postoperative impairment was noted.

Ultrastructural relation between cortical efferents and terminals containing enkephalin-like immunoreactivity in rat neostriatum

The interrelationships between cortical efferents and terminals containing enkephalin-like immunoreactivity (ELI) were examined by combining anterograde degeneration with electron microscopic immunocytochemistry in the adult rat neostriatum. Two days following unilateral removal of the cerebral cortex, the brains were fixed by aortic arch perfusion, then sectioned and processed for the immunocytochemical localization of an antiserum directed against methionine (Met 5)-enkephalin. The observed relationships between the degenerating cortical efferents and immunocytochemically labeled terminals were of two types. In the first, the degenerating and ELI containing terminals converged on the same unlabeled dendrite or dendritic spine. In the second, terminal and preterminal axons of the ELI containing neurons had one surface directly apposed to the plasma membrane of a degenerating axon terminal. These findings support the concept that neurons containing opioid peptides and cortical efferents modulate the output of common recipient neurons and may also directly interact with each other through presynaptic axonal mechanisms in the rat neostriatum.

A glutamatergic innervation of the nucleus basalis/substantia innominata

The possibility of there being a glutamatergic innervation of the nucleus basalis/substantia innominata, was investigated in the rat. High affinity glutamate uptake, and a calcium-dependent, potassium-evoked release of endogenous glutamate in this tissue, were demonstrated. In contrast to the striatum, however (which is known to receive a major, probably glutamatergic, corticofugal input), removal of the fronto-parietal cortex failed to modify these parameters. Thus, while the nucleus basalis/substantia innominata appears to possess an important glutamatergic innervation, its origins are as yet unknown. The existence of such an innervation, however, may be of relevance for the degeneration in Alzheimer's disease of the magno-cellular cholinergic neurones, which show a particular sensitivity to excitotoxic agents.

The effects of unilateral neonatal removal of visual cortex on transmitter parameters in the adult superior colliculus and lateral geniculate body

High affinity glutamate uptake was reduced in the ipsilateral lateral geniculate body by 75% and in the ipsilateral superior colliculus by 50% one week after ablation of the visual cortex in the adult rat. Six days after neonatal removal of visual cortex, there were no effects on the high affinity glutamate uptake in these regions indicating that there were few functionally corticofugal fibres established at birth. Seventy-five days after unilateral neonatal ablation of visual cortex, the glutamate uptake in both ipsi- and contralateral superior colliculus was reduced 50% compared to unoperated controls. The glutamate uptake in the lateral geniculate body was reduced 55% ipsilateral to and 38% contralateral to the lesion. The neonatal lesion had therefore affected the development of glutamate nerve terminals bilaterally in these target regions. Destruction of the visual cortex on the unoperated side caused in these adults an additional bilateral decrease of the glutamate uptake in the superior colliculus, showing the presence of aberrant glutamatergic fibres crossing from the unoperated visual cortex. In the lateral geniculate body, a similar lesion was accompanied only by a reduction in glutamate uptake on the ipsilateral side. The neonatal ablation of visual cortex also induced small changes in glutamate decarboxylase and GABA uptake in superior colliculus 75 days after the operation.

Cortex removal at 12 o'clock.

A simple, safe, and effective method for removing residual cortex at 12 o'clock is presented. This technique can be used by surgeons who perform extracapsular cataract extractions and also facilitates the superior loop placement of a posterior chamber lens within the remaining capsule.